Ab Initio Study of α-Chlorinated Ethyl Hydroperoxides CH₃CH₂OOH, CH₃CHClOOH, and CH₃CCl₂OOH:  Conformational Analysis, Internal Rotation Barriers, Vibrational Frequencies, and Thermodynamic Properties

Abstract

Ab initio calculations were performed on CH3CH2OOH, CH3CHClOOH, and CH3CCl2OOH molecules using the Gaussian92 system of programs. Geometries of stable rotational conformers and transition states for internal rotation were optimized at the RHF/6-31G* and MP2/6-31G* levels of theory. Harmonic vibrational frequencies were computed at the RHF/6-31G* level of theory. Potential barriers for internal rotations were calculated at the MP2/6-31G**/HF/6-31G* level. Parameters of the Fourier expansion of the hindrance potentials have been tabulated. Standard entropies (S°298) and heat capacities (C p (T)'s, 300 ≤ T/K ≤ 1500) were calculated using the rigid-rotor−harmonic-oscillator approximation based on the information obtained from the ab initio studies. Contributions from hindered rotors were calculated by summation over the energy levels obtained by direct diagonalization of the Hamiltonian matrix of hindered internal rotations. Enthalpies of formation for these three molecules were calculated using isodesmic reactions. Enthalpies of formation were calculated to be ΔH f°298(CH3CH2OOH) = −41.5 ± 1.5 kcal mol-1, ΔH f°298(CH3CHClOOH) = −50.9 ± 3.4 kcal mol-1, and ΔH f°298(CH3CCl2OOH) = −55.3 ± 2.2 kcal mol-1. Entropies (S°298) are calculated to be 76.1, 79.2 and 86.6 cal mol-1 K-1 for CH3CH2OOH, CH3CHClOOH, and CH3CCl2OOH, respectively.

Thermochemical Properties of Hydroxycyclohexadienyl Peroxy Isomers from Reaction of O2 with the Benzene-OH adduct

“…The values from X//MP2(full)/6-31G(d,p) (X=G3(MP2), CBS-Q, CBS-4 and CBS-lq) are listed in [35]; (C=CCOH) = −29.55±0.35 [36]; (C=CCOOH) = −13.59±0.14 [37]; (C2COH) = −65.07±0.22 [38]; (C2COOH) = −48.99 ± 0.32 [39]; (CCOOH) = −39.70 ± 0.30 [23]; (CCOO•) = −6.72 ± 2.3 [40]; (1,4-cyclohexadiene) = 25.04 ± 0.14 [41]; (1,3-cyclohexadiene) = 25.00 ± 0.15 [41]; (cyclohexene) = −1.03±0.23 [42]; (benzene) = 19.82±0.12 [43]; (phenol) = −23.03±0.14 [44]; (toluene) = 11.95±0.15 Entropies and heat capacities from 50 K to 5000 K were calculated using the rigid-rotor-harmonic-oscillator approximation based on scaled vibrational frequencies (the two torsion frequencies corresponded to -OO and -OH rotors are excluded), molecular mass, and moments of inertia of the optimized B3LYP/6-31G(d, p) structures. The ROTATOR program is used to calculate internal rotor energy levels from the structure and the calculated one-dimensional uncoupled intramolecular rotation potential energy curves [18,19]. It solves the Schrodinger Eqn using free rotor wave functions and then calculates o ( ) and ( ) from the partition function.…”

“…The number of optical isomers and spin degeneracy of unpaired electrons were also incorporated for calculation of o ( )'s and ( )'s. Lay et al [18], Green and Sumanthi et al [20] and Speybroeck et al [21] report that analysis of internal rotors is important for kinetics where internal rotor are involved. Speybroeck also studied effects of coupling between internal rotors and report that the coupling has only, a minor influence on the kinetics, relative to treating all internal rotors as uncoupled.…”

“…trema of angular positions. Details on the method to calculate contributions from the internal rotors are reported by method of Lay et al [18,19]. Thermal corrections to enthalpy are calculated from the integration of heat capacities at finite temperature steps using Simpson's Rule [24].…”

A Multiscale Simulation Approach for the MOCVD of GaN Using a Single‐Molecule Precursor in a Vertical Stagnation Flow Reactor

“…With the ªQuantum Rotator V 1.5º program [45] the 1D Schrödin-ger equation (Eq. 5) for ±p £ h < p (where W(h) is the wave function) was solved for sufficient eigenvalues, e, to achieve convergence in the partition function.…”

A priori falloff analysis for OH + NO2

“…The OH hindered rotor was next assumed to have a rigid axis of rotation (the bond) attached to HO 9 N a rigid "frame" such that the moments of inertia for internal rotation and overall rotation were considered constant and unrelated (e.g., [31]). The potential in (3) was applied to a computer code by Shokhirev and Krasnoperov that evaluated the energy levels for a hindered rotor with this potential via diagonalization of the Schroedinger equation Hamiltonian for a hindered rotation [32,33]. With the zero-point…”