Ozonolysis of Geraniol-trans, 6-Methyl-5-hepten-2-one, and 6-Hydroxy-4-methyl-4-hexenal: Kinetics and Mechanisms

Abstract

A combined density functional theory and transition-state theory study of the mechanisms and reaction coefficients of gas-phase ozonolysis of geraniol-trans, 6-methyl-5-hepten-2-one, and 6-hydroxy-4-methyl-4-hexenal is presented. The geometries, energies, and harmonic vibrational frequencies of each stationary point were determined by B3LYP/6-31(d,p), MPW1K/cc-pVDZ, and BH&HLYP/cc-pVDZ methods. According to the calculations, the ozone 6-methyl-5-hepten-2-one reaction is faster than the ozone 6-hydroxy-4-methyl-4-hexenal reaction, but both are slower than the ozone geraniol-trans reaction. By using the BH&HLYP/cc-pVDZ data, a global rate coefficient of 5.9 x 10(-16) cm(3) molecule(-1) s(-1) was calculated, corresponding to the sum of geraniol-trans, 6-methyl-5-hepten-2-one, and 6-hydroxy-4-methyl-4-hexenal reactions with the ozone. These results are in good agreement with the experimental studies.

Modeling the Time-Dependent Concentrations of Primary and Secondary Reaction Products of Ozone with Squalene in a University Classroom

“…47 The second-order rate constant of ozone with 6-MHO is measured to be 3.8 × 10 −5 s −1 ppb −1 (1.5 × 10 −15 cm 3 molecule −1 s −1 after unit conversion), which is higher than experiments conducted by Grosjean et al and Leonardo et al (3.94 × 10 −16 and 5.9 × 10 −16 cm 3 molecule −1 s −1 , respectively). 27,28 The above two cases are all conducted without human presence. Wisthaler and Weschler 29 used the gas-phase reaction rate constant (4.03 × 10 −16 cm 3 molecule −1 s −1 ) to estimate the 4-OPA concentration in an office occupied by occupants and found that the calculated concentration was much lower than the measured data (<5%), meaning that the rate constant should be higher when an occupant is involved.…”

Theoretical studies of atmospheric reaction mechanisms in the troposphere

“…isoprene, [120][121][122][123][124] a-pinene, [125][126][127] b-pinene, 128 and geraniol. 129 In contrast to simple alkenes, H-abstraction can be an important initiation channel, contributing for over 30%. [130][131][132][133] The H-abstraction can be enhanced due to the formation of allylresonance stabilized alkyl radicals, 128,134 but also due to strain in small cycles.…”

“…The rate coefficients for the reactions of alkenes with O 3 span many orders of magnitude, depending mostly on the substitution around the double bond. The van der Waals pre-reactive complex, the transition state for cycloaddition, and the formation of the POZ have been characterized theoretically for many compounds; recent examples include (substituted) alkenes, [144][145][146][147][148][149][150][151][152][153] butadiene, 154 cycloalkenes, [155][156][157] terpenoids, 129,[158][159][160][161][162][163][164][165][166][167] and acetylene. 149,150,153 An accurate quantum chemical description of the 1,3-dipolar ozone addition requires particular attention, owing to the strong multi-reference character of the wavefunctions for ozone, pre-reactive complex, and addition transition state.…”

Application of GC × GC coupled with TOF–MS for the trace analysis of chemical components and exploration the characteristic aroma profile of essential oils obtained from two tree peony species (Paeonia rockii and Paeonia ostii)

“…In addition, geranyl acetone, 6-methyl-5-hepten-2-one and 2-octanone were the main ketones in FengDan EO, while they were not found in ZiBan EO. Moreover, 6-methyl-5-hepten-2-one is an endogenous metabolite with a fatty and citrus-like flavor [33,34]. At the same time, it has a strong chemical reaction ability and is an important intermediate for the synthesis of medicine, flavors and fragrances.…”

“…At the same time, it has a strong chemical reaction ability and is an important intermediate for the synthesis of medicine, flavors and fragrances. For example, it is an intermediate for the synthesis of linalool [34]. Moreover, 2-octanone is an essential contributor to floral fragrance as well as an important raw material for the preparation and synthesis of fragrances, foaming agents and surfactants [35].…”