Anharmonic effect of the unimolecular dissociation of Glycerol to Glycidol

The unimolecular dissociation rate constants of the dehydration of Glycerol to Glycidol were calculated at the MP2/6–311G(d,p) level using the Rice–Ramsperger–Kassel–Marcus (RRKM) theory. The anharmonic effect of the reactions was examined by comparing the rate constants at temperatures (700–3000[Formula: see text]K) of the canonical case and total energies (25654–53089[Formula: see text]cm[Formula: see text]) of the microcanonical system. The calculations showed that high temperatures are required for the reaction to proceed. As the temperatures and total energies increased, the rate of reactions increased. However, the growth rate of the unimolecular dissociation rate constants was high and slower both in the canonical and microcanonical systems. Comparative analysis showed that the anharmonic effect was most significant for the reaction [Formula: see text] and least significant for the reaction [Formula: see text]. The anharmonic effect became more significant as the temperatures and total energies increased. Compared with the microcanonical situation, the anharmonic effect of the canonical system was more pronounced.

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Calculation of anharmonic effect on the dissociation of ethylene glycol

Journal of Theoretical and Computational Chemistry ◽

10.1142/s0219633617500778 ◽

2017 ◽

Vol 16 (08) ◽

pp. 1750077

Author(s):

Qian Li ◽

Li Yao ◽

S. H. Lin

Keyword(s):

Ethylene Glycol ◽

Rate Constants ◽

Critical Role ◽

Canonical System ◽

Dissociation Rate ◽

Elimination Reaction ◽

Anharmonic Effect ◽

Bond Dissociation ◽

Total Energies ◽

Dissociation Rate Constants

The unimolecular dissociation rate constants of ethylene glycol were examined using the MP2/6-311[Formula: see text]G(d,p) method based on the Rice–Ramsperger–Kassel–Marcus (RRKM) theory. The effect of anharmonicity on the dissociation rate constants was evaluated at 500–4000[Formula: see text]K temperatures of the canonical system and 25,182–50,235[Formula: see text]cm[Formula: see text] total energies of the microcanonical system. The comparison of the results showed that the H2O elimination reaction played a critical role in the decomposition processes of ethylene glycol. The results of the rate constant calculations indicated that the H2O elimination reaction dominated at low temperatures, whereas the direct C–C bond dissociation reaction (CH2OHCH2OH [Formula: see text] CH2OH[Formula: see text][Formula: see text][Formula: see text]CH2OH) dominated at high temperatures. For channel 1, CH2OH[Formula: see text][Formula: see text][Formula: see text]CH2OH, the anharmonic effect of the canonical system was not observed, while it became more obvious with the increasing total energies in the microcanonical system. For channels 2–5, CH3CHO[Formula: see text][Formula: see text][Formula: see text]H2O, CH2CHOH[Formula: see text][Formula: see text][Formula: see text]H2O, CH3OH[Formula: see text][Formula: see text][Formula: see text]CHOH, and CH2OHCHO[Formula: see text][Formula: see text][Formula: see text]H2, the anharmonic effect of canonical and microcanonical systems became more obvious with increasing temperatures and total energies. The comparison showed that, for channels 1 and 4, C–C bond dissociation and the anharmonic effect of the microcanonical system were more evident, whereas the anharmonic effect of the canonical system was more predominant for channels 2 (CH3CHO[Formula: see text][Formula: see text][Formula: see text]H2O), 3 (CH2CHOH[Formula: see text][Formula: see text][Formula: see text]H2O), and 5 (CH2OHCHO[Formula: see text][Formula: see text][Formula: see text]H2).

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Calculated R.R.K.M. unimolecular dissociation rate constants for hydrazine

Canadian Journal of Chemistry ◽

10.1139/v69-428 ◽

1969 ◽

Vol 47 (14) ◽

pp. 2593-2599 ◽

Cited By ~ 6

Author(s):

D. W. Setser ◽

W. C. Richardson

Keyword(s):

Experimental Data ◽

Lower Bounds ◽

Rate Constants ◽

Chemical Activation ◽

Dissociation Rate ◽

Upper And Lower Bounds ◽

Unimolecular Dissociation ◽

Complex Models ◽

Dissociation Rate Constants ◽

Activated Complex

Unimolecular rate constants for hydrazine dissociation by thermal and chemical activation have been calculated according to the R.R.K.M. theory. The two activated complex models used in the calculations represent plausible upper and lower bounds to the rate constants. The calculations are mainly directed toward establishing expected decomposition to stablilization ratios of N2H4 produced by combination of NH2 radicals; however, a general comparison to available experimental data for hydrazine dissociation is made.

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