Experimental and theoretical studies of the elimination kinetics of 3-hydroxy-3-methyl-2-butanone in the gas phase

• Published in: Journal of physical organic chemistry 2005-07, Vol.18 (7), p.595-601
• Main Authors: Graterol, Mariana, Rotinov, Alexandra, Cordova, Tania, Chuchani, Gabriel
• Format: Article
• Language: English
• Subjects: 3-hydroxy-3-methyl-2-butanone; DFT B3LYP/6-31G; elimination; kinetics; MP2/6-31G; pyrolysis; RHF/6-31G
• ISSN: 0894-3230; 1099-1395
• DOI: 10.1002/poc.913

The kinetics of the gas‐phase elimination of 3‐hydroxy‐3‐methyl‐2‐butanone was investigated in a static system, seasoned with allyl bromide, and in the presence of the free chain radical inhibitor toluene. The working temperature and pressure range were 439.6–489.3°C and 81–201.5 Torr (1 Torr = 133.3 Pa), respectively. The reaction was found to be homogeneous, unimolecular and to follow a first‐order rate law. The products of elimination are acetone and acetaldehyde. The temperature dependence of the rate coefficients is expressed by the following equation: log[k1(s−1)] = (13.05±0.53)−(229.7±5.3) kJ mol−1 (2.303RT)−1. Theoretical estimations of the mechanism of this elimination suggest a molecular mechanism of a concerted non‐synchronous four‐membered cyclic transition‐state process. An analysis of bond order and natural bond orbital charges suggests that the bond polarization of C(OH)—C(O)—, in the sense of C(OH)δ+&·C(O)δ−, is rate limiting in the elimination reaction. The rate coefficients obtained experimentally are in reasonably good agreement with the theoretical calculations. The mechanism of 3‐hydroxy‐3‐methyl‐2‐butanone elimination is described. Copyright © 2005 John Wiley & Sons, Ltd. The kinetics of elimination 3‐hydroxy‐3‐methyl‐2‐butanone in the gas phase were investigated in a static system (439–489°C and 81–201 Torr). The reaction is homogeneous, unimolecular and follows a first‐order rate law. Theoretical calculations suggest a molecular mechanism of a concerted non‐synchronous four‐membered cyclic transition‐state process. The rate coefficients obtained experimentally are in reasonably good agreement with the theoretical calculations. The mechanism of this elimination is described.