Uses
and
Economic
Preparation
of Organic Arsenic Compounds
ROLAND M. KARY
1
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Central Research Laboratories, American Smelting and Refining Co., South Plainfield, N. J.
O r g a n o a r s e n i c compounds, generally known as b a c t e r i c i d e s f o r strictly m e d i c i n a l p u r p o s e s , a p p e a r i n c r e a s i n g l y useful i n a g r i c u l t u r a l a s w e l l a s i n i n d u s t r i a l pest c o n t r o l . The similarity in subatomic elec tronic configurations with nitrogen, phosphorus, a n d particularly with c a r b o n (greater electropositivity d u e to g r e a t e r d i s t a n c e f r o m nucleus) a p p e a r s to a c c o u n t f o r the v a r i e t y o f p o s s i b l e m o l e c u l a r s t r u c tures o f t h e a r s e n i c a l f u n c t i o n a l g r o u p s , s o m e o f which exhibit pesticidal properties. The simplicity and f a v o r a b l e e c o n o m y o f t h e p r o c e d u r e s t o p r e pare known a n d novel pesticidal compounds m a y b e e x p l a i n e d b y : the g r e a t v a r i e t y o f a r s e n i c a l f u n c t i o n a l g r o u p s , such a s a r s o n i c a n d a r s i n i c a c i d s , arsine oxides, h a l i d e s , cycloarsines, etc., a n d their interchangeability; noninterference with carbon functionalities in the same molecule; a n d inde p e n d e n t substitution o n b o t h a r s e n i c a l a n d c a r bon functional groups. Novel compounds were synthesized, including arsenomethane, arsenic-1,2disulfide, a n d derivatives, found to be potential agricultural pesticides. The arsonosiloxanes contrib ute m o l d - c o n t r o l l i n g properties to the industrial a p p l i c a t i o n s of the r e g u l a r silicones. Formation of organic nitrogen-base arsenites w a s investigated and r e s u l t e d in t h e d e t e r m i n a t i o n of t h e b a s i c c o n stant (Kb = n X 10 or greater) as the controlling f a c t o r , i r r e s p e c t i v e of the structure of t h e o r g a n i c part. -8
^ ) f a l l t h e k n o w n o r g a n o m e t a l l i c s , t h e t h o u s a n d s of o r g a n i c a r s e n i c a l s h a v e r e t a i n e d a n i m p r e s s i v e l e a d i n n u m b e r a n d i n v a r i e t y . T h e c o n s i d e r a b l e efforts i n r e s e a r c h a n d d e v e l o p m e n t of these c o m p o u n d s h a v e p r o d u c e d n u m e r o u s m e d i c i n a l s , a few w a r f a r e agents, a n d some pesticides. I t n o w a p p e a r s t h a t o r g a n i c arsenicals h a v e s h i f t e d f r o m the p r e d o m i n a n t l y m e d i c i n a l a p p l i c a t i o n as g e r m i c i d e s t o a g r i c u l t u r a l uses as pesticides, w i t h m o r e t h a n a s u b s t a n t i a l p r o m i s e of c a r r y i n g t h e i r p e s t i c i d a l p r o p e r t i e s i n t o the p a p e r p u l p , t e x t i l e , a n d p l a s t i c s i n d u s t r i e s . T h e i m p r o v e m e n t of 1P resent address, Research L a b o r a t o r i e s , M e t a l & T h e r m i t C o r p . , R a h w a y , N. J. 319
METAL-ORGANIC COMPOUNDS Advances in Chemistry; American Chemical Society: Washington, DC, 1959.
320
ADVANCES IN CHEMISTRY SERIES
m a t e r i a l s o f e s t a b l i s h e d u t i l i t y b y i n c o r p o r a t i o n o f t h e arsenic a t o m i n t o m o l e c u l a r s t r u c t u r e s h a s b e c o m e a definite p o s s i b i l i t y . A r s e n i c i s a v a i l a b l e as a n e x t r e m e l y e c o n o m i c a l c o m p o u n d c o m m o d i t y i n t h e f o r m of arsenic t r i o x i d e , A s 0 , also c a l l e d w h i t e a r s e n i c . I t f o r m s s o d i u m a r s e n i t e w i t h c a u s t i c soda o r s o d i u m h y d r o x i d e . T h i s i s t h e s t a r t i n g m a t e r i a l f o r t h e s y n t h e s i s o f a t y p i c a l arsenical functional group, the arsono o r arsonic a c i d group. M a n y organic a r s e n i c a l s t r u c t u r e s f o l l o w v e r y closely t h e p a t t e r n o f n i t r o g e n , p h o s p h o r u s , a n d even carbon functionalities. A s illustrated i n Table I , the similarity of t h e subatomic 2
Table I. C s 2s 2p
Functionality of Similar Electronic Structures Ν s 2s 2p3
2
2
3
P s 2s 2p6
2
2
As s 2s 2p6
2
2
2
2
2
3s*3p*3d™
3s 3p»
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2
Outer shells R—NH R =NH R =N Amines basic
R—PH R =PH R ==P Phoshines less basic
R—AsHa R =AsH R =As Arsines feebly basic or amphoteric
(H C) N gas, B.P. = 2.9°C. R IUN Ammonium very basic
(H3Q3P liquid, B.P. = 40-2°C. R =P Phosphonium very basic
(HiC) As liquid B.P. = 59-60°C. R =As Arsonium very basic
2
2
2
2
3
3
3
4
CH "CH I ^CH? 2
2
1,2,3,4-Tetrahydronaphthalene
3
+
CH ^CH
4
+
2
3
CH
2
Ν I R
S
2
*
Not known
1,2.3.4-Tetrahydroquinoline
?
2
1,2,3,4-Tetrahydroarsinoline
2
Unknown
ÇH
As I R
3
2
2
^CHz
H C H C—CH I I H C—CH
+
4
/CHa As—As
N
Unknown
|
|
As—As
?
HC 3
Br
/
N
CH
3
Dimeric polyarsenomethane oil
Cyclobutane gas
Unknown
JT\ Unknown
/Mg-8r
(f y—As X=/ Mg—Br N
Phenylmagnesium bromide Carbon, Grignard
Phenylarsine di-(magnesium bromide) Arsenic, Grignard
e l e c t r o n i c c o n f i g u r a t i o n o b v i o u s l y results i n a s o m e w h a t s i m i l a r f u n c t i o n a l i t y f o r c a r b o n , n i t r o g e n , p h o s p h o r u s , a n d arsenic. H o w e v e r , t h e g r e a t e r e l e c t r o p o s i t i v i t y of arsenic o n account of t h e greater distance of the outer valence shell f r o m t h e nucleus p o i n t s t o as y e t u n k n o w n p o s s i b i l i t i e s of o r g a n i c a r s e n i c a l s t r u c t u r e s m o r e closely related t o organic carbon t h a n t o organic phosphorus o r nitrogen. A n o t h e r i m p o r t a n t f a c t o r responsible f o r b o t h t h e v a r i e t y a n d e c o n o m y o f o r g a n i c arsenical structures is their ability t o form functional groups, illustrated i n T a b l e I I , b y syntheses, t h e s i m p l i c i t y o f w h i c h i s a l m o s t u n e q u a l e d b y t h e r e a c t i o n s o f t h e o t h e r elements o f s i m i l a r e l e c t r o n i c s t r u c t u r e s . T h u s , t h e basic s y n t h e s i s f o r a l k y l a r s o n i c a c i d i s M e y e r ' s r e a c t i o n (S). I t e s s e n t i a l l y consists o f b r i n g i n g t o g e t h e r
METAL-ORGANIC COMPOUNDS Advances in Chemistry; American Chemical Society: Washington, DC, 1959.
321
KARY-ORGANIC ARSENIC COMPOUNDS Table II.
Synthesis of Typical Arsenical Functional Groups Functional Group
0
II
R-As-0~H
+
1
0~H
+
R arsonic acid Example of Reaction If R is alkyl
Meyer's Reaction
0"Να
0"'Na\ I >C1 " ~ ^O Na 0"Na
+
H C-C1
+
3
:
:As~0~Na 0~Na
>-
+
H 3 C
A s
+
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Methylchloride
:
+
H
3
C
" ~
A
s
_
r
N
a
+
+
N
a
C
1
+
Theor. intermediate
Disodium methylarsonate
Sodium chloride
Bart's Reaction:
0"Να I + :As—0"Na
. /
