线性氟代烷烃电子相关能的基团加和性(英文)

Additivity of Group Contribution of Electron Correlation Energies in Linear Alkyl Fluorides

应用Meld程序在MP2-OPT2/6-311++G(d)水平计算了线性氟代烷烃分子CH3(CH2)mF(m=0-5)中-CH3、-CH2-和-F基团电子相关能贡献值.计算结果表明,在CH3(CH2)mF(m=0-5)体系中,端基-F、-CH3基团电子相关能贡献值Ecorr(-F)和Ecorr(-CH3)随着m的增大而逐渐减小.分子中α位置-CH2-基团电子相关能贡献值Ecorr(-CH2-)大于其他位置的贡献值.通过计算结果可以推断,在CH3(CH2)mF体系中随着m的逐渐增大,远离端基-F的-CH2-基团电子相关能贡献值逐渐减小并将趋于不变,此-CH2-基团可看作一个标准的亚甲基且其Ecorr(-CH2-)的数值在CH3(CH2)mF体系中具有传递性.应用Meld程序在MP2-OPT2/6-311++G(d)水平对CH3(CH2)mF(m=2-5)体系的计算结果和应用Gaussian98程序在MP2/6-311++G(d)//HF/6-311++G(d)水平对CH3(CH2)mF(m=2-10)体系的计算结果均表明,体系总电子相关能与体系中(m-1)数值呈线性关系.

Correlation energy contributions of the --CH3, ----CH2-- and --F functional groups in linear alkyl fluorides CH3（CH2）mF （m=0-5） were calculated and studied at MP2-OPT2/6-311＋＋G（d） level using Meld program. We found that with an increase in the number of intervening methylene groups in the studied systems, values of Ecorr（--F） and Ecorr（--CH3） decreased in the CH3（CH2）mF （m=0-5） series. Values of Ecorr（--CH2--） are different in different positions with respect to the --F group in the system. The value of Ecorr （--CH2--） for the α position is larger than the values for methylene groups in other positions within the same system. The farther the -----CH2-- is from the --F group in the molecule, the smaller the value of Ecorr（---CH2----） is in CH3（CH2）mF （m=1-5） systems. We predict that with an increase in the number m in the system, values of Ecorr （---CH2----）, which are those of---CH2---- groups relatively far from the terminal --F group, would converge to the value of a ＂standard＂ ------CH2---- group. This Ecorr（-----CH2----） value is transferable between CH3（CH2）m homologous systems. Results for CH3（CH2）mF （m=2-5） systems from Meld program at MP2-OPT2/6- 311＋＋G（d） level and results for CH3（CH2）,,F （m=2-10） systems from Gaussian 98 program at MP2/6-311＋＋G（d）//HF/ 6-31 1＋＋G（d） level show that the total correlation energy is a linear function of （m-l）, where m is the number of methylene groups in the system.