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ISSN 0036ꢀ0244, Russian Journal of Physical Chemistry A, 2010, Vol. 84, No. 7, pp. 1112–1117. © Pleiades Publishing, Ltd., 2010.
Original Russian Text © V.I. Anikeev, I.V. Il’ina, K.P. Volcho, A. Ermakova, N.F. Salakhutdinov, 2010, published in Zhurnal Fizicheskoi Khimii, 2010, Vol. 84, No. 7, pp. 1233–1239.
CHEMICAL THERMODYNAMICS
AND THERMOCHEMISTRY
The Thermolysis of αꢀPinene and Verbenone Epoxides
in Supercritical Solvents
V. I. Anikeeva, I. V. Il’inab, K. P. Volchob, A. Ermakovaa, and N. F. Salakhutdinovb
a Boreskov Institute of Catalysis, Siberian Division, Russian Academy of Sciences,
pr. Akademika Lavrent’eva 5, Novosibirsk, 630090 Russia
b Vorozhtsov Institute of Organic Chemistry, Siberian Division, Russian Academy of Sciences, Novosibirsk, Russia
eꢀmail: anik@catalysis.nsk.su
Received July 3, 2009
Abstract—Thermal transformations of
vents with complex compositions, including CO2, lower alcohols (ethanol and isopropanol), and water, over
the temperature and pressure ranges 387–575 K and 135–215 atm. The main product from ꢀpinene epoxide
in a supercritical solvent containing water was campholenic aldehyde and pinocamphone; the total content
of these products in the reaction mixture was 80%. Suggestions concerning the mechanism of the thermal
isomerization of ꢀpinene epoxide depending on the acidity of supercritical solvents were made. The direcꢀ
α
ꢀpinene and verbenone epoxides were studied in supercritical solꢀ
α
α
tion of verbenone epoxide transformations was independent of the presence of water in the mixture. The main
identified products were ketoalcohols with paraꢀmenthane and camphane frameworks.
DOI: 10.1134/S0036024410070058
INTRODUCTION
supercritical twoꢀcomponent solvents containing СО2
and ethanol or isopropanol and certain amounts of
water if necessary. The use of supercritical СО2 allowed
us to decrease the critical temperature of the solvent
compared with that of, for instance, water or lower
alcohols. The reaction could therefore be performed
under supercritical conditions at a lower temperature.
Monoterpenoids are widespread in nature and are
valuable renewable raw material for pharmaceutical
and cosmetic industries and the production of gustaꢀ
tory additives, pesticides, etc. [1, 2]. Many transforꢀ
mations leading to the production of valuable subꢀ
stances from monoterpenes and their derivatives are
related to acidꢀcatalyzed skeletal rearrangements [3].
At the same time, monoterpenoids, as a rule, experiꢀ
ence many transformations in acid media and give
complex mixtures of products, which decreases the
effectiveness of their technological applications on the
one hand and imposes severe requirements on selecꢀ
tive catalysts on the other. For instance, transformaꢀ
EXPERIMENTAL
We used (ꢀ)ꢀ ꢀpinene epoxide (ACROS ORGANꢀ
α
ICS) containing 95.0% major component. Verbenone
epoxide was synthesized by the epoxidation of verꢀ
benone with hydrogen peroxide in the presence of
NaOH as recommended in [11]; the content of the
major component was no less than 98.0%.
tions of ꢀpinene epoxide in acid media can produce
α
200 different compounds in addition to the desired
product, campholenic aldehyde, which is a key comꢀ
pound in the synthesis of many fragrant substances [4].
Experimental studies of ꢀpinene and verbenone
α
epoxide transformations were performed on a laboraꢀ
tory unit [6–10, 12] with the use of tubular reactors 3
and 6 m long with an inside diameter of 1.75 mm
(reactor volumes were 7.2 and 14.4 cm3). Reaction
mixtures were supplied to the reactors in two flows.
The first flow was supercritical СО2; it was introꢀ
duced into a mixer by a syringe pump situated at the
entrance of the reactor through a heat exchanger,
where it was heated to the temperature of the reacꢀ
tion. СО2 flow rate varied from 2.5 to 4.0 ml/min.
Reactions based on terpenoid transformations in
supercritical solvents are an alternative to the methods
applied currently. Studies of the thermolysis of
αꢀ and
β
ꢀpinene monoterpenes and sulfate turpentine in
supercritical lower alcohols showed that, when
monoterpenes react in supercritical solvents, the rate
of their transformations increases substantially comꢀ
pared with similar reactions in the gas or liquid phases
[6–10]. At the same time, the reactivity of such labile
compounds as terpenoid epoxides has not been studꢀ
ied in supercritical solvents.
The second flow was a mixture of
benone epoxide with a solvent (alcohol); it was introꢀ
duced into the same mixer by a piston pump. The
ꢀpinene or verbenone epoxide,
ꢀpinene and verbenone epoxides in alcohol, and water was : 89.4 : 9.6, respectively.
α
ꢀpinene or verꢀ
In this work, we for the first time studied the transꢀ molar ratio between
formations of
α
α
∼
1
1112