III International Conference

PP-I-47FORMOSE REACTION AS A CATALYTIC PROCESS WITH CHAIN MECHANISMSimonov A.N., Zasipkina O.A., Pestunova O.P., Parmon V.N.Boreskov Institute of Catalysis SB RAS, Novosibirsk, RussiaNovosibirsk State University, Novosibirsk, RussiaE-mail: san@catalysis.ruThe formose reaction can be regarded as a unique example of a catalytic process withchain mechanism with confluent branching that does not involve free radicals. The kineticsand products of the individual stages of the process were investigated. The overall detailedscheme of the reaction was proposed. A computer program for modeling of the kinetics of theformose reaction was created and results on the rate constants of different stages wereacquired.For the long time oligomerization of formaldehyde yielding carbohydrates, catalyzed byinorganic and organic bases in aqueous medium, known as the formose or Butlerov reactionwas supposed to be autocatalytic. Over the XX century a variety of expected autocatalyticcycles were proposed (e.g. see the review [1]), but none of them could be supposed torepresent the actual route of the carbohydrate formation from formaldehyde. Finally, it wasfound that the nature of the autocatalysis of the formose reaction is connected with theretroaldol cleavage of the higher monosaccharides [2-4].As a result of the breaking up of one molecule of a higher carbohydrate two molecules oflower carbohydrates are formed. The latter condense with each other or formaldehyde in thecourse of the aldol condensation reactions and yield other higher carbohydrates. The overallscheme of the formose reaction is presented below:[ ]CH O ⎯⎯⎯⎯→ CaCH O ⎯⎯⎯→ C H O + C H OCa( OH ) 22HO2n 2n n←⎯⎯ ⎯2HOn 2n n n−m 2( n−m) n−m m 2m m2C H O + CH O⎯⎯⎯⎯→ C H O(2)Ca( OH ) 2m 2m m 2 m+ 1 2m+ 2 m+1CH O + CH O⎯⎯⎯⎯→ C H O(3)Ca( OH ) 2j 2 j j i 2i i i+ j 2( i+ j)i+jwhere n = 4-6, m = 2-3; i, j = 2-5. (i+j < 8)Actually, the above scheme can be regarded as a chain mechanism with the confluentbranching (active species – lower carbohydrates C 2 -C 3 and formaldehyde) rather than aclassic autocatalytic reaction A+ A⎯⎯→ P+ A. If the formose reaction is initiated by highermonosaccharide C n H 2n O n (n = 4-6), the stage (1) is the initialization stage – the formation oftwo lower carbohydrates C n-m H 2n-2m O n-m and C m H 2m O m (m = 2-3). If the reaction starts from alower carbohydrate, no initialization stage is needed and the reaction starts from the chain93(1)