ozone chemistry and technology - American Chemical Society

Initial Attack of Ozone on an Unsaturated System PHILIP S. BAILEY, SHEAFFERS S. BATH, and JOSEPH B. A S H T O N

Downloaded by TUFTS UNIV on June 3, 2018 | https://pubs.acs.org Publication Date: January 1, 1959 | doi: 10.1021/ba-1959-0021.ch022

University of Texas, Austin, Tex.

A general theory of attack, which is supported by work from the University of Texas, is deduced from the ideas of many people. A two-step attack is pro posed. The first step is electrophilic a n d is made by a terminal oxygen atom. The central atom, which is nucleophilic, completes the attack. The position of at tack on anthracene a n d the specificity of attack which occurs with unsymmetrical olefins support this theory.

I h e C r i e g e e m e c h a n i s m {13-15, 17) f o r o z o n o l y s i s h a s b e e n of t r e m e n d o u s i m p o r t a n c e i n g i v i n g a b e t t e r u n d e r s t a n d i n g of t h e course o f t h e o z o n o l y s i s r e a c t i o n — i n p a r t i c u l a r , t h e n a t u r e a n d fate o f t h e a c t i v e o x y g e n - c o n t a i n i n g o z o n o l y s i s p r o d u c t s . I t leaves i n d o u b t , h o w e v e r , t h e n a t u r e of t h e i n i t i a l a t t a c k o f ozone o n a n u n s a t u r a t e d s y s t e m a n d o f t h e i n t e r m e d i a t e s l e a d i n g t o t h e f o r m a t i o n of t h e p r i m a r y cleavage p r o d u c t s , the z w i t t e r i o n ( I V ) a n d t h e aldehyde or ketone ( V ) .

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T h e i n i t i a l ozone a t t a c k c o u l d o c c u r i n t w o g e n e r a l w a y s . T h e first is a o n e - s t e p s i m u l t a n e o u s a t t a c k o f b o t h r e a c t i v e centers of t h e ozone m o l e c u l e o n b o t h r e a c t i v e centers of t h e u n s a t u r a t e d m o l e c u l e . T h i s m e c h a n i s m is c h a m p i o n e d b y t h e A u s t r a l i a n s , 143

OZONE CHEMISTRY AND TECHNOLOGY Advances in Chemistry; American Chemical Society: Washington, DC, 1959.

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B r o w n (9, 11) a n d B a d g e r (1-4). T h e o t h e r p o s s i b i l i t y is a t w o - s t e p a t t a c k of t h e r e a c t i v e centers of t h e ozone m o l e c u l e o n t h e u n s a t u r a t e d s y s t e m . A f t e r a d e c i s i o n b e t w e e n these t w o b r o a d , g e n e r a l m e c h a n i s m s is r e a c h e d , a d d i t i o n a l questions m u s t b e a n s w e r e d . I f t h e first m e c h a n i s m is i n effect, does t h e a t t a c k i n volve t h e t e r m i n a l oxygen atoms or adjacent oxygen atoms? I f t h e second m e c h a n i s m is i n effect, does t h e first s t e p i n v o l v e a n e l e c t r o p h i l i c , n u c l e o p h i l i c , o r r a d i c a l a t t a c k ? D o e s t h e first s t e p i n v o l v e a t e r m i n a l o r a c e n t r a l a t o m ? I f i t i n v o l v e s a t e r m i n a l a t o m , i s t h e a t t a c k c o m p l e t e d i n t h e s e c o n d step b y t h e m i d d l e o r t h e o t h e r t e r m i n a l a t o m ? F u r t h e r , one m u s t e x p l a i n w h y t h e d o u b l e b o n d is so e a s i l y c l e a v e d a n d w h y n o i n t e r m e d i a t e f r o m t h e i n i t i a l ozone a t t a c k h a s ever been i s o l a t e d . T h i s p a p e r a t t e m p t s t o m o l d t h e ideas of m a n y p e o p l e i n t o a general t h e o r y a n d r e p o r t s w o r k f r o m t h e U n i v e r s i t y of T e x a s w h i c h a d d s s u p p o r t t o t h e t h e o r y .

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A g r e e m e n t seems finally t o h a v e been r e a c h e d t h a t t h e ozone m o l e c u l e h a s a n o b t u s e a p e x angle a n d , t h e r e f o r e , s h o u l d be c o n s i d e r e d a h y b r i d of t h e f o l l o w i n g s t r u c t u r e s (20, 26). T h e w o r k of W i b a u t a n d c o w o r k e r s (6, 19, 21, 24, 25, 27, 28) h a s :0=0—0:

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f u r n i s h e d s t r o n g evidence f o r t h e t w o - s t e p a t t a c k , t h e first step b e i n g e l e c t r o p h i l i c . I t h a s been g e n e r a l l y a s s u m e d t h a t t h e c e n t r a l , p o s i t i v e l y c h a r g e d a t o m m a k e s t h e e l e c t r o p h i l i c a t t a c k . M e i n w a l d (22), h o w e v e r , h a s p o i n t e d o u t t h a t i n s t r u c t u r e s X I V a n d X V , w h i c h a r e t h e o n l y ones c o n s i d e r e d t o m a k e a n y a p p r e c i a b l e c o n t r i b u t i o n t o t h e ozone h y b r i d , t h e c e n t r a l o x y g e n a t o m h a s i t s f u l l q u o t a of eight electrons a n d c a n n o t b e e l e c t r o p h i l i c . O n l y i n s t r u c t u r e s X V is t h e r e a n e l e c t r o p h i l i c center a n d i t is t h e t e r m i n a l o x y g e n a t o m . I n the proposed theory a t e r m i n a l oxygen atom makes the initial, electrophilic attack. A f t e r this, either the central or other t e r m i n a l atom could complete the attack, because b o t h a r e n u c l e o p h i l i c . C o m p l e t i o n b y t h e o t h e r t e r m i n a l a t o m w o u l d l e a d t o the f o r m a t i o n of i n t e r m e d i a t e X V I , whereas X V I I w o u l d be p r o d u c e d i f t h e c e n t r a l atom completed the attack.

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cause t h e o x y g e n - o x y g e n b o n d t o b r e a k c o m p l e t e l y — e . g . , X — t o p r o d u c e X I w h i c h l i k e w i s e w o u l d b e h i g h l y u n s t a b l e . T h e p o s i t i v e charge o n t h e o x y g e n a t o m of X I w o u l d w e a k e n t h e c a r b o n - c a r b o n b o n d of X I , c a u s i n g b r e a k d o w n t o t h e p r o v e d i n t e r m e d i a t e s o f t h e C r i e g e e {13-15, 17) m e c h a n i s m ( X I I a n d X I I I ) . W o r k c a r r i e d o u t a t t h e U n i v e r s i t y of T e x a s s u p p o r t s t h i s p i c t u r e . T w o a p proaches t o t h e solution of t h e p r o b l e m are being made. T h e first deals w i t h t h e position of a t t a c k o n various aromatic systems. A c c o r d i n g t o t h e molecular o r b i t a l t h e o r y , t h e one-step s i m u l t a n e o u s a t t a c k of a " d o u b l e - b o n d " reagent u p o n a n a r o m a t i c s y s t e m w i l l o c c u r first a t t h e b o n d w i t h t h e lowest " b o n d l o c a l i z a t i o n e n e r g y " ( t h e one w i t h t h e greatest d o u b l e b o n d c h a r a c t e r ) , whereas t h e t w o - s t e p a t t a c k w i l l o c c u r i n i t i a l l y a t t h e position w i t h t h e lowest " a t o m localization energy" (most reactive c a r b o n a t o m i n t h e m o l e c u l e ) {7-11, 18). W i t h s o m e a r o m a t i c substances, s u c h as a n t h r a c e n e , these p o s i t i o n s a r e d i f f e r e n t . W i t h a n t h r a c e n e t h e b o n d w i t h t h e lowest b o n d l o c a l i z a t i o n e n e r g y i s t h e 1,2 b o n d {7-11,18). O s m i u m tetroxide, a k n o w n double b o n d reagent, a t t a c k s here {12). T h e p o s i t i o n s w i t h t h e l o w e s t a t o m l o c a l i z a t i o n energies a r e t h e 9,10 p o s i t i o n s . H e r e e l e c t r o p h i l i c s u b s t i t u t i o n a n d o x i d a t i o n o c c u r . W h a t w i l l ozone d o ? W a t e r s {23) h a s o z o n i z e d a n t h r a c e n e i n acetic a n h y d r i d e a n d o b t a i n e d a n t h r a q u i n o n e . H e d i d n o t state h i s y i e l d , h o w e v e r , n o r s h o w h o w m u c h ozone w a s a b s o r b e d . I t i s n o t c e r t a i n w h e t h e r ozone, o r o x y g e n c a t a l y z e d b y ozone, produced the anthraquinone. T h e o z o n o l y s i s o f a n t h r a c e n e i s b e i n g s t u d i e d i n d e t a i l a t t h e U n i v e r s i t y of T e x a s . I n acetic a c i d t h e ozone i s a b s o r b e d n i c e l y a n d t h e a n t h r a c e n e s l o w l y goes i n t o s o l u t i o n as i t r e a c t s . I t r e q u i r e s t h e r e a c t i o n of a p p r o x i m a t e l y 3 m o l e s o f ozone p e r m o l e o f a n t h r a c e n e t o c o m p l e t e t h e r e a c t i o n . A t t h e e n d some a n t h r a q u i n o n e h a s p r e c i p i t a t e d i n t h e r e a c t i o n vessel. T h i s a m o u n t s t o a 2 8 % y i e l d . T h e filtrate i s p e r o x i d i c . U p o n r e d u c t i o n w i t h s o d i u m i o d i d e , a 4 1 % y i e l d of a n t h r a q u i n o n e r e s u l t s , m a k i n g a t o t a l y i e l d of 6 9 % . I t i s c e r t a i n t h a t t h e a n t h r a q u i n o n e f o r m a t i o n is d u e t o t h e ozone r e a c t i o n , because (1) a n a c t i v e o x y g e n - c o n t a i n i n g c o m p o u n d i s p r o d u c e d w h i c h i s r e d u c e d t o a n t h r a q u i n o n e , (2) o x y g e n alone u n d e r t h e same c o n d i t i o n s gives n o r e a c t i o n , a n d ( 3 ) o x y g e n p l u s a t r a c e of ozone p r o d u c e s a n t h r a q u i n o n e i n a m o u n t s r o u g h l y p r o p o r t i o n a l t o t h e a m o u n t of ozone passed t h r o u g h t h e s y s t e m , b u t n o t a t a l l p r o p o r t i o n a l t o t h e a m o u n t of o x y g e n passed t h r o u g h t h e s y s t e m . T h i s i s excellent e v i d e n c e f o r t h e t w o - s t e p a t t a c k . I n r e g a r d t o t h e exact m e c h a n i s m of t h e a n t h r a q u i n o n e f o r m a t i o n , w h i c h i s 6 9 % of t h e r e a c t i o n , i t does n o t seem l i k e l y t h a t t h e e n t i r e 3 m o l e s of ozone i s r e q u i r e d . P e r h a p s t h e o t h e r 3 1 % of t h e r e a c t i o n occurs b y t h e o n e - s t e p m e c h a n i s m a t t h e 1,2 b o n d of a n t h r a c e n e . I f t h i s o c c u r r e d , t h e r e a c t i o n s h o u l d c o n t i n u e u n t i l b o t h o u t e r r i n g s a r e d e s t r o y e d . T h i s w o u l d r e q u i r e a c o n s i d e r a b l e p r o p o r t i o n o f t h e 3 m o l e s of ozone a b s o r b e d d u r i n g t h e r e a c t i o n . T w o facts m u s t b e t a k e n i n t o a c c o u n t i n a n y m e c h a n i s m suggestion. S o m e a n t h r a q u i n o n e is p r o d u c e d b y s p o n t a n e o u s d e c o m p o s i t i o n of a n a c t i v e o x y g e n - c o n t a i n i n g p r o d u c t a n d t h e r e m a i n d e r is p r o d u c e d b y r e d u c t i o n of an active oxygen-containing product. T h e f o l l o w i n g m e c h a n i s m m e e t s these r e q u i r e m e n t s . O z o n e a t t a c k s a t t h e 9,10 p o s i t i o n s t o g i v e a n i n t e r m e d i a t e s u c h as X I X , w h i c h r e a r r a n g e s t o X X I , o r t h e corresponding perhydroquinone. S p o n t a n e o u s loss of w a t e r , f a c i l i t a t e d b y t h e g l a c i a l acetic a c i d s o l v e n t , w o u l d p r o d u c e a n t h r a q u i n o n e ( X X ) d i r e c t l y . O x i d a t i o n of X X I (or t h e c o r r e s p o n d i n g p e r h y d r o q u i n o n e ) w o u l d l e a d t o z w i t t e r i o n ( X X I I I ) w h i c h w o u l d s t a b i l i z e i t s e l f b y r e a c t i o n w i t h t h e s o l v e n t t o give X X I I . R e d u c t i o n of X X I I would produce anthraquinone ( X X ) . T h e o t h e r a p p r o a c h b e i n g m a d e a t t h e U n i v e r s i t y of T e x a s h a s t o d o w i t h t h e s p e c i f i c i t y o f ozone a t t a c k w h i c h o c c u r s w i t h u n s y m m e t r i c a l olefins. T h i s i s a n a l o g o u s t o t h e s p e c i f i c i t y o b s e r v e d i n t h e a d d i t i o n s of u n s y m m e t r i c a l reagents s u c h as h y d r o g e n c h l o r i d e t o u n s y m m e t r i c a l olefins. T h i s m a y first b e i l l u s t r a t e d w i t h a n e x a m p l e a l r e a d y r e p o r t e d {5, 13), t h e o z o n o l y s i s of i s o b u t e n e ( X X I V ) i n i n e r t s o l v e n t s . T h e m a j o r p r o d u c t i s a n o z o n i d e


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( X X X I ) . T h i s w o u l d h a v e t o b e p r o d u c e d b y i n t e r a c t i o n of i n t e r m e d i a t e s X X X , a n d n o t X X X I I , as C r i e g e e (13-15, 17) f o u n d t h a t z w i t t e r i o n s d o n o t a d d t o t h e c a r b o n y l g r o u p of o r d i n a r y k e t o n e s . T h i s preferential p r o d u c t i o n of intermediates c a n be e x p l a i n e d o n t h e basis o f t h e t e r m i n a l o x y g e n a t o m , e l e c t r o p h i l i c a t t a c k , p l u s i n d u c t i v e effects i n i s o b u t e n e , l e a d i n g t o t h e f o r m a t i o n o f X X V I I . O n the other h a n d , a central o x y g e n e l e c t r o p h i l i c a t t a c k , besides b e i n g u n l i k e l y , w o u l d r e s u l t i n t h e p r e f e r e n t i a l f o r m a t i o n of X X V I I I , w h i c h w o u l d b r e a k d o w n t o g i v e t h e w r o n g i n t e r m e d i a t e s ( X X X I I ) f o r ozonide ( X X X I ) f o r m a t i o n . T h e a t t a c k s h o w n i n X X V I i s u n l i k e l y , a l t h o u g h i t could be argued that, i f i t broke down, i t w o u l d give intermediates X X X preferentially, o n t h e basis t h a t t h e z w i t t e r i o n of X X X , b e i n g a t e r t i a r y c a r b o n i u m i o n , w o u l d be m o r e stable t h a n t h e one i n X X X I I . T o t h e p r e s e n t a u t h o r t h e a d d i t i o n of ozone a c c o r d i n g t o M a r k o w n i k o f T s r u l e t o give a n u n s t a b l e a d d u c t ( X X V I I ) , w h i c h c a n b r e a k d o w n i n o n l y one w a y , is a s o u n d e r e x p l a n a t i o n o f t h e s p e c i f i c i t y of ozone a t t a c k . T h i s places t h e ozone a t t a c k o n a d o u b l e b o n d i n t h e same c a t e g o r y as t h a t of o t h e r reagents w h i c h s h o w a s p e c i f i c i t y i n t h e i r r e a c t i o n s w i t h u n s y m m e t r i c a l olefins. T h e c o n c l u s i o n s r e a c h e d i n t h e p r e c e d i n g e x a m p l e a r e b a s e d o n i n d i r e c t evidence, w h i c h is t h a t c e r t a i n i n t e r m e d i a t e s ( X X X ) a r e necessary t o p r o d u c e t h e ozonide (XXXI). I t w o u l d b e b e t t e r t o get a b s o l u t e evidence b y a c t u a l l y " t r a p p i n g " a n d i d e n t i f y i n g t h e z w i t t e r i o n p r e f e r e n t i a l l y f o r m e d . T h i s has been d o n e a t t h e U n i v e r s i t y of T e x a s b y t h e o z o n o l y s i s of 1 , 2 - d i b e n z o y l p r o p e n e ( X X X I I I ) i n m e t h a n o l . T h e p r o d u c t s were p h e n y l g l y o x a l ( X X X V I I ) i n 6 1 % y i e l d a n d t h e m e t h o x y h y d r o peroxide ( X X X V ) (melting point 6 0 - 1 ° ) i n 7 4 % y i e l d . I t was felt t h a t t h e actual y i e l d s were m u c h b e t t e r . T h e m a t e r i a l s were difficult t o i s o l a t e . T h e m e t h o x y h y d r o peroxide ( X X X V ) h a d t o originate f r o m zwitterion X X X V I w h i c h w a s " t r a p p e d " t h r o u g h i t s r e a c t i o n w i t h m e t h a n o l . T h i s s p e c i f i c i t y o f r e a c t i o n c a n b e e x p l a i n e d , as i n t h e o t h e r case, b y t h e t e r m i n a l o x y g e n a t t a c k of ozone a n d i n d u c t i v e effects i n 1,2-


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XXXV Literature (1) (2) (3) (4) (5) (6) (7)

Φ - C — C - 0 - 0 II I 0 CH 3

Φ - C — c=o II I Ο Η

XXXVI

XXXVII

Cited

Badger, G. M., J. Chem. Soc. 1949, 456. Badger, G. M., Quart. Revs. 5, 155 (1951). Badger, G. M., Cook, J. W., Gibb, A. R., J. Chem. Soc. 1951, 3456. Badger, G. M., Lynn, K. R., Ibid., 1950, 1726. Bailey, P. S., Chem. Ber. 88, 795 (1955). Boer, H., Sixma, F. L. J., Rec. trav. chim. 70, 997 (1951). Brown, R. D., Australian J. Sci. Research 2A, 564 (1949).

Society OZONEAmerican CHEMISTRY Chemical AND TECHNOLOGY Advances in Chemistry; American Chemical Society: Washington, DC, 1959. Library

A D V A N C E S IN

148

CHEMISTRY SERIES

Brown, R. D., J. Am. Chem. Soc. 75, 4077 (1953). Brown, R. D., J. Chem. Soc. 1 9 5 0 , 3249. Ibid., 1 9 5 1 , 1950. Brown, R. D., Quart. Revs. 6, 63 (1952). Cook, J. W., Schoental, R., Nature 1 6 1 , 237 (1948). Criegee, R., Blust, G., Zinke, H., Chem. Ber. 8 7 , 766 (1954). Criegee, R., Kerckow, Α., Zinke, H., Ibid., 8 8 , 1878 (1955). Criegee, R., Lohaus, G., Ann. 5 8 3 , 6 (1953). Criegee, R., Pilz, H., Flygare, H., Ber. 7 2 , 1799 (1939). Criegee, R., Wenner, G., Ann. 5 6 4 , 9 (1949). Dewar, M. J. S., J. Am. Chem. Soc. 7 4 , 3357 (1952). Dijk, J. van, Rec. trav. chim. 6 7 , 945 (1948). Hughes, R. Η., J. Chem. Phys. 2 4 , 131 (1956). Kampschmidt, L. W. F., Wibaut, J. P., Rec. trav. chim. 7 3 , 431 (1954). Meinwald, J., Chem. Ber. 8 8 , 1889 (1955). Roitt, I. M., Waters, W. Α., J. Chem. Soc. 1 9 4 9 , 3060. Sixma, F. L. J., Rec. trav. chim. 7 1 , 1124 (1952). Sixma, F. L. J., Boer, H., Wibaut, J. P., Ibid., 7 0 , 1005 (1951). Trambarulo, R. F., Ghosh, S. N., Burrus, C. Α., Jr., Gordy, W., J. Chem. Phys. 2 1 , 851 (1953). (27) Wibaut, J. P., Sixma, F. L. J., Rec. trav. chim. 7 1 , 761 (1952).


(8) (9) (10) (11) (12) (13) (14) (15) (16) (17) (18) (19) (20) (21) (22) (23) (24) (25) (26)

(28) Wibaut, J. P., Sixma, F. L. J., Kampschmidt, L. W. F., Boer, H., Ibid., 6 9 , 1355 (1950). RECEIVED for review M a y 17, 1957.

Accepted June 19, 1957.


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