Investigations of the reactivity of pyridine carboxylic acids with diazodiphenylmethane in protic and aprotic solvents, Part I: Pyridine mono-carboxylic acids

Abstract

Rate constants for the reaction of diazodiphenylmethane with isomeric pyridine carboxylic acids were determined in chosen protic and aprotic solvents at 30 °C, using the well known UV spectrophotometric method. The values of the rate constants of the investigated acids in protic solvents were higher than those in aprotic solvents. The second order rate constants were correlated with solvent parameters using the Kamlet-Taft solvatochromic equation in the form: logk = logk0 + s¶*+ aα + bβ. The correlation of the obtained kinetic data were performed by means of multiple linear regression analysis taking appropriate solvent parameters. The signs of the equation coefficients were in agreement with the postulated reaction mechanism. The mode of the influence of the solvent on the reaction rate in all the investigated acids are discussed on the basis of the correlation results.

Konstante brzina reakcije između diazodifenilmetana i izomernih piridin-karbonskih kiselina su određene u odabranim protičnim i aprotičnim rastvaračima na 30 °C, korišćenjem poznate UV spektrofotometrijske metode. Vrednosti konstanti brzina ispitivane reakcije u protičnim rastvaračima imaju veće vrednosti u poređenju sa vrednostima konstanti u aprotičnim rastvaračima. Konstante brzina su korelisane sa parametrima rastvarača korišćenjem Kamlet–Taft jednačine oblika: logk = logk0 + s¶*+ aα + bβ. Korelacije dobijenih kinetičkih rezultata sa odgovarajućim parametrima rastvarača su izvedene metodom višestruke linearne regresione analize. Znak koeficijenata u dobijenim korelacijama je u saglasnosti sa pretpostavLJenim reakcionim mehanizmom. Uticaj rastvarača na vrednosti reakcionih konstanti je diskutovan na osnovu dobijenih korelacionih rezultata.