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We have computationally studied the bimolecular nucleophilic substitution (SN2) reactions of MnNH2 (n−1) + CH3Cl (M+ = Li+, Na+, K+, and MgCl+; n = 0, 1) in the gas phase and in tetrahydrofuran solution at OLYP/6-31++G(d,p) using polarizable continuum model implicit solvation. We wish to explore and understand the effect of the metal counterion M+ and of solvation on the reaction profile and the stereochemical preference, that is, backside (SN2-b) versus frontside attack (SN2-f). The results were compared to the corresponding ion-pair SN2 reactions involving F− and OH− nucleophiles. Our analyses with an extended activation strain model of chemical reactivity uncover and explain various trends in SN2 reactivity along the nucleophiles F−, OH−, and (Formula presented.), including solvent and counterion effects.

4-Mercaptophenylboronic acid (4-mpba, C6H7BO2S) was investigated experimentally by vibrational spectroscopy. The molecular structure and spectroscopic parameters were studied by computational methods. The molecular dimer was investigated for intermolecular hydrogen bonding. Potential energy distribution analysis of normal modes was performed to identify characteristic frequencies. The present work provides a simple physical picture of the OH stretch vibrational spectra of 4-mpba and analogues of the compound studied. When the different computational methods are compared, there is a strong evidence of the better performance of the BLYP functional than the popular B3LYP functional to describe hydrogen bonding in the dimer. The findings of this research work should be useful to experimentalists in their quests for functionalised 4-mpba derivatives. (C) 2015 Elsevier B.V. All rights reserved.

The effects of varying halogen and solvent, in terms of vibrational and electronic properties, on the different conformers of 1-pentanamine [CH3(CH2)4NH2] and 1,1-dihalogeno-pentan-1-Amines [CH3(CH2)3CX2NH2; X = F, Cl or Br] were investigated by employing the density functional theory (DFT) and time-dependent density functional theory (TD-DFT) methods. The B3LYP functional was used with the 6-31++G(d,p) basis set. Computations were focused on the 10 conformational isomers of the compounds in the gas phase and both in non-polar (benzene) and polar (methanol) solvents. The present work explores the effects of the halogen and the medium on the conformational preference, and geometrical parameter, dipole moment, NH2 vibrational frequency, UV spectrum, highest occupied and lowest unoccupied molecular orbitals (HOMO-LUMO) orbital and DOS diagram of the conformers. The atypical characteristics of fluorine and bromine affecting the electrical bandgap, chemical hardness, electronegativity, PDOS or OPDOS plots and the absorption band are observed correspondingly. The findings of this work can be useful to those systems involving changes in the conformations analogous to the compounds studied. © World Scientific Publishing Company.

4-Mercaptophenylboronic acid (4-mpba, C6H7BO2S) was investigated experimentally by vibrational spectroscopy. The molecular structure and spectroscopic parameters were studied by computational methods. The molecular dimer was investigated for intermolecular hydrogen bonding. Potential energy distribution analysis of normal modes was performed to identify characteristic frequencies. The present work provides a simple physical picture of the OH stretch vibrational spectra of 4-mpba and analogues of the compound studied. When the different computational methods are compared, there is a strong evidence of the better performance of the BLYP functional than the popular B3LYP functional to describe hydrogen bonding in the dimer. The findings of this research work should be useful to experimentalists in their quests for functionalised 4-mpba derivatives.

The atmospherically relevant reactions between dimethyl selenide (DMSe) and the molecular halogens (X(2) = Cl(2), Br(2), and I(2)) have been studied with ab initio calculations at the MP2/aug-cc-pVDZ level of theory. Geometry optimization calculations showed that the reactions proceed from the reagents to the products (CH(3)SeCH(2)X + HX) via three minima, a van der Waals adduct (DMSe:X(2)), a covalently bound intermediate (DMSeX(2)), and a product-like complex (CH(3)SeCH(2)X:HX). The computed potential energy surfaces are used to predict what molecular species are likely to be observed in spectroscopic experiments such as gas-phase photoelectron spectroscopy and infrared matrix isolation spectroscopy. It is concluded that, for the reactions of DMSe with Cl(2) and Br(2), the covalent intermediate should be seen in spectroscopic experiments, whereas, in the DMSe + I(2) reaction, the van der Waals adduct DMSe:I(2) should be observed. Comparison is made with previous related calculations and experiments on dimethyl sulfide (DMS) with molecular halogens. The relevance of the results to atmospheric chemistry is discussed. The DMSeX(2) and DMSe:X(2) intermediates are likely to be reservoirs of molecular halogens in the atmosphere which will lead on photolysis to ozone depletion.

The reactions of dimethylsulfide (DMS) with molecular iodine (I(2)) and iodine monochloride (ICl) have been studied by infrared matrix isolation spectroscopy by co-condensation of the reagents in an inert gas matrix. Molecular adducts of DMS + I(2) and DMS + ICl have also been prepared using standard synthetic methods. The vapour above each of these adducts trapped in an inert gas matrix gave the same infrared spectrum as that recorded for the corresponding co-condensation reaction. In each case, the infrared spectrum has been interpreted in terms of a van der Waals adduct, DMS : I(2) and DMS : ICl, with the aid of infrared spectra computed for their minimum energy structures at the MP2 level. Computed relative energies of minima and transition states on the potential energy surfaces of these reactions were used to understand why they do not proceed further than the reactant complexes DMS : I(2) and DMS : ICl. The main findings of this research are compared with results obtained earlier for the DMS + Cl(2) and DMS + Br(2) reactions, and the atmospheric implications of the conclusions are also considered.