HANDLING AND USES OF THE ALKALI METALS

Manufacture, Handling, and Uses of Sodium Hydride M. D. BANUS and A. A. HINCKLEY Chemical Research Laboratory, Metal Hydrides, Inc.

Downloaded by MICHIGAN STATE UNIV on August 1, 2013 | http://pubs.acs.org Publication Date: January 1, 1957 | doi: 10.1021/ba-1957-0019.ch011

Beverly, Mass.

Two types of sodium hydride are available com mercially: a dry, granular material about 8 to 200 mesh in size, and a semidispersion of micron -sizedcrystals in mineral oil. The oil-dispersed so dium hydride is the safer and easier to handle, as the high reactivity of the hydride is protected by the oil. The principal use of sodium hydride is to carry out condensation and alkylation reactions which proceed through the formation of a car banion (base-catalyzed). The sodium h y d r i d e dispersion has been evaluated in c o m p a r i s o n with dry sodium hydride, sodium metal, soda mide, and sodium methylate. Yields and reac tion rates in the self-condensation of esters, ester -keto condensations, and the Dieckmann condens ation have been outstandingly superior. Amines can be successfully alkylated by a new technique employing polar solvents. Dehalogenations do not occur, nor does reduction unless there is no α-hydrogen present. Acyloin formation and re duction side reactions do not interfere when so dium hydride is used.

Τ H E reaction of the metal, sodium, w i t h the gas, h y d r o g e n , produces a c o m p o u n d , s o d i u m h y d r i d e , w h i c h is i n m a n y w a y s s i m i l a r to b u t i n other w a y s different f r o m the parent metal. S o d i u m h y d r i d e is a white, crystalline solid w i t h the s o d i u m c h l o r i d e - t y p e structure, h i g h l y reactive a n d v e r y useful. T h e h y d r o g e n is present i n the crystal lattice as the H ~ anion, positioned w h e r e it w o u l d be i n s o d i u m c h l o r ide. L i k e a l l the saline a n d alloy hydrides, it gives u p this h y d r o g e n again or d i s sociates w h e n heated. T h i s h y d r o g e n can also be liberated b y reaction of the h y d r i d e w i t h compounds containing O H ~ groups such as water a n d a l c o h o l s — a v e r y vigorous reaction i n the case of water a n d the lower alcohols. T h e p r i n c i p a l p h y s i c a l properties are s u m m a r i z e d i n T a b l e I. S o d i u m h y d r i d e is c o m m e r c i a l l y available as a d r y , g r a n u l a r , g r a y p o w d e r a n d as a pale gray semidispersion i n inert h y d r o c a r b o n o i l at concentrations of 25 a n d 50 weight % of s o d i u m h y d r i d e . T h e d r y , g r a n u l a r m a t e r i a l has a m i n i m u m 106

In HANDLING AND USES OF THE ALKALI METALS; Advances in Chemistry; American Chemical Society: Washington, DC, 1957.

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Table I. Physical Properties of Sodium Hydride Density

1.40 grams per cc.

Heat of f o r m a t i o n

Δ H ° 2 5 ° C . = -13.7 k c a l . per mole

(46)

Δ Η = -31.5 k c a l . per mole N a H

(21)

f

Heat of reaction w i t h H 0 2

Dissociation pressure NaH±^Na+ yK 2

(0-500°)

s

N a H ^ N a (dissolved in NaH) + i/ H (500-600°) 2

2


M e l t i n g point

log Ρ c m . =

-6100 T,° K .

+ 10.66

-5070 log Ρ c m . =

T,° K .

+ 9.49

(31)

(3)

U n d e t e r m i n e d , because of dissociation

Insoluble i n organic a n d inorganic solvents except fused salts or fused caustic assay of 9 5 % (balance caustic, s o d i u m metal, a n d s o d i u m organics) w i t h a b u l k density of about 38 pounds p e r cubic foot. P a r t i c l e size is between 8 a n d 200 mesh, w i t h the m a j o r p o r t i o n 20 to 100 mesh. T h e particle shape c a n v a r y f r o m porous, cokelike particles to dense spheres. T h e o i l - d i s p e r s e d s o d i u m h y d r i d e , o n the other h a n d , is i n fine needles of 5- to 5 0 - m i c r o n size; the average is 25 microns. M i n i m u m assay is 9 8 . 5 % — t h a t is, 98.5% of the s o d i u m is present as s o d i u m h y dride. T h e rest is unreacted m e t a l a n d traces of s o d i u m organics. T h e 2 5 % c o n centration is a n easily p u m p e d l i q u i d containing 7.75 pounds of h y d r i d e p e r g a l l o n of dispersion. T h e 5 0 % concentration is a g r a n u l a r m e a l w i t h a p a c k i n g density of 30 to 37 pounds per cubic foot. T h e o i l serves to protect the surface of the h i g h l y reactive h y d r i d e crystals, m a k i n g the product both safe a n d easy to h a n d l e a n d e x t r e m e l y efficient to use. P h o t o m i c r o g r a p h s of the two types are shown i n F i g ures 1 a n d 2.

Figure 1. Photomicrographs of dry granular sodium hydride Left,

χ 40

Right.

X 120

Manufacture G r a n u l a r s o d i u m h y d r i d e is m a n u f a c t u r e d at M e t a l H y d r i d e s , Inc., u n d e r exclusive license f r o m Ε. I. d u P o n t de N e m o u r s & C o . (11, 26, 27, 40, 66). S o d i u m is a d d e d as i n d i v i d u a l blocks or as a l i q u i d to a horizontal, agitated b a t c h reactor w h i c h is kept u n d e r a slight positive pressure of pure, d r y h y d r o g e n . T h e a g i t a tor is a double-flight r i b b o n t y p e ; the outer flight, i n d r i v e rotation, p u l l s the m a t e r i a l f r o m the ends to the center, the i n n e r flight r e v e r s i n g this motion. F o r d i s -



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A D V A N C E S IN CHEMISTRY SERIES

Figure 2. Photomicrographs of sodium hydride-oil dispersion Left. X 40 Right, χ 120

charge, the rotation is reversed, m o v i n g the m a t e r i a l to the ends a n d out the discharge line. A heel is always kept i n the reactor to act as a dispersion b e d for the fresh sodium, w h i c h is f e d at several points along the top of the reactor. C a r e f u l c o n t r o l of the s o d i u m - h y d r o g e n balance is r e q u i r e d to prevent the presence of a l i q u i d phase w h i c h w i l l stop the reaction a n d cause r a p i d scale b u i l d - u p . E x c e s s ive temperature w i l l also cause scale. Dispersants such as kerosine, anthracene, a n d acetylene are added to increase reaction rates, v a r y particle size, color, etc. T h e q u a l i t y of the p r o d u c t a n d reaction rate are v e r y difficult to control i n such equipment, the p u r i t y of the s o d i u m a n d the h y d r o g e n p l a y i n g a n i m p o r t a n t part. S k i l l e d a n d experienced operators are r e q u i r e d to produce at capacity. T h e p r o d uct is discharged hot t h r o u g h a closed system into large hoppers. A f t e r cooling,

Figure 3. General view of sodium hydride production reactor and auxiliary equipment


BANUS A N D HINCKLEY—SODIUM HYDRIDE

it is sized to r e m o v e particles of scale larger t h a n 8 - m e s h ; then it is p a c k a g e d or sent to other processes. T h e p r i n c i p a l control analysis is s o d i u m h y d r i d e assay, w i t h sieve size w h e n r e q u i r e d .


T h e p r o d u c t i o n was 83,000 pounds i n 1954, a n d 57,000 pounds i n 1955. T h e rated capacity of each unit is 350 pounds p e r d a y . T h e dispersion of s o d i u m h y d r i d e i n o i l is p r o d u c e d b y a continuous process (for w h i c h patents are p e n d i n g ) . A pilot plant, n o w t u r n e d over to p r o d u c t i o n , produces 250 pounds p e r h o u r of s o d i u m h y d r i d e . It requires one man's attention, mostly to r e a d dials a n d check levels i n storage tanks. T h e dispersion m e d i u m is a n i n d u s t r i a l white o i l , B a y o l - 8 5 . O t h e r oils of lower a n d h i g h e r v a p o r pressure can a n d w i l l be used, i f sufficient markets are developed. T h e h y d r i d e dispersion is stored i n gently agitated, 1000-gallon tanks, unless it is to be concentrated to 50%. T h i s is the highest p r a c t i c a l concentration, for above this the o i l f i l m no longer f u l l y protects the h y d r i d e particles, the m a t e r i a l r a p i d l y loses its r e a c t i v i t y on exposure, a n d h a n d l i n g hazards increase. T h e 25% dispersion is r e a d i l y p u m p e d a n d metered, w h i l e the 5 0 % m e a l c a n be h a n d l e d i n screw conveyors. S o d i u m h y d r i d e i n dilute dispersion settles s l o w l y o n standing. It c a n be r a p i d l y r e d i s persed i n cans or d r u m s b y the use of a p a i n t - c a n shaker or a n e n d - o v e r - e n d d r u m tumbler.

Handling H a n d l i n g problems w i t h g r a n u l a r s o d i u m h y d r i d e are caused b y two p r o p e r ties of the m a t e r i a l : It is a flammable solid w h i c h c a n f o r m fine dusts; a n d it r e acts v i o l e n t l y w i t h water i n a n y f o r m , l i b e r a t i n g h y d r o g e n (15 cubic feet p e r p o u n d ) . It is shipped i n sealed cans, w i t h polyethylene liners for units larger t h a n 1 p o u n d . These cans or pails should be stored a w a y f r o m heat a n d w h e r e moisture

Figure 4. Details of screening equipment for granular sodium hydride


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cannot come i n contact w i t h them, i n an area free f r o m steam pipes, s p r i n k l e r systems, dampness, a n d water seepage. A s the s h i p p i n g containers are filled w i t h d r y inert gas, large units, once opened, s h o u l d be entirely used. T h e h y d r i d e w i l l adsorb moisture f r o m the atmosphere, reacting to f o r m h y d r o g e n a n d caustic. T h i s caustic coating i n t u r n adsorbs moisture, w h i c h reacts more slowly w i t h the h y d r i d e . T h u s a reclosed container can b u i l d up a pressure inside w h i c h m a y cause a dust cloud to b l o w out w h e n the container is reopened. S u c h a dust c l o u d can ignite; at the v e r y least, it causes caustic irritation to personnel. A l t h o u g h s o d i u m h y d r i d e is insoluble i n a l l organic solvents, the g r a n u l a r f o r m is generally s l u r r i e d w i t h a solvent for use, frequently a flammable one. Solvents must be p r o v e d d r y and free f r o m compounds containing reactive h y d r o gens. S o d i u m h y d r i d e should not be h a n d l e d i n the open i n the presence of f l a m m a b l e solvents. S o l v e n t a n d h y d r i d e should be h a n d l e d i n separate areas a n d brought together i n an inert m e d i u m or inert atmosphere such as nitrogen. It is safer to a d d the h y d r i d e to the reactor u n d e r inert atmosphere a n d then a d d the solvent. Some users have f o u n d it p r a c t i c a l to a d d the h y d r i d e i n the polythene bag, break the bag under the solvent, and remove it either before or after the reaction. E q u i p m e n t for h y d r i d e reactions must be scrupulously d r y before use. T h i s includes v a l v e bonnets, outlets to gages, vent lines, a n d traps. T h e atmosphere should contain less than 1% o x y g e n b y analysis. P u r g i n g w i t h inert gas (carbon dioxide is not inert!) is excellent. T h e h y d r i d e is added t h r o u g h an entrance lock for bags or b y a hopper whose connecting v a l v e a n d pipe can be p u r g e d . Reactors s h o u l d be heated or cooled w i t h o i l or D o w t h e r m , even for condensers. W h e n the reaction is complete, excess h y d r i d e is best destroyed b y a l c o h o l ; the higher alcohols give less vigorous reactions. P r o v i s i o n s h o u l d be made for v e n t i n g the e v o l v e d h y d r o g e n safely and for cooling the reactor or refluxing the alcohol. W a t e r s h o u l d never be used to decompose the h y d r i d e , nor should it be a d d e d to the reactor after the h y d r i d e is decomposed, as the reactor w i l l then have to be c a r e f u l l y d r i e d p r i o r to the next use. It is better to p u m p the reaction m i x t u r e to a second vessel i f water is to be added. T h e h a n d l i n g of s o d i u m h y d r i d e - i n - o i l is considerably simpler, as the dust h a z a r d is r e m o v e d a n d the o i l prevents the r a p i d reaction w i t h moisture. T h e same precautions as to storage, purification of solvents, a n d d r y i n g of equipment s h o u l d be observed. H o w e v e r , because the dispersions can either be p u m p e d or s c r e w - c o n v e y e d to the reactor, the addition p r o b l e m is m i n o r . F u r t h e r m o r e , c o n tinuous reactions are s i m p l y c a r r i e d out. T h e o i l acts as a "heat s i n k " for vigorous reactions, w h i l e t a k i n g the place of a s l u r r y m e d i u m generally r e q u i r e d b y the granular hydride. E m p t y containers for either grade of h y d r i d e should be p r o m p t l y placed o u t doors to " w e a t h e r . " A s m a l l amount of kerosine or f u e l o i l can be added to each a n d ignited to " b u r n " t h e m out. T h e y can then be c a r e f u l l y hosed out a n d the cans j u n k e d . Waste h y d r i d e is best disposed of b y b u r n i n g i n shallow i r o n pans. O i l or kerosine w i l l assist i n sustaining combustion of the g r a n u l a r h y d r i d e . L a r g e q u a n tities should be r a k e d over d u r i n g combustion to be sure the entire mass is c o n sumed. F i r e s w i t h s o d i u m h y d r i d e are dangerous p r i m a r i l y because of a n y organic solvents used. B y itself, the h y d r i d e b u r n s q u i e t l y i n two stages: F i r s t the h y d r o gen b u r n s w i t h a b r i g h t orange flame, then the s o d i u m b u r n s w i t h intense heat a n d clouds of white s o d i u m oxide smoke. S t a n d a r d f i r e - e x t i n g u i s h i n g m e d i a such as water, c a r b o n dioxide, or c a r b o n tetrachloride must not be used, as they w i l l cause explosions (as w i t h s o d i u m m e t a l ) . D r y , g r o u n d limestone or salt can be used w i t h a l o n g - h a n d l e d shovel to smother s m a l l fires. A n s u l D u - G a s a n d d r y c h e m i c a l f i r e - e x t i n g u i s h i n g equipment p r o p e l l e d b y nitrogen are r e c o m m e n d e d both for the h y d r i d e a n d for solvent fires. In the p r o d u c t i o n plant, M e t a l H y d r i d e s , Inc., uses 150-pound and 300-pound wheeled units w i t h smaller portable units for laboratory a n d pilot plant. Once a fire is extinguished, the residues s h o u l d be carefully r e m o v e d to the disposal area, a n d the operation covered b y fire e x t i n guishers, as the residues m a y reignite.


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S o d i u m h y d r i d e is not a great health h a z a r d . I n contact w i t h s k i n a n d body tissues, its effect is s m i l i a r to caustic. I n addition, there is a large amount of heat f r o m the reaction w i t h moisture i n the s k i n . Operators or persons i n the h y d r i d e area should w e a r goggles, p r e f e r a b l y face shields, a n d h e a v y m o l e s k i n gloves a n d flame-proofed coveralls. Asbestos clothing must not be used. A safety shower can be placed just outside the h y d r i d e area for persons w h o come i n major contact w i t h the h y d r i d e . Loose h y d r i d e should be b r u s h e d off w i t h dolomite before enter ing the shower. O i l dispersions should be w i p e d off p r i o r to flooding the s k i n w i t h water. I n using s o d i u m h y d r i d e , training, experience a n d alert operators w i l l result i n safe, efficient production.

Uses of Sodium Hydride S o d i u m h y d r i d e is one of the


INORGANIC PREPARATION OF OTHER HYDRIDES.

est r a w materials for the p r o d u c t i o n of other h y d r i d e s . p r e p a r e d c o m m e r c i a l l y b y the reaction: 4 NaH + B(OCH ) 3

> NaBH, + 3 NaOCH

3

cheap

S o d i u m b o r o h y d r i d e is (50)

3

O t h e r t y p i c a l h y d r i d e s p r e p a r e d f r o m it a r e : Sodium aluminum hydride 4 N a H + AlCla > NaAlH* + 3 NaCl A l u m i n u m hydride 3 N a H + A1C1, > A1H, + 3 NaCl Sodium trimethoxyborohydride NaH + B(OCH ) > NaBH(OCH ) 3

3

3

Sodium triphenylborohydride N a H + Β (CeH ) > N a B H (CeH ) 5

3

5

Diborane 6 N a H + 8 B F : 0 (C,H ) 3

5

2

>B H 2

PREPARATION OF SODIUM ALCOHOLATES. the general reaction: ROH + NaH

e

(19) (19) (48)

3

(64)

a

+ 6 NaBF* + 8 (C H ) 0 2

S o d i u m alcoholates > RONa +

H

6

2

(49)

c a n be p r e p a r e d b y (26)

2

T h e finely d i v i d e d h y d r i d e makes it possible to prepare alcoholates of certain difunctional alcohols more r e a d i l y than w i t h s o d i u m metal. S o d i u m reacts w i t h the double bonds of conjugated unsaturated alcohols a n d reduces n i t r i l e a n d c a r b o n y l groups i n d i f u n c t i o n a l group alcohols. W i t h s o d i u m h y d r i d e the alcoholates of these compounds c a n be formed. REDUCTION OF METAL SALTS. A t temperatures over 300 ° C , s o d i u m h y d r i d e b e comes a moderately p o w e r f u l r e d u c i n g agent, l i b e r a t i n g m e t a l or m e t a l h y d r i d e f r o m certain salts. F o r e x a m p l e : 300°C. TiCl CrCl

4

3

+ 4 NaH

> TiH

2

+ 4 NaCl +

2 H

400 ° C . + 3 NaH > C r + 3 N a C l + 3/2 H

2

2

(6) (7)

It is possible that i n these reactions r e d u c t i o n is c a r r i e d out b y s o d i u m f r o m the p a r t i a l dissociation of the h y d r i d e , as the m e t a l is e q u a l l y effective. A t lower temperatures s o d i u m h y d r i d e reacts more selectively a n d has been used to remove v a n a d i u m a n d other impurities f r o m t i t a n i u m tetrachloride. MISCELLANEOUS. S o d i u m h y d r i d e , p a r t i c u l a r l y as the dispersion, is effective for r e m o v i n g the last traces of water, alcohols, oxygen, a n d some sulfur compounds f r o m solvents a n d certain gases. It reacts w i t h a m m o n i a to f o r m s o d i u m amide, w i t h c a r b o n oxides to f o r m products i n c l u d i n g formate a n d oxalate, a n d w i t h sulfur dioxide to f o r m s o d i u m hydrosulfite. S m a l l e y (52) has t r i e d it for the desulfurization of i r o n a n d steel. Its advantage over s o d i u m m e t a l for these r e a c tions is that it holds its fine particle size a n d reactive surface u p to 400 ° C , w h i l e s o d i u m melts a n d coalesces at 100 °C. unless continually redispersed. ORGANIC. S o d i u m h y d r i d e c a n be used i n organic reactions i n various ways. M u c h of the e x p e r i m e n t a l w o r k recently completed at M e t a l H y d r i d e s , Inc., was directed t o w a r d the comparison of the h y d r i d e , p a r t i c u l a r l y the o i l dispersion,


A D V A N C E S IN CHEMISTRY SERIES

112

w i t h other s o d i u m compounds i n reduction, condensation, a n d a l k y l a t i o n reactions. A brief cost comparison is a good starting point.

Table II. Costs Compound S o d i u m metal NaH NaOCHs (dry basis) NaNH NaOCsHs 2

M o l . Wt. 23 24 54 39 68

Commercial Price/Lb. $0.17 0.95 0.44 1.55 0.44

Cost/Lb. Mole $ 3.91 22.80 23.80 60.05 29.10


O n a cost basis, s o d i u m h y d r i d e is v e r y attractive c o m p a r e d w i t h a l l b u t sodium metal. O n a reaction rate a n d y i e l d basis, it is f a r superior i n most cases. S o d i u m h y d r i d e is not a strong r e d u c i n g agent; thus it w i l l not dehalogenate a l k y l or a r y l halides at temperatures u p to 180°C. (13). It does not c a r r y out the B o u v e a u l t - B l a n c reduction a n d generally does not reduce c a r b o n y l or n i t r i l e groups. H o w e v e r , w i t h benzophenone, where there is no α-hydrogen, reduction can be forced so that yields of b e n z h y d r o l are 8 3 % i n b o i l i n g x y l e n e a n d 5 6 % i n b o i l i n g toluene. T h i s lack of reduction prevents side reactions, w h i c h lower yields if metallic s o d i u m is used. A s a catalyst, s o d i u m h y d r i d e has several interesting uses. H u g e l a n d c o workers (32,33) have s h o w n that it is a n effective hydrogénation catalyst, b u t its activity is restricted to those parts of the molecule w i t h w h i c h s o d i u m is capable of c o m b i n i n g ; thus styrene is hydrogenated to pheny le thane, naphthalene to t e t r a hydronaphthalene, etc., at pressures above 200 pounds p e r square i n c h a n d t e m peratures above 300 °C. K h a r a s c h a n d coworkers (34) have shown that s o d i u m h y d r i d e is a n excellent catalyst f o r the p o l y m e r i z a t i o n of butadiene to f o r m n e a r l y transparent rubbers of excellent properties. Ester-ester exchange (4,18,42) is catalyzed b y s o d i u m h y d r i d e , p r e f e r a b l y 0.05 to 0.5% of the m i x t u r e , at temperatures of 0° to 120°C. a n d i n the absence of water, without the formation of undesired b y - p r o d u c t esters or materials h a v i n g unesterified O H groups. S u c h interchanges include the molecular rearrangement of completely e s t e r i fied esters of g l y c e r o l a n d m i x t u r e s of fatty acids, such as vegetable a n d a n i m a l oils—e.g., cottonseed o i l or t a l l o w ; the ester-ester exchange between aromatic c a r b o x y l i c a c i d esters of a m o n o h y d r i c alcohol, such as o-CeH* (COsCHsK a n d aliphatic c a r b o x y l i c a c i d esters of a p o l y h y d r i c alcohol, s u c h as t r i a c e t i n ; or b e tween m o n o h y d r i c alcohol esters of aliphatic c a r b o x y l i c acids—e.g., e t h y l stéarate — a n d fatty acid esters of p o l y h y d r i c alcohol—e.g., t r i b u t y r i n or triolein.

Condensation Reactions C l a i s e n acylation a n d carbethoxylation of ketones a n d esters to f o r m /3-diketones a n d β-keto esters have g e n e r a l l y been effected b y means of s o d i u m alkoxides, sodium, or s o d i u m amide (23,25,29). E x c e p t i n acylations w i t h h i g h l y reactive esters l i k e e t h y l oxalate or e t h y l formate, the usefulness of s o d i u m a l k o x i d e is limited, because alkoxides are not strong enough bases to produce satisfactory yields. S o d i u m amide is a m u c h stronger base, b u t it frequently attacks the c a r b o n y l group of esters to f o r m amides (39). T h e a p p l i c a b i l i t y of s o d i u m i n the selfcondensation of esters is correspondingly l i m i t e d b y the tendency for b i m o l e c u l a r r e d u c t i o n w i t h the f o r m a t i o n of acyloins. H a n s l e y (23,25,29) has s h o w n that s o d i u m h y d r i d e produces better yields than these other c o m m o n reagents i n c e r tain acylations of ketones a n d especially self-condensation of esters. S w a m e r (58) has s h o w n that s o d i u m h y d r i d e effects the self-condensation of e t h y l isovalerate, w h i c h is not condensed u n d e r forcing conditions b y s o d i u m ethoxide. I n contrast to s o d i u m amide, s o d i u m h y d r i d e does not attack the c a r b o n y l group of esters. Self-condensations of esters are r a p i d l y c a r r i e d out w i t h a n e s t e r - h y d r i d e ratio of mole for mole. T h e general procedure of heating the ester to the t e m p e r a ture listed i n T a b l e III w i t h the r a p i d addition of the s o d i u m h y d r i d e o i l d i s p e r sion gives the best results. T a b l e III summarizes the comparison.


113


S e v e r a l successful m i x e d ester condensations have been c a r r i e d out w i t h s o d i u m h y d r i d e (47). T h e major side reaction is self-condensation of the esters. T e c h n i q u e s are b e i n g w o r k e d out to m i n i m i z e t h e m w i t h s o d i u m h y d r i d e - o i l d i s persions ( T a b l e I V ) . W i t h keto-ester

condensations

the procedure of first converting the ketone

to be acylated to its sodio derivative a n d then a d d i n g the a c y l a t i n g ester, e m p l o y e d p r e v i o u s l y w i t h s o d i u m amide (1 )> has generally not been satisfactory w i t h s o d i u m h y d r i d e , as considerable self-condensation

occurs.

T h e general m e t h o d

adopted

for " m i x e d " condensations b y s o d i u m h y d r i d e consists i n slowly a d d i n g the corn-


Table III. Self-Condensation of Esters Ref.

% Yield

Reaction Time, Hours

Ester

Reagent

Reaction Temp., °C.

E t h y l acetate

N a H dispersion

78

1

88

N a O E t forced

78

8

75-76

(45)

28-38

(34, 55)

Na N a dispersion E t h y l propionate

100

3

100

83

0.75

N a H dispersion

95

NaOEt

95

16

N a O E t forced

95

10

NaOEt

95

16

N a O E t forced

95

N a H dispersion N a H dry, ground

E t h y l laurate

(46)

81

(45)

46-47 81

(40)

15-32

(54)

135

1.5

97.7

125

3.9

97

(24)

4

79

(23)

120/15 mm.

N a O E t forced

(45)

46-47

Na M e t h y l laurate

(60)

8

NaNHz

M e t h y l stéarate

N a H dispersion

145

2.0

97.0

M e t h y l oleate

N a H dispersion

145

2.0

98.5

M e t h y l caproate

N a H dispersion

120

2.0

64.0

E t h y l p h e n y l acetate

N a H dispersion

105

5.5

88.0

Table IV. Mixed Ester Condensations with Sodium Hydride Ester Acetylated

Acetylating Ester

Reaction Time, Hours

Yield

%

Ref.

Me

benzoate

M e proprionate

5

28

(47)

Me

benzoate

t e r t - B u propionate

6.5

33

(47)

Me

benzoate

Me

6

65

(59)

6

56

M . H . I.

n-butyrate

Et

benzoate

E t propionate

Et

benzoate

E t laurate

7

68

(59)

Et

benzoate

E t isovalerate

3.5

56

(59)

Me

furoate

M e propionate

6

42

(47)

E t nicotinate

E t n-butyrate

4

68

(59)

Et

E t isovalerate

2

36

(59)

oxalate

ponent to be acylated to a stirred suspension of s o d i u m h y d r i d e i n the acylating ester, i n the presence of a n inert solvent (58). T h e condensation thus proceeds c o n t i n u a l l y as the component to be acylated is converted to its sodio d e r i v a t i v e .

ο

ο

II Μ R-C-OR' + CeH C-CH 5

Γ

3

+ 2 NaH

>

Ι

ο

ο

Ί

II i! Ι ~Na + NaOR' + 2Η C H C-CHC-R J ^ +

e

2

5

S e v e r a l condensations were tested a n d the yields a n d reaction conditions f o u n d are r e p o r t e d i n T a b l e V .


ADVANCES IN CHEMISTRY SERIES

114

Table V. Keto-Ester Condensations Ester

Ketone

Reagent

E t h y l acetate

Acetophenone

N a H disp. N a H , ground NaOEt Na N a H disp. N a H , ground NaNH

E t h y l propionate

Cyclohexanone

2

%

React. Temp., °C. 33 100 135 135 33 50 33

React. Time, Hours 2 14 14 7 4 2

Yield 91 89 64 65 50 29 4

Ref.

(24) (2) (2) (59) (37)


In c a r b e t h o x y l a t i o n of ketones, s o d i u m h y d r i d e has g e n e r a l l y p r o d u c e d higher yields than s o d i u m ethoxide, or s o d i u m , a n d e v e n somewhat better t h a n s o d i u m amide (38). In c a r b e t h o x y l a t i o n of esters, s o d i u m h y d r i d e has g i v e n yields e q u a l to those w i t h s o d i u m ethoxide, b u t w i t h s o d i u m h y d r i d e the use of f o r c i n g p r o cedures w h i c h are r e q u i r e d w i t h s o d i u m ethoxide is not necessary (59).

Table VI. Carbethoxylation of Cyclohexanone with Sodium Hydride and Other Common Reagents Condensing Agent NaH N a H disp. NaOCHa NaNH 2

Re a c t i ο η Time, Temp., °C. hours _ r. t. r. t. 1.5 _

_

2

33

%

Yield 37 50 0 18

Ref. (59) (62) (38)

In the Stobbe condensation side reactions encountered b y the use of other reagents are considerable—e.g., i n the condensation of benzophenone a n d d i e t h y l succinate w i t h s o d i u m ethoxide a n d ether, a significant amount of b e n z h y d r o l is always obtained (16). T h e condensation of benzophenone w i t h d i e t h y l succinate, using s o d i u m h y d r i d e dispersions, was completed r a p i d l y a n d gave a n excellent y i e l d (95.7%) o f / 3 - c a r b e t h o x y - 7 , 7 - b i p h e n y l v i n y l acetic acid. 1

Table VII. Condensation of Benzophenone and Diethyl Succinate with Basic Catalysts Reaction Condensing Agent NaOEt

Time

S e v e r a l days N o t reported 6 days NaH 8 hours N a H disp. 1 hour A U reactants g r o u n d i n a b a l l m i l l .

Temp., °C. R o o m temp. 100 R o o m temp. R o o m temp. R o o m temp.

Solvent Et 0 None EtOH EtiîO Hexane 2

% Yield 60 90 50 97* 95.7

Ref. (56, 57) (56, 57) (56, 57) (15)

a

In the D i e c k m a n n condensation certain esters h a v i n g h y d r o g e n o n the α-carbon atom w h i c h is activated (generally b y a c a r b o n y l group) undergo i n t r a m o l e c u l a r cyclization. These reactions m a y be i l l u s t r a t e d b y the f o r m a t i o n of a - c a r b e t h o x y cyclopentanone f r o m d i e t h y l adipate. T h e cyclization procedure using s o d i u m h y d r i d e dispersions is r a p i d a n d gives comparable yields to s o d i u m . T h e h i g h temperatures a n d l o n g reaction times needed w i t h other reagents are e l i m i n a t e d , as are the r e d u c t i o n side reactions.

Table VIII. Comparison of Yields and Reaction Conditions in Intramolecular Cyclization of Ethyl Adipate Condensing Agent Sodium S o d i u m amide N a H disp.

Reaction Time, Temp., hours °C. 7 110 6 1.5 40

% Yield 74-76 70-80 65-80

Ref. (44) (22)

T h e self-condensation of benzaldehyde is a case w h e r e o n l y a s m a l l amount of s o d i u m h y d r i d e results i n a h i g h y i e l d of b e n z y l benzoate. P r o b a b l y a s m a l l amount of the aldehyde is r e d u c e d to s o d i u m benzylate, w h i c h then catalyzes the reaction to the ester (58).


BANUS AND HINCKLEY—SODIUM HYDRIDE

115

Table IX. Self-Condensation of Benzaldehyde Condensing A g e n t N a H (ball-milled) M g [ A l (OEt) ] A l (OEt)s N a H - o i l disp. 4

% Yield 92 57 None 92

2

Ref. (58)

Alkylation Reactions T h e p r e p a r a t i o n of Ν,Ν-disubstituted amides f r o m the N-substituted amide has b e e n evaluated b y F o n e s (20), using g r a n u l a r s o d i u m h y d r i d e , w i t h excellent results. A c o m p a r i s o n was m a d e w i t h s o d i u m h y d r i d e - o i l dispersions w h i c h r e sulted i n a m u c h faster reaction rate at l o w temperature w i t h excellent yields.


Table X. Preparation of 2V-Alkyl Acetanilides with Sodium Hydride

a

R e a c t i o n Time, Temp., hours °C. 10 135 30 135 2 42 4 r. t.

Condensing Agent A l k y l Halide N a H ground M e iodide N a H ground B u bromide N a H disp. M e iodide N a H disp. E t bromide D i m e t h y l ether or diethylene glycol.

Solvent Xylene Xylene Toluene Diglyme

% Yield 89 79 100 70

a

Ref. (20) (20)

In the case of disecondary amines, of the procedures p r e v i o u s l y a p p l i e d to the synthesis of i\r,i\T'-diphenyl-a,œ-diaminoalkanes, the most w i d e l y used m e t h o d has been the reaction of aniline w i t h an α,ω-dihaloalkane i n the presence of a n a l k a l i m e t a l carbonate (57) or a large excess of aniline (10,11,34,36,51). However, this procedure f r e q u e n t l y yields heterocyclic compounds as the p r i n c i p a l products (8, 9,12). T h e use of the s o d i u m d e r i v a t i o n of acetanilide as a n intermediate was s u c cessfully reported b y B i l l m a n a n d C a s w e l l (5) a n d b y F o n e s (20). B o t h used s o d i u m h y d r i d e , as it reacts m o r e r a p i d l y t h a n s o d i u m a n d does not react w i t h halides. A repeat of B i l l m a n ' s procedure using s o d i u m h y d r i d e dispersions w i t h a c e tanilide a n d d i b r o m o b u t a n e gave a 2 0 % better y i e l d (98%) of i ^ N ' - d i a c e t y l - i ^ N ' biphenyl-a,œ-diaminobutane i n slightly less time. T h e acetylated compounds, unless the alkane is methane, are easily h y d r o l y z e d to the amine. T h e a l k y l a t i o n of amines was f o u n d to be dependent o n the p o l a r i t y of the solvent, rather t h a n the temperature of the reaction. T h u s it was possible to i m p r o v e o n f o r m e r methods w h i c h r e q u i r e h i g h pressures a n d / o r h i g h temperatures a n d give poor y i e l d s of monoamines. S o d i u m h y d r i d e - o i l dispersions react q u a n titatively w i t h aromatic amines such as aniline a n d p - a n i s i d i n e to f o r m the m o n o s o d i u m d e r i v a t i v e i n p o l a r solvents. T h e sodio salt m a y t h e n be a l k y l a t e d w i t h a h a l o a l k a n e . W h e n the monosubstituted amine has been f o r m e d , the second h y d r o gen is r e p l a c e d b y s o d i u m h y d r i d e a n d c a n t h e n be a l k y l a t e d i n the same m a n n e r but at a m u c h slower rate. These reactions m a y be c a r r i e d out stepwise. p-CHaOCeHJSTH* + N a H > [p-CH 0-C H NH]-Na + H [p-CH 0-C H NH]-Na + R X > p-CH.OC«ILNHR + N a X p-CH 0-C H NHR + NaH > [p-CH 0-C H NR]-Na + H [p-CH OCeHJSrR]-Na + R X > p-CH OC H NR + NaX 3

3

6

3

e

e

4

3

+

3

+

4

2

+

4

3

6

4

6

4

+

2

2

T h e reaction is l i m i t e d b y steric effects, however, i n that the completely s u b stituted amine cannot be f o r m e d b y b u l k y halides. T h e m e t h o d should be a p p l i c able to f o r m a t i o n of u n s y m m e t r i c a l amines as N - e t h y l - i V - m e t h y l a n i l i n e , b y r e p l a c i n g aniline w i t h e t h y l b r o m i d e , then m e t h y l b r o m i d e . Results are listed i n Table X I .

Table XI. Alkyation of p-Anisidine with Alkyl Halides Using Sodium Hydride-Oil Dispersion Reaction Temp., °C. 135 6 180 5.5 R o o m temp. E t Iodide 3 80b A l l H evolved i n 2 to 3 minutes. E t B r present w h e n E t iodide added after 80% of theoretical H e v o l v e d . Halide Et bromide

Time, hours

a

a b

% Yield Solvent Xylene Bayol Diglyme Diglyme N a H added.

Mono59-64 0 81


Di10 80

116

A D V A N C E S IN CHEMISTRY SERIES The

(63)

a l k y l a t i o n of 8 - q u i n o l i n o l w i t h b e n z y l c h l o r i d e as r e p o r t e d b y W h e a t l e y

u s i n g d r y s o d i u m h y d r i d e to f o r m 7 - b e n z y l - 8 - q u i n o l i n o l

(58%

y i e l d ) was r e

peated u s i n g a d i s p e r s i o n of s o d i u m h y d r i d e i n B a y o l d i l u t e d w i t h toluene. t i o n conditions w e r e a p p r o x i m a t e l y the same, but a 70%

Reac

y i e l d was o b t a i n e d u s i n g

the d i s p e r s i o n .

Advantages of Dispersions The

advantages of

s o d i u m h y d r i d e - o i l dispersions

increased reaction rate; lower reaction temperature;

for

these recations

increased yields;

are:

decreased

side reactions; a n d substitution of s o d i u m h y d r i d e for m o r e e x p e n s i v e reagents.


Literature Cited (1) A d a m s , J. T . , Hauser, C . R., J. A m . Chem. Soc. 66, 1220 (1944). (2) A d k i n s , H . , K u t z , W . , Coffman D . D . , Ibid., 52, 3220 (1930). (3) Banus, M. D . , M c S h a r r y , J. J., S u l l i v a n , Ε. Α . , Ibid., 77, 2007 (1955). (4) B i l l i c a , H. R., U. S. Patent 2,662,093 (1953). (5) B i l l m a n , J. H., Caswell, L. R., J. Org. Chem. 16, 1041 (1951). (6) B i l l y , M . , Ann. chim. 16, 5 (1921). (7) B i l l y , M . , Compt. rend. 158, 578 (1914). (8) Bischoff, C., Ber. 22, 1777 (1899). (9) B r a u n , S. V. v o n . , Ibid., 37, 3210 (1904). (10) Ibid., 42, 4541 (1909). (11) Ibid., 43, 2859 (1910). (12) C r a i g , L. C., H u x o n , R. M., J. Am. Chem. Soc. 52, 804 (1930). (13) C r i s t o l , S. J., Ragsdale, J. W . , M e e k , J. S., Ibid., 71, 1863 (1944). (14) D a u b , G . H., J o h n s o n , W . S., Ibid., 70, 418 (1948). (15) Ibid., 72, 501 (1950). (16) D a u b , G . H., J o h n s o n , W . S., " O r g a n i c R e a c t i o n s , " V o l . V I , W i l e y , N e w Y o r k , 1951. (17) D o w n i n g , Ε. B . , Patterson, C. J. (to Ε. I. d u Pont de N e m o u r s & C o . ) , U . S. Patent 2,373,021 ( A p r i l 3, 1945). (18) E c k e y , E. W . , Ibid., 2,558,547 (1951). (19) F i n h o l t , A. Office of N a v a l Research, Project N R 356,228, Contract N o . Nonr-664 (00), T e c h . Rept. II ( M a r c h 1, 1954). (20) Fones, W . S., J. Org. Chem. 14, 1099 (1949). (21) H a g e n , H . , Sieverts, Α . , Ζ. anorg. allgem. Chem. 185, 254 (1929). (22) H a l l e r , Α . , C o r n u b e r t , R., Bull. soc. chim. (4) 39, 1626 (1926). (23) H a n s l e y , V . L., I n d . Eng. Chem. 43, 1760 (1951). (24) Hansley, V. L., U. S. Patent 2,158,071 (1939). (25) Ibid., 2,218,026 (1940). (26) Ibid., 2,267,733 (1941). (27) Ibid., 2,372,670 (1945). (28) Ibid., 2,372,671 (1945). (29) H a n s l e y , V . L., Carlisle, P . M . , Chem. Eng. News 23, 1332 (1941). (30) Hanssen, Α . , Ber. 20, 781 (1877). (31) H e r o l d , Α . , Compt. rend. 228, 686 (1949). (32) H u g e l , G . , Friess, J., Bull. soc. chim. 49, 1042 (1931). (33) H u g e l , G., G i d a l y , Ibid., 51, 639 (1932). (34) Inglis J. Κ . H . , Roberts, K . C . , Org. Syntheses, C o l l . V o l . 1, 235 (1932). (35) K h a r a s c h , M . , private c o m m u n i c a t i o n . (36) L e r m o n o t o w , Ber. 7, 1255 (1874). (37) L e v i n e , R., C o n r o y , J. Α . , A d a m s , J. T., J. Am. Chem. Soc. 67, 1511 (1945). (38) L e v i n e , R., Hauser, C . R., Ibid., 66, 1768 (1944). (39) L e v i n e , R., K i b l e r , R. F., Hauser, C . R., Ibid., 68, 26 (1946). (40) M c E l v a i n , S. M., Ibid., 51, 3124 (1929). (41) Muckenfuss, A . M., U. S. Patent 1,958,012 (1934). (42) Nelson, D . , M a t t i l , K. F., Ibid., 2,625,487 (1952). (43) N i c h o l s o n , D . G., Ibid., 2,457,917 (1949). (44) P i n k n e y , P . S., Org. Syntheses, C o l l . V o l . 2, 160 (1937). (45) Roberts, D . C., M c E l v a i n , S. M., J. Am. Chem. Soc. 59, 2007 (1937). (46) Rossini, F . D . , W a g m a n , D . D . , E v a n s , W . H., L e v i n , E., Jaffe, B . , N a t l . B u r . Standards, C i r c . 500 (1950). (47) Royals, E. E., T u r p i n , D . G., J. Am. Chem. Soc. 76, 5452 (1954). (48) Schlesinger, H. I., B r o w n , H. C. Ibid., 75, 192 (1953). (49) Ibid., p. 195. (50) Ibid., p . 205. (51) Schouten, Α . , Rec. trav. chim. 56, 541 (1935). (52) Senier, Α . , G o o d w i n , B., J. Chem. Soc. 81, 280 (1902).



Snalley, O . , Brit. Patent 666,095 (1952). S n e l l , J. M., M c E l v a i n , S. M., J. Am. Chem. Soc. 53, 750 (1931). Ibid., p . 2310. Stobbe, H. Ann. 82, 280 (1894). Ibid., 89 (1899). Swamer, F . W . , Hauser, C . R., J. Am. Chem. Soc. 68, 2647 (1946). Ibid., 72, 1352 (1950). T i t h e r l y , A. W . , Ibid., 81, 1520 (1902). V i n i n g , W . H., U. S. P a t e n t 2,474,021 (1949). W a l l i n g f o r d , V . H., H o m e y e r , A . H., Jones, D . M., J. Am. Chem. Soc. 63, 2252 (1941). Wheatley, W . B., C h e n e y , L. C . , B i n k l e y , S. B., Ibid., 71, 3795 (1949). W i t t i g , G e o r g , K e r c h e r , G e o r g , R i i c h e r t , A l f r e d , Raff, P a u l , Ann. 563, 110 (1949).


(53) (54) (55) (56) (57) (58) (59) (60) (61) (62) (63) (64)

117


HANDLING AND USES OF THE ALKALI METALS

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