Mechanistic investigation of the reaction of thiourea with dialkyl acetylenedicarboxylates: a theoretical study

<div><p>In this work, mechanistic investigation of the addition–cyclization reaction between thiourea (TU) and dialkyl acetylenedicarboxylate (DAAD) was made theoretically with the B3LYP method using a 6-311++G(2d,2p) basis set. In order to investigate the effect of substituted alkyl groups, the reaction was evaluated in the presence of dimethyl acetylenedicarboxylate, diethyl acetylenedicarboxylate and di-<i>tert</i>-butyl acetylenedicarboxylate. To evaluate the effect of structure and dielectric constant of the solvent, all structures were optimized in different solvent phases such as dichloromethane and acetone at the B3LYP/6-311++G(2d,2p) level of theory. Different orientations of alkyl groups make different kinetic paths. Results indicated that the reaction mechanism did not change with different orientations of COOMe, COOEt or COOtBu groups, but caused significant changes in the potential energy surfaces of the reaction coordinate. The reaction product (alkyl E-2-(2-imino-4-oxo-1,3-thiazolane-5-yliden) acetates) can be converted to different tautomeric forms in two proton transfer processes. So, in order to investigate the effect of different substituted alkyl groups, intermolecular proton transfer in the product was investigated both in gas phase and in the presence of methanol, ethanol and <i>tert</i>-butanol molecules as a bridge to facilitate the proton transfer process.</p></div

Theoretical study of interaction of NH₂X (X = H, CH₃, CH₂OCH₃, and CH₂COOH) molecules with AlN and AlP nanotubes

<p></p> <p>In this work, we have studied the interaction of NH₃, NH₂CH₃, NH₂CH₂OCH₃, and NH₂CH₂COOH with aluminum nitride (AlN) and aluminum phosphide (AlP) nanotubes (NT) by means of the B3LYP hybrid density functional method using 6-31G(d) basis set. The results show that these molecules can be chemically adsorbed on the top of the aluminum atom of AlNNTs and AlPNTs. Also, the AlP nanotubes are the most energetically favorable candidates for adsorption of these molecules. It was found that the interaction these molecules with nanotubes results in changes in the electronic properties of NTs. Based on the NBO analysis, in all complexes charge transfer occurs from these molecules to nanotubes. The AIM results show that, the Al…N interaction has a partial covalent nature. Also, this interaction in the AlP complexes is stronger than that in the AlN complexes. In both types of complexes, the results obtained for complexes containing electron-donating molecules are better than complexes containing electron-withdrawing ones.</p