Enthalpies of formation and substituent effects of ortho-, meta-, and para-aminotoluenes from thermochemical measurements and from ab initio calculations.
The molar enthalpies of vaporization of 2-amino-, 3-amino-, and 4-aminotoluenes were obtained from the temperature dependence of the vapor pressure measured by the transpiration method. The molar enthalpy of sublimation of 4-aminotoluene was measured in the same way. The standard (p(o) = 0.1 MPa) molar enthalpy of formation delta fH(o)m(cr) at the temperature T = 298.15 K of crystalline 4-aminotoluene was measured using combustion calorimetry. The thermochemical investigations of aminotoluenes available in the literature were collected and combined with our own experimental results to obtain our own reliable standard molar enthalpies of formation at T = 298.15 K in the gaseous state. Ab initio calculations of aminotoluenes have been performed using the MP2Full/6-31G(d) and G3(MP2) basis sets, and the results from the bond separation method are in excellent agreement with the experiment. These new results help to resolve the uncertainty in the available thermochemical data on aminotoluenes. Weak mutual interactions of substituents in aminotoluenes have been realized using an isodesmic reaction procedure.
Emel'yanenko
Vladimir N
VN
Department of Physical Chemistry, University of Rostock, Hermannstrasse 14, 18051 Rostock, Germany.
Verevkin
Sergey P
SP