The hydroxyl groups internal rotations in a methanediol molecule

Abstract

Internal rotation of two of hydroxyl groups in a methanediol molecule is analyzed by constructing the 2D surfaces of the potential energy, kinematic coefficients and dipole moment.The molecular characteristics in the nodes of 2D grids with different densities for distinct pairs of dihedral angles of O-H groups were calculated at the MP2/cc-pVQZ level of theory with optimization of the geometry for all other structural parameters. For optimized at the MP2/cc-pVQZ level of theory geometries, the potential energy was additionally calculated at the MP2/cc-pVTZ level of theory in the same grid nodes and then the extrapolation of energies in every node to the complete basis set limit was performed. The kinematic parameters were calculated using the formalism of the Wilson vectors. The Hamiltonian matrix was compiled using the DVR method. As a result of its diagonalization, the wave functions and energies of stationary torsional states were determined. The calculated torsional wave functions were classified by irreducible representations of the C 2V (M) molecular symmetry group. The frequencies and intensities of the torsional spectrum of a methanediol molecule were calculated at different temperatures for the trans-and cis-conformers. The tunneling frequencies for both conformers were calculated too.

Synthesis of methanediol [CH 2 (OH) 2 ]: The simplest geminal diol

“…Prior theoretical work has been devoted to exploring the stability and catalytic decomposition dynamics of 1 ( 8 – 10 , 25 – 29 ). Kent et al.…”

The torsional spectrum of the hydrogen trioxide molecule

“…The symmetry properties of the 2D surfaces of the potential energy, dipole momentum and kinematic coefficients of the HT molecule are very close to those of the methanediol molecule (MD), for which the internal rotation was recently analyzed [43]. In [43] the symmetry elements of the 2D surfaces were connected with symmetry elements of the C2V(M) molecular symmetry group. According to [43] let's call the plane which is perpendicular to the coordinate plane ,  and intersect it along diagonal (0 0 ,0 0 -360 0 ,360 0 ) plane 1.…”

“…In [43] the symmetry elements of the 2D surfaces were connected with symmetry elements of the C2V(M) molecular symmetry group. According to [43] let's call the plane which is perpendicular to the coordinate plane ,  and intersect it along diagonal (0 0 ,0 0 -360 0 ,360 0 ) plane 1. The plane which is perpendicular to the coordinate plane ,  and intersects it along diagonal (0 0 ,360 0 -360 0 ,0 0 ) will be plane 2.…”

“…Configurations optimized in each node were used to calculate the kinematic coefficients using Wilson vectors ( s -vectors) [53]. The vibrational Schrödinger equation with reduced dimensionality for the torsional vibrations of two hydroxyl groups can be written as follows [43,[54][55][56]:…”

“…In addition, the symmetry of the spin wave functions must be saved during the torsional transitions. Relative intensities of the IR bands for torsional transitions from the initial state i to the final state f were calculated using the next formulas [43,40,[67][68][69][70][71] where i g is the multiplicity of degeneracy of the initial torsional state, the value of which is coordinated with the type of symmetry of the torsional wave function in accordance with the data of Table 8 and 9, i s and f s are the specifiers of the initial and final states, the value of which is 1 for the torsional states of the А1 and А2 type and -1 for the torsional states of the В1 and В2 as shown in Table 9, () QT -partition function. With the use of these data, the relative intensities of the IR absorption bands at different temperatures were calculated from the formula (17).…”