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Kinetics of the formation and hydrolysis of the schiff's base of 4-pyridinecarboxaldehyde with N-hexylamine in water-dioxan mixtures

✍ Scribed by Juan Llor; Salvador Asensio; Jose Manuel Sanchez-ruiz

Publisher: John Wiley and Sons
Year: 1989
Tongue: English
Weight: 499 KB
Volume: 21
Category: Article
ISSN: 0538-8066
DOI: 10.1002/kin.550210105

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✦ Synopsis

We have carried out a kinetic study of the 4-pyridinecarboxaldehyde plus n-hexy-Iamine system, at 25T, in water-dioxan mixtures (0-608 v/v) and in the pH range pK, + 1.5 > pH > pK, -1.5, where pK, is the pK value of the conjugate acid of the amine. The results obtained could be interpreted in terms of a rate constant for Schiffs base hydrolysis and a rate constant for the reaction between the nonprotonated n-hexylamine and the nonhydrated form of 4-pyridinecarboxaldehyde. Both constants decrease sharply as the dioxan content of the solvent increases, in a manner consistent with Marshall's model [J. Phys. Chem., 74, 346 (1970)l. It is suggested that the transition state of the rate-limiting step (carbinolamine dehydration) is highly solvated by water molecules and has a high separation of charges.

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