Abstract：
A theoretical analysis of free Gibbs Energy and NMR 1H 13C chemical shifts of the effect of introduce methyl groups on diphenyl rings, to produce different isomers of (E)-1-(α,Ꞵ-dimethylbenzylidene)-2,2-diphenylhydrazine, is presented. IR vibrational frequencies, Mulliken charges, molecular electrostatic potential (MEP), Gibbs free energy (G) and 1H- and 13C-NMR chemical shifts were obtained by theoretical calculations. In this analysis it was found that the position of the methyl group affects the values of the 1H- and 13C-NMR chemical shifts and the ∆G and ∆H thermodynamic properties of formation and reaction, these properties vary with the same trend, for the isomers studied. Gibbs free energy calculations show that the theoretical (E)-1-(3,4-Dimethylbenzylidene)-2,2-diphenylhydrazine isomer is the most stable, which explains the success of the experimental synthesis of this compound among the other isomers. For this molecule, the C of the HC=N group is the most nucleophilic and the H is the least acidic. The 1H-NMR chemical shifts of protons show a strong correlation with the C=N distance. It was also observed that methyl affects the ν(C=N) frequencies, the C=N distance increases when the inductive effect of the methyl groups is in the structure.
摘要：
对引入甲基对二苯环的影响的自由吉布斯能量和NMR1H13C化学位移的理论分析，产生不同的异构体（E）-1-（α，ε-二甲基亚苄基)-2,2-二苯基肼,是presented。红外振动频率,Mulliken指控,分子静电势（MEP），通过理论计算获得吉布斯自由能(G)和1H-和13C-NMR化学位移。在此分析中，发现甲基的位置影响1H和13C-NMR化学位移的值以及ΔG和ΔH的形成和反应的热力学性质，这些属性以相同的趋势变化，对于所研究的异构体。吉布斯自由能计算表明，理论(E)-1-(3,4-二甲基亚苄基)-2,2-二苯基肼异构体是最稳定的，这解释了该化合物在其他异构体中的实验合成的成功。对于这个分子，HC=N基团的C是最亲核的,并且H是最不酸性的。质子的1H-NMR化学位移显示出与C=N距离的强相关性。还观察到甲基影响ν(C=N)频率，当甲基的诱导效应在结构中时,C=N距离增加。
