ba-1959-0023.ch012

Preparation, Properties, and Uses of Borate Esters ROBERT M. WASHBURN, ERNEST LEVENS, CHARLES F. ALBRIGHT, and FRANKLIN A. BILLIG

Downloaded by UNIV OF CALIFORNIA SAN FRANCISCO on December 8, 2014 | http://pubs.acs.org Publication Date: January 1, 1959 | doi: 10.1021/ba-1959-0023.ch012

Research Department, American Potash & Chemical Corp., Whittier, Calif.

The esters of orthoboric a c i d , although known for more than 100 years (58), have only recently become commercially a v a i l a b l e . This paper presents process development d a t a ; the synthesis a n d properties of a new series of hydrolytically stable borates; the v a r i a tion in boiling point, density, index of refraction, a n d viscosity with temperature; a summary of reactions and uses; a n d physical evidence that tetracoordinate boron is involved in the reactions of borate esters.

A n u m b e r o f m e t h o d s f o r p r e p a r i n g b o r a t e esters h a v e been d e s c r i b e d . They i n c l u d e : r e a c t i o n o f a n a l c o h o l ( o r p h e n o l ) w i t h b o r o n t r i c h l o r i d e (48, 134) ( E q u a t i o n 1 ) ; b o r o n a c e t a t e (8, 146) ( E q u a t i o n 2 ) ; b o r i c a c i d (47, lp) ( E q u a t i o n 3 ) ; b o r o n o x i d e (188) ( E q u a t i o n 4 ) ; o r s o d i u m b o r o h y d r i d e (36) ( E q u a t i o n 5 ) ; a n d t r a n s e s t e r i f i c a t i o n w i t h a l o w e r b o i l i n g b o r a t e ester (170, 204) ( E q u a t i o n 6 ) . W h e n w a t e r is a p r o d u c t o f t h e e s t e r i f i c a t i o n , i t h a s been r e m o v e d b y a z e o t r o p i c d i s t i l l a t i o n w i t h a n excess o f t h e a l c o h o l (14, 92, 164) t m e d i u m (149) ; o r b y d e h y d r a t i o n w i t h s u l f u r i c a c i d (45, 197), c o p p e r s u l f a t e (56, 93), o r b o r o n o x i d e (120, 126, 172, 197) ( E q u a t i o n 7 ) . o

r

a

n

m

e

r

3 R O H + B C 1 -> ( R O ) B + 3 H C 1 3

(1)

3

6 R O H + ( C H C O O ) B 0 -> 2 ( R O ) B + 4 C H C O O H + H 0 3

4

2

3

3

2

3 R O H + H B 0 -> ( R O ) B + 3 H 0 3

3

3

6 R O H + B 0 -> 2 ( R O ) B + 3 H 0 2

3ROH + NaBH

4

3

3

(4)

2

+ H + -> ( R O ) B + 4 H + N a 3

(2) (3)

2

2

(5)

+

3 R O H + ( R O ) B -> 3 ( R O ) B + 3 R O H

(6)

3 R O H + B 0 -> ( R O ) B + H B 0

(7)

3

2

3

3

3

3

3

S t a n l e y (180) h a s c l a i m e d t h e p r e p a r a t i o n of b o r a t e esters as a n i n t e r m e d i a t e s t e p i n t h e c o n v e r s i o n o f a l k y l e n e s i n t o alcohols. T h e alkylene is converted t o the a l k y l sulfate, a l k y l phosphate, o r a l k a r y l sulfonate b y absorption into acid o r acid ester; t h e b o r a t e ester f o r m e d o n s u b s e q u e n t r e a c t i o n w i t h b o r i c a c i d i s t h e n d i s t i l l e d a n d hydrolyzed to the alcohol: 3S0 (OEt) 2

2

+ H B 0 -> 3 S 0 ( O E t ) O H 4- ( E t O ) B 3

3

2

8

1

H 3 B

°

3

> 3H S0 + (EtO) B 2

4

8

129

In METAL-ORGANIC COMPOUNDS; Advances in Chemistry; American Chemical Society: Washington, DC, 1959.

(8)

130

ADVANCES IN CHEMISTRY SERIES

B a r n e s a n d c o w o r k e r s (15) r e c e n t l y c l a i m e d t h e p r o d u c t i o n o f m e t h y l , e t h y l , p r o p y l , a n d b u t y l borates b y reaction of b o r o n trifluoride etherate w i t h the alcohol and sodium alcoholate:


BF

3

: 0(C H ) 2

5

2

+ 3NaOCH

3

+ C H O H - • [B(OCH ) + CH OH] azeotrope 3

3

3

3

+ 3NaF + (C H ) 0 2

6

2

(9)

I n g e n e r a l , a t t e m p t s t o p r e p a r e m i x e d b o r a t e esters o f m o n o h y d r o x y c o m p o u n d s r e s u l t i n d i s p r o p o r t i o n a t i o n t o t h e c o r r e s p o n d i n g s y m m e t r i c a l esters (47, 48, 170, 188). M i x e d esters h a v e , h o w e v e r , b e e n s y n t h e s i z e d b y use o f a p o l y h y d r i c a l c o h o l ( e t h y l e n e glycol) or phenol (catechol) i n conjunction w i t h a monoalcohol t o give t h e cyclic p r o d u c t s , I a n d I I (118, 188): OCH

2

HOB

ROB< OCH,

χ

Ο

\

0

I

II T h e s i m p l e b o r a t e s o f p o l y h y d r i c a l c o h o l s h a v e b e e n d e s c r i b e d (3, 4$, 146> 151, 170). T h e effectiveness o f c e r t a i n p o l y h y d r i c a l c o h o l s ( m a n n i t o l , g l y c e r o l ) u s e d i n t h e s t a n d a r d a l k a l i n e t i t r a t i o n o f b o r i c a c i d h a s b e e n a t t r i b u t e d b y B ô e s e k e n (23, 26, 27) t o t h e f o r m a t i o n i n w a t e r o f s t r o n g a c i d s i n w h i c h t h e esterified b o r o n a t o m has become tetracoordinate ( I I I ) : OCH

HCO

H

+

OCH

HCO III

T h e t e t r a h e d r a l s t r u c t u r e o f b o r o n i n esters o f c i s - c l i h y d r o x y c o m p o u n d s w a s e s tablished b y resolution of b o r o n bis-(y-chlorocatechol) a n d of b o r o n b i s - ( 3 - n i t r o c a t e chol), each into two optically active forms. S i m i l a r l y , the borosalicylate ion a n d the α - h y d r o x y b u t y r a t e d e r i v a t i v e w e r e f o u n d t o b e o p t i c a l l y a c t i v e (23-25). O n the other h a n d , catechol borate, p r e p a r e d b y m e l t i n g together catechol a n d boron oxide, w a s assigned t h e s t r u c t u r e ( I V ) : -O

( ) - ^ \ ^>B--O—i*/

-ο

ο IV

A l t h o u g h t h e ester is h y d r o l y z e d b y w a t e r , t h e salts are s t a b l e (165-167). This suggests t h a t b o r a t e s h a v i n g t r i g o n a l c o p l a n a r b o r o n are f o r m e d u n d e r a n h y d r o u s c o n d i t i o n s , w h i l e b o r a t e s h a v i n g t e t r a h e d r a l b o r o n as t h e c e n t e r o f s y m m e t r y r e s u l t w h e n water is present. T h e u n u s u a l l y h i g h resistance t o h y d r o l y s i s of t h e a l k a n o l a m i n e b o r a t e s a n d a m i n o e t h y l diarylborinates has been a t t r i b u t e d t o t h e tetrahedral configuration of boron i n a t r y p t i c h structure resulting f r o m the transannular coordination of a p a i r of electrons o n t h e n i t r o g e n a t o m w i t h t h e o p e n sextet o n t h e b o r o n (85, 62, 119, 181). T h a t triisopropanolamine borate is considerably more hydrolysis-resistant t h a n t r i e t h a n o l a m i n e b o r a t e (181) m a y r e s u l t f r o m t h e a d d i t i o n a l s t e r i c effect i n t h e f o r m e r . T h e p o l y f u n c t i o n a l i t y of boric acid ( o r b o r o n oxide) a n d the p o l y h y d r o x y c o m pounds r e a d i l y leads t o t h e f o r m a t i o n of condensation p o l y m e r s a n d copolymers. S e v e r a l p a t e n t s d e s c r i b i n g s u c h m a t e r i a l s are l i s t e d i n T a b l e X I X .


131


WASHBURN, LEVENS, ALBRIGHT, AND BILLIG—BORATE ESTERS

Figure 1. of

Apparatus for laboratory study

azeotropic distillation

method

A. Miter flask B. Vigreux column C. Water-cooled azeotrope decanter T h e o n l y p a r t i a l l y esterified b o r i c a c i d [ R O B ( O H ) ] w h i c h has b e e n r e p o r t e d i s 1 - m e t h y l b o r i c a c i d (142). S c a t t e r g o o d , M i l l e r , a n d G a m m o n (164) a n d S t e i n b e r g a n d H u n t e r (181) h a v e suggested t h a t t h e p a r t i a l l y esterified b o r i c a c i d s o c c u r a s i n t e r m e d i a t e s i n t h e stepwise h y d r o l y s i s o f t h e f u l l y esterified c o m p o u n d s . G e r r a r d 2



132


Figure 2.

Apparatus

for large-scale laboratory

azeotropic distillation

a n d L a p p e r t (73) p o s t u l a t e d a s i m i l a r m e c h a n i s m f o r t h e d e a l k y l a t i o n o f t h e t r i e s t e r s b y h y d r o g e n h a l i d e s , a l t h o u g h n o e v i d e n c e f o r the i n t e r m e d i a t e d e a l k y l a t e d f o r m s was f o u n d . T h e m a g n e s i u m , a l u m i n u m , c a l c i u m , b a r i u m , t i n , a n d c h r o m i u m salts o f m a n y m o n o - a n d disubstituted a l k o x y a n d a r y l o x y boric acids have been claimed i n patents (U,

W).

Process

Development

I n d e v e l o p i n g processes f o r t h e m a n u f a c t u r e o f v a r i o u s b o r a t e esters, t h e a u t h o r s have used azeotropic distillation ( M e t h o d I , E q u a t i o n s 3 a n d 4) ; transesterification



133


( M e t h o d I I , E q u a t i o n 6) ; o r d e h y d r a t i o n w i t h b o r o n oxide ( M e t h o d I I I , E q u a t i o n 7 ) . T h e r e l a t i v e efficiencies i n M e t h o d I of b o r i c a c i d vs. b o r o n oxide a n d o f a v a r i e t y of a z e o t r o p i c m e d i a w e r e i n v e s t i g a t e d i n a series o f s t a n d a r d e x p e r i m e n t s u s i n g t h e a p p a r a t u s s h o w n i n F i g u r e 1. T h e w a t e r - c o o l e d t r a p (designed b y t h e a u t h o r s ; c o n structed b y Stanford Glassblowing Laboratories, Palo A l t o , Calif.) was m u c h more s a t i s f a c t o r y f o r s e p a r a t i n g t h e azeotropes t h a n t h e c o m m o n l y u s e d D e a n - S t a r k t r a p . T h e a l c o h o l (used as r e c e i v e d ) a n d t h e s t o i c h i o m e t r i c a m o u n t of b o r o n c o m p o u n d ( b o r i c a c i d o r b o r o n o x i d e ) were h e a t e d a t a c o n s t a n t p o w e r i n p u t selected t o g i v e a m o d e r a t e b o i l - u p r a t e (219 w a t t s ) . A n e q u a l w e i g h t of r e a c t a n t s (500 g r a m s ) w a s u s e d i n e a c h case. T h e r e a c t i o n w a s f o l l o w e d b y m e a s u r i n g t h e a m o u n t o f w a t e r c o l l e c t e d i n t h e t r a p , a n d was t e r m i n a t e d w h e n a p p r o x i m a t e l y t h e t h e o r e t i c a l a m o u n t h a d been r e m o v e d . T h e ester was p u r i f i e d b y s t r i p p i n g t h e a z e o t r o p i c m e d i u m a t a t m o s p h e r i c p r e s s u r e , r e moving a n y unreacted alcohol under moderate v a c u u m (aspirator), then distilling through a short V i g r e u x o r packed c o l u m n a t about 5 m m . ( m e t h y l a n d ethyl borate f o r m a z e o t r o p e s ; i s o p r o p y l b o r a t e r e q u i r e s efficient f r a c t i o n a t i o n t o o b t a i n good s e p a r a t i o n f r o m t h e a l c o h o l ) . L a r g e r - s c a l e l a b o r a t o r y p r e p a r a t i o n s were c o n d u c t e d i n t h e apparatus shown i n F i g u r e 2. T y p i c a l c u r v e s o f t h e progress o f t h e s t a n d a r d r e a c t i o n s a r e g i v e n i n F i g u r e 3. T h e rate of f o r m a t i o n is t a k e n as t h e slope of t h e least squares l i n e c a l c u l a t e d f o r t h e i n i t i a l l i n e a r p o r t i o n of t h e p l o t o f ester f o r m e d (based o n w a t e r c o l l e c t e d ) vs. r e a c t i o n t i m e . M o n o - o l e f i n s ( T a b l e I ) g i v e f a s t e r rates o f ester f o r m a t i o n o f t h e a l i p h a t i c

Table I.

Comparison of Effect of Azeotropic Medium on Rate of Ester Formation ( S t a n d a r d reaction w i t h B 0 ) 2

Azeotropic Medium l-Butanol l-Dodecanol Benzene* Xylene* Diisobutylene' 1-Octene' Tripropylene* Tetrapropylene* b

c

^ Weight % H () in Binary Azeotrope" 42.5 — 8.83 35.8 13.0 34.7 28.6 66.0 2

3

Rate, Moles/Hour η-Butyl borate 1.12 — 2.21 — 2.56 2.78 2.58 2.48

n-Dodecyl borate — 1.56 1.45 1.47 2.16 2.01 1.74 1.74

Azeotrope data for butanol, benzene, and xylene from (87). Union Carbide Chemicals Corp. Aceto Chemical Co. Baker and Adamson. « Phillips Petroleum Co.; mixture of meta- and para-isomers. / Atlantic Refining Co.; approximately 4:1 mixture of 2,4,4-trimethyl-lpentene and 2,4,4-trimethyl-2-pentene. ο Matheson, Coleman and Bell. Enjay Co.; mixture of mono-olefins: 33 vol. % Ce, 50 vol. % Cg, 17 vol. % Cio. * Enjay Co.; mixture of mono-olefins. α

b c

d

A

b o r a t e s t h a n does a n excess o f t h e a l c o h o l o r t h e c o m m o n a r o m a t i c a z e o t r o p i c m e d i a ; b o r o n oxide ( T a b l e I I ) reacts f a s t e r t h a n b o r i c a c i d . F o r a r o m a t i c b o r a t e s , t h e m o n o olefins a r e also m o r e effective, a l t h o u g h here b o r i c a c i d seems t o b e a b e t t e r b o r o n source t h a n b o r o n oxide. T a b l e I shows t h a t t h e h i g h e r efficiency o f t h e olefins r e l a t i v e t o t h e o t h e r m e d i a is n o t r e l a t e d t o t h e a m o u n t of w a t e r i n t h e c o r r e s p o n d i n g b i n a r y a z e o t r o p e . A l though the m a t t e r was n o t studied i n detail, a brief investigation of the m i n i m u m boiling t e r n a r y azeotrope, diisobutylene-butanol-water (Table I I I ) , demonstrated t h a t a s u b s t a n t i a l a m o u n t of t h e a l c o h o l i s c a r r i e d o v e r ; t h e olefin a n d a l c o h o l a r e , o f course, r e t u r n e d t o t h e s y s t e m w h e n t h e c o o l e d d i s t i l l a t e i s d e c a n t e d . T h e c o m p o s i t i o n of the t e r n a r y azeotrope was obtained b y distillation of a m i x t u r e of t h e c o m ponents, removal of water f r o m the total distillate w i t h potassium carbonate, a n d i n f r a red analysis of the organic layer. T h e a m o u n t of water r e m a i n i n g i n the organic layer was f o u n d b y K a r l F i s c h e r t i t r a t i o n .



134


0

1

2

3

0

1

2

3

REACTION TIME, HOURS

Figure 3 . Comparison of rates of η - b u t y l borate formation with boron oxide a n d boric acid by azeotropic distillation A c o m p a r i s o n w a s also m a d e , o n a 1-liter scale, o f t h e a z e o t r o p i c d i s t i l l a t i o n ( M e t h o d I ) a n d t r a n s e s t e r i f i c a t i o n ( M e t h o d I I ) processes f o r t h e p r e p a r a t i o n o f a technical grade of the aliphatic borates. T h e compounds included i n the comparison were t h e η - b u t y l , c y c l o h e x y l , 2 - e t h y l h e x y l , 2 , 6 , 8 - t r i m e t h y l - 4 - n o n y l , a n d 2 - m e t h y l - 7 Table II. and

Comparison of Effect of Boron

Boric A c i d on Rate of Ester

Oxide

Formation

( S t a n d a r d reaction w i t h d i i s o b u t y l e n e )

Alcohol 1-Butanol 5

2-Ethylhexanol

b

2-Metbyl-2 pentanol

6

2-Methyl-7-ethyl-4-undecanol l-Dodecanol

b

c

Rate, Moles/Hour

Alcohol, Moles 5.83 5.27

Boron Compound, Moles 0.971 1.76

3.52 3.31

0.586 1.10

2.57

4.39 4.07

0.731 1.36

2.03

2.20 2.12

0.367 0.708

1.88

2.52 2.41

0.420 0.804

2.16

B 0 2.56 2

3

HaBCV

e

1.45 1.75 1.50 1.18 1.30

° American Potash & Chemical Corp. Union Carbide Chemicals Corp. Aceto Chemical Co. b

c

ethyl-4-undecyl borates. I n the azeotropic distillation study, diisobutylene was used as t h e i n e r t m e d i u m ; i n t h e t r a n s e s t e r i f i c a t i o n e x p e r i m e n t , i s o p r o p y l b o r a t e w a s u s e d as t h e exchange ester. F o r b o t h sets o f e x p e r i m e n t s , t h e a p p a r a t u s w a s s i m i l a r t o t h a t s h o w n i n F i g u r e 1, e x c e p t t h a t t h e flask h a d a n e x t r a n e c k f o r t h e w i t h d r a w a l of Table III.

Composition of Diisobutylene-

Butanol-Water

Azeotrope Weight %

Phase Organic Water Azeotrope

Water 0.3 12.3 12.6

1-Butanol 9.2 0.3 9.5

Diisobutylene 77.9 — 77.9

Total 87.4 12.6 100.0


135



s a m p l e s a n d a c o l u m n (45 X 2.54 c m . ) p a c k e d w i t h 0 . 2 4 - i n c h p r o t r u d e d stainless steel p a c k i n g (Scientific D e v e l o p m e n t C o r p . , State College, P a . ) was used. I n the t r a n s esterification experiments the azeotrope t r a p was replaced b y a W h i t m o r e - L u x c o l u m n h e a d {202) m a n u a l l y set a t a reflux r a t i o of a p p r o x i m a t e l y 4 t o 1. W h e n t h e r e a c t i o n s w e r e c o m p l e t e d , as i n d i c a t e d b y c o l l e c t i o n o f a p p r o x i m a t e l y the theoretical amount of water o r 2-propanol, the c o l u m n was replaced b y a Claisen h e a d a n d ice-cooled r e c e i v e r , a n d t h e r e a c t i o n m i x t u r e w a s s t r i p p e d a t a t m o s p h e r i c pressure to a m a x i m u m of 250°C. S a m p l e s were w i t h d r a w n f r o m t h e p o t a t i n t e r v a l s w i t h o u t i n t e r r u p t i n g t h e d i s t i l l a t i o n . T h e same p r o c e d u r e w a s t h e n r e p e a t e d o n e a c h reaction mixture a t 20 a n d 5 m m . T y p i c a l data relating t o the boron a n d alcohol content t o the s t r i p p i n g operation are shown for b u t y l borate i n T a b l e I V . Table

IV.

Relation of Boron a n d Alcohol Content

of Tri(n-butyl) Borate to Stripping Temperature at Atmospheric Pressure Pot Temp., °C. 125 130 150 175 200 225 235

Boron, Alcohol, % % Azeotropic Distillation Method 3.11 21.8 3.51 20.4 4.28 7.7 4.48 3.5 4.55 2.5 4.63 0.9 4.66 0.3

175 200 225 250

Transesterification Method 4.55 5.2 4.57 2.4 4.66 1.4 4.68 0.1

Ester, % (on Boron) 66.2 74.7 91.1 95.3 96.8 98.5 99.2 96.8 97.2 99.2 99.6

O n t h e basis o f t h e i n f o r m a t i o n t h u s o b t a i n e d , a n e w r u n w a s m a d e f o r e a c h ester u n d e r process c o n d i t i o n s selected t o p r o v i d e p r o d u c t s o f h i g h p u r i t y i n g o o d y i e l d . W i t h b u t y l b o r a t e as a n e x a m p l e , t h e s t o i c h i o m e t r y a n d r e a c t i o n c o n d i t i o n s a n d m a t e r i a l balances f o r t h e t w o m e t h o d s b e i n g c o m p a r e d a r e s h o w n i n T a b l e s V , V I , a n d V I I . A s u m m a r y o f t h e results o b t a i n e d w i t h t h e v a r i o u s esters b y b o t h preparative methods is given i n Table V I I I . Table V.

Stoichiometry a n d Reaction Conditions

for Preparation of Tri(n-butyl) Borate by Azeotropic Distillation under Selected Conditions Reactants Alcohol, grams Boron oxide, grams

185.30 (2.5 moles) 29.25 (0.42 mole)

Water removed Pot temp., °C. Head temp., °C. Heating time to remove water, hr. Water removed, ml. (theory 22.7)

99-114 81-98 0.33 22.2

Azeotropic medium recovered (diisobutylene) Pot temp., °C. Head temp., ° C . Pressure, mm. Hg Heating time, hr. DIB recovered, ml. Boron, %

113-122 100-107 760 0.2 176 0.06

Products Pot temp., °C. (sampled) Pressure, mm. Hg Boron, % (theory 4.70) Alcohol, % Total heating time for reaction, hr. Yield grams (theory 191.7)

%

Purity (% ester) Based on boron content Based on alcohol content

227 760 4.67 2.8 1.33 190 99.1 99.4 97.2


136

ADVANCES IN CHEMISTRY SERIES Table VI. Stoichiometry a n d Reaction Conditions for Preparation of Tri(n-butyl) Borate by Transesterification under Selected Conditions


Reactants Alcohol, grams Isopropyl borate, grams

185.30 (2.5 moles) 156.66 (0.83 mole)

Alcohol removed Pot temp., °C. Head temp., °C. Heating time to remove alcohol, hr. Alcohol removed M l . (theory 191.4) Grams Boron, %

103-126 81-106 0.75 193 150.1 0.02

Products Pot temp., °C. (sampled) Pressure, mm. Hg Boron, % (theory 4.70) Alcohol, % Total heating time for reaction, hr. Yield Grams (theory 191.7)

232 760 4.69 0.55 3.27 189.2 98.7

%

Purity (% ester) Based on boron content Based on alcohol content

Table VII.

99.8 99.4

Materials Balance for Preparation of Tri(n-butyl) Borate Azeotropic Distillation

Materials in, grams Alcohol Boron oxide Diisobutylene Isopropyl borate

0

Transesteri fication

Total

Materials out, grams Water Diisobutylene Isopropyl alcohol Ester

156.66

243.55

341.96

22.20 126.82

Total

Loss, grams Loss, %

6

185.30

185.30 29.25 128.00

190.00

150.10 189.21

339.02 3.53 1.03

339.31 2.65 0.78

° Operating conditions shown in Table V . Operating conditions shown in Table V I .

b

Table VIII.

Comparison of Azeotropic Distillation a n d Transesterification for the Preparation of Aliphatic Borate Esters

Methods

( T e c h n i c a l grade) Ester Purity, %

Yield, % « Borate Ester Butyl

Azeotropic distillation 99.1

Transesterification 98.7

Basis of calculation Boron Alcohol

Azeotropic distillation 99.4 97.2

Transesterification 99.8 99.4

Cyclohexyl

102.0

98.0

Boron Alcohol

99.7 97.6

98.6 97.8

2-Ethylhexyl

101.7

99.4

Boron Alcohol

99.3 97.3

101.1 100.0

99.8

100.1

Boron Alcohol

99.0 92.3

98.4 97.3

101.3

101.2

Boron Alcohol

99.4 93.1

101.2 98.8

2,6,8-Trimethyl-4-nonyl 7-Ethyl-2-methyl-4-undecyl

• Not adjusted for alcohol content.


137


I t m a y b e c o n c l u d e d t h a t t e c h n i c a l grades o f b o r a t e esters h a v i n g b e t t e r t h a n 9 0 % p u r i t y (based o n a l c o h o l c o n t e n t ) c a n b e p r e p a r e d i n g o o d y i e l d ( > 9 0 % ) b y e i t h e r a z e o t r o p i c d i s t i l l a t i o n o r t r a n s e s t e r i f i c a t i o n . P r o c e s s flow d i a g r a m s i l l u s t r a t i n g b o t h methods are shown f o r technical grade η-butyl borate (Figures 4 a n d 5 ) .

FRACTIONATION COLUMN


DECANTER

DIB-HgO

Figure 4.

ALCOHOL

FLASH STILL

REACTOR

U

ALCOHOL

2

AZEOTROPE

481.9 lb. (75.82 gel.) B 20 3 9

H 0 118.391b. H4.20gal.)

Î

PRODUCT 100 lb. (I4.06qal.)

97.49 lb. (14.34 gal.)

Flow diagram for batch preparation of η - b u t y l

borate

by azeotropic

distillation DIB. Diisobutylene ISOPROPYL ALCOHOL 79.361b. (12.02gal.)

FRACTIONATION COLUMN UNREACTED ISOPROPYL BORATE -i 1-BUTANOL ISOPROPYL BORATE 82.79 lb. (11.99gal.)

FLASH STILL

ALCOHOL 97.88 lb. (I4.39gal.) Figure 5.

PRODUCT I00 lb.

Flow diagram for batch preparation of η - b u t y l borate by transesterification

A s i m i l a r process flow d i a g r a m f o r t h e p r e v i o u s l y r e p o r t e d c o n t i n u o u s p r e p a r a t i o n of i s o p r o p y l b o r a t e (120) b y M e t h o d I I I ( d e h y d r a t i o n w i t h b o r o n o x i d e ) i s g i v e n i n F i g u r e 6. Borates of Polyhydric Compounds A l t h o u g h catechol borate ( I V ) , when prepared i n a n anhydrous m e d i u m , is h y d r o l y z e d b y w a t e r , i t s salts a r e s t a b l e (65, 165-167). T h e authors have synthesized s o d i u m c a t e c h o l b o r a t e m o n o h y d r a t e ( f o r m u l a t e d m o s t s i m p l y as s h o w n i n E q u a t i o n 10) b y d i r e c t r e a c t i o n o f c a t e c h o l (1.33 m o l e s ) , b o r a x (0.333 m o l e ) , a n d aqueous s o d i u m h y d r o x i d e (0.665 m o l e ) : -OH

i—Ο B O N a - H 0 + 1 4 H 0 (10)

+ N a B 0 · 1 0 H O + 2 N a O H -> 4 2

V

—OH

4

7

2

2

V

-o


2

138

ADVANCES IN CHEMISTRY SERIES 2°3

i-C H 0H

455.6

927.8

B

3

i-C H 0H

?

3

7

(WASH)

_ i

250.0 «

i


REACTOR

I

« ALCOHOL

ALCOHOL DISTILLATE ESTER26.9 ALCOHOL - 2 5 9 . 8

137.4

CRYSTALLIZER 1

SLURRY 2020.0 *

FILTER

BOROXINE 210.5

FILTRATE E S T E R - 1565.0

H3BO3 - 5 0 . 5

WET WASHED C A K E A L C O H O L - 137.4 H3BO3 404.3

ALCOHOL-112.6 t

ALCOHOL COLUMN

DRYER Γ ALCOHOL 137.4

1 E S T E R COLUMN F E E D ESTER 1228.9 BOROXINE - 210.5 L

ALCOHOL CONDENSER

ESTER COLUMN

ISOPROPYL

BORATE

1228.9 Figure 6.

H B0 (TO 3

3

B 0 PLANT) 2

3

404.3

Flow diagram for continuous preparation of isopropyl borate by boric acid precipitation

A f t e r t h e r e a c t a n t s h a d been h e a t e d t o 8 4 ° C , t h e n cooled, t h e solids w e r e r e m o v e d by filtration a n d washed w i t h e t h y l alcohol t o y i e l d 217 grams (92.3%) of gray, shiny plates. A n a l y s i s of t h e v a c u u m - d r i e d product gave: Calculated

for C H 0 B N a . Found. 6

6

4

N a , 13.08; N a , 12.97;

B , 6.14 B , 6.13

A n u m b e r o f v i s c o u s t o g l a s s y p o l y m e r i c b o r a t e s were b r i e f l y i n v e s t i g a t e d t o d e t e r m i n e q u a l i t a t i v e l y t h e effect o f cross l i n k i n g o n resistance t o h y d r o l y s i s . A s e x a m p l e s , b o r i c a c i d , e t h y l e n e g l y c o l , a n d p h e n o l i n a m o l e r a t i o o f 1 t o 2 t o 0.3 g a v e a


139


p r o d u c t w h i c h was viscous w h e n h o t a n d h a r d w h e n cooled; a mole ratio of 1 t o 2 t o 1 yielded a material which was tacky at room temperature: H3BO3 + H O C H C H O H + C H O H 2

2

6

5

->> ΓΓ— —CCHH CCHH 0 0——ΒΒ——ΟΟ——" IΊ 2

-H 0 2

2

2

2

R e a c t i o n o f b o r i c a c i d a n d e t h y l e n e g l y c o l alone r e s u l t e d i n a t a c k y p r o d u c t . ethylene glycol borates copolymers

obtained

were

from

readily hydrolyzed b y water.

t h e reaction

( H )

!

0

of boric

These

I n c o n t r a s t , t h e glassy

acid a n d maleic

anhydride

with


glycerol a n d w i t h p e n t a e r y t h r i t o l were o n l y slowly a t t a c k e d b y water.

2,6-Di-ferf-butylphenyl

Borates

T h e a u t h o r s h a v e p r e p a r e d a series o f n e w , h y d r o l y s i s - r e s i s t a n t , m i x e d esters

o f 2,6-di-ieré-butylphenols

b y t h e transesterification reaction

Ç H (terO 4

borate II):

CJÎ (tert) 9

9

\—OJJ

Il—/

(Method

OB(OR')

+

Y

2

+ R O H

(12)

- f

C H (ferO C H (ferO T h e s e c o m p o u n d s , some p h y s i c a l c o n s t a n t s f o r w h i c h a r e g i v e n i n T a b l e I X , a r e of c o n s i d e r a b l e i n t e r e s t because o f t h e h i g h s t e r i c h i n d r a n c e i n v o l v e d . T h e s t a r t i n g 4

9

4

Table IX.

9

2,6-Di-ferf-butylphenyl-dialkyl Borates CiB. (tert) 9

.—O—B(OR')2 CiHtitert)

Compound R H— CH — CH — CH —°

R' IS0-C3H7— Iso-CsHr— 71-C4H9— CH =CH—CH —

CH —

CH3CII—CH2CH ^

8

3

3

3

2

b

(tert)d¥i — 9

2

B.P., °C./Mm. 80/0.5 — 140/0.6 130-131/0.4

CHo

Iso-C H — 3

7

M.P., °C. ~ 88-89 — —

153/0.5

—

—

209-215

" d4° = 0.9727 - 0.0007727 t. ηζ°· = 1.5004 - 0.0003794 t. Viscosity (cs.)i°C. = 169 ·β; 4ϋ.0 · ; 21.237.s. b d^° - = 0.9121 - 0.0001700 t. ηζ°· = 1.4826 - 0.0003657 t. Viscosity (cs.)i°C. = 521»·*; 20835-2; 85.5 . a

6

23

2

c

460

phenols do n o t undergo the usual phenolic reaction—to f o r m the s o d i u m phenate, f o r e x a m p l e , i t i s necessary t o use m e t a l l i c s o d i u m i n l i q u i d a m m o n i a (183). A s a n e x a m p l e o f t h e h y d r o l y s i s resistance o f t h e h i n d e r e d esters, t h e 2 , 6 - d i - i e r i b u t y l - 4 - m e t h y l p h e n y l diisopropyl borate was recovered q u a n t i t a t i v e l y after 8 hours' reflux i n 3 7 . 5 % aqueous a c e t o n e f o l l o w e d b y storage i n t h e m o t h e r l i q u o r f o r 13 w e e k s ; no boron was f o u n d i n t h e filtrate. D e t a i l s o f t h e p r e p a r a t i v e m e t h o d s f o r these c o m p o u n d s sequent p u b l i c a t i o n .

will be given i n a sub

Physical Properties T h e p h y s i c a l p r o p e r t i e s o f a n u m b e r o f b o r a t e esters h a v e been s u m m a r i z e d b y L a p p e r t (116) a n d b y S t e i n b e r g a n d H u n t e r (181). A d d i t i o n a l d a t a have been obtained f o r several borates o n t h e v a r i a t i o n w i t h t e m p e r a t u r e of v a p o r pressure (Tables Χ , X I ) , density (Table X I I ) , refractive index (Table X I I I ) , a n d viscosity


140

ADVANCES IN CHEMISTRY SERIES Table X.

V a p o r Pressures of Borate Esters Log Pm

A - B/T

B.P., °C. (Calcd.), 10 M m .

Borate Ester Primary aliphatic Methyl Ethyl* n-Butyl 2-Ethylhexyl n-Octyl n-Decyl n-Dodecyl

8.1073 8.4156 8.3986 9.4290 8.4776 9.4317 8.2793

1785 2167 2804 4080 3682 4478" 4126

68.3™> H8760 106 211 219 258 294

(181, 197) (181, 197) (73, 181) (181) (181) (116) (80, 181)

Secondary aliphatic Isopropyl sec-Butyl Methylisobutylcarbinyl 2,6,8-Trimethyl-4-nonyl 2-Methyl-7-ethyl-4-undecyl

8.1877 7.8840 8.2400 8.4144 8.1154

2190 2350 2833 3585 3791

140760 197760

118 210 260

(111, 181) (73, 181) (164, 181) (181) New compound

Aromatic o-Cresyl

9.0080

3883

212

(149, 181)

7.6396 10.834 9.0910 12.576

2614 4457 3664 5466

121 180 180 199

(164) New compound (123, 181) (76)

Β

References


0

Miscellaneous 2-Methoxyethyl 2-2'-Methoxyethoxyethyl Tri (hexyleneglycol) biborate Tetrahydrofurfuryl borate β

Values from (197).

b

Reference reported log ρ = 8.8553 —

e

This value may be too low.

Table XI.

2298.

Melting Points of Solid Borate Esters

Borate Ester Diisopropylcarbinyl Diisobutylcarbinyl Neopentyl glycol Cyclohexyl Phenyl p-Cresyl 2,5-Dimethylphenyl 3.4- Dimethylphenyl 3.5- Dimethylphenyl 2.6- Dimethylphenyl 2,6-Diisopropylphenyl

M.P., 0 60.4-61.4 97-98 123-124 54-55 89-91 137-140 147-148 72-73 145-148 156-157 286-290 0

b

a 6

References (164) (181) (164) (198, (181, (116) New New New New New

204) 204) compound compound compound compound compound

Uncorrected. Sample probably impure.

Table XII.

Densities of Borate Esters A — Bt

Borate Ester Primary aliphatic Methyl Ethyl n-Propyl n-Butyl 2-Ethylhexyl n-Octyl n-Decyl n-Dodecyl

Β X 10*

d*> (Calcd.)

0.9578 0.8853 0.8808 0.8735 0.8743 0.8661 0.8641 0.8704

13.62 11.48 12.89 8.229 7.553 6.658 6.077 7.654

0.9306 0.8623 0.8550 0.8570 0.8592 0.8528 0.8519 0.8551

(181, 197) (181, 197) (45, 181) (73, 181) (181) (181) (116) (80, 181)

Secondary aliphatic Isopropyl sec- Butyl Methylisobutylcarbinyl 2,6,8-Trimethyl-4-nonyl 2-Methyl-7-ethyl-4-undecyl

0.8404 0.8495 0.8368 0.8544 0.8591

10.69 9.043 7.242 7.393 6.436

0.8190 0.8314 0.8223 0.8396 0.8462

(111, 181) (73, 181) (164, 181) (181) New compound

Aromatic o-Cresyl w-Cresyl 2,4-Dimethylphenyl

1.1037 1.0949 1.0711

7.515 8.203 7.063

1.0887 1.0784 1.0570

(149, 181) (49) New compound

0.9400 1.0508 1.0789 0.9992 0.9249 1.1214

10.62 10.29 9.150 8.330 7.184 7.360

0.9188 1.0302 1.0606 0.9825 0.9105 1.1067

(13, 98) (164) New compound (198, 204) New compound (76)

Miscellaneous Allyl 2-Methoxyethyl 2-2 -Methoxyethoxyethyl Cyclohexyl 3,3,5-Trimethylcyclohexyl Tetrahydrofurfuryl ,


References

141

WASHBURN, LEVENS, ALBRIGHT, AND BILLIG—BORATE ESTERS Refractive Indices of Borate Esters

Table XIII.

A - Bt Β Χ 10

n (Calcd.)

1.3668 1.3825 1.4029 1.4129 1.4441 1.4430 1.4492 1.4546

4.360 4.359 4.000 2.949 3.615 3.496 3.487 3.484

1.3581 1.3738 1.3948 1.4070 1.4369 1.4360 1.4422 1.4476

(181, 197) (181, 197) (45, 181) (73, 181) (181) (181) (116) (80, 181)


1.3850 1.4038 1.4182 1.4453 1.4543

4.380 4.026 3.895 3.513 3.333

1.3762 1.3957 1.4104 1.4383 1.4476

(111, 181) (73, 181) (164, 181) (181) New compound

Aromatic o-Cresyl m-Cresyl 2,4-Dimethylphenyl

1.5637 1.5637 1.5535

3.718 4.077 3.282

1.5563 1.5555 1.5469

(149, 181) (49) New compound

Miscellaneous Allyl 2-Methoxyethyl 2-2 -Methoxyethoxyethyl 3,3,5-Trimethylcyclohexyl Tri(hexyleneglycol) biborate Tetrahydrofurfuryl

1.4359 1.4235 1.4418 1.4658 1.4457 1.4674

4.471 3.743 3.385 3.487 3.362 3.308

1.4270 1.4160 1.4350 1.4588 1.4390 1.4608

(13, 93) (164) New compound New compound (123, 181) (76)


Borate Ester Primary aliphatic Methyl Ethyl n-Propyl n-Butyl 2-Ethylhexyl n-Octyl n-Decyl n-Dodecyl

4

,

Table XIV.

References

? 0

Viscosities of Borate Esters Viscosity, Centistokes

Temp., °C.

Viscosity, Centistokes

Temp., °C.

Viscosity, Centistokes

Temp., °C.

Primary aliphatic Methyl Ethyl n-Propyl n-Butyl 2-Ethylhexyl* n-Octyl n-Decyl n-Dodecyl

21.2 21.4 7.0 21.4 20.8 20.6 21.4 21.0

0.416 0.615 1.59 1.99 11.0 11.1 19.3 30.5

39.8 40.0 23.8 39.8 39.6 40.0 40.0 39.6

0.347 0.503 1.09 1.47 6.18 6.38 10.3 15.1

60.0 60.0 43.4 63.6 60.0 60.0 60.0 60.0

0.295 0.424 0.845 1.08 3.80 3.93 6.66 8.89


21.4 20.8 21.4 21.4 20.6

1.03 1.90 4.30 121. 139.

39.6 39.6 40.0 39.6 39.6

0.797 1.37 2.77 33.7 46.5

59.8 60.0 63.6 60.0 63.6

0.631 1.04 1.70 15.4 16.9

Aromatic o-Cresyl ra-Cresyl 2,4-Dimethylphenyl

21.4 20.6 60.0

175. 192. 35.1

39.8 39.6 70.0

35.9 37.0 17.3

60.0 60.0 76.6

11.9 10.8 12.8

Miscellaneous Allyl 2-Methoxyethyl 2-2'-Methoxyethoxyethyl 3,3,5-Trimethylcyclohexyl Tri(hexyleneglycol) biborate Tetrahydrofurfuryl

7.0 21.2 20.8 60.0 23.4 21.4

1.25 2.90 8.57 87.9 433. 22.6

23.2 39.8 39.6 70.0 37.8 40.0

0.902 1.99 5.05 43.3 97.8 6.93

37.8 59.8 60.2 79.0 48.2 60.0

0.747 1.39 3.23 25.5 44.5 4.35

Borate Ester

a

(100) report 1.94 (210°F.); 6.28 (100°F.); 433 ( - 4 0 ° F . ) .

(Table X I V ) .

These d a t a were

fitted

b y t h e m e t h o d of least squares.

T h e melting

p o i n t s of s o m e s o l i d esters a r e g i v e n i n T a b l e X L The

v a p o r pressure d a t a were o b t a i n e d w i t h

shown i n Figure

7 (designed b y H . S. M y e r s ,

the modified Cottrell

C. F . Braun

ebullioscope

Co.,Alhambra,

Calif.;

constructed b y Stanford Glassblowing Laboratories, Palo A l t o , Calif.) using a Cartesian manostat Densities

(Emil were

Greiner

Co., N e w York,

determined i n 5- a n d 10-ml.

Ν. Y . ) to maintain volumetric

flasks

reduced pressures.

with

extended necks,

calibrated w i t h distilled water, a n d suspended i n a constant temperature bath. refractive

indices were

determined with

a n Abbé

refractometer

(Bausch


The

& Lomb


142


Figure 7.

Modified Cottrell ebullioscope of H. S. Myers A. Ebullioscope B. Cartesian manostat

Optical C o . , T y p e 3 3 - 4 5 - 5 6 ) , calibrated w i t h distilled water, having water at t h e r e q u i r e d t e m p e r a t u r e c i r c u l a t i n g t h r o u g h t h e p r i s m . V i s c o s i t i e s were d e t e r m i n e d i n C a n n o n - F e n s k e - O s t w a l d viscometers ( C a n n o n I n s t r u m e n t C o . , State College, P a . ) sus pended i n a constant temperature bath. A v e r a g e densities of p r i m a r y a l i p h a t i c , s e c o n d a r y a l i p h a t i c , a n d a r o m a t i c b o r a t e s a r e g i v e n i n F i g u r e 8. T h e r e l a t i v e l y h i g h d e n s i t y of m e t h y l b o r a t e m a y b e a t t r i b u t e d t o s h o r t e n i n g o f t h e Β — Ο b o n d l e n g t h , as s h o w n b y a s h i f t o f t h e i n f r a r e d Β — Ο s t r e t c h i n g v i b r a t i o n f r o m t h e a v e r a g e o f 1335 c m . f o r a l k y l borates t o 1352 c m . T h e refractive indices of p r i m a r y a n d secondary a l i p h a t i c borates are shown i n F i g u r e 9 as a f u n c t i o n o f t h e n u m b e r o f c a r b o n a t o m s i n t h e a l c o h o l m o i e t y . -

1

1


WASHBURN, LEVENS, ALBRIGHT, AND BILUG—BORATE ESTERS 1

t c. e

d

143

1

= A - Bt

1.100 ROMATIC


1.050

1.000

0.950 THYL BOR ATE

>CO Ζ Id

Q

0.900

e

I

i

ALIPHATIC THYL BOR/\ΊΕ) (EXC LUDING ME

2 ° ALIPHA1

0.800

0.750 -20

0

20

40

60

TEMPERATURE,

Figure 8.

e

80

100

120

C.

Densities of borate esters

I n v e s t i g a t i o n o f t h e specific v i s c o s i t y o f d i l u t e s o l u t i o n s of l o n g - c h a i n b o r a t e esters ( n - o e t y l t o n - d e c y l ) i n benzene a n d c a r b o n t e t r a c h l o r i d e i n d i c a t e d t h a t t h e esters a r e i n e x t e n d e d f o r m as e x p e c t e d f r o m t h e p a r a c h o r v a l u e s (7). T h e p l a n a r configuration of the B 0 group was demonstrated b y a n electron dif f r a c t i o n s t u d y o f m e t h y l b o r a t e (16). T h e b o n d angles were f o u n d t o b e 120° f o r B — 0 , a n d 113° ± 3 ° f o r B — 0 — C . T h e b o n d d i s t a n c e s w e r e : B — 0 , 1.38 ± 0.02 Α . ; C — 0 , 1.43 ± 0 . 0 3 A . T h e d a t a suggested c o n s i d e r a b l e r o t a t i o n of t h e C H g r o u p s a b o u t t h e l i n e o f t h e Β — Ο b o n d ; t h i s i n t e r n a l r o t a t i o n w a s i n t e r p r e t e d as b e i n g s y n c h r o n i z e d so t h a t t h e C — C d i s t a n c e is a l w a y s g r e a t e r t h a n 3.5 Α . , as t h e r e a p p e a r e d to be insufficient r o o m f o r independent m o v e m e n t . T o this s y n c h r o n i z a t i o n of t h e m e t h y l groups was attributed a small dipole moment. 3

3

T h e p a r a c h o r constants f o r b o r o n i n simple a l k y l borates were f o u n d t o range f r o m 15.9 t o 17.8 (185). Subsequently, Jones a n d others (93) f o u n d t h a t tri-2-chloroethyl borate, B ( 0 C H § C H C 1 ) , a n d tri-2,2-dichloroisopropyl borate, §

3


144

ADVANCES IN CHEMISTRY SERIES 1.45 n

D

- Bt

= A

1.43 Ο CVJ

x"


UJ Ο

1.41

s

Δ

bJ >

Ο

a m y l > h e x y l , e t c . , a n d p r i m a r y > secondary > tertiary. T h e r a p i d hydrolysis of highly hindered aromatic a n d c h l o r i n e - s u b s t i t u t e d a l i p h a t i c esters w a s a t t r i b u t e d t o a s h i f t f r o m steric t o elec tronic controlling factors. B r a d l e y a n d C h r i s o p h e r (29) i n v e s t i g a t e d t h e h y d r o l y s i s o f a l k y l b o r a t e s i n a n h y d r o u s acetone. T h e y reported t h e e q u i l i b r i u m constants a t 0 ° C . t o be m e t h y l b o r a t e , 1 6 . 0 ; η - p r o p y l b o r a t e , 2 . 7 ; η - b u t y l b o r a t e , 2 . 1 ; a n d n - a m y l b o r a t e , 1.8. B o r a t e esters react w i t h c a r b o x y l i c acids t o f o r m t h e c o r r e s p o n d i n g esters (85, 86, 170) : ( R O ) B + 3 R ' C O O H -> 3 R ' C O O R + H B 0 3

3

T h e r e a c t i o n w i t h acetic a n h y d r i d e t o f o r m b o r o n acetate (120): 2(RO) B + 5(CH CO) 0 3

3

2

(CH COO) BOB(OOCOH ) 3

2

3

(13)

3

h a s also b e e n

2

+ 6CH COOR 3

described (14)

F r i e d e l - C r a f t s a l k y l a t i o n s h a v e been c a r r i e d o u t w i t h b o r a t e esters i n p l a c e o f t h e a l k y l o r a l k a r y l h a l i d e . F o r e x a m p l e , w i t h a l u m i n u m c h l o r i d e as c a t a l y s t , i s o b u t y l b o r a t e r e a c t e d w i t h m - x y l e n e t o f o r m £er£-butylxylene, w i t h anisole t o f o r m p-tertbutylanisole, w i t h phenol t o f o r m p-ieré-butylphenol, a n d w i t h bromobenzene t o f o r m p - b r o m o - i e r i - b u t y l b e n z e n e ; b e n z y l b o r a t e a n d benzene gave d i p h e n y l m e t h a n e (96). Benzene a n d b u t y l borate, w i t h a l u m i n u m chloride, gave a n unidentified organoboron c o m p o u n d , l e a d i n g t o t h e c o n c l u s i o n t h a t t h e b o r a t e esters m a y e i t h e r d o n a t e t h e a l k y l g r o u p o r a d d b o r o n t o t h e benzene r i n g (191). A l u m i n u m i s o p r o p o x i d e h a s b e e n u s e d t o reduce a l d e h y d e s a n d ketones i n t h e M e e r w e i n - P o n d o r f f - V e r l e y r e a c t i o n (203). Somewhat lower yields a t higher t e m p e r a -



146

t u r e s ( 1 5 0 ° t o 1 7 5 ° C . ) were o b t a i n e d b y K u i v i l a , S l a c k , a n d S i i t e r i (111), w h o i n v e s t i g a t e d t h e use o f a l k y l b o r a t e s f o r t h e same p u r p o s e :

(

\)ΗΟ


R ^

J Β + 3 R ' C O R " -> 3 R C O R + (

Κ

\ ) H O JΒ

V R " ^

Κ

(15)

A r o m a t i c a l d e h y d e s were r e d u c e d i n g o o d y i e l d b y i s o p r o p y l b o r a t e ; a l i p h a t i c a l d e h y d e s g a v e p o o r y i e l d s . K e t o n e s were n o t r e d u c e d b y i s o p r o p y l b o r a t e a n d o n l y i n low y i e l d b y allyl borate. T h e b o r a t e esters r e a c t w i t h G r i g n a r d reagents t o g i v e , successively, b o r o n i c a c i d s , R B ( O H ) ; b o r i n i c a c i d s , R B O H ; a n d b o r i n e s , R B (98). T h e m e c h a n i s m of t h i s r e a c t i o n has b e e n discussed i n some d e t a i l (196). O f the a l k y l borates, only m e t h y l borate appears t o react w i t h a m m o n i a a n d p r i m a r y a n d secondary amines t o f o r m stable, solid coordination compounds (77-79, 168, 198) : 2

2

3

( C H 0 ) B + RxNH _x -> ( C H 0 ) B · N H _ R 3

3

3

3

3

3

X

X

(16)

T h e a r y l b o r a t e s , w h i c h are s t r o n g e r L e w i s a c i d s t h a n t h e a l k y l esters, g e n e r a l l y f o r m s i m i l a r c o m p o u n d s , w i t h some s t e r i c l i m i t a t i o n s (47, 48). A n u m b e r o f b o r a t e esters were i n v e s t i g a t e d as c a t a l y s t s f o r t h e p o l y m e r i z a t i o n o f d i a z o m e t h a n e t o p o l y m e t h y l e n e (181). T h e o r d e r of effectiveness w a s a p p r o x i m a t e l y i n the order of increasing a c i d i t y of the esters: i s o p r o p y l < e t h y l < m e t h y l < a l l y l < b e n z y l < β-methoxyethyl < β-chloroethyl < β-trichloroethyl. B o r a t e esters r e a c t w i t h m e t a l a l k o x i d e s t o f o r m t h e c o r r e s p o n d i n g m e t a l t e t r a a l k o x y b o r o h y d r i d e (171): (RO) B + N a O R - » NaB(OR) 3

(17)

4

H o w e v e r , steric l i m i t a t i o n s a p p e a r t o decrease t h e r a t e o f f o r m a t i o n a n d s t a b i l i t y o f t h e tetraisopropoxy compound. R e a c t i o n w i t h metal hydrides yields t h e corresponding metal trialkoxyborohydrides : ( R ( ) ) B + N a H -> N a B H ( O R ) :i

3

(18)

Tetracoordinate Boron in Borates T h e a b i l i t y o f b o r o n c o m p o u n d s t o a c t a s L e w i s a c i d s has l o n g b e e n k n o w n a n d t h e effect has b e e n u s e d t o c o r r e l a t e v a r i o u s aspects o f b o r o n c h e m i s t r y . F o r e x a m p l e , S c h l e s i n g e r a n d B r o w n (171) u s e d t h e L e w i s g e n e r a l i z e d a c i d - b a s e c o n c e p t t o c o r r e l a t e t h e r e a c t i o n s of d i b o r a n e a n d r e l a t e d c o m p o u n d s . B r o w n (84) has g i v e n a n excellent s u m m a r y o f h i s w o r k ( c o n c e r n e d t o a g r e a t e x t e n t w i t h t h e c o o r d i n a t i o n of v a r i o u s bases w i t h b o r o n c o m p o u n d s ) o n t h e c h e m i c a l effects o f s t e r i c s t r a i n s . K u i v i l a a n d c o w o r k e r s (105-114) have determined kinetically that a tetracoordi nate boronate a n i o n i s the i m p o r t a n t intermediate i n the electrophilic displacement of the boronate m o i e t y f r o m areneboronic acids b y halogen o r peroxide. Bôeseken a n d c o w o r k e r s (24) c o n f i r m e d t h e t e t r a c o o r d i n a t e s t r u c t u r e o f t h e b o r o n a t o m i n eis-diol compounds b y separating the o p t i c a l isomers of b o r o n b i s - ( y - c h l o r o catechol) a n d b o r o n b i s - ( 3 - n i t r o c a t e c h o l ) . T h e i m p o r t a n c e of tetracoordinate b o r o n d u r i n g the p r e p a r a t i o n of benzeneboronic a c i d f r o m m e t h y l b o r a t e a n d p h e n y l m a g n e s i u m b r o m i d e has been d e m o n s t r a t e d (196). A l t h o u g h t h e r e are m a n y e x a m p l e s of t e t r a c o o r d i n a t e b o r o n c o m p o u n d s , c o m p a r a t i v e l y l i t t l e i s k n o w n a b o u t t h e f a c t o r s a f f e c t i n g t h e L e w i s a c i d i t y o f b o r a t e esters. E v i d e n c e is available t o support the hypothesis t h a t boron compounds undergo reac t i o n b y c o o r d i n a t i o n w i t h a base. F o r e x a m p l e , w h e n a n o p t i c a l l y a c t i v e b o r a t e i s h y d r o l y z e d , t h e a l c o h o l f o r m e d r e t a i n s i t s c o n f i g u r a t i o n (72, 164), i n d i c a t i n g cleavage


147



of a b o r o n - o x y g e n b o n d . T h i s c o u l d o c c u r as s h o w n i n F i g u r e 10. T h e second a n d t h i r d steps of t h e h y d r o l y s i s a r e i d e n t i c a l t o t h e first. T h e f o u r t h step p r o b a b l y leads t o t h e t e t r a h y d r o x y b o r a t e a n i o n (61). W h e t h e r t h e h y d r o l y s i s i s c o n c e r t e d o r

Figure 10.

Hydrolysis a n d reaction mechanism involving tetracoordinate boron

stepwise i s n o t d e f i n i t e l y k n o w n , b u t a stepwise m e c h a n i s m is suggested, o r p e r h a p s a " s t e p w i s e - c o n c e r t e d " m e c h a n i s m , i n w h i c h s o l v e n t i s first d i s p l a c e d b y a n o t h e r base ( w a t e r f o r h y d r o l y s i s ) as s h o w n i n F i g u r e 1 1 , f o l l o w e d b y t h e m e c h a n i s m d e p i c t e d i n F i g u r e 10.

Ο

Figure 11.

Generalized displacement mechanism applied to borate esters

S u c h a m e c h a n i s m w o u l d e x p l a i n w h y t h e rates of h y d r o l y s i s of b o r a t e esters a r e m u c h s l o w e r i n aqueous acetone, t e t r a h y d r o f u r a n , a n d d i o x a n e o r o t h e r L e w i s bases w i t h a n u n h i n d e r e d e l e c t r o n p a i r t h a n i n aqueous m e t h a n o l . F u r t h e r e v i d e n c e s u p p o r t i n g this m e c h a n i s m f o r h y d r o l y s i s ( a n d reaction) is afforded b y c o m p a r i n g t h e r e l a t i v e i n e r t n e s s of t e r t i a r y a m i n e - b o r o n t r i c h l o r i d e c o o r d i n a t i o n c o m p o u n d s t o c o l d w a t e r w i t h t h e a l m o s t v i o l e n t h y d r o l y s i s of b o r o n t r i c h l o r i d e itself. T h i s i s also t r u e for sodium tetramethoxyborohydride a n d t r i m e t h y l b o r a t e ; t h e borohydride is only s l o w l y h y d r o l y z e d , w h e r e a s t h e b o r a t e ester h y d r o l y z e s v e r y r a p i d l y . T h e a u t h o r s h a v e i n v e s t i g a t e d t h e i n f r a r e d s p e c t r a of b o r a t e esters. B e t h e l l a n d S h e p p a r d (21) r e p o r t e d a v e r y s t r o n g a b s o r p t i o n a t 1450 c m . f o r crystalline boric a c i d . T h i s w a s assigned t o a s y m m e t r i c a l Β — Ο s t r e t c h i n g , as i t d i d n o t change a p p r e c i a b l y f o r d e u t e r a t e d b o r i c a c i d . W e r n e r a n d O ' B r i e n (198) d e t e r m i n e d t h e i n f r a r e d s p e c t r a o f s e v e r a l b o r a t e esters. T h e y assigned t h e s t r o n g b a n d a t 1340 ± 10 c m . — t o t h e Β — Ο s t r e t c h i n g v i b r a t i o n . T h e a u t h o r s find a n a v e r a g e o f 1335 c m . for Β — Ο s t r e t c h i n g i n a l k y l b o r a t e esters ( T a b l e X V I ) a n d a n average of 1354 c m . - f o r a r y l b o r a t e esters. A b s o r p t i o n b a n d s f o r t h e s t a b l e , m i x e d a l k y l - a r y l b o r a t e s a r e s h o w n in Table X V I I . - 1

1

- 1

1

American Chemical Society Library


ADVANCES IN CHEMISTRY SERIES Table XVI. Infrared Data for A l i phatic Borate Esters


Borate Ester

Cm.-i

Methyl

1352 VS 683 W 662 M

Ethyl

1335 VS 693 W 665 M

n-Propyl

1334 VS 692 W 667 M

n-Butyl

1335 VS 690 W 663 M

n-Octyl

1336 VS 690 W 664 M

2-Ethylhexyl

1334 VS 688 W 663 M

n-Decyl

1337 VS 690 W 664 M

n-Dodecyl

1337 VS 688 W 663 M

Isopropyl

1327 VS 692 W 663 M

sec-Butyl

1332 VS 688 VW 663 M

Cyclohexyl

1325 VS 688 W 662 M

Methylisobutylcarbinyl

1330 VS 687 W 663 M

Diisopropylcarbinyl

1334 VS 678 W 657 M

Diisobutylcarbinyl

1340 VS 681 W 661 M

3,3,5-Trimethylcyclohexy 1

1338 VS 690 VW 664 M

3,6,8-Trimethylnony 1

1335 VS 681 W 657 M

Tetradecyl

1330 VS 680 W 657 M

2-Methoxyethyl

1333 VS 686 W 662 M

2-2'-Methoxyethoxyethyl

1333 VS 684 W 661 M

Tetrahydrofurfuryl

1334 VS 686 W 662 M

Tri(hexyleneglycol)

biborate

1309 VS 690 W 664 M


WASHBURN, LEVENT ALBRIGHT, AND BILLIG—BORATE ESTERS Table XVII.

Β — Ο Absorption

for Aromatic a n d M i x e d

Aliphatic-Aromatic Borate Ester

Esters

Aromatic Esters

Phenyl o-Cresyl n-Cresyl p-Cresyl 3,5-Dimethylphenyl


149

Cm.-i

Phase

1354 1357 1352 1354

ecu Film Film ecu Film ecu CeHu ecu Film CHCh CHCh ecu ecu

1356 1356 1352 1352 1358 1353 1353 1353

3,4-Dimethylphenyl 2,4-Dimethylphenyl 2,6-Dimethylphenyl 2,6-Diallylphenyl 2,6-Diisopropylphenj l 6-Chloro-l-cresyl r

Mixed Aliphatic-Aromatic Esteri Film KBr

1329 1319 1328 1333 1335 1325

2,6-Di-B

/ \

RO

OR

ο

R T h i s i s also o b s e r v e d f o r m e t h a n o l - m e t h y l b o r a t e ( F i g u r e 1 4 ) , c o n f i r m i n g t h e f o r m u l a t i o n o f S y r k i n a n d D y a t k i n a (186). I t is significant t h a t w i t h increasing steric i n t e r ference o f t h e L e w i s a c i d ( b o r a t e ) a n d base ( e t h e r ) , t h e a b s o r p t i o n s a t 1250 a n d


152



FREQUENCY IN CM.-!

8

9

WAVE LENGTH IN MICRONS

Figure 14. Infrared absorption of tetracoordinate boron compounds in the region from 1110 to 1300 c m . 1

1190 c m . d i s a p p e a r , t h e a b s o r p t i o n a t 1250 c m . " d i s a p p e a r i n g f i r s t . sities o f t h e a b s o r p t i o n s f o r t h e esters a r e i n t h e o r d e r ( T a b l e X V I I I ) : - 1

T h e inten

1

(CH 0) B > (C H 0) B > ( C H = C H C H O ) B > (n-C H 0) B > (n-C H 0) B 3

3

2

5

3

2

3

3

7

3

4

9

3

T h i s ester a b s o r p t i o n w a s n o t seen f o r o t h e r a l i p h a t i c b o r a t e esters unless t h e y also c o n t a i n e d e t h e r o x y g e n ; t h e esters 2 - m e t h o x y e t h y l , 2 - [ 2 - m e t h o x y e t h o x y ] e t h y l , t e t r a h y d r o f u r f u r y l borate, a n d tri(hexyleneglycol) biborate a l l show m e d i u m t o strong a b s o r p t i o n s , f u r t h e r suggesting o x y g e n - b o r o n i n t r a m o l e c u l a r i n t e r a c t i o n . T h e spectra of the a r y l borates are more complex a n d no correlations have y e t been m a d e . I t a p p e a r s t h a t t h e r e is a n a b s o r p t i o n m a x i m u m j u s t o u t s i d e t h e r a n g e of r o c k salt o p t i c s ( 6 5 0 c m . ) f o r a l l o f t h e a r y l b o r a t e s . F u r t h e r d e t a i l s w i l l b e presented i n a subsequent paper. /

- 1

Toxicity L i t t l e i n f o r m a t i o n appears t o have been p u b l i s h e d about t h e t o x i c i t y of borate esters. I n s c r e e n i n g tests w i t h e t h y l a n d b u t y l b o r a t e s t h e f o l l o w i n g were f o u n d (41 ) :


153


WASHBURN, LEVENS, ALBRIGHT, AND BILLIG—BORATE ESTERS Test Snail control

Triethyl Borate Mortality 1/10 at 10 p.p.m.

Tributyl Borate Mortality 0/10 at 10 p.p.m.

Toxicity

Mouse mortality 0/3 at 15.6 cu. mm./kg.; ataxia at 125 to 500 cu. mm./kg. No response in brown trout, bluegill, goldfish

Mouse mortality 1/5 at 500 cu. mm./kg. ; ataxia, depres sion; recovery in 20 min.

Antibacterial

Slight activity against S. au reus; negative against B. globigii

Negative against S. aureus, E. coli, B. globigii

Plant growth regulator

No apparent effect on red kid ney bean seeds Negative results at 225 cu. mm./kg.

Cancer

S a x (163) cites e x p e r i m e n t a l l y i n d u c e d eye d a m a g e f r o m m e t h y l a n d e t h y l b o r a t e s . I n g e n e r a l , f o r esters w h i c h h y d r o l y z e r a p i d l y , i t seems reasonable t o a s c r i b e t h e p r i n c i p a l effects t o t h e r e s u l t i n g a l c o h o l o r ( p h e n o l ) a n d b o r i c a c i d . B o r i c a c i d i s s a i d t o Table XIX.

Uses of Borate Esters

Use Antidiscolorant (aromatic amines) Antioxidant Alcohol Rubber Azeotropic separation Catalyst Cracking Oxidation acetylenic 7-glycols Polymerization diazomethane Polymerization drying oils Sulfurization fatty oils Synthesis /3-lactones Coating Flame-resistant Water-repellant Colorimetric reagent (hydroxyquinones) Cosmetic preparations Curing agent (epoxy resins) Dehydrating agent Hydrogen peroxide Polymerization silicones Road aggregates Deterrent (smokeless powder) Electrolytic condensers Flux (brazing, welding) Fungicide Gelling agent (castor oil) Germicide Inhibitor (SO3 polymerization) Insecticide Lubricant (textile) Petroleum additive Antioxidant Corrosion inhibitor Dehydrating agent Demulsifier Improve gasoline performance Prevent wax precipitation Pharmaceutical preparations Plasticizer Polymer Adhesive Binder Coating Resin Purification Alcohols, phenols Cottonseed oil Recovery boron values (saltpeter) Refractories (bonding, impregnation) Resin modifier (pine wood resin) Rubber accelerator Stabilizer (PVA films) Surface active agent (detergent, dispersant, emulsifier, foaming, wetting) Wax or resin substitute

References (176) (88) (38, 144) (184) (199) (33) (131)

(201)

(63) (81)

(12) (143) (δ) (10, 19, 76) (121) (153) (132, 177, 178) (162) (10, 19,31, 60, 68-71, 148, 160) (6, 126, 168, 195) (149, 187) (66, 135) (90, 149) (127) (1,55) (200) (44, 54, 49,117, 154) (44, 54, 174, 190) (64) (99) (52, 67, 88,117) (122) (10, 11, 19, 31, 4^, 43, 50, 51, 125, 152, 189 (18, 31, 80, 103, 138, 162, 178) (10, 19, 31, 138, 150) (46, 138) (10, 19, 31) (10, 13, 19, 22, 28, 31, 82, 46, 57, 82, 89, 104, 128, 189, 156, 157, 175) (87, 40, 84, 97, 101, 123, 138, 141, 158, 205) (169) (39) (194) (161) (65) (22, 115) (20, 31, 74, 80, 91, 94, 95, 124, 129, 130, 140, 14?, 159, 162, (182)



154

affect t h e c e n t r a l n e r v o u s s y s t e m a n d t o a c c u m u l a t e i n t h e b r a i n , l i v e r , a n d b o d y f a t . S a x states t h a t t h e f a t a l dose of o r a l l y i n g e s t e d b o r i c a c i d is 15 t o 2 0 g r a m s f o r a d u l t s a n d 5 t o 6 g r a m s f o r i n f a n t s . S p e c t o r (179) gives t h e b o r i c a c i d r a n g e of LD for l a b o r a t o r y a n i m a l s as 4740 t o 5580 m g . p e r k g . F o r 2,6-di-£er£-butyl-4-methylphenyl d i i s o p r o p y l b o r a t e , o n e o f t h e n e w s t a b l e esters s h o w n i n T a b l e I X , t h e o r a l LD i n r a t s w a s f o u n d t o b e 5.2 g r a m s p e r k g . ( t o x i c i t y test c o n d u c t e d b y S c i e n t i f i c A s s o c i a t e s , S t . L o u i s , M o . ) , w h i c h is i n g o o d a g r e e ment w i t h the value just cited for boric acid. 50

m


Uses of Borate Esters I n a d d i t i o n t o t h e s y n t h e t i c p o s s i b i l i t i e s f o r b o r a t e esters, a l a r g e n u m b e r o f m i s c e l l a n e o u s uses h a v e b e e n d e s c r i b e d , p r i n c i p a l l y i n t h e p a t e n t l i t e r a t u r e . S o m e of these a r e s u m m a r i z e d i n T a b l e X I X .

Bibliography (1) (2) (3) (4) (5) (6)

Abbey, Α., Brit. Patent 668,763 (1952). Ahmad, T., Haider, S. Z., Khundkar, M . H., J. Appl. Chem. 4, 543 (1954). Ahmad, T., Khundkar, M. H., Chem. & Ind. (London) 1954, 248. Almy, E. G., Griffiin, W. C. Wilcox, C. S., Ind. Eng. Chem.,Anal.Ed. 12, 392 (1940). Anderson, J. R. Α., O'Brien, K . G., Reuter, F. H., Anal. Chim. Acta 7, 226 (1952). Appel, F. J., U. S. Patent 2,217,354 (1940) ; Ε. I. du Pont de Nemours & Co., Brit. Patent 542,528 (1942). (7) Arbuzov, Β. Α., Vinogradova, V. S., Bull. Acad. Sci. (U.S.S.R.), Div. Chem. Sci. 1952, 773. (8) Arbuzov, Β. Α., Vinogradova, V. S., J. Phys. Chem. (U.S.S.R.) 22, 303 (1948). (9) Asahara, T., Kanabu, K., J. Chem. Soc. Japan, Ind. Chem. Sect. 55, 589 (1952). (10) Atlas Powder Co., Brit. Patent 511,641 (1939). (11) Austin, J. Α., U . S. Patent 2,007,786 (1935). (12) Balassa, L., Spencer, N. C., Ibid., 2,550,134 (1951). (13) Ballard, S. Α., Ibid., 2,431,224 (1947) ; Brit. Patent 595,502 (1947). (14) Bannister, W. J., U. S. Patent 1,668,797 (1928). (15) Barnes, R. F., Diamond, H., Fields, P. R., Ibid., 2,739,979 (1956). (16) Bauer, S. H., Beach, J. Y., J. Am. Chem. Soc. 63, 1394 (1941). (17) Bauer, S. H., Finlay, G. R., Laubengayer, A. W., Ibid., 67, 339 (1945). (18) Beears, W. L., U . S. Patent 2,650,908 (1953). (19) Bennett, H., Ibid., 1,953,741 (1934). (20) Bent, F. Α., Ibid., 2,197,462 (1940). (21) Bethell, D. E., Sheppard, N., Trans. Faraday Soc. 51, 9 (1955). (22) Binda, F. J., U . S. Patent 2,554,850 (1951). (23) Böeseken, J., Meulenhoff, J., Proc. Acad. Sci. Amsterdam 27, 174 (1924). (24) Böeseken, J., Mijs, J. Α., Rec. trav. chim. 44, 758 (1925). (25) Böeseken, J., Muller, H . D., Japhongjouw, R. T., Ibid., 45, 919 (1926). (26) Böeseken, J., Vermaas, N., J. Phys. Chem. 35, 1477 (1931). (27) Böeseken, J., Vermaas, N., Küchlin, A. T., Rec. trav. chim. 49, 711 (1930). (28) Boughton, W. Α., Mansfield, W. R., U . S. Patent 2,084,261-2 (1937). (29) Bradley, J. Α., Christopher, P. M., Division of Organic Chemistry, 129th Meeting, ACS, April 1956. (30) Brandenberg, W., Galat, Α., J. Am. Chem. Soc. 72, 3275 (1950). (31) Bremer, C., U . S. Patents 2,223,349, 2,223,948, 2,223,949, 2,224,011 (1940). (32) Britton, E. C., Davis, C. W., Taylor, F. L., Ibid., 2,160,942 (1939). (33) Brothman, Α., Ibid., 2,663,715 (1953). (34) Brown, H . C., J. Chem. Soc. 1956, 1248. (35) Brown, H . C., Fletcher, Ε. Α., J. Am. Chem. Soc. 73, 2808 (1951). (36) Brown, H . C., Mead, E . J., Shoaf, C. J., Ibid., 78, 3613 (1956). (37) Bruson, Η. Α., U. S. Patent 2,305,236 (1942). (38) Bunbury, H . M . , Davies, J . S. H., Naunton, W. J . S., Ibid., 1,923,911 (1933) ; Brit. Patent 363,483 (1930). (39) Calvert, R. P., Thomas, O. L., U . S. Patents 1,308,576-7 (1919). (40) Chang, Η. M . , Ibid., 2,760,993 (1956). (41) Chemical-Biological Coordination Center, "Summary Tables of Biological Tests," 1949-55. (42) Chemische Fabrik H . Weitz, German Patent 291,935 (1916).



WASHBURN, LEVENS, ALBRIGHT, AND BILLIG—BORATE ESTERS (43) (44) (45) (46) (47) (48) (49) (50) (51) (52) (53) (54) (55) (56) (57) (58) (59) (60) (61)

155

Clark, M . M., U . S. Patent 2,613,219 (1952). Clayton, J. O., Farrington, Β. B., Ibid., 2,312,208 (1943). Cohn, G., Pharm. Zentralhalle 52, 479 (1911). Colbeth, I. M., U. S. Patents 2,125,544 (1938) ; 2,278,425-7 (1942) ; 2,469,370 (1949). Colclough, T., Gerrard, W., Lappert, M. F., J. Chem. Soc. 1955, 907. Ibid., 1956, 3006. Councler, C., Ber. 9, 485 (1876) ; 10, 1655 (1877) ; 11, 1106 (1878). Craver, A. E., U . S. Patent 1,859,653 (1932). Curtis, D., Ibid., 2,582,191 (1952). Darling, S. M., Fay, P. S., Szabo, L. S., Ibid., 2,741,548 (1956). Dean, J. Α., Thompson, C., Anal. Chem. 27, 42 (1955). Denison, G. H., Jr., Condit, P. C., U. S. Patent 2,346,155 (1944). Dreisbach, R. R., Martin, R. Α., Erbel, A. J., Ibid., 2,507,506 (1950). Dupire, Α., Compt. rend. 202, 2086 (1936). Du Pont, Ε. I. de Nemours & Co., Brit. Patent 577,456 (1946). Ebelmen, J. J., Bouquet, M., Ann. chim. phys. 3, 17, 54 (1846) ; Ann. 60, 251 (1846). Eby, L. T., Mikeska, L. Α., U. S. Patent 2,462,616 (1949). Edenburg, L., Ibid., 1,924,711 (1933) ; Reissued 19,604 (1935). Edwards, J. O., Morrison, G. C., Ross, V. F., Schultz, J. W., J. Am. Chem. Soc. 77, 266 (1955). (62) Elbling, I. N., Langer, S. H., U . S. Patent 2,785,192 (1957). (63) Fawcett, J. S., Ibid., 2,492,562 (1949). (64) Fay, P. S., Szabo, L . S., Ibid., 2,767,069 (1956). (65) Forman, D. B., Radcliff, R. R., Mayo, L. R., Ind. Eng. Chem. 42, 686 (1950). (66) French Thomson-Houston Co., French Patent 955,359 (1950). (67) Garner, P. J., Brit. Patents 722,537-8 (1955). (68) Gaut, G. C., Phillips, D. J. P., Huggins, B. F., U . S. Patent 2,190,285 (1940). (69) Ibid., 2,190,286 (1940). (70) Georgiev, Α., Ibid., 1,815,768 (1931). (71) Georgiev, A. M., Campbell, J. J., Ibid., 2,505,180 (1950). (72) Gerrard, W., Lappert, M . F., J. Chem. Soc. 1951, 1020. (73) Ibid., p. 2545. (74) Gilmann, H . H., U. S. Patent 2,441,063 (1948). (75) Gore, R. C., Waight, E . S., p. 195, in Braude and Nachod, "Determination of Organic Structures by Physical Methods," Academic Press, New York, 1955. (76) Gottfried, S., U. S. Patent 2,506,921 (1950). (77) Goubeau, J., Böhm, U., Z. anorg. u. allgem. Chem. 266, 161 (1951). (78) Goubeau, J., Ekhoff, E., Ibid., 268, 145 (1952). (79) Goubeau, J., Link, R., Ibid., 267, 27 (1951). (80) Graves, G. D., Werntz, J. H., U . S. Patent 2,053,474 (1936). (81) Hagemeyer, H . J., Jr., Ibid., 2,469,110 (1949). (82) Harmon, J., Ibid., 2,423,497 (1947). (83) Hellthaler, T., Peter, E., Ibid., 1,947,989 (1934). (84) Hertkorn, J., Ibid., 901,293 (1908). (85) Hirao, N., Yabuuchi, T., J. Pharm. Soc. Japan 74, 1073 (1954). (86) Hirao, N., Yagi, S., J. Chem. Soc. Japan, Ind. Chem. Sect. 56, 371 (1953). (87) Horsley, L. H., Advances in Chem. Series, No. 6 (1952). (88) Hughes, E. C., Darling, S. M., Bartleson, J. D., Klingel, A. R., Jr., Ind. Eng. Chem. 43, 2841 (1951). (89) Irany, E . P., U. S. Patent 2,523,433 (1950). (90) Jablonski, Ε. M., Brit. Patent 511,473 (1939) ; French Patent 848,459 (1939). (91) Johnson, F. W., U . S. Patent 2,040,997 (1936). (92) Johnson, J. R., Tompkins, S. W., Org. Syntheses 13, 16 (1933). (93) Jones, W. J., Thomas, L . H., Pritchard, E. H., Bowden, S. T., J. Chem. Soc. 1946, 824. (94) Katz, J., U . S. Patent 2,216,618 (1940). (95) Katzman, M. B., Epstein, A. K., Ibid., 2,178,173-4 (1939). (96) Kaufmann, Α., French Patent 720,034 (1931), German Patent 555,403 (1930). (97) Kaufmann, Α. Α., U. S. Patent 1,886,885 (1932) ; Brit. Patent 359,953 (1929) ; Swiss Patent 150,611 (1932). (98) Kharasch, M . S., Reinmuth, O., "Grignard Reactions of Nonmetallic Substances," p. 1335, Prentice-Hall, New York, 1954. (99) Kirkpatrick, W. H., U. S. Patents 2,654,714 (1953) ; 2,755,296 (1956). (100) Klaus, Ε. E., Fenske, M . R., ASTM Bull. No. 215, 87-94 (1956). (101) Klipstein, K . H., U . S. Patent 2,068,415 (1937). (102) Kolthoff, I. M., Sandell, Ε. B., 3rd ed., p. 534, "Textbook of Quantitative Inorganic Analysis," Macmillan, New York, 1952.



156


(103) Krieble, R. H., U . S. Patent 2,440,101 (1948) ; British Thomson-Houston Co., Brit. Patent 643,298 (1950). (104) Kropa, E. L., U. S. Patent 2,249,768 (1941). (105) Kuivila, H . G., J. Am. Chem. Soc. 76, 870 (1954). (106) Ibid., 77, 4014 (1955). (107) Kuivila, H . G., Benjamin, L. E., Ibid., 77, 4834 (1955). (108) Kuivila, H . G., Esterbrook, Ε. K., Ibid., 73, 4629 (1951). (109) Kuivila, H . G., Hendrickson, A. R., Ibid., 74, 5068 (1952). (110) Kuivila, H . G., Keough, A. H., Soboczenski, E. J., J. Org. Chem. 19, 780 (1954). (111) Kuivila, H . G., Slack, S. C., Siiteri, P. K., J. Am. Chem. Soc. 73, 123 (1951). (112) Kuivila, H . G., Soboczenski, E. J., Ibid., 76, 2675 (1954). (113) Kuivila, H . G., Wiles, R. Α., Ibid., 77, 4830 (1955). (114) Kuivila, H . G., Williams, R. M., Ibid., 76, 2679 (1954). (115) Land, E. H., U. S. Patent 2,445,581 (1948). (116) Lappert, M . F., Chem. Revs. 56, 959 (1956). (117) Lawrence, F. I. L., Smith, R. K., Pohorilla, M . J., U . S. Patents 2,721,180-1 (1955). (118) Letsinger, R. L., Skoog, I., J. Am. Chem. Soc. 76, 4174 (1954). (119) Ibid., 77, 2491 (1955). (120) Levasheff, V. V., Levens, E., May, F. H., Washburn, R. M., Division of Industrial and Engineering Chemistry, 128th Meeting, ACS, September 1955. (121) Levitan, N . I., Kuoch, R., U . S. Patent 2,386,484 (1945). (122) Lieber, E., Hodges, C. E., Ibid., 2,383,605 (1945). (123) Lippincott, S. B., Ibid., 2,642,453 (1953). (124) Lonza Electrizitätswerke & Chemische Fabriken A. G., Swiss Patent 239,746 (1916). (125) Lüdecke, K., U. S. Patent 1,788,680 (1931). (126) Lytle, A. R., Vaughn, T. H., Ibid., 2,262,023, 2,262,187 (1941). (127) McCann, H . G., Townsend, R. V., Ibid., 2,492,706 (1949). (128) McLeod, E. D., Ibid., 2,352,796 (1944). (129) Mauersberger, Ε. Α., Ibid., 2,036,593 (1936). (130) Ibid., 2,042,952 (1936). (131) Meerwein, H., Angew. Chem. A60, 78 (1948). (132) Mertens, E. W., Stevens, D. E., U . S. Patent 2,408,924 (1950). (133) Michael, V. F., Ibid., 2,606,936 (1952). (134) Michaelis, Α., Hillringhaus, F., Ann. 315, 41 (1901). (135) Miller, H . F., Flowers, R. G., U. S. Patent 2,544,342 (1951). (136) Mitchell, J., Jr., Smith, D. M., Bryant, W. M. D., J. Am. Chem. Soc. 62, 4 (1940). (137) Ibid., 63, 2927 (1941). (138) Morgan, W. L., U. S. Patent 2,408,332 (1946). (139) Ibid., 2,501,783 (1950). (140) Muncie, F. W., Ibid., 2,209,634 (1940). (141) O'Connor, B., Pearce, F. G., Ibid., 2,587,753 (1952). (142) O'Connor, G. L., Nace, H . R., J. Am. Chem. Soc. 77, 1578 (1955). (143) Patnode, W. I., U. S. Patent 2,434,953 (1948). (144) Paul, P. T., Ibid., 2,259,175 (1941). (145) Pauling, L., "Nature of the Chemical Bond," 2nd ed., pp. 210, 235, Cornell University Press, Ithaca, Ν. Y., 1948. (146) Pictet, Α., Geleznoff, Α., Ber. 36, 2219 (1903). (147) Piggott, Η. Α., U . S. Patent 2,052,192 (1936). (148) Pitt, A. T., Ibid., 2,078,772 (1937). (149) Prescott, R. F., Dosser, R. C., Sculati, J. J., Ibid., 2,260,336-9 (1941) ; 2,300,006 (1942). (150) Raczynski, W. Α., Ibid., 2,510,904 (1950). (151) Rippere, R. E., La Mer, V. Κ., J. Phys. Chem. 47, 204 (1943). (152) Roblin, R. O., Jr., U . S. Patent 2,266,993 (1941). (153) Rochow, E . G., Ibid., 2,371,068 (1945). (154) Rogers, D. T., McNab, J. G., Ibid., 2,526,506 (1950). (155) Rosenblum, I., Ibid., 2,189,833 (1940). (156) Roth, H., Angew. Chem. 50, 593 (1937). (157) Rothrock, H . S., U. S. Patent 2,276,094 (1942). (158) Rottig, W., Ibid., 2,746,984 (1956). (159) Rozenbroek,M.D., Ibid., 2,224,360 (1940) ; Dutch Patent 49,219 (1940). (160) Ruben, S., U . S. Patents 1,891,206-7 (1932). (161) Rummelsburg, A. L., Ibid., 2,354,774 (1944). (162) Ibid., 2,417,180 (1947). (163) Sax, Ν. I., "Handbook of Dangerous Materials," Reinhold, New York, 1951. (164) Scattergood, Α., Miller, W. H., Gammon, J., Jr., J. Am. Chem. Soc. 67, 2150 (1945). (165) Schäfer, H., Angew. Chem. A60, 73 (1948). (166) Schäfer, H., Z. anorg. Chem, 259, 86, 255 (1949). In METAL-ORGANIC COMPOUNDS; Advances in Chemistry; American Chemical Society: Washington, DC, 1959.



(167) (168) (169) (170) (171) (172) (173) (174) (175) (176) (177) (178) (179) (180) (181) (182) (183) (184) (185) (186) (187) (188) (189) (190) (191) (192) (193) (194) (195) (196) (197) (198) (199) (200) (201) (202) (203) (204) (205)

157

Schäfer, H., Braun, O., Naturwissenschaften, 39, 280 (1952). Schechter, W. H., U. S. Patent 2,629,732 (1953). Schellmann, M., Ibid., 1,981,605 (1934). Schiff, H., Ann. Suppl. 5, 158 (1867). Schlesinger, Η. I., Brown, H . C., J. Am. Chem. Soc. 75, 186 (1953). Schlesinger, Η. I., Brown, H . C., Mayfield, D. L., Gilbreath, J. R., Ibid., 75, 213 (1953). Schuler, E . B., U . S. Patent 2,114,985 (1938). Shoemaker, B. H., Loane, C. M., Ibid., 2,160,917 (1939). Signaigo, F. K., Ibid., 2,444,712 (1948). Smith, R. K., Ibid., 2,422,503 (1947). Smith, V. R., Stevens, D. E., Ibid., 2,508,428 (1950). Smith, V. R., Stevens, D. E., Mertens, E . W., Ibid., 2,508,430 (1950). Spector, W. S., "Handbook of Toxicology," vol. I, W. B. Saunders, Philadelphia, 1956. Stanley, J., U. S. Patent 2,077,967 (1937). Steinberg, H., Hunter, D. L., Ind. Eng. Chem. 49, 174 (1957). Stickdorn, K., U . S. Patent 2,187,334 (1940) ; German Patent 692,487 (1940). Stillson, G. H., Sawyer, D. W., Hunt, C. K., J. Am. Chem. Soc. 67, 303 (1945). Stribley, J. M., Lake, G. R., U. S. Patent 2,463,919 (1949). Sugden, S., "The Parachor and Valency," Routledge, London, 1930. Syrkin, Y . K., Dyatkina, M . E., "Structure of Molecules and the Chemical Bond," p. 109, Interscience, New York, 1950. ter Horst, W. P., U . S. Patent 2,220,981 (1940). Thomas, L . H., J. Chem. Soc. 1946, 823. Thron, H., U. S. Patent 841,738 (1907), Vereinigte Chininfabrieken Zimmer, German Patent 188,703 (1907). Trautman, C. E., U . S. Patents 2,497,521 (1950) ; 2,468,472 (1951). Tronov, Β. V., Petrova, A. M., Zhur. Obshchei Khim. 23, 1019 (1953). Ulrich, H., Kuespert, K., U. S. Patent 2,185,480 (1940). Urs, S. V., Gould, E . S., J. Am. Chem. Soc. 74, 2948 (1952). Vaughn, T. H., U . S. Patent 2,058,844 (1936). Ibid., 2,088,935 (1937) ; 2,114,866 (1938). Washburn, R. M., Levens, E., Albright, C. F., Billig, F. Α., Cernak, E . S., Division of Industrial and Engineering Chemistry, 131st Meeting, ACS, Miami, Fla., April 1957. Webster, S. H., Dennis, L . Μ., J. Am. Chem. Soc. 55, 3233 (1933). Werner, R. L., O'Brien, K . G., Australian J. Chem. 8, 355 (1955). West, J. P., U. S. Patent 2,584,405 (1952). Whitehead, W., Ibid., 2,188,167 (1940). Whiting, L . R., Ibid., 2,480,206 (1949). Whitmore, F. C., Lux, A. R., J. Am. Chem. Soc. 54, 3451 (1932). Wilds, A. L., "Organic Reactions," vol. II, p. 178, Wiley, New York, 1944. Wuyts, M. H., Duquesne, Α., Bull. soc. chim. Belg. 48, 77 (1939). Zeitschel, F. O., U . S. Patent 1,733,440 (1929); German Patents 444,640, 448,419 (1927). RECEIVED for review May 10, 1957. Accepted June 1, 1958.


ba-1959-0023.ch012

Recommend Documents