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Activation parameters and kinetic isotope effect in the system tropaeolin O‐OH −
Author(s) -
PerlmutterHayman Berta,
Shinar Ruth
Publication year - 1978
Publication title -
international journal of chemical kinetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.341
H-Index - 68
eISSN - 1097-4601
pISSN - 0538-8066
DOI - 10.1002/kin.550100406
Subject(s) - chemistry , kinetic isotope effect , deprotonation , ionic strength , kinetics , kinetic energy , ion , reaction rate constant , solvent , ionic bonding , aqueous solution , deuterium , organic chemistry , physics , quantum mechanics
The kinetics of the deprotonation of tropaeolin O by OH − ions was investigated between 9° and 30°C, and by OD − ions at 24.7°C. The pH range was 10.7–12.5, and the ionic strength 0.1 M throughout. All results were obtained by the temperature jump method. On the basis of a mechanism suggested earlier, rate constants k 31 for the reaction between OL − and the internally bonded weak acid and k 32 for the opening of the internal hydrogen bond were evaluated. The activation energies in ordinary water were found to be Δ H ≠ 31 = 3.6 kcal/mol, Δ S ≠ 31 = –19 eu, and Δ H ≠ 32 = 27 kcal/mol, Δ S ≠ 32 = 46 eu. The kinetic isotope effect was k 31 H 2 O / k 31 D 2 O∼ 1.5 and k 32 H 2 O / k 32 D 2 O∼ 0.9. The unusual results for reaction pathare discussed in terms of solvent participation.