Formation of Hydrogen Bonds in Complexes between Dimethylcuprate(I) Anion and Methane, Propane, or Dimethyl Ether. A Theoretical Study

Complexes of the neutral ligands methane, propane, and dimethyl ether (DME) with a dimethylcuprate(I) anion (DMCA) were studied using B3LYP and MP2 methods. The quantum theory of atoms in molecule and the second-order perturbation natural bond orbital analysis were applied to analyze the electron density distributions of these complexes and to elucidate the nature of weak closed-shell interactions between the C−H bonds of the ligands and different atoms and bonds of DMCA. The presented results show that the copper center of DMCA interacts with the C−H bonds of methane, propane, and DME via formation of Cu···H−C hydrogen bonds, with the Cu center being an electron charge donor (hydrogen bond acceptor). The formation of weak dihydrogen bonds and C−H···C hydrogen bonds between C−H bonds of the neutral ligands and methyl groups of DMCA additionally stabilizes these complexes. Second-order orbital interactions of C−Cu bonds with C−H bonds contribute also to the formation of the complexes. Each of these interactions is very weak, but the sum of these interactions may have the potential to influence the structures of organocuprates(I), possessing very flat potential energy surfaces

Cyclization of the substituted N-(ortho-cyclopropylphenyl)-N'-aryl ureas and thioureas in the gas phase and solution

Electron ionization (EI), chemical ionization (CI), tandem mass spectrometry, high-resolution measurements, and labeling studies as well as quantum chemical calculations were used to understand the behavior of the molecular radical cations (EI) and protonated molecules (CI) of substituted N-(ortho-cyclopropylphenyl)-N′-aryl ureas and N-(ortho-cyclopropylphenyl)-N′-aryl thioureas in a mass spectrometer. Fragmentation schemes and possible mechanisms of primary isomerization were proposed. According to the fragmentation pattern, formation of the corresponding benzoxazines and benzothiazines was considered as the major process of isomerization of the original M+· and MH+, although some portions of these ions definitely transformed into other structures. The treatment of N-(ortho-cyclopropylphenyl)-N′-phenyl urea and N-(ortho-cyclopropylphenyl)-N′-phenylthiourea in solution with strong acids formed predicted 4-ethyl-N-phenyl-4H-3,1-benzoxazin-2-amin and 4-ethyl-N-phenyl-4H-3,1-benzothiazin-2-amine as principal products