Accurate prediction of thermodynamic properties of alkyl peroxides by combining density functional theory calculation with least‐square calibration

Owing to the significance in kinetic modeling of the oxidation and combustion mechanisms of hydrocarbons, a fast and relatively accurate method was developed for the prediction of Δ f H   o 298of alkyl peroxides. By this method, a raw Δ f H   o 298value was calculated from the optimized geometry and vibration frequencies at B3LYP/6‐31G(d,p) level and then an accurate Δ f H   o 298value was obtained by a least‐square procedure. The least‐square procedure is a six‐parameter linear equation and is validated by a leave‐one out technique, giving a cross‐validation squared correlation coefficient q 2 of 0.97 and a squared correlation coefficient of 0.98 for the final model. Calculated results demonstrated that the least‐square calibration leads to a remarkable reduction of error and to the accurate Δ f H   o 298values within the chemical accuracy of 8 kJ mol −1 except (CH 3 ) 2 CHCH 2 CH 2 CH 2 OOH which has an error of 8.69 kJ mol −1 . Comparison of the results by CBS‐Q, CBS‐QB3, G2, and G3 revealed that B3LYP/6‐31G(d,p) in combination with a least‐square calibration is reliable in the accurate prediction of the standard enthalpies of formation for alkyl peroxides. Standard entropies at 298 K and heat capacities in the temperature range of 300–1500 K for alkyl peroxides were also calculated using the rigid rotor‐harmonic oscillator approximation. © 2008 Wiley Periodicals, Inc. J Comput Chem, 2009