Theoretical study ab initio calculation

The mechanism of the acid-catalyzed decomposition of 1-alkyltriazolines has been studied <93JOC2097>. The hydrolytic decomposition of these triazolines in aqueous buffers leads predominantly to 1-alkylaziridines with lesser amounts of 2-(alkylamino)ethanol, alkylamines, and acetaldehyde. The rate of hydrolysis of 1-alkyltriazolines is about twice as fast as that of the analogous acyclic 1,3,3-trialkyltriazenes and varies in the order t-butyl > isopropyl > ethyl > butyl > methyl > propyl > benzyl <92JOC6448>. The proposed mechanism, involving rate-limiting formation of a 2-(alkylamino)ethyldiazonium ion, is shown in Scheme 65. A theoretical study ab initio calculation) of the acid-induced decomposition of 4,5-dihydro-l,2,3-triazolines has also been reported <91JA7893>. 

Seitz and East selected five isomeric protonated octane isomers (CgH "1"), all featuring C—H—C or C—H—H 3c-2e bonds for their theoretical studies (ab initio calculations at the MP2/6-3 lG(d) level of theory).847 In most cases, dissociation into ion-molecule complexes was found to be again barrierless. Proton affinities of C—C and C—H bonds are in the range 154—187 kcal mol 1 and 139-150kcalmol-1, respectively. 

Gas-phase decarboxylation of /1-ketocarboxylic acids XCOCH2COOH (X = H, OH, and CH3) has also been the subject of theoretical studies." Ab initio calculations reveal that decarboxylation via a six-membered (rather than four-membered) ring transition state is favoured. Activation barriers of 23.8, 23.3 and 28.5 kcal mol have been calculated for decarboxylation of 3-oxopropanoic acid, acetoacetic acid, and malonic acid, respectively. Only marginal effects of solvent on the energy barriers and on the geometries of the reactants and transition structures are predicted. The activation energy predicted for reaction of malonic acid agrees well with the experimental value and rate constants have been predicted for decarboxylation of 3-oxopropanoic acid and acetoacetic acid in the gas phase. 

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