metal-organic compounds - ACS Publications

Chemical Reactions of Tetraethyllead

R. L. MILDE Ethyl Corp., Baton Rouge, La. Η. A. BEATTY

Downloaded by UNIV OF MICHIGAN ANN ARBOR on February 18, 2015 | http://pubs.acs.org Publication Date: January 1, 1959 | doi: 10.1021/ba-1959-0023.ch029

Ethyl Corp., Detroit, Mich.

This report gives a compilation of the periodical and patent literature on the known chemical reactions of tetraethyllead (TEL). These are by no means con fined to antioxidant and antiknock effects. Of par ticular interest are those reactions wherein ethyl radicals, liberated from TEL by photolysis or pyrolysis, induce the polymerization, chlorination, or oxidation of other compounds. Many different diethyl- and triethyllead salts are readily obtained from the parent compound. TEL is used to prepare other organome tallic compounds, and its reaction with heavy metal chlorides produces Ziegler-type catalysts for the polymerization of olefins. In view of its ready avail ability, these relatively unexplored end uses for TEL constitute an area of considerable research potential.

Tetraethyllead—commonly abbreviated to TEL—is the outstanding example of the simple or R M type of organometallic compound of moderate chemical reactivity. It has been known for over 100 years, as it was one of the first of these compounds to be isolated, and it is now unique in industrial importance. As a consequence, the reac tions of T E L have been widely investigated. However, there still remain many oppor tunities for worthwhile research in this field. The chemistry of organolead compounds in general has often been reviewed (58, 113, 120), notably by Calingaert (17), Krause (82), and most recently Gilman (45, 83) and their coworkers: men who have contributed much of the important ex perimental work on the subject. Reviews in particular have been made by German and Russian workers (81, 131), but these are not readily accessible and are now out of date. Considering the variety of chemical reactions into which T E L can enter, and its ready availability at a relatively low cost, there may well be good use for the follow ing compilation of the available information on these reactions. n

Photolysis T E L is readily dissociated by light. The vapor shows continuous absorption in the ultraviolet with the formation of metallic lead and ethyl radicals, the latter being detected by the Paneth method (33, 103, 124) · Maximum absorption occurs at about 306

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

MILDE—CHEMICAL REACTIONS OF TETRAETHYLLEAD

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A2000, b u t t h e l i m i t f o r e i t h e r t h e v a p o r o r l i q u i d s o l u t i o n s i s a r o u n d Λ3500 (85) a n d p u r e T E L i s s l i g h t l y s e n s i t i v e e v e n t o diffuse d a y l i g h t . I n t h e l i q u i d phase, t h e d i s s o c i a t i o n l i k e w i s e m a y y i e l d m e t a l l i c l e a d , b u t as a r u l e t h e presence o f d i s s o l v e d a i r o r c a r b o n d i o x i d e a n d w a t e r causes t h e a p p e a r a n c e o f a w h i t e haze a n d subsequent p r e c i p i t a t i o n o f u n i d e n t i f i e d p r o d u c t s (85). T h e q u a n t u m y i e l d i n t h e p h o t o l y s i s o f t h e v a p o r o r o f d i l u t e s o l u t i o n s is e v i d e n t l y a b o u t u n i t y o r less (85) ; f o r p u r e l i q u i d T E L , i t h a s n o t b e e n m e a s u r e d . A s w o u l d be e x p e c t e d , t h e d i s s o c i a t i o n i n s o l u t i o n s is g r e a t l y r e d u c e d b y s c r e e n i n g agents s u c h as d y e s (108).

Pyrolysis T E L is v e r y stable a t r o o m temperature, b u t o n heating i t undergoes a n exothermic dissociation, g i v i n g a complex of reaction products. L i q u i d T E L dissociates a t a r a t e r e p o r t e d t o b e a b o u t 2 % p e r h o u r a t 1 0 0 ° C . (18), w h i l e a t 2 0 0 ° C . t h e d i s s o c i a t i o n i s c o m p l e t e i n p e r h a p s a m i n u t e . T h i s i s e v i d e n t l y a c h a i n r e a c t i o n , since i t c a n b e s u p p r e s s e d f o r a l o n g p e r i o d o f t i m e — e . g . , f o r o v e r 10 h o u r s a t 1 3 0 ° C . — b y t h e a d d i t i o n o f as l i t t l e as 0 . 0 1 % o f a n effective s t a b i l i z e r s u c h as s t y r e n e o r n a p h t h a l e n e (18) o r b y d i l u t i o n w i t h a n i n e r t s o l v e n t . T h e r e a c t i o n l i b e r a t e s gases a n d i s h i g h l y e x o t h e r m i c , a n d t h e h e a t o f r e a c t i o n increases m a r k e d l y w i t h temperature. T h u s i n h a n d l i n g b u l k quantities precaution has t o be t a k e n t o a v o i d l o c a l o v e r h e a t i n g w i t h r e s u l t i n g d e v e l o p m e n t o f v e r y r a p i d d e c o m p o s i t i o n (18). T h e reaction products, i n a d d i t i o n t o metallic lead, are p r i n c i p a l l y ethane a n d ethylene t o g e t h e r w i t h some b u t a n e a n d butylène a n d m i n o r a m o u n t s o f h i g h e r paraffins a n d olefins (94). T h e p r o p o r t i o n o f these h e a v i e r h y d r o c a r b o n p r o d u c t s w i l l increase w i t h t h e t e m p e r a t u r e a t w h i c h t h e d i s s o c i a t i o n o c c u r s , t h e r e b y i n c r e a s i n g t h e heat o f t h e reaction. N o d e t a i l e d s t u d y o f t h e r e a c t i o n m e c h a n i s m h a s been m a d e , b u t i t i s e v i d e n t l y complex. T h e i n i t i a l process i s p r e s u m a b l y t h e f o r m a t i o n o f a n e t h y l r a d i c a l a n d a triethyllead radical. R e a c t i o n of the e t h y l radical w i t h T E L could y i e l d the observed e t h a n e , e t h y l e n e , a n d b u t a n e , t o g e t h e r w i t h t r i e t h y l l e a d . H o w e v e r , i t i s n o t clear h o w this l a t t e r r a d i c a l continues t h e c h a i n : T h e f o r m a t i o n a n d subsequent reaction of h e x a e t h y l d i l e a d w o u l d n o t b e e x p e c t e d t o y i e l d free e t h y l (88). I t m a y b e t h a t t h e t r i e t h y l l e a d q u i c k l y dissociates t o d i e t h y l l e a d , r e g e n e r a t i n g t h e e t h y l r a d i c a l . T E L v a p o r is f a r m o r e stable t h a n t h e l i q u i d , a n d i t s d i s s o c i a t i o n h a s been i n v e s t i g a t e d i n some d e t a i l . P a n e t h (99), a n d l a t e r P e a r s o n (100), a n d t h e i r c o w o r k e r s showed that m i r r o r s of zinc, c a d m i u m , arsenic, a n t i m o n y , a n d lead are removed b y the e t h y l radicals formed o n pyrolysis of dilute T E L v a p o r i n hydrogen. A t temperatures f r o m 245° t o 2 7 5 ° C . a n d pressures o f 13 t o 52 m m . , L e e r m a k e r s (84) f o u n d t h a t t h e d i s s o c i a t i o n o f t h e v a p o r i s n e a r l y h o m o g e n e o u s a n d first-order, w i t h a v e l o c i t y c o n s t a n t o f k - 1.2 X 1 0 e °/ s e c . - ; t h e r a t e i s n o t affected b y t h e presence o f azomethane o r hydrogen. U s i n g t h e flow m e t h o d , a t 5 0 0 ° C . a n d 0 . 5 - m m . p r e s s u r e M e i n e r t (94) o b t a i n e d c o m p l e t e d i s s o c i a t i o n i n a f e w t e n t h s o f a second, w h i c h is a b o u t w h a t w o u l d b e e x p e c t e d , b u t a t a t m o s p h e r i c p r e s s u r e a n d t e m p e r a t u r e s f r o m 300° t o 4 7 5 ° C . h i s d a t a i n d i c a t e rates c o n s i d e r a b l y l o w e r t h a n p r e d i c t e d b y t h e a b o v e r e l a t i o n . T h e r e a c t i o n p r o d u c t s o f t h e v a p o r phase d i s s o c i a t i o n a r e d i s t i n c t l y different f r o m those o b t a i n e d i n t h e l i q u i d p h a s e . H y d r o g e n a p p e a r s i n q u a n t i t y a n d t h e a m o u n t o f b u t a n e is m u c h g r e a t e r (44, 94, 99). U s i n g b o t h s t a t i c a n d flow m e t h o d s o v e r a w i d e r a n g e o f c o n d i t i o n s , M e i n e r t (94) c o n c l u d e d t h a t t h e p r o d u c t s r e s u l t l a r g e l y f r o m r e a c t i o n s o f e t h y l r a d i c a l s a t t h e w a l l s , e i t h e r w i t h T E L t o f o r m ethane o r w i t h one a n o t h e r t o f o r m b u t a n e o r e t h y l e n e a n d h y d r o g e n ; t h e gas p h a s e r e a c t i o n o f t w o e t h y l r a d i c a l s t o g i v e ethane p l u s e t h y l e n e occurs t o a lesser e x t e n t . I n n o n e o f these i n v e s t i g a t i o n s i s t h e r e a n y i n f o r m a t i o n as t o t h e h i s t o r y o f t h e l e a d a t o m p r i o r t o i t s u l t i m a t e a p p e a r a n c e as m e t a l l i c l e a d . A s m e n t i o n e d a b o v e , t h e initial p r o d u c t is p r e s u m a b l y a t r i e t h y l l e a d r a d i c a l . T h i s should b e m u c h more stable 1 2

3 6 9 0

i 2 r

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t h a n t h e e t h y l r a d i c a l , b u t i t m a y s i m p l y dissociate f u r t h e r before i t h a s a n o p p o r t u n i t y to react o t h e r w i s e . E x p e r i m e n t s o n t h e p y r o l y s i s of m i x e d R P b c o m p o u n d s m i g h t t h r o w light on this subject. A process f o r c o a t i n g i r o n w i t h l e a d b y p y r o l y s i s of T E L i s d e s c r i b e d i n a n e a r l y p a t e n t (70). F o r t h e m o s t p a r t , h o w e v e r , t h e d i s s o c i a t i o n i s used as a source o f e t h y l radicals t o promote polymerizations o r other reactions. 4


Polymerization of Olefins and Other Compounds T h e l i b e r a t i o n o f free e t h y l a n d a l k y l l e a d r a d i c a l s i n t h e d i s s o c i a t i o n of T E L offers a t t r a c t i v e p o s s i b i l i t i e s f o r u s i n g these t o p r o m o t e o t h e r c h e m i c a l r e a c t i o n s . E v e n before P a n e t h ' s d e m o n s t r a t i o n (99) of t h e free e t h y l r a d i c a l , T a y l o r a n d J o n e s (123) s h o w e d t h a t d i s s o c i a t i o n o f T E L v a p o r a t 250° t o 3 5 0 ° C . i n d u c e s p o l y m e r i z a t i o n o f e t h y l e n e gas t o a h i g h - b o i l i n g l i q u i d . S u b s e q u e n t l y , C r a m e r (29) h e a t e d a 28 v o l u m e % s o l u t i o n of T E L i n benzene i n a n a u t o c l a v e a t a b o u t 200° t o 2 5 0 ° C a n d 70 a t m . , a n d o b t a i n e d p r i n c i p a l l y ethane a n d a l i g h t p o l y e t h y l e n e o i l ; t h e benzene w a s i n e r t , as w a s a d d e d h y d r o g e n . W h e n a n a d d i t i o n a l a m o u n t of ethylene was added a t t h e s t a r t , m o s t o f i t also p o l y m e r i z e d , e v e n t h o u g h t h e a m o u n t o f T E L w a s r e d u c e d t o o n l y 0 . 2 % . D i s s o c i a t i o n of T E L i n n a p h t h a l e n e is l i k e t h a t i n benzene, t h e r e b e i n g n o d e t e c t a b l e r e a c t i o n w i t h t h e s o l v e n t (30). T h i s is r e m a r k a b l e i n v i e w of t h e effective ness o f n a p h t h a l e n e as a s t a b i l i z e r i n t h e d e c o m p o s i t i o n a t l o w e r t e m p e r a t u r e s (18). I n t h e s i m i l a r h i g h - t e m p e r a t u r e d i s s o c i a t i o n o f T E L i n p a r a f f m i c , n a p h t h e n i c , o r olefmic s o l v e n t s , t h e e t h y l r a d i c a l s a t t a c k t h e s o l v e n t , a b s t r a c t i n g h y d r o g e n t o f o r m ethane o r a l k y l a t i n g t h e d o u b l e b o n d , a n d y i e l d i n g l i g h t c o l o r e d oils (30, 31). P r o p y l e n e i s m u c h less r e a d i l y p o l y m e r i z e d b y e t h y l r a d i c a l s f r o m T E L t h a n i s e t h y l e n e , b o t h a t 1 a t m . a n d 4 0 0 ° C (7) a n d a t 250 a t m . a n d 3 0 0 ° C . (128). Even u n d e r t h e l a t t e r c o n d i t i o n , n o m o r e t h a n 480 moles of p r o p y l e n e are p o l y m e r i z e d p e r m o l e o f T E L , a n d m u c h o f t h e p r o d u c t i s o f l o w m o l e c u l a r w e i g h t , whereas e t h y l e n e gives l a r g e l y a n o i l b o i l i n g a b o v e 2 0 0 ° C . a t 15 m m . (80). A t a t m o s p h e r i c p r e s s u r e , the yields a n d molecular weights of the polymers are v e r y l o w for b o t h ethylene a n d p r o p y l e n e (7). T h e s e a r e t h e o n l y disclosures w h i c h i n c l u d e p a t e n t c l a i m s o f T E L as a p r o m o t e r f o r t h e p o l y m e r i z a t i o n o f e t h y l e n e , a l t h o u g h t h e r e a r e a n u m b e r of p a t e n t s w h i c h l i s t T E L a l o n g w i t h o t h e r k n o w n c o m p o u n d s f o r t h i s use. E x a m p l e s r e f e r t o e t h y l e n e alone (109) o r i n s o l u t i o n (111) o r i n t e l o m e r i z a t i o n r e a c t i o n s (110, 115). T E L i s s p e c i f i c a l l y c l a i m e d , h o w e v e r , as one o f t h e p r o m o t e r s f o r t h e t e l o m e r i z a t i o n of e t h y l e n e w i t h h y d r o g e n c h l o r i d e : A t 50° t o 1 5 0 ° C . a n d 400 t o 1000 a t m . t h i s r e a c t i o n y i e l d s a m i x t u r e of a l k y l c h l o r i d e s o f w h i c h a l a r g e p a r t i s grease a n d w a x o f m o l e c u l a r w e i g h t a b o u t 400 (60). T h e r e a r e fewer p a t e n t references t o t h e use of T E L f o r t h e p o l y m e r i z a t i o n of h e a v i e r olefins s u c h as, f o r e x a m p l e , b u t a d i e n e a n d b u t a d i e n e - s t y r e n e m i x t u r e s (39). A n o t h e r r e a c t i o n of t h e e t h y l r a d i c a l f r o m T E L i s t h e a b s t r a c t i o n o f h y d r o g e n f r o m a n a r y l a l k a n e o r f r o m t r i p t a n e t o f o r m ethane, after w h i c h the resulting radical d i m e r i z e s — f o r e x a m p l e , toluene gives b i b e n z y l (125). T h i s i s effected a t 2 5 0 ° C , o r in sunlight at room temperature. R e l a t i v e l y l i t t l e has been a c c o m p l i s h e d i n t h e T E L - p r o m o t e d p o l y m e r i z a t i o n of c o m p o u n d s o t h e r t h a n olefins, a l t h o u g h a n e a r l y (1930) p a t e n t (136) specifies a n d c l a i m s T E L f o r use w i t h v i n y l c h l o r i d e a n d v i n y l acetate. I t is noteworthy that the t e m p e r a t u r e specified i n t h i s case i s o n l y 8 0 ° o r 100° C . 3 - C h l o r o - 2 - m e t h y l p r o p e n e i n s o l u t i o n w i t h T E L is d i m e r i z e d w h e n t h e T E L is d i s s o c i a t e d b y exposure t o l i g h t (133). O n e g r o u p o f p a t e n t s (105, 132) describes t h e p r o d u c t i o n o f v i n y l i d e n e c h l o r i d e p o l y m e r s o r c o p o l y m e r s b y t h e use o f T E L i n c o n j u n c t i o n w i t h b e n z o y l p e r o x i d e a n d a polychloro compound and copper. T E L h a s b e e n p r o p o s e d as a n i n i t i a t o r f o r t h e p o l y m e r i z a t i o n o f d e h y d r o g e n a t e d




309

r o s i n d e r i v a t i v e s , i n c l u d i n g a c i d s , esters, a l c o h o l s , a n d r o s i n o i l (10). P o l y m e r i z a t i o n is effected o v e r the t e m p e r a t u r e range o f 200° t o 2 5 0 ° C . R u b b e r c o m p o u n d s h a v e b e e n t r e a t e d w i t h T E L f o r t h e p u r p o s e of h a r d e n i n g : R e i n f o r c i n g c o m p o u n d s a r e c l a i m e d t o be p r o d u c e d i n p l a c e b y d e c o m p o s i t i o n o f t h e T E L (127). T h e c h l o r i n a t i o n o f c e r t a i n h y d r o c a r b o n s c a t a l y z e d b y T E L has b e e n c o m p r e h e n s i v e l y s t u d i e d b y V a u g h a n a n d R u s t (129, ISO). These hydrocarbons include ethane, p r o p a n e , a n d c y c l o p e n t a n e i n t h e v a p o r phase, a n d n - p e n t a n e i n t h e l i q u i d p h a s e . A l l c h l o r i n a t i o n s were c o n d u c t e d i n t h e d a r k . S m a l l a m o u n t s of T E L (0.002 m o l e % ) i n m i x t u r e w i t h c h l o r i n e a n d ethane r e s u l t i n c o m p l e t e r e a c t i o n o f c h l o r i n e a t 1 2 0 ° C . T h e p r o d u c t o b t a i n e d consists o f 8 0 m o l e % e t h y l c h l o r i d e a n d 2 0 m o l e % h i g h e r c h l o r i d e s , t h e same d i s t r i b u t i o n as i n t h e h i g h - t e m p e r a t u r e t h e r m a l r e a c t i o n . Under the a b o v e c o n d i t i o n s , h o w e v e r , n o r e a c t i o n a t a l l o c c u r s i n t h e absence o f T E L . S i m i l a r reactions h a v e b e e n c a r r i e d o u t w i t h p r o p a n e a t 136° t o 1 4 0 ° C , c y c l o p e n t a n e a t 1 3 5 ° C , and n-pentane a t 10°C. T h e a u t h o r s assume t h a t t h e c h l o r i n a t i o n i s i n i t i a t e d b y h i g h l y r e a c t i v e species, s u c h as a n e t h y l r a d i c a l f o r m e d d u r i n g t h e r e a c t i o n o f t h e c h l o r i n e a n d T E L . T h e m e c h a n i s m w h e r e b y s u c h a r a d i c a l i s l i b e r a t e d i n t h i s process is n o t e v i d e n t . T e t r a e t h y l l e a d has b e e n p a t e n t e d as a free r a d i c a l i n i t i a t o r f o r t h e a d d i t i o n o f h y d r o g e n b r o m i d e , h y d r o g e n sulfide, a n d m e r c a p t a n s t o p r o p y l e n e (38), f o r m i n g t h e n o r m a l p r o p y l derivative ( c o n t r a r y t o M a r k o w n i k o f f s r u l e ) . T h e T E L i s dissociated b y the a c t i o n o f u l t r a v i o l e t l i g h t t o e t h y l r a d i c a l s w h i c h i n i t i a t e t h e a b n o r m a l a d d i t i o n of t e m p e r a t u r e s n o t i n excess o f 2 5 ° C . W h e n T E L is added t o cupric nitrate i n a n alcoholic solution containing styrene, m e t h y l methacrylate, o r aerylonitrile, there is r a p i d p o l y m e r i z a t i o n of the unsaturated c o m p o u n d a t r o o m t e m p e r a t u r e (6). W i t h s i l v e r n i t r a t e i n p l a c e o f t h e c o p p e r s a l t , t h i s does n o t o c c u r . I t a p p e a r s , t h e r e f o r e , t h a t t h i s p o l y m e r i z a t i o n is n o t a free r a d i c a l process, b u t t h a t the i n i t i a t i o n i s p r o b a b l y d e t e r m i n e d b y a r e d o x s y s t e m i n v o l v i n g copper ions. A recent p a t e n t (95) states t h a t T E L m a y b e s u b s t i t u t e d f o r a l u m i n u m , m a g n e s i u m , o r zinc a l k y l s i n p r e p a r i n g Z i e g l e r - t y p e 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 α - o l e fins. S p e c i f i c a l l y , t h e c a t a l y s t is p r e p a r e d b y r e a c t i n g T E L w i t h h a l i d e s o f t h e t r a n s i t i o n m e t a l s o f g r o u p s I V t o V I I I o f t h e p e r i o d i c t a b l e . E x a m p l e s o f these are t i t a n i u m tetrachloride and m o l y b d e n u m and v a n a d i u m pentachlorides. The polymerization re a c t i o n is c a r r i e d o u t i n a p a r a f f i n i c s o l v e n t a t a t e m p e r a t u r e o f 90° t o 1 8 0 ° C . a n d o r d i n a r y o r e l e v a t e d pressures. T h i s m e t h o d gives a c r y s t a l l i n e p o l y e t h y l e n e i n a n a m o u n t 50 t i m e s t h a t o f t h e T E L u s e d . A p a t e n t has been issued o n the use of T E L as a c o n d e n s a t i o n c a t a l y s t t o f o r m p o l y e s t e r resins, s u c h as m a y b e o b t a i n e d f r o m m e t h y l t e r e p h t h a l a t e a n d g l y c o l (16). I n a n e x a m p l e , 0 . 0 3 % T E L b a s e d o n t h e w e i g h t of m e t h y l t e r e p h t h a l a t e i s u s e d . T h e r e a c t i o n r a t e i s c l a i m e d t o b e t w o t o five t i m e s t h a t g i v e n b y c o n v e n t i o n a l c a t a l y s t s . E m p h a s i s is p l a c e d o n the s t a b i l i t y o f t h e a l k y l l e a d c o m p o u n d a t t h e h i g h t e m p e r a t u r e s e m p l o y e d , a n d o n the a v o i d a n c e of w a t e r a n d free a c i d . T h e n a t u r e of t h e a c t u a l c a t a l y s t i n t h i s case is n o t a t a l l e v i d e n t , a n d f u r t h e r i n v e s t i g a t i o n a l o n g t h i s l i n e w o u l d be o f i n t e r e s t .

Reaction with Hydrogen T h e d i s s o c i a t i o n o f T E L b y h y d r o g e n t o give e t h a n e a n d m e t a l l i c l e a d has b e e n s t u d i e d u n d e r n o n c a t a l y t i c c o n d i t i o n s (71, 72) a t t e m p e r a t u r e s f r o m 100° t o 2 2 5 ° C . a n d w i t h i n i t i a l pressures o f h y d r o g e n o f some 6 0 a t m . I n benzene s o l u t i o n s , u s i n g a r e a c t i o n p e r i o d o f 24 h o u r s , 1 5 % of t h e l e a d is l i b e r a t e d a t 1 0 0 ° C , 5 0 % a t 1 7 5 ° C . , a n d 9 9 % at 2 2 5 ° C . A p p a r e n t l y , t h e c a t a l y t i c h y d r o g é n a t i o n o f T E L has n o t b e e n s t u d i e d . H o w e v e r , t h e n i c k e l - c a t a l y z e d h y d r o g é n a t i o n of t e t r a - n - h e p t y l l e a d gives a t least a 6 2 % y i e l d of the R - R product, tetradecane (137).



310


Oxidation and Antioxidant Action L i q u i d T E L oxidizes i n a i r , v e r y s l o w l y a t r o o m t e m p e r a t u r e a n d r a p i d l y a t t e m p e r a t u r e s o v e r 100° C . T h e v a p o r is m u c h m o r e r e s i s t a n t t o o x i d a t i o n t h a n t h e l i q u i d , a t a g i v e n t e m p e r a t u r e . H o w e v e r , t h e r e h a s been n o p u b l i c a t i o n o f t h e n a t u r e a n d p r o d u c t s o f t h e o x i d a t i o n , o r o f t h e effects o f c a t a l y s t s , i n h i b i t o r s , e t c . S t r o n g o x i d i z i n g agents s u c h as p o t a s s i u m p e r m a n g a n a t e , s u l f u r y l c h l o r i d e , a n d c a l c i u m h y p o c h l o r i t e effect c o m p l e t e d e c o m p o s i t i o n o f T E L a t l o w t e m p e r a t u r e . These reagents a r e t h e ones u s e d i n i n d u s t r y f o r d e c o n t a m i n a t i o n o f T E L s p i l l s a n d f o r f i n a l cleaning of equipment contaminated w i t h T E L or its partial-decomposition products. T h e t o x i c i t y o f T E L a n d o t h e r o r g a n o l e a d c o m p o u n d s a n d t h e i r insidiousness ( f o r t h e y a r e i n n o sense s e l f - w a r n i n g ) m a k e i t m a n d a t o r y t o use a d e q u a t e p r e c a u t i o n s i n h a n d l i n g . I n d e c o n t a m i n a t i o n , care m u s t b e t a k e n t o use t h e a b o v e o x i d a n t s i n sufficient excess t o a c c o m p l i s h c o m p l e t e d e c o m p o s i t i o n o f T E L , a n d i n a d e q u a t e d i l u t i o n i n a p p r o p r i a t e s o l v e n t s so as t o c o n t r o l t h e speed o f t h e r e a c t i o n , w h i c h o t h e r w i s e m a y b e violent. T E L i n a dilute solution—e.g., i n gasoline—is oxidized at l o w temperature b y nitrogen dioxide, f o r m i n g diethyllead dinitrate w h i c h is readily separated f r o m the solvent (107). A f u r t h e r e x a m p l e o f t h e o x i d i z a b i l i t y of T E L is afforded b y a p a t e n t o n m i x t u r e s of T E L a n d t e t r a n i t r o m e t h a n e a s a n e x p l o s i v e o f u n u s u a l s t r e n g t h a n d h i g h r a t e o f d e t o n a t i o n (134). O n t h e o t h e r h a n d , a n o t h e r p a t e n t states t h a t a d d i t i o n o f a s m a l l a m o u n t ( a b o u t 1%) o f T E L l o w e r s t h e b u r n i n g r a t e o f a m i x t u r e of t e t r a n i t r o m e t h a n e w i t h 10 t o 2 0 % o f benzene t o t h e p o i n t w h e r e t h i s c a n b e successfully u s e d a s a p r o p e l l a n t (61). T h e s e t w o results a r e n o t d i s c o r d a n t : I n t h e f o r m e r case, T E L serves as a f u e l h a v i n g a h i g h h e a t o f c o m b u s t i o n p e r u n i t v o l u m e ; i n t h e l a t t e r case i t e v i d e n t l y exerts i t s c h a r a c t e r i s t i c a n t i o x i d a n t a c t i o n . T h i s a n t i o x i d a n t a c t i o n o f T E L w a s a t once s u s p e c t e d w h e n i t s a n t i k n o c k effect b e c a m e k n o w n . S o o n t h e r e a f t e r , M o u r e a u a n d D u f r a i s s e (96) r e p o r t e d t h a t T E L i s a n antioxidant for benzaldehyde at room temperature, a n d numerous investigators o b s e r v e d i t s i n h i b i t o r y effect i n t h e s l o w o x i d a t i o n o f h y d r o c a r b o n s a t e l e v a t e d t e m p e r a t u r e s (92). S i n c e t h a t t i m e t h e r e h a s been a great d e a l o f w o r k c a r r i e d o u t w h i c h i n v o l v e d these a n t i k n o c k a n d a n t i o x i d a n t effects. H o w e v e r , t h e r e h a s been n o s t u d y o f t h e m e c h a n i s m a n d p r o d u c t s of t h e r e a c t i o n s w h i c h t h e T E L i t s e l f undergoes i n e x e r t i n g these effects. U n d e r c e r t a i n c i r c u m s t a n c e s , T E L m a y also a c t as a p r o m o t e r o f o x i d a t i o n r e a c t i o n s , p r e s u m a b l y b y s u p p l y i n g free r a d i c a l s . F o r e x a m p l e , i n a h y d r o c a r b o n reference f u e l , a v e r y h i g h c o n c e n t r a t i o n o f T E L ( f a r b e y o n d t h e r a n g e o f n o r m a l usage) a c t u a l l y has a p r o k n o c k effect. I n t h e l i q u i d phase o x i d a t i o n o f a l k y l b e n z e n e s c a t a l y z e d b y a m e t a l oxide o r s a l t , a d d i t i o n o f T E L is c l a i m e d t o increase t h e y i e l d o f t o l u i c acids (66).

Reaction with Halogens T h e r e a c t i o n o f T E L h a s been s t u d i e d w i t h c h l o r i n e , b r o m i n e , a n d i o d i n e . There are n o l i t e r a t u r e r e p o r t s o n t h e b e h a v i o r o f T E L w i t h e l e m e n t a l fluorine. T h e r e a c t i o n of halogens w i t h T E L i n v o l v e s cleavage o f t h e l e a d - c a r b o n b o n d , a n d t h e i n i t i a l p r o d ucts are dependent u p o n the reaction temperatures a n d amounts of halogen employed (59). W i t h chlorine, the reaction m a y be indicated b y the steps: -00°

Et Pb 4

-10°

> EtaPbCl

> E t P b C l -> E t P b C l -> P b C l + E t C l 2

2

3

2

A t — 6 0 ° C , t h e c h l o r i n a t i o n o f T E L i n e t h y l acetate gives a q u a n t i t a t i v e y i e l d o f t r i ethyllead chloride. Increasing the temperature t o — 10°C. after the initial chlorination at — 60°C. a n d continuing the chlorination give a q u a n t i t a t i v e y i e l d of diethyllead d i c h l o r i d e (59). C o n t i n u i n g t h e c h l o r i n a t i o n b e y o n d t h a t stage, b y u s i n g m o r e d r a s t i c



311

c o n d i t i o n s , does n o t a l l o w i s o l a t i o n o f a n e t h y l l e a d t r i c h l o r i d e , because i t i s u n s t a b l e and converts immediately t o lead chloride and e t h y l chloride. S i m i l a r studies h a v e b e e n r e p o r t e d f o r b r o m i n e a n d i o d i n e . B r o m i n a t i o n o f T E L i n e t h e r s o l u t i o n a t — 70° C . r e s u l t s i n a q u a n t i t a t i v e y i e l d o f t r i e t h y l l e a d b r o m i d e (59, 122). I n c o n t r a s t t o c h l o r i n a t i o n , h o w e v e r , t h e f u r t h e r b r o m i n a t i o n o f T E L gives o n l y l o w y i e l d s o f t h e d i b r o m i d e . T r i e t h y l l e a d i o d i d e has b e e n p r e p a r e d i n 7 3 % y i e l d b y t h e r e a c t i o n o f T E L w i t h i o d i n e i n e t h e r s o l u t i o n a t - 6 0 ° C . {23, 78, 86). T h e c o m p l e t e d e c o m p o s i t i o n o f T E L b y b r o m i n e a n d c h l o r i n e , as i n d i c a t e d b y t h e equations : Et Pb + 3Br - » PbBr


4

2

E t P b + 3C1 -> P b C l 4

2

2

+ 4 E t B r (28, 32, 36, 102)

2

+ 4EtCl

(114)

a n d the reaction w i t h iodine : E t P b + I - > E t s P b l + E t I (26, 36, 64) 4

2

h a v e b e e n t h e basis f o r s e v e r a l a n a l y t i c a l p r o c e d u r e s proceed quantitatively.

f o r T E L , since these

reactions

Reaction with Alkalies D i l u t e a n d c o n c e n t r a t e d aqueous a l k a l i e s d o n o t react w i t h T E L a t o r d i n a r y t e m p e r a t u r e s (17), w h i l e a t h i g h t e m p e r a t u r e a p p a r e n t l y n o s t u d y has b e e n m a d e . This i n e r t n e s s t o a l k a l i i s p r o b a b l y n o t s i m p l y due t o l i m i t e d s o l u b i l i t y , f o r i t i s b e l i e v e d t h a t a l c o h o l i c p o t a s h i s also u n r e a c t i v e . M o r e o v e r , T E L i s i n e r t t o p h e n y l l i t h i u m i n e t h e r s o l u t i o n a t r o o m t e m p e r a t u r e , i n c o n t r a s t t o t h e m o d e r a t e l y r a p i d exchange b e t w e e n t e t r a p h e n y l l e a d a n d e t h y l l i t h i u m u n d e r t h e same c o n d i t i o n s (51).

Reaction with Inorganic Acids S t u d i e s o f t h e r e a c t i o n o f T E L w i t h h a l o g e n acids h a v e b e e n r e p o r t e d f o r h y d r o g e n c h l o r i d e a n d h y d r o g e n b r o m i d e . T h e g e n e r a l e q u a t i o n f o r the r e a c t i o n i s : Et Pb + H X ° 4

S

l v e n t

) Et PbX + C H 3

2

6

H y d r o g e n c h l o r i d e reacts w i t h T E L a t r o o m t e m p e r a t u r e t o g i v e g o o d y i e l d s o f t r i e t h y l l e a d c h l o r i d e (12, 13, 15, 23, 53, 101, 135). A v a r i e t y o f s o l v e n t s a n d gaseous o r c o n c e n t r a t e d h y d r o g e n c h l o r i d e m a y b e u s e d . U s e o f t h e gas a n d a hexane s o l v e n t a p p e a r s t o b e best o n t h e basis o f b o t h y i e l d (86 t o 9 7 % ) a n d p u r i t y o f p r o d u c t (23). U n d e r m o r e d r a s t i c c o n d i t i o n s , the r e a c t i o n m a y p r o c e e d b e y o n d t h e t r i e t h y l l e a d stage. T h u s , i n one s t u d y r e p o r t e d u s i n g t o l u e n e as a s o l v e n t a n d a t e m p e r a t u r e o f 9 0 ° C , a m i x t u r e was o b t a i n e d c o n t a i n i n g 5 0 % l e a d c h l o r i d e , 3 0 % t r i e t h y l l e a d c h l o r i d e , a n d 2 0 % d i e t h y l l e a d d i c h l o r i d e (135). U n d e r even more rigorous conditions, lead chloride is t h e final p r o d u c t o f t h e t r e a t m e n t w i t h e i t h e r h y d r o g e n c h l o r i d e gas o r c o n c e n t r a t e d h y d r o c h l o r i c a c i d (24, 40, 42, 121). T h e reaction of T E L w i t h h y d r o g e n bromide proceeds i n a similar m a n n e r . Using t h e gas w i t h p e t r o l e u m e t h e r as a s o l v e n t , a y i e l d o f 8 4 % o f t r i e t h y l l e a d b r o m i d e h a s b e e n r e p o r t e d (49)- T h e h a l o g e n a c i d m a y c o n v e n i e n t l y b e p r o v i d e d i n t h e f o r m o f a n a d d i t i o n p r o d u c t w i t h a t r i a l k y l a m i n e , R H N B r - 2 H B r (76). T h e r e a p p e a r s t o be n o p u b l i s h e d i n f o r m a t i o n o n t h e r e a c t i o n o f T E L w i t h h y d r o gen i o d i d e o r fluoride. T h e d i - a n d t r i e t h y l l e a d h a l i d e s c o n v e n i e n t l y serve a s i n t e r m e d i a t e s f o r t h e p r e p a r a t i o n o f o t h e r d i - a n d t r i e t h y l l e a d salts b y a m e t a t h e s i s (23, 45, 83). D i l u t e n i t r i c a n d sulfuric acids react w i t h T E L only v e r y slowly, i f a t a l l , a t r o o m t e m p e r a t u r e (17). H o w e v e r , o n h e a t i n g T E L w i t h t h e d i l u t e a c i d s o r o n c o n t a c t o f i t w i t h c o n c e n t r a t e d a c i d s a t o r d i n a r y t e m p e r a t u r e s , a n a t t a c k does t a k e p l a c e . Thus, 3



312


h e a t i n g T E L w i t h 5 0 % s u l f u r i c a c i d leads t o t h e f o r m a t i o n o f t r i e t h y l l e a d s u l f a t e a n d e t h a n e (17). C o n c e n t r a t e d n i t r i c a c i d h a s b e e n r e p o r t e d t o d e c o m p o s e T E L c o m p l e t e l y t o l e a d n i t r a t e (17, 74) ; t h i s c a n b e a v i o l e n t r e a c t i o n . I t h a s also b e e n r e p o r t e d t h a t T E L i n c h l o r o f o r m s o l u t i o n reacts w i t h c o n c e n t r a t e d n i t r i c a c i d w i t h t h e f o r m a t i o n of d i e t h y l l e a d d i n i t r a t e a n d a s m a l l a m o u n t of t r i e t h y l l e a d n i t r a t e (68). W h e n a v a p o r m i x t u r e of T E L a n d nitric acid is diluted w i t h carbon dioxide a n d passed t h r o u g h a h e a t e d glass t u b e a t 1 5 0 ° C , t h e r e i s a c o m p l e t e c o n v e r s i o n o f t h e e t h y l r a d i c a l s t o n i t r o m e t h a n e a n d e t h y l n i t r a t e (87). T E L has also been r e p o r t e d t o react w i t h c o n c e n t r a t e d p h o s p h o r i c a c i d i n t h e p r e s ence o f s i l i c a g e l t o give t r i e t h y l l e a d d i h y d r o g e n p h o s p h a t e i n a 2 6 % y i e l d (54).

Reaction with Organic Acids T h e r e a c t i o n o f T E L w i t h o r g a n i c acids h a s been s t u d i e d b o t h i n t h e presence a n d absence o f s i l i c a gel. G e n e r a l l y s p e a k i n g , r e a c t i o n is g r e a t l y p r o m o t e d b y t h e presence of a s m a l l q u a n t i t y o f s i l i c a gel, a l t h o u g h t h e r e a r e a n u m b e r of a n o m a l i e s . I n some i n s t a n c e s , n o r e a c t i o n a t a l l is o b t a i n e d e i t h e r w i t h o r w i t h o u t s i l i c a gel ; i n o t h e r cases, complete d e a l k y l a t i o n of T E L takes place. Table I summarizes the literature infor m a t i o n o n t h e subject.

Table I. Acid Acetic Acetic Benzoic Bromoacetic 0

0

0

ra-Bromobenzoic° Butyric d-Camphor- 10-sulf onic° Chloroacetic Cyanoacetie Decanoic Dibromoacetic Di chloroacetic Fluoroacetic Formic Furanacrylic Furoic Heptanoic Hexanoic Isobutyric Isovaleric Malonic, monohexyl ester Mercaptoacetic o-M ercaptoben zoic 2-Naphthalenesulfonie m-Nitrobenzoic (in ethanol) τη-Nitrobenzoic (in benzene) p-Nitrobenzoic Nonanoic Octanoic Phenylacetic 2- Phenylhy dra zi nesulf onic° Propionic 3- Quinolinecarboxylic° Salicylic Stearic p-Toluenesulf onic o-Toluenesulfonic Trichloroacetic Valeric 0

0

0

a

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

Reaction of TEL with Organic Acids Products Ethylene, ethane, ethyl acetate, lead acetate Triethyllead salt Diethyllead salt Triethyllead salt f Diethyllead salt \ Triethyllead salt Triethyllead salt Triethyllead salt Triethyllead salt No reaction Not identified Triethyllead salt Triethyllead salt Triethyllead salt Lead formate Triethyllead salt Triethyllead salt Triethyllead salt Triethyllead salt Triethyllead salt Triethyllead salt Triethyllead salt Triethyllead salt Triethyllead salt Triethyllead salt Triethyllead salt Diethyllead salt Triethyllead salt Triethyllead salt Triethyllead salt Triethyllead salt No reaction Triethyllead salt No reaction Triethyllead salt Not identified Triethyllead salt Triethyllead salt Triethyllead salt Triethyllead salt

Yield, % —

References (73)

95 — — 9.8 3.6 — 96.4 — — — — — 79.1 — — — — — — — — — — — 26 62 25 — — — — — — — — — — — —

(12, 54) (63) (12) (56) (12) (δδ) (12) (δδ) (12) (12) (12) (112) (δδ) (54) (54) (12) (3, 12) (12) (12) (δ, 106) (63) (54) (62) (δδ) (δδ) (δδ) (12) (12) (12, 04) (54) (12, 62) (δδ) (δ4, 62) (12) (δ3, 62) (62) (12, 62) (12)

° In presence of silica gel.

A c i d halides react i n a m a n n e r s i m i l a r t o t h e h a l o g e n acids, a l t h o u g h t h e r e a r e differences b e t w e e n t h e r e a c t i v i t i e s of i n d i v i d u a l m e m b e r s . A c e t y l chloride w i t h T E L i n t h e presence o f s i l i c a g e l a t r o o m t e m p e r a t u r e gives t r i e t h y l l e a d c h l o r i d e (12). B e n z o y l chloride likewise reacts; however, only lead chloride could be isolated f r o m t h e r e a c t i o n m i x t u r e (12).



313

Reaction with Phenols and Thiols A n u m b e r o f p h e n o l s a n d n a p h t h o l s h a v e been r e a c t e d w i t h T E L i n t h e presence of s i l i c a g e l t o g i v e d i - a n d t r i e t h y l l e a d d e r i v a t i v e s . Specific c o m p o u n d s w h i c h h a v e been p r e p a r e d i n t h i s m a n n e r are l i s t e d i n T a b l e I I .


Table II

Phenolic Derivatives

Compound Triethyllead phenolate Triethyllead picrate Diethylleadbis (p-nitrophenolate) Bis (triethyllead) resorcinolate BÎ3 (triethyllead) pyrocatecholate Triethyllead m-cresolate Triethyllead p-cresolate Triethyllead o-cresolate Triethyllead o-bromophenolate Triethyllead 1-naphtholate Triethyllead 2-naphtholate Triethyllead guaiacolate

Yield, % 63.5

— — — — — 90.0 31.0

—

— — —

References (27, 35) (2) (112) (27, 35) (27) (27) (27) (27) (27) (27) (27) (27)

T h e m o r e a c i d i c p h e n o l s — e . g . , 2 , 4 - d i n i t r o p h e n o l a n d p i c r i c a c i d — a r e also c a p a b l e of r e a c t i o n w i t h T E L i n t h e absence o f s i l i c a gel, a l t h o u g h t h e p r o d u c t s o b t a i n e d h a v e n o t been i d e n t i f i e d {52). T h e t h i o l s react w i t h T E L m u c h m o r e r e a d i l y t h a n alcohols a n d m o s t p h e n o l s . T h e presence o f s i l i c a g e l i s n o t r e q u i r e d i n o r d e r t o o b t a i n a r e a c t i o n . T h i o l s w h i c h h a v e been s t u d i e d a r e t h e f o l l o w i n g : 1-butane-, 1-heptane-, α-toluene-, benzene-, a n d 2 - n a p h t h a l e n e t h i o l , a n d m e r c a p t o b e n z o t h i a z o l e {52). T h e n a t u r e o f t h e p r o d u c t s o b t a i n e d has n o t y e t been p u b l i s h e d , b u t t h e y a r e p r e s u m a b l y o f t h e t y p e E t P b S R a n d Et Pb(SR) . 3

2

2

Reaction with Metal and Metalloid Salts A l u m i n u m c h l o r i d e i n t h e presence o f s o l v e n t s has been r e a c t e d w i t h T E L t o f o r m t r i e t h y l l e a d c h l o r i d e a n d l e a d c h l o r i d e {12, £8, 90). A t t h e same t i m e , v a r y i n g a m o u n t s o f a l k y l a l u m i n u m c o m p o u n d s are f o r m e d , d e p e n d i n g u p o n t h e r e l a t i v e a m o u n t s of t h e reagents {48). T h e r e a c t i o n o f e t h y l a l u m i n u m s e s q u i c h l o r i d e w i t h T E L l i k e wise results i n cleavage o f t h e c a r b o n - l e a d b o n d {48). T h e a c t i v e agent here i s p r o b ably e t h y l a l u m i n u m dichloride and not d i e t h y l a l u m i n u m chloride. A n u m b e r o f m e t a l c h l o r i d e s h a v e been s h o w n t o b e r e d u c e d b y T E L . T h u s t i t a n i u m t e t r a c h l o r i d e i s c o n v e r t e d t o a l o w e r o x i d a t i o n stage, as i n d i c a t e d b y t h e p u r p l e c o l o r of t i t a n i u m t r i c h l o r i d e {12). T h e r e a c t i o n p r o d u c t s o f T E L w i t h t i t a n i u m t r i a n d t e t r a c h l o r i d e s , t h e h i g h e r c h l o r i d e s of m o l y b d e n u m , v a n a d i u m , c h r o m i u m , a n d manganese, a n d t h e halides of the other t r a n s i t i o n metals of groups I V t o V I I I , have been p r o p o s 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 of olefins {95). T h a l l i u m t r i c h l o r i d e {57) a n d f e r r i c c h l o r i d e (48, 89) a r e s i m i l a r l y r e d u c e d b y T E L , w i t h t h e f o r m a t i o n o f thallous a n d ferrous chlorides, while t h e T E L is converted t o a m i x t u r e of ethyllead chlorides. C h l o r o p l a t i n i c acid is i m m e d i a t e l y reduced b y T E L t o metallic p l a t i n u m (48). O x i d a t i o n w i t h s t a n n i c c h l o r i d e has been p r o p o s e d as a m e a n s o f r e m o v i n g T E L f r o m d i l u t e s o l u t i o n i n gasoline (25, 43), since t h e p r o d u c t s — d i e t h y l l e a d a n d d i e t h y l t i n d i c h l o r i d e s — a r e i n s o l u b l e . N o r e a c t i o n occurs b e t w e e n T E L a n d t h e f o l l o w i n g m e t a l halides: ferrous chloride, ferrous iodide, cobaltous bromide, a n d nickelous bromide, u n d e r t h e c o n d i t i o n s e m p l o y e d f o r f e r r i c c h l o r i d e (48). H o w e v e r , f e r r o u s c h l o r i d e i n a n a c t i v e f o r m i s s a i d t o r e m o v e T E L f r o m gasoline (11). P h o s p h o r u s pentachloride a n d silicon tetrachloride react w i t h T E L t o produce t r i e t h y l l e a d c h l o r i d e (12). N o m e n t i o n is m a d e o f o t h e r p r o d u c t s f r o m these r e a c t i o n s . A r s e n i c t r i c h l o r i d e a n d t h e analogous p h o s p h o r u s a n d a n t i m o n y c o m p o u n d s h a v e been r e a c t e d w i t h T E L t o g i v e p r o d u c t s i n d i c a t e d b y t h e f o l l o w i n g e q u a t i o n s :


314

ADVANCES IN CHEMISTRY SERIES Et Pb + 3AsCl 4

E t P b + 3PC1 4

3

1 Q Q

° ') 3EtAsCl C

95-97%

> 3EtPCl

3

+ E t C l + P b C l (77)

2

2

+ E t C l + P b C l (77)

2

2

89-96%

Et Pb + 3SbCl 4

> 3EtSbCl

3

+ E t C l + P b C l (77)

2

2


71%

T h e reaction proceeds i n stages; a t 2 5 ° C . o n l y two e t h y l groups are cleaved, whereas at 100°C. the reaction proceeds t o lead chloride. R e f l u x i n g phosphorus trichloride w i t h T E L h a s also b e e n r e p o r t e d t o y i e l d d i e t h y l p h o s p h i n o u s c h l o r i d e (H). The re action of T E L w i t h 10-chloro-5,10-dihydrophenarsazine (Adamsite) is similar to t h e a b o v e r e a c t i o n s (104) ·

+

Et Pb

I

4

II "

Il

I

+

Et PbCl 3

T h e c o r r e s p o n d i n g 1 0 - f o r m y l d e r i v a t i v e reacts s i m i l a r l y w i t h T E L t o g i v e t h e 1 0 - e t h y l d e r i v a t i v e a n d l e a d f o r m a t e (104). B i s m u t h t r i c h l o r i d e also cleaves T E L , t h o u g h less a c t i v e l y t h a n does a l u m i n u m chloride. T h e products f o r m e d are t r i e t h y l l e a d chloride, lead chloride, a n d perhaps ethylbismuth compounds (48,91). A n u m b e r o f p a t e n t s a n d p u b l i c a t i o n s d e a l w i t h t h e r e a c t i o n s o f m e r c u r i c salts w i t h T E L . T h e s e a r e t h e basis f o r t h e p r e p a r a t i o n o f c e r t a i n o r g a n i c m e r c u r y f u n g i cides. I n these r e a c t i o n s , i n d i c a t e d b e l o w , t h e l e a d is c o n v e r t e d t o a n e t h y l l e a d o r i n organic salt. Et Pb + HgCl 4

EtOH 2

Na C0 2

Et Pb + Na S0 + HgCl 4

2

4

> E t H g C l (34, 67, 75, 89) 8

EtOH 2

(92%)

> (EtHg) S0 2

4

(37)

Na2COs

Et Pb + H P 0 4

3

4

+ HgO -^2>

( E t H g ) H _ P 0 (1, 67) n

3

n

4

( T h i s r e a c t i o n gives m o n o , b i s , o r t r i s e t h y l m e r c u r i p h o s p h a t e d e p e n d i n g o n r a t i o s o f r e a c t a n t s , t e m p e r a t u r e , a n d s o l v e n t i f used.) E t P b + H g ( O A c ) - > E t H g O A c (75) 4

2

S i l v e r a n d c u p r i c n i t r a t e s o n r e a c t i o n w i t h T E L a t l o w t e m p e r a t u r e s (—70° t o — 8 0 ° C . ) y i e l d e t h y l s i l v e r a n d e t h y l c o p p e r p l u s t h e t r i e t h y l l e a d salt (56, 116-118). W h e n t h e s o l u t i o n s o f these m e t a l a l k y l s are w a r m e d , d e c o m p o s i t i o n o f t h e R M c o m p o u n d occurs w i t h the evolution of butane, ethane, a n d ethylene. T h e t r i e t h y l l e a d salt is e v i d e n t l y unaffected b y this decomposition. T h e combination of cupric nitrate a n d T E L i n t h e presence of a m o n o m e r s u c h as s t y r e n e , m e t h y l m e t h a c r y l a t e , o r a c r y l o n i t r i l e does n o t r e a c t w i t h f o r m a t i o n o f e t h y l c o p p e r . H o w e v e r , t h e m o n o m e r s are r a p i d l y p o l y m e r i z e d (6). L e a d t e t r a a c e t a t e has b e e n r e p o r t e d t o r e a c t w i t h T E L a t 0 ° C . t o g i v e a m i x t u r e of t r i e t h y l l e a d acetate a n d l e a d acetate (79). T r i e t h y l l e a d c h l o r i d e o r b r o m i d e is f o r m e d f r o m t h e c o r r e s p o n d i n g d i e t h y l l e a d s a l t a n d T E L i n s o l u t i o n a t r o o m t e m p e r a t u r e : T h e r e a c t i o n i s r e v e r s i b l e (4, 82). T h i s i m p l i e s a r e a d y i n t e r c h a n g e o f t h e h a l o g e n a t o m a n d e t h y l r a d i c a l b e t w e e n different molecules. S u c h a n interchange is most s i m p l y shown b y observing a m i x t u r e of t r i e t h y l l e a d c h l o r i d e a n d T E L , one o f w h i c h c o n t a i n s r a d i o a c t i v e l e a d a s a t r a c e r (22).



315

Reaction with Metals T h e r e h a v e been a f e w r e p o r t e d r e a c t i o n s o f T E L w i t h a c t i v e m e t a l s .

Thus, for

e x a m p l e , s o d i u m i n l i q u i d a m m o n i a a n d e t h y l e t h e r reacts w i t h T E L t o g i v e t r i e t h y l p l u m b i d e a n d ethane

sodium

(SO). T h e s o d i u m d e r i v a t i v e was n o t i s o l a t e d , b u t

was

r e a c t e d w i t h a n u m b e r of o r g a n i c h a l i d e s t o g i v e t h e c o r r e s p o n d i n g u n s y m m e t r i c a l t r i ethyllead compound. n-C H Br, 4

C H Br, 77%; 6

T h e f o l l o w i n g y i e l d s were o b t a i n e d w i t h these o r g a n i c h a l i d e s :

91 t o 9 5 % ;

9

sec-C H Br, 82%; 4

2

£er£-C H Br,

9

and C H = C H C H C 1 , 727 .

5

2

be e q u a l l y effective f o r t h i s cleavage

4

9

nil; C H CH C1, 10%; 6

5

2

C a l c i u m a n d l i t h i u m are also r e p o r t e d t o

0

I n c o n t r a s t , finely d i v i d e d b i s m u t h does n o t

(9).


r e a c t w i t h T E L a t 100° t o 1 3 0 ° C . (48).

Redistribution with Other Metal Alkyls I n t h e presence of a s m a l l a m o u n t o f c a t a l y s t s u c h a s a l k y l a l u m i n u m o r a l k y l l e a d halide, Calingaert a n d coworkers

showed

t h a t T E L undergoes

interchange

reactions

w i t h o t h e r lead a l k v l s a n d w i t h c e r t a i n o t h e r m e t a l a l k y l s t o g i v e a m i x t u r e o f p r o d u c t s (19,

21).

W h e r e t h e p r o d u c t s h a v e s i m i l a r t y p e s o f b o n d s , as i n t h e R P b m i x t u r e s , 4

t h e a m o u n t s o f e a c h c o m p o u n d o b t a i n e d c o r r e s p o n d t o those e x p e c t e d f r o m a r a n d o m distribution of the radicals.

C o m p o u n d s w h i c h h a v e been r e a c t e d w i t h T E L i n c l u d e

t e t r a m e t h y l - a n d t e t r a - n - p r o p y l l e a d a n d a m i x t u r e of the two, t e t r a m e t h y l t i n , d i m e t h y l mercury, and trimethyllead bromide.

T h i s r e a c t i o n has b e e n r e v i e w e d

(20).

Miscellaneous Reactions I t has b e e n r e p o r t e d t h a t T E L reacts w i t h selenious a c i d t o g i v e d i e t h y l l e a d selenite i n 1 5 . 5 % y i e l d (55). temperature

(150°

P h e n y l a r s i n e has been reacted w i t h T E L a t a r e l a t i v e l y h i g h

to 170°C),

w i t h p r o d u c t i o n o f m e t a l l i c l e a d (98) a n d

arsenoben-

zene as s h o w n b y t h e e q u a t i o n : Et Pb + 2C H AsH 4

6

6

150° to 170°C 2

Benzene

>C H A s = A s C H 6 + Pb + 4 C H 6

6

2

6

6

T h e i n t r o d u c t i o n o f s u l f u r d i o x i d e i n t o T E L i n a s o l u t i o n o f e t h e r c o n t a i n i n g some w a t e r p r o d u c e s d i e t h y l l e a d sulfite i n a y i e l d o f 9 9 %

(62).

Earlier workers have r e

p o r t e d different r e s u l t s f r o m t h i s r e a c t i o n (41, 126). T h e reaction of T E L w i t h carbon tetrachloride takes place slowly a t r o o m

tem

perature i n ether solution a n d gives, over a p e r i o d of 30 days, u p t o 9 0 % yields of t r i e t h y l l e a d c h l o r i d e p l u s a n u n i d e n t i f i e d gaseous p r o d u c t .

C a r b o n tetrabromide

and

hexabromoethane likewise react w i t h T E L i n the presence of oxygen t o give d i e t h y l l e a d dibromide, w i t h evolution of carbonyl bromide

A c a r b o n d i s u l f i d e s o l u t i o n of

(65).

T E L t u r n s d a r k r e d a n d gives a b l a c k p r e c i p i t a t e , n o t i d e n t i f i e d (12). V e r y little h a s been

published o n so-called

G r i g n a r d - t y p e reactions

C h l o r a l has b e e n r e p o r t e d (93) t o r e a c t w i t h T E L a t a h i g h t e m p e r a t u r e ,

with T E L . subsequent

h y d r o l y s i s g i v i n g a 2 0 % y i e l d of l , l , l - t r i c h l o r o - 2 - b u t a n o l , as i n d i c a t e d b y the

follow

ing equation: 170°C

CClaCHO + E t P b 4

HC1

» Et PbOCH(Et)CCl 3

3

> CCl CH(Et)OH 3

H o w e v e r , r e p e t i t i o n o f t h i s r e a c t i o n b y o t h e r w o r k e r s d i d n o t c o n f i r m these (47).

results

Benzaldehyde a n d T E L do n o t react under conditions used f o r t h e G r i g n a r d

r e a c t i o n (46).

L i k e w i s e k e t e n e , w h i c h reacts s m o o t h l y w i t h d i e t h y l z i n c a n d v i o l e n t l y

w i t h d i e t h y l m a g n e s i u m , shows n o t e n d e n c y t o r e a c t w i t h T E L (69). A n u m b e r of patents m e n t i o n o r c l a i m the f o r m a t i o n of lead derivatives c o n t a i n i n g olefinic a n d a c e t y l e n i c l i n k a g e s o n p a s s i n g e t h y l e n e o r a c e t y l e n e t h r o u g h T E L a t o r d i n a r y t e m p e r a t u r e s a n d pressures (119). TEL

Other workers have shown, however, that

does n o t r e a c t w i t h t h e a c t i v e h y d r o g e n

of acetylene

or ethynylbenzene


(52).


316

Reference should be made to the fact that triethylethynyllead and ethynylenebis (tri ethyllead) have recently been synthesized by a reaction involving triethyllead bromide and sodium acetylide in liquid ammonia (8). It is reported that triethylethynyllead is unstable even at —34°C, and disproportionates to ethynylenebis (triethyllead) and acetylene. The bis compound is found to be sensitive to moisture, being immediately destroyed by contact with water. Finally, T E L , even in dilute solution in gasoline, reacts strongly with an activated clay such as Filtrol (97). This is not merely an adsorption, because the lead cannot be removed by any means short of strong acids.


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