The Determination of Kinetic Parameters for the Reactions of Oxidation of Organic Compounds by Cerium Perchlorate. The Numerical Study (Part III)

A C T A U N T V E R S I T A T I S L O D Z I E N S I S _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ FOLIA C H I M I C A 8, 1988

M a k s y m i l i a n Ignaczak*, S t a n i s ł a w K o m i s a r s k i *

THE D E T E R M I N A T I O N OF KINE TIC P A R A M E T E R S FDR THE R E A C T I O N S OF O X I D A T I O N OF OR GA N I C C O M P O U N D S BY C E R I U M P E R C H LO RA TE

THE NU ME RIC AL S T UD Y (PART III**)

The pr es ent p a pe r is a c o n t i n u a t i o n of e a r l i e r w o rk s c o n ­ c e r n ing the m e th od of d e t e r m i n a t i o n of k i n e t i c p a r a m e t e r s for the o x i d a t i o n r e a c t i o n s of or ga n i c c o m p o u n d s by cerium perchlorate in a s o l u t i o n of p e r c h l o r i c acid.

This pa per deals with the case of o x i d a t i o n of or ga n i c acids c o n t a i n i n g the -C=C- bond and d e s c r i b e s the i n f l u e n c e of p e r ­ c h l o ric acid on the r e a c tio n rate of o x i d a t i o n at the c o m p o u n d s b e ing re ga rde d as a base a c c o r d i n g to the B r o n s t e d theory.

D u r i n g the o x i d a t i o n of acids: fu ma ric [l], m a l e i n i c [2] and ac ry l i c one [3] by the use of C e ri um p e r c h l o r a t e one can observe, in pr actise, the zero - th r e a c t i o n order in rega rd to reductor, wh ile the r e a c tio n order in resp ect to the o x i d i z e r is equal 1 [4] . The i n v e s t i g a t i o n s upon the o x i d a t i o n r e a c t i o n s of saturated, a l i p h a t i c c a r b o x y l i c acids have shown, that the p r o c e s s of o x i d a ­ tion of these c o m p o u n d s does not occur, however, there are formed re l a t i v e l y stab le complexes.

So, one may c o n c l u d e that d u ri ng the o x i d a t i o n of c a r b o x y l i c acids c o n t a i n i n g the C=C bond that p r o c e s s is r e al ize d by the decay of J - e l e c t r o n c o m p l e x e s be ing form ed with the e l e c t r o n s of the C=C doub le bond.

That p r o c ess can be i n t r odu ce d as it follows:

#

In st itu te of Ch em ist ry , U n i v e r s i t y of Ł ódź.

Part I - Ki ne tik a and Kataliz, XXV, 78 8- 793 (1984); Part II K i n e t i k a AND Ka ta l i z (in press).

R H . I I +4 ßi R - C = C - C 0 0 H + Ce « = = ♦ C e *4

II

ß 2 R H R - C = C - C 0 0 H

R

H

n

I I S 0 ''. R - C = C - CT .Ce V o - * + 3

f u r t her (fast) reaction.

Ce

A s s u m i n g an e x ce ss of ox idizer, the s y s t e m of e q u a t i o n s has the form:

d C e * 4 dt

= n . . ^com ple x IIJ (1)

[ c o m p l e x I] C t C e +4 ' C tR [complex I] . H + C t C e +4 • C tR ( 2) [complex II] C t C e +4 • C tR (3) C p +4 - C + + 4

C q R --- -- - - = [complex ij + [complex II] + C tR (4)

w h e r e :

C t C R +4 - C e +4 c o n c e n t r a t i o n in time t,

C tR - c o n c e n t r a t i o n of the free r e d u c t o r in time t, C Q c e +4 - initial c o n c e n t r a t i o n of ox id ize r,

C Q p - initial c o n c e n t r a t i o n of re du ctor, n - e l e c t r o n i c i t y of the pr ocess.

If the c o n c e n t r a t i o n of p e r c h l o r i c acid was c o n s t a n t d u r i n g tha m e a s u r e m e n t of r e a c t i o n rate, one c a n take into a c c o u n t on l y the c o n d i t i o n a l s t a b i l i t y c o n s t a n t of the c o m p l e x I(ft^). Th er efo re , in or de r to o b t a i n the K^, p a r a m e t e r s it is n e c e s s a r y to make

the f o l l o w i n g t r a n s f o rm at ion s: d i v i d i n g e q u a t i o n (2) by the e q u a ­ tion (3) we get:

^ 1 [complex i]

[complex II] ^

fl2

D e t e r m i n i n g from equs. (4) and (5) the value co mp l e x II we get:

[complex II] * ■ r C o C e +4 ” C t C e +4 r oR n " tR h . P 2 + 1 b e c o u s e C tR = J c o m p l e x II] C t C e +4 ' * 2 h e n c e , we h a v e : r C o C e +4 ' C t C e +4 [complex II] = *1 A2

the final e q u a t i o n is as it follows

d Ce -- dt + 4 C oR . C e C e * 4 ~ C t C e * 4 = n

1

P>. * 1 + JtCe 1 •Tift

(

6

)

The K^, flj, $2 *n e q u a t i o n (6) we d e t e r m i n e by m e an s of the no n l i n e a r least sq ua res m e th od (the same as the d e t e r m i n i n g the first d e r i v a t i v e of C e +4 c o n c e n t r a t i o n in r e s p ect to time). In the

case of the d e p e n d e n c e of r e a c t i o n rate up on the p e r c h l o r i c ac id c o n c e n t r a t i o n the s u f f i c i e n t c o n d i t i o n is that = ftJ/H+ . D u ri ng the o x i d a t i o n of non - s a t u r a t e d c a r b o x y l i c acids the r e a c t i o n order equal to I is ch ar a c t e r i s t i c .

The most o f te n met o x i d a t i o n r e a c t i o n s of o r g a n i c c o m p o u n d s are that ones, in which, the d e p e n d e n c e of r e a c t i o n rate upon the p e r ­ c h l o r i c acid c o n c e n t r a t i o n is very small, for e x a m p l e the o x i d a t i o n of: e t h y l e n e a l c o hol and g l i c e r i n e [5], p r o p a n o l e and i s o p r o p a n o l e

[6] b u t a n e d i o l e s and b u t e n e - 2 - d i o l - l , 4 [7].

The d o u b l e i n c r e a s e of acid c o n c e n t r a t i o n in the r a ng e 0.5- -5 m o l e / c m 3 c a us es the i n c r eas e of r e a c t i o n rate fr om 5% up to 35%. This fact is due to the pa rt i a l h y d r o l y s i s of C e +4 ions and also it is c a us ed by the c h an ge of a c t i v i t y c o e f f i c i e n t s in very c o n ­ c e n t r a t e d e l e c t r o l y t e [8], [9]. Also, th ere are k n o w n the p r o c e s s e s , in which, the i n c r e a s e of p e r c h l o r i c acid c o n c e n t r a t i o n causes rather s i g n i f i c a n t l o w e r i n g of r e a c t i o n rate (about half in the case of the d o ub le i n c r e a s e of acid c o n c e n t r a t i o n ) . See the o x i d a t i o n of hydr o- xy p i r i d i n e [10] and of p i c o lin es , l u t i d i n e s [ll] .

That m e c h a n i s m can be made e l ea r a f te r the n e c e s s a r y a s s u m p t i o n that the c o m p l e x is f o rm ed b e t w e e n the n o n p r o t o n a t e d am ine and C e r i u m (IV) ion, a c c o r d i n g to the f o l l o w i n g scheme:

K [Amine - H + ] ^ ■ » A m i n e + H + + A A m in e + Ce - r co mp l e x K c o m p l e x ---- --- m R + C e + ^ + H + R + (n - 1) C e + * + ( x ^ O ) --- fast— .. final p r o d u c t s

Be cause, the v a lu es of K for that a m in es are k n o w n or easy for d e ­ t e r m i n a t i o n by the p o t e n c j o m e t r i c m e t h o d (for the amin es m e n t i o n e d ab ove the valu es of K are in ( 1 0- 5 , 1 0 " 5 ) in te rva l) we p r o p o s e the m e t h o d of d e t e r m i n a t i o n only the valu es and ¡ i ,

The s y s t e m of e q u a t i o n s w i th an a s s u m p t i o n of an e x c e s s of o x i d i z e r has the form:

. [c o m p l e x]___ Am ine c t C e +4

(

8)

C p +4 - C +r +4

C . - - - = [Amine] + [complex] + [Amine - H ] (9)

'oA n

[Amine] [H+]

K = — --- — ( 10)

[Amine H ]

where: C qA - initial r e d u cto r c o nc ent ra ti on.

That s y s t e m can be t r a n s f o r m e d in a f o l l o w i n g way: from e q u a ­ tion (10) we d e t e r m i n e [Amine - H +] and s u b s t i t u t e this in e q u a t i o n (9). Th er efo re , we get: C q A -- — - - - -— — — = [Amine] (1 + -^-^-) + [complex] M a k i n g use of e q u a t i o n (8) we obtain:

f

o» - n r •... . , . ft . c tCe.»

V

and the final form of the e q u a tio n is:

C„p„ +4 - C.p +4 r 'oCe tCe . P +4 b oA n d _ C | _ . Ki . n - - - (11) 1 ♦ JJ f l -+ 1

The K^,/i p a r a m e t e r s can be d e t e r m i n e d by m e an s of the least sq ua res m e t h o d or usin g the a p p r o x i m a t e m e t h o d s b e in g d e s c r i b e d in details- in pa per [12]. It is also p o s s i b l e to d e t e r m i n e the K c o n s t a n t if one will make use of a three - p a r a m e t e r equation, however, in that case one mu st p e r f o r m the m e a s u r e m e n t s of a hi gh a c c u r a c c y (2%) w h i c h is rather d i f f i c u l t in a k i n e t i c s i n v e s t i g a t i o n s . If the value of K is m i s s e d in c a l c u l a t i o n s the d e t e r m i n a t i o n of ft leads a big

error, ho wever, the o b t a i n e d Kj valu e m a y be r e g a r d e d as a good a p p r o x i m a t i o n . R e f e r e n c e s [1] i g n a c z a k M . , D z i e g i e ć J . , S a w i c k i J., Actai U n i v . L o d z ., 1976, 33-44 [2] I 9 n a c z a k M . , D z i e g i e ć J ., P o li sh J . C h e m . ( R oczniki Chemii), 46, 947 (1972). [3] I g n a c z a k M . , D e k a J. , K o m i s a r s k i S.„Polish J. Chem. (in p r e s s ) . [4] I 9 n a c z a k M. , D e k a J. , K o m i s a r s k i S., P o li sh J. Chem. (in press).

[5] I g n a c z a k M . , D z i e g i e ć J ., P o li sh J . Chem. , 52 , 2467 (1978).

[6] i g n a c z a k M . , D z i e g i e ć J., M a r k i e w i c z M., _{Poli sh J . Chem . , j>4Li 1121 (1980) .}

[7] i g n a c z a k M . , M a r k i e w i c z M., P o li sh J. Chem., 55, 671 (1981). [8] H a r d w i c k T . , R 0 b e r t s o n E ., C a n . J . C h e m ., 29, 818 (1951). [9] B a k e r F . , N e w t 0 n T . , K a 1h n M . , J . Phys . C h e m . , 64. 109 (1960).

[10] _{I g n a c z a k} M . , K 0 m i s a r s k i S ., Acta Univ. Lodz., Fo lia chim., 47 (1985). [ U ] K o m i s a r s k i S. ( u n p u b l i s h e d works). [12] I g n a c z a k M . , K 0 m i s a r s k i S., Kinetik i Kataliz, XXV, 788 (1984). M a k s y m i l i a n Ignaczak, S t a n i s ł a w K o m i s a r s k i W Y Z N A C Z A N I E P A R A M E T R Ó W K I N E T Y C Z N Y C H R E A K CJI U T L E N I A N I A Z W I Ą Z K Ó W O R G A N I C Z N Y C H N A D C H L O R A N E M C E R O W Y M ZA P O M O C Ą ETO (III)

Ni n i e j s z a pr aca jest k o n t y n u a c j ę w c z e ś n i e j p r z e d s t a w i o n y c h prac d o t y c z ą c y c h m e t o d y k i w y z n a c z a n i a p a r a m e t r ó w k i n e t y c z n y c h reakcji u t l e n i a n i a z w i ą z k ó w o r g a n i c z n y c h n a d c h l o r a n e m c e r o w y m w ś r o d o w i s k u kw asu n a dc hlo ro we go.

Pr z e d s t a w i a ona m e t o d y k ę ich w y z n a c z a n i a w p r z y p a d k u u t l e n i a n i a k w as ów o r g a n i c z n y c h z a w i e r a j ą c y c h w i ą z a n i e -C=C- oraz o p i s u j e w p ły w kw asu n a d c h l o r o w e g o na s z y b k o ś ć re ak cji u t l e n i a n i a zw iązków, b ę d ą ­ cych z a s a dam i zg od n i e z teorią Br on ste da .