7216-56-0Relevant academic research and scientific papers
A comparative study on the gas-phase and liquid-phase thermal isomerization reaction of α-pinene
He, Jindong,Gong, Yan,Zhao, Wentao,Tang, Xiangyang,Qi, Xin
, p. 15 - 22 (2013/03/13)
In this paper, a method of preparation of ocimene is investigated, which is obtained from isomerization reaction of α-pinene. Two kinds of experimental apparatus are established for the investigation of the thermal isomerization reaction of α-pinene. The behavior of thermal isomerization reaction of α-pinene is respectively discussed in the gas phase and in the liquid phase. Under gas phase conditions, the conversion of α-pinene is 80% and the selectivity of ocimene is 30%-33%. Under liquid phase conditions, the conversion of α-pinene is 60% and the selectivity of ocimene is 50%-54%. According to the kinetic-molecular theory of ideal gases, two kinds of reaction models are proposed to visualize the reaction process. In addition, the mechanism and kinetics of thermal isomerization reaction of α-pinene are respectively discussed. The conclusion is that the gas phase reaction temperature is calculated to be 390-450 °C and the liquid phase reaction temperature is calculated to be 450-550°C. From a bond dissociation energy point of view, results support the hypothesis that the reaction involves biradical intermediates. Copyright
Kinetic and mechanistic study on the thermal isomerization of ocimene in the liquid phase
He, Jindong,Xie, Meng,Tang, Xiangyang,Qi, Xin
scheme or table, p. 373 - 378 (2012/07/30)
The rate of thermal isomerization of ocimene in the liquid phase has been investigated in the range 90-150°C. The rate constant for the disappearance of ocimene may be expressed by k=1.3×1010e -11994.2/T(min-1), from which we can infer that the activation energy is 99.7kJmol-1 and the pre-exponential factor is 1.3×1010min-1. The half-life for the disappearance of ocimene may be expressed by t1/2=5.2×10-11e 11994.2/T(min). The conclusion has been supported by the study results that the ocimene is safe when temperature is below 100°C. A discussion of the mechanism concerning the conversion is included. Copyright
Kinetics of thermal conversions of monoterpenic compounds in supercritical lower alcohols
Anikeev,Ermakova,Chibiryaev,Kozhevnikov
scheme or table, p. 162 - 193 (2010/09/04)
The most important information concerning thermal conversions of vegetable terpenes (α-pinene, β-pinene, turpentine, and cis-verbenol) in supercritical lower alcohols is systematized. The kinetics of selected reactions is reported and is compared with the kinetics of the same reactions in the gas and liquid phases. Thermodynamic calculations of the phase states and kinetic parameters are presented for a number of multicomponent multiphase systems containing terpenes and lower alcohols. The effect of the supercritical solvent pressure on the rate and selectivity of the selected reactions is reported.
Mechanistic and kinetic insights into the thermally induced rearrangement of α-pinene
Stolle, Achim,Ondruschka, Bernd,Findeisen, Matthias
supporting information; scheme or table, p. 8228 - 8235 (2009/04/11)
(Chemical Equation Presented) The thermal rearrangement of α-pinene (1) is interesting from mechanistic as well as kinetic point of view. Carrier gas pyrolyses with 1 and its acyclic isomers ocimene (2) and alloocimene (3) were performed to investigate the thermal network of these hydrocarbons. Kinetic analysis of the major reaction steps allows for a deeper insight in the reaction mechanism. Thus it was possible to explain the racemization of 1, the formation of racemic limonene (4), and the absence of the primary pyrolysis product 2 in the reaction mixture resulting from thermal rearrangement of 1. Results supported the conclusion that the reactions starting with 1 involve biradical transition states.
The influence of water on the isomerization of α-pinene in a supercritical aqueous-alcoholic solvent
Ermakova,Chibiryaev,Mikenin,Sal'nikova,Anikeev
, p. 62 - 67 (2008/09/16)
The influence of water as a cosolvent and catalyst of the isomerization of α-pinene in a supercritical aqueous-alcoholic (ethanol) solvent was studied experimentally. At T = 657 K and p = 230 atm, an increase in the concentration of water in the reaction mixture was found to increase the rate of the reaction and its selectivity with respect to the desired product, limonene. Water exhibited the properties of an acid catalyst because of its ionization. Mathematical experimental data processing was performed to evaluate and separate the contributions of the radical and ionic paths to the total rate of the reactions that occurred during the thermal isomerization of α-pinene.
Thermolysis of α-pinene in supercritical lower alcohols
Chibiryaev,Anikeev,Yermakova,Mikenin,Kozhevnikov,Sal'nikova
, p. 987 - 992 (2008/02/01)
Thermal isomerization of α-pinene in supercritical solvents, viz., ethanol, methanol, and propan-1-ol, was carried out, and differences in the rate and selectivity of the process were revealed. In supercritical ethanol the reaction rate increases sharply and the selectivity remains unchanged with an increase in the temperature (from 290 to 390°C) or pressure (from 90 to 270 atm). The main reaction products are limonene, isomeric alloocimenes, and pyronenes. The selectivity for limonene in propan-1-ol is higher than in other alcohols when the conversion of α-pinene not higher than 50%. In supercritical ethanol (430°C, 120 atm, 140 s) limonene is more stable than α-pinene (conversion 8%).
Isomerization equilibria and thermodynamic properties of triene hydrocarbons
Garist,Stolyarova,Emel'yanenko,Roganov
, p. 1565 - 1571 (2007/10/03)
The isomerization equilibrium between 2,6-dimethyloctatriene-2,tran-4,tran- 6, 2,6-dimethyloc-tatriene-2,tran-4,cis-6, 2,6-dimethyloctatriene-1,trans-3, trans-5, 2-methyl-6-methyleneoctadiene-2,trans-4, and 2,6-dimethyloctatriene-1, trans-3,cis-5 was studied by pulsed-mode reaction gas chromatography in a microreader connected to the line of a gas Chromatograph over a temperature range of 498-623 K, and the thermodynamic characteristics of the reactions were obtained. It was established that the stability increases with the degree of alkyl substitution of the terminal carbon atoms involved in the conjugation system, with one substitution stabilizing the system by 10 kJ/mol; the differences in the entropies of the isomers are largely associated with the differences in the symmetry numbers of the internal rotors of their molecules. Ab initio calculations were used to study the conformational state of the molecules and to obtain analytical expressions for the potential energy surfaces of the joint internal rotations of the asymmetric tops in the trans-2-methylhexatriene-1,3,5, trans-3-methylhexatriene-1,3,5, trans,trans-heptatriene-1,3,5, trans,trans,trons-octatriene-2,4,6, and 2,5-dimethylhexatriene-l,3,5 molecules. Molecular parameters and spectral data were used to calculate the thermodynamic characteristics of these compounds in the state of an ideal gas in the temperature range of 298.15-1000 K. Copyright
Photosensitized Geometric Isomerization of Alloocimene. The Triplet Torsitional Potential Surface of a Conjugated Ttriene
Butt, Yondani C. C.,Singh, Anil K.,Baretz, Bruce H.,Liu, R. S. H.
, p. 2091 - 2097 (2007/10/02)
The photostationary state compositions and quantum yields of the benzophenone-sensitized geometric isomerization of alloocimene, a model triene, have been studied in detail.The results arte discussed in terms of two reaction schemes for four isomer systems (one for steady-state concentrations of isomers and one for partially eequilibrated isomeric triplets).A triplet torsional potential surface of the triene is also presented which was constructed to reflect the photochemical properties of the triene.From quenching data, the average lifetime of an alloocimene triplet at room temperature was determined to be 2E-7 s.
