Investigation of the reactivity of 4-pyrimidinecarboxylic, 6-hydroxy-4-pyrimidinecarboxylic and 5-hydroxyorotic acids with diazodiphenylmethane in various alcohols: Part III

Abstract

Rate constants for the reaction of diazodiphenylmethane (DDM) with 4-pyrimidinecarboxylic, 6-hydroxy-4-pyrimidinecarboxylic and 5-hydroxyorotic acids were determined in twelve protic solvents at 30 °C using the well known UV-spectrophotometric method. The second order rate contants for the examined acids were correlated using the appropriate solvent parameters by the equation log k = log k0 + af(e) + bs * + cngH were f(e) is the Kirkwood function of relative permittivity [(e-l)/(2e + 1 )], s * is the Taft polar constant for the alkyl group R in the alcohol ROH, and nyH is themumber of hydrogen atoms in the (-position in the alcohol. The results obtained for the investigated acids were compared with the corresponding results for benzoic, 2- and 3-hydroxybenzoic acids and the influence of the structure of the investigated acids on the reactivity in hydroxylic solvents is discussed. It was also possible to evaluate and distinguish the specific and non-specific solvent effects and their influence on the reaction rate.

Konstante brzina reakcija diazodifenilmetana (DDM) sa 4-pirimidinkarboksilnom, 6-hidroksi-4-pirimidinkarboksilnom i 5-hidroksiorotinskom kiselinom su određene u dvanaest protičnih rastvarača na 30 °C korišćenjem poznate UV-spektrofotometrijske metode. Konstante brzina reakcija drugog reda su korelisane sa odgovarajućim parametrima rastvarača korišćenjem solvatohromne jednačine u sledećem obliku: k = log k0 + af(e) + bs * + cngH gde je broj f(e) Kirkwood-ova funkcija permittivity [(e-l)/(2e + 1 )] relativne permitivnosti,, s * je Taft-ova konstanta alkil-grupe R alkohola ROH, i nyH je broj (-vodonikovih atoma. Dobijeni rezultati su poređeni sa rezultatima korelacija za benzoevu, kao i 2- i 3-hidroksibenzoevu kiselinu kako bi se diskutovao uticaj strukture ispitivanih kiselina u hidroksilnim rastvaračima na njihovu reaktivnost. Takođe su procenjeni specifični i nespecifični efekti rastvarača i njihov uticaj na brzinu ispitivanih reakcija.