چكيده
The work is undertaken to carry out in that alkyl isocyanides (contains tert-butyl isocyanide, cyclo hexyl isocyanide) with dialkyl acetylenedicarboxylates (contains dimethyl acetylenedicarboxylate, diethyl acetylenedicarboxylate, di-tert-butylacetylenedicarboxylate) in the presence of acetic anhydride in gas phase and in the presence of solvent molecules (such as dichloromethane and acetone) to investigate the stability of each structures and transition barriers. Alkyl isocyanides are used as the important mediate in synthesis of wide range of compounds. Isocyanides undergo a formal [2+3] cycloaddition reaction with conjugated electrophile produced heterocyclic five-membered ring systems (furan). Quantum mechanics computations were carried out with the GAUSSIAN 09 series of programs. Full geometry optimizations of stable species and transition states were performed in the gas phase by employing the B3LYP level using 6-311++g(d,P) basis set. Results indicate that different substituted groups in structures, the reaction mechanism doesn’t change, but cause some sizable changes in potential energy surface of reaction coordinate. However, the barrier energy in more structures increased in that dicholromethane solvent, but, the barrier energy decreased in acetone solvent. Understanding of the strength and the nature of the hydrogen bonds, natural bond orbital analysis and topological properties were performed using NBO and AIM programs.
