AIM To study the stability of ligustilide with solvent effect and try to disclose the relationship between its stability and solvent effect, so as to develop a useful method for its preservation. METHODS The model of PCM solvent effect was used to carry out quantum chemistry calculation. The GC/MS spectrum was used to study the stability of ligustilide in solvent at room temperature. RESULTS Ligustilide is more stable in cyclohexane and chloroform than in air. The isomerization rate of ligustilide decreased remarkably to 1 6% and 6 7% in cyclohexane and chloroform compared to 58% in air. CONCLUSION The stability of ligustilide is greatly improved with the solvent effect. Keeping ligustilide in proper organic solvent is helpful to prevent its isomerization.
We modified Mulikens overlap population n(A, B)=2∑Bλ∑Aμ∑in_ic~*_A,μic_B,λis_Aμ,Bλ and obtained an experiential formula N(A,B)=N_A(A,B)+N_B(A,B) of judging bond strength, where N_A(A, B)=\{Z_AN^2_A(2∑Bλ∑Aμ∑i\}n_ic~*_A,μic_B,λis_Aμ,Bλ), N_B(A, B)=Z_BN^2_B(2∑Bλ∑Aμ∑in_ic~*_A,μic_B,λis_Aμ,Bλ). Twenty-eight bonds calculated by IEHM method and 11 monohydrides calculated by using 6-31G~** basis sets at Hartree-Fock level, electronic correlation effects are also considered through MP2/6-31G~**, were used to verify our experiential formula. Compared with the judgment of chemical bond strength by means of Mulikens overlap population, our experiential formula has a more obvious improvement as a judgment of bond strength than Mulikens overlap population. As a judgment of chemical bond strength between atoms in molecules, the experiential formula has conquered some limitations of Mulikens overlap population, and accorded with the experimental results.
