- Ring-Opening Reactions of α- And β-Pinenes in Pressurized Hot Water in the Absence of Any Additive
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Reactions of α- and β-pinenes in pressurized hot water were examined in a batch reactor made of a SS316 1/2-in. tube at temperatures of 250-400 C, pressures of 4-30 MPa, and reaction times of 1-30 min in the absence of any additive under an argon atmosphere. The maximum yields of limonene from α-pinene were ca. 70% in 20 min at 300 C or 1 min at 400 C. Limonene was obtained from β-pinene in ca. 16% yield for 30 min at 300 C and 1 min at 400 C. Reversible production of myrcene in 14% yield and formation of unidentified C20 dimer fractions were noted for 1 min at 370 C from β-pinene. The conversion of α-pinene to limonene took place under anhydrous conditions, albeit at slightly lower yield of 65% compared to processes conducted in the presence of water, where increased limonene yield of 70% was observed for 1 min at 400 C. The conversion of β-pinene to limonene under anhydrous conditions was limited to 6.1% in contrast to 11.9% in the presence of water for 7 min at 370 C. In the presence of oxygen, p-cymene was formed in 23% and 24% yield at the expense of limonene from α- and β-pinenes, respectively, for 30 min at 400 C.
- Kawahara, Tomomi,Henmi, Yui,Onda, Natsu,Sato, Toshiyuki,Kawai-Nakamura, Akiko,Sue, Kiwamu,Iwamura, Hiizu,Hiaki, Toshihiko
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supporting information
p. 1485 - 1491
(2014/01/06)
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- Kinetic and mechanistic study on the thermal isomerization of ocimene in the liquid phase
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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
- He, Jindong,Xie, Meng,Tang, Xiangyang,Qi, Xin
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scheme or table
p. 373 - 378
(2012/07/30)
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- Kinetics of thermal conversions of monoterpenic compounds in supercritical lower alcohols
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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.
- Anikeev,Ermakova,Chibiryaev,Kozhevnikov
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scheme or table
p. 162 - 193
(2010/09/04)
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- Fate of monoterpenes in near-critical water and supercritical alcohols assisted by microwave irradiation
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The rearrangement of α- and β-pinene was studied under microwave irradiation in near-critical water and supercritical lower aliphatic alcohols, with the aim of identifying the pathway of α- and β-pinene isomerization. Generally, two pathways occur, pyroly
- Szuppa, Tony,Stolle, Achim,Ondruschka, Bernd
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experimental part
p. 1560 - 1567
(2010/07/04)
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- Amberlyst-15-catalyzed efficient cyclization of γ-and δ-unsaturated alcohols: Green synthesis of oxygen heterocycles
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Amberlyst-15 (H+) resin catalyzes efficient cationic endo-cyclization of-and-unsaturated alcohols to yield tetrahydro-(2H)-pyrans and oxepanes. The merits of the present protocol are good yield of the products under mild conditions, simple workup, and reusability of the resin.
- Singh, Soni A.,Kabiraj, Shilpi,Khandare, Reena P.,Nalawade, Shrikant P.,Upar, Kiran B.,Bhat, Sujata V.
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experimental part
p. 74 - 80
(2010/03/24)
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- Mechanistic and kinetic insights into the thermally induced rearrangement of α-pinene
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(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.
- Stolle, Achim,Ondruschka, Bernd,Findeisen, Matthias
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supporting information; scheme or table
p. 8228 - 8235
(2009/04/11)
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- The influence of water on the isomerization of α-pinene in a supercritical aqueous-alcoholic solvent
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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.
- Ermakova,Chibiryaev,Mikenin,Sal'nikova,Anikeev
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- Photosensitized Geometric Isomerization of Alloocimene. The Triplet Torsitional Potential Surface of a Conjugated Ttriene
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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.
- Butt, Yondani C. C.,Singh, Anil K.,Baretz, Bruce H.,Liu, R. S. H.
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p. 2091 - 2097
(2007/10/02)
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