| Structure Identification: |
| J Pharm Sci. 1983 Apr;72(4):369-72. | | Solvent effects on the cinnamoylation of n-propyl alcohol catalyzed by N-methylimidazole and 4-dimethylaminopyridine.[Pubmed: 6864472] |
METHODS AND RESULTS:
The kinetics of reaction of trans-Cinnamic anhydride or trans-cinnamoyl chloride with n-propyl alcohol, catalyzed by N-methylimidazole or 4-dimethylaminopyridine, were studied spectrophotometrically at 25 degrees in methyl ethyl ketone, ethylene dichloride, methylene chloride, and toluene. The acid chloride reacted in all solvents via the intermediate formation of the N-acyl catalyst, which underwent reaction with the alcohol catalyzed by another molecule of the base. The anhydride did not form the intermediate in any of the solvents, but underwent direct general base catalysis.
CONCLUSIONS:
The rate of the anhydride reactions was not sensitive to solvent polarity, whereas the rate of the chloride reactions tended to increase as the solvent polarity decreased.
A kinetic analysis is given of the effect of ion-pair formation on the kinetics of acyl transfer in systems where the charged N-acyl catalyst intermediate is formed. | | J Pharm Sci. 1983 Apr;72(4):366-9. | | Kinetics and mechanism of hydroxy compound cinnamoylation in acetonitrile catalyzed by N-methylimidazole and 4-dimethylaminopyridine.[Pubmed: 6864471] |
METHODS AND RESULTS:
The kinetics of reaction of the acylating agents trans-Cinnamic anhydride and trans-cinnamoyl chloride with the hydroxy compounds n-propyl alcohol and water in the presence of N-methylimidazole and 4-dimethylaminopyridine were studied spectrophotometrically in acetonitrile solution at 25 degrees. The acid chloride reacted via the intermediate formation of the N-acyl catalyst, which underwent general base-catalyzed reaction with the hydroxy compound. The anhydride did not form the N-acyl intermediate, but instead underwent direct general base catalysis. In the presence of water, all systems formed the N-acyl intermediate.
CONCLUSIONS:
The mechanistic route followed by the system was determined by the nucleophilicity of the catalyst, the ability of the leaving group, and the polarity of the solvent. |
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