Group Contribution Model for Estimate of Correlation Energies of Linear Alkyl Alcohols

Abstract

AbstractThe correlation energy contribution of a polar group in a molecular system was defined and the contributions of HO, CH3, and CH2 groups in CH3(CH2)mOH (m=0–4) linear alkyl alcohols were calculated and studied at MP2‐OPT2/6‐311++G(d) level. It is revealed that the Ecorr(HO) and Ecorr(CH3) values of two terminal groups decrease somewhat with increase of number m in CH3(CH2)mOH (m=0–4) series. The value of Ecorr(CH2) in the α position is larger than those values of methylene groups in other positions in the same system, and the farther the CH2 from HO group in the molecule, the smaller the value of Ecorr(CH2) in CH3(CH2)mOH (m=1–4) systems. Therefore, it was predicted that with the increase of number m in CH3(CH2)mOH systems the values of Ecorr(CH2) that are those of CH2 groups relatively far from the terminal HO group would show a converging trend to that of a "standard" CH2 group and its value of Ecorr(CH2) would be transferable in CH3(CH2)mOH homologous systems. The excellent fitting relationships between the total correlation energy and the number of (m−1) where m is the number of methylene groups were obtained from both results at MP2‐OPT2/6‐311++G(d) level for CH3(CH2)mOH (m= 2–4) systems by Meld program and at MP2/6‐311++G(d)//HF/6‐311++G(d) level for CH3(CH2)mOH (m=2–7) systems by Gaussian 98 program, which show that the total correlation energy is a linear function of the number of (m−1).