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Ab initio calculations are performed to characterize the best molecular shape and dimensions of diisopropylnaphthalene (DIPN) isomer concerning molecular transportation in the channel system of mordenite (M) zeolite. Theoretical and experimental studies revealed the selective formation of 2,6-isomer of DIPN over HM zeolite main channel due to operative product selectivity.

Issues concerning the dynamics and energetics of the protonation of the naphthalene molecule at the Hartree-Fock and correlated levels are discussed. Calculations at correlated levels reproduced the gas-phase proton affinity and basicity of naphthalene effectively.

A scaled effective one-electron approximate quantum chemical method was applied to investigate the conformational properties of unbranched aliphatic alkanes. Eleven, 35 and 107 conformers were discovered for the pentane, hexane and heptane molecules, respectively, and their conformational spectra were also the same at Hartree-Fock and second-order Moeller-Plesset levels. The results enable the derivation of four principles which can reproduce the number and sequences of the existing conformers up to undecane.

The existence of carbocations in acid-catalyzed reactions may be proven by the presence of characteristic group frequencies for infrared radiation and chromophoric groups for ultraviolet-vis absorption. The processes that govern hydrocarbon transformations are mediated by zeolites, crystalline-alumino-hydro-silicates that feature pores of molecular dimensions. These compounds are highly acidic and are typically characterized by relatively weak complexation energies, varying photon transfer energies and steric constraints.

The effect of an adiabatic approximation, named adiabatic Jacobi correction (AJC) and introduced in J. Chem. Phys. 126, 024102 (2007), was investigated on the complete set of vibrational levels of H2+ and its isotopologues, most importantly on the highest-lying vibrational states of HD+. In order to perform clamped nuclei calculations employing finite nuclear masses a constrained Hamiltonian has been derived utilizing interparticle coordinates. The Born–Oppenheimer (BO) potential, the adiabatic potential obtained after taking into account the traditional diagonal Born–Oppenheimer correction (DBOC), as well as the AJC-corrected potential have been determined by an accurate fitting to computed energy values. These potentials were included in one-dimensional variational computations and yielded the complete set of energy levels for H2+, D2+, and HD+. A detailed investigation of the potential and the complete set of vibrational energy levels show the merits and the deficiencies of the BO, DBOC, and AJC treatments. In particular, it is shown that the AJC corrections are systematically smaller and have a different distance dependence than the DBOC corrections. For a large part of the spectrum of H2+ and its isotopologues the adiabatic correction to the vibrational energy levels is smaller than the nonadiabatic correction, the adiabatic DBOC correction has the highest overall accuracy for the prediction of vibrational energy levels, it is surpassed by the AJC correction only for the highest energy levels of HD+, and thus the use of the AJC correction is clearly the best choice only for states close to the dissociation limit of nonsymmetric isotopologues. [ABSTRACT FROM AUTHOR]

Systematic quantum chemical calculations to obtain precise estimate of the equilibrium and vibrationally averaged molecular structure and electric dipole moment of vinylacetylene (VA, 1-buten-3-yne). It was found that the electric dipole moment of VA is 0.45D using a simple quantitative structure-property relationship (QSPR) model.

The focal‐point analysis (FPA) technique is used for the definitive characterization of conformational interconversion parameters, including activation energy barriers, activation free energies, and kinetic rate coefficients at 298 K, of two n‐alkanes, n‐butane, and n‐pentane, yielding the first complete analysis of their interconversion kinetics. The FPA implementation developed in this study is based on geometry optimizations and harmonic frequency computations carried out with density functional theory methods and single‐point energy computations up to the CCSD(T) level of electronic structure theory using atom‐centered Gaussian basis sets as large as cc‐pV5Z. The anharmonic vibrational computations are carried out, at the MP2/6‐31G* level of theory. Reflecting the convergence behavior of the Gibbs free‐energy terms and the interconversion parameters, well‐defined uncertainties, mostly neglected in previous theoretical studies, are provided. Finally, the effect of these uncertainties on the concentrations of the conformers of n‐butane and n‐pentane is examined via a global Monte–Carlo uncertainty analysis. © 2017 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]