W2SDD theory for computational thermochemistry: study of the addition of hydrogen halide to propene

The Weizmann-n theories are characterized by a rigorous and well-defined series of ab initio calculations avoiding any empirical correction. W1 and W2 are two compound methods that aim for high accuracy by combining the results of several calculations. To expand W2 applicability to large molecules, an effective core potential, including relativistic effects, was included in its computational procedure, referred to as W2SDD. The cost-effective (accuracy/computational cost) W2SDD approach has a good performance in predicting both proton affinity and enthalpy of formation for a selected group of molecules containing halide atoms. The values obtained by W2SDD are very close to the original W2 theory. The W2SDD approach has also been applied to the mechanism for the hydrohalogenation of propene, and only one transition state for the reaction mechanism in cyclohexane medium has been found. In addition, the TD-DFT electronic circular dichroism spectrum of 2-chlorobutane shows a signal inversion for the gas-phase versus in cyclohexane solvent.