Reaction of α-pinene with haloacetic acids

Article abstract of DOI:10.1023/A:1016185024931

The reactions of α-pinene with chloro-, bromo-, and trichloroacetic acids, accompanied by isomerization of α-pinene, were studied.

Full text of DOI:10.1023/A:1016185024931

Russian Journal of Applied Chemistry, Vol. 75, No. 2, 2002, pp. 310 314. Translated from Zhurnal Prikladnoi Khimii, Vol. 75, No. 2, 2002,
pp. 319 324.
Original Russian Text Copyright
2002 by A. Radbil’, Zolin, Shkapova, B. Radbil’.
MACROMOLECULAR CHEMISTRY
AND POLYMERIC MATERIALS
Reaction of -Pinene with Haloacetic Acids
A. B. Radbil’, B. A. Zolin, Yu. A. Shkapova, and B. A. Radbil’
Lesma Research and Promotion Limited Liability Company, Nizhni Novgorod, Russia
Lesosibirsk Rosin Extraction Plant, Open Joint-Stock Company, Lesosibirsk, Krasnoyarsk krai, Russia
Received September 25, 2001
Abstract The reactions of -pinene with chloro-, bromo-, and trichloroacetic acids, accompanied by isom-
erization of -pinene, were studied.
-Pinene I, one of the major components of turpen-
tine, is an important representative of unsaturated
monoterpene hydrocarbons. Esters derived from
-pinene show a wide spectrum of scents [1] and are
used as components of diverse perfume formulations.
Also, these compounds are components of plastics,
rubbers, drugs, cosmetics, and disinfectants [2].
Monoterpene esters show particular promise in pro-
duction of detergents to impart to them pleasant odor
and to mask the odor originating from petroleum raw
materials used for detergent manufacture [3].
ing to other papers [6 8], the yield of borneol esters
in reactions of -pinene with some haloacetic acids
does not exceed 20%, with low reaction selectivity.
In this work, we studied the reaction of -pinene
with chloro-, bromo-, and trichloroacetic acids. The
results are given in the table and in Figs. 1 and 2.
We found that addition of haloacetic acids to
-pinene is accompanied by its isomerization and
yields both mono- and bicyclic terpenoids. As seen
from the table, the qualitative composition of the
isomerization products is similar in all cases: cam-
phene II, dipentene III, -terpinene IV, -terpinene
V, terpinolene VI, and fenchene VII are detected.
With chloro- and bromoacetic acids, the correspond-
ing fenchol, borneol, and -terpineol esters are formed,
and with trichloroacetic acid, a minor amount of the
isoborneol ester is also detected. Furthermore, with
Esters derived from -pinene are widely used as
intermediates in synthesis of biologically and physio-
logically active substances [2, 4, 5]. Of most inter-
est in this respect is the report [5] on synthesis of
borneol with high yield and selectivity by reaction of
-pinene with chloroacetic acid, followed by saponi-
fication of the reaction mixture with NaOH. Accord-
Fig. 1. Curves of product accumulation in reactions of -pinene with (a) chloro-, (b) trichloro-, and (c) bromoacetic acids
(70 C, molar ratio -pinene : acid = 1 : 1). (x) Product content and ( ) time. (1) Terpene esters, (2) terpene hydrocarbons,
and (3) polyterpenes; the same for Fig. 2.
1070-4272/02/7502-0310 $27.00 2002 MAIK Nauka/Interperiodica

REACTION OF -PINENE WITH HALOACETIC ACIDS
311
Fig. 2. Influence of temperature T on the composition of products formed in reactions of -pinene with (a) chloroacetic and
(b) trichloroacetic acids (1 h, molar ratio -pinene : acid = 1 : 1).
trichloroacetic acid, oligoterpenes are formed along
with the addition and isomerization products.
Fig. 2, the patterns for terpene esters are similar with
both acids. Below 50 C, formation of terpene esters is
negligible, and at 65 70 C their content sharply in-
creases. With the temperature rising further, the curve
of the ester content flattens out. For -pinene isomeri-
zation products, the patterns observed with chloroace-
tic and trichloroacetic acids are different. In the first
The yield of products in reactions of -pinene with
haloacetic acids largely depends on the reaction condi-
tions and on particular acid.
Figure 1 illustrates the difference in the rates of
accumulation of terpene esters and terpene hydrocar- case, the content of terpene hydrocarbons increases
bons in reactions with different acids. In reaction of
-pinene with chloroacetic acid at 70 C, the yields
of esters and isomeric terpene hydrocarbons in 0.5 h
are 35 and 30%, respectively, with 35% of -pinene
remaining unchanged. After 3 h, the content of ter-
pene hydrocarbons is almost doubled (55%), whereas
the content of esters changes insignificantly (Fig. 1a).
steadily with temperature, whereas in the second case
their content passes through a pronounced maximum
(33 35%) at 70 C. Also, oligoterpenes are formed
with trichloroacetic acid, and their content consider-
ably increases with temperature.
It should be noted that oligoterpenes are formed
from -pinene only in the presence of trichloroacetic
acid. Furthermore, a distinctive feature of this reac-
tion, as compared witho the reaction with monohalo-
acetic acids, is its sensitivity to the temperature of
Isomerzation of -pinene into other terpene hydro-
carbons is the major transformation pathway in its
reaction with bromoacetic acid at the same tempera-
ture (Fig. 1c). However, in contrast to chloroacetic reactant mixing (see table). When the starting com-
acids, the accumulation curves of terpene hydrocar-
bons and terpene esters are smoother, and even in 4 h
the content of these products does not exceed 31 and
20 wt %, respectively, with approximately 50% con-
version of -pinene.
pounds, -pinene and CCl3COOH, are cooled to 5 C,
carefully mixed with warming up avoided, and then
kept in a thermostat at the required temperature for
1 h, the resulting mixture contains 33% terpene esters,
54% terpene hydrocarbons, and 2% oligoterpenes.
When -pinene is slowly added with stirring to tri-
chloroacetic acid preheated to 70 C and then the mix-
ture is kept at this temperature for 1 h, the content of
oligoterpenes sharply increases (to 35%), and the con-
tent of terpene hydrocarbons decreases to 36%. The
content of terpene esters changes only slightly. Pre-
sumably, when -pinene is mixed with trichloroacetic
acid without controlling the temperature, local over-
heatings due to the heat of reaction cause secondary
transformations of terpene hydrocarbons with accu-
mulation of oligoterpenes. A similar assumption was
made in [6, 9]. In reactions of -pinene with chloro-
and bromoacetic acids, the temperature of reactant
mixing has no effect on the product composition.
In the reaction of -pinene with trichloroacetic acid
(Fig. 1b), changes in the composition of the reaction
products with time are the sharpest. The content of
terpene hydrocarbons passes through a maximum. It is
seen that the highest (57%) content of isomeric ter-
pene hydrocarbons is attained in 0.5 h, after which it
gradually decreases, reaching 43% in 4 h, with simul-
taneous increase in the content of oligoterpenes. The
accumulation pattern of terpene esters is similar to
that observed with monohaloacetic acids.
The influence of temperature on the composition
of reaction products, examined with chloro- and tri-
chloroacetic acids, is also significant. As seen from
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 75 No. 2 2002

312
RADBIL’ et al.
Compositions of reaction mixtures from reactions of -pinene with haloacetic acids
Reaction mixture composition, wt %
Pinene : acid
molar ratio
T,
C
, h
-pinene isomerization produts (monoterpene hydrocarbons)
camphene dipentene -terpinene -terpinene terpinolene fenchene total
Chloroacetic acid
-pinene
1 : 1
1 : 1
1 : 1
1 : 1
1 : 1
1 : 1
1 : 1
2 : 1
70
70
70
70
70
50
90
70
0.5
1
34.8
29.5
24.8
18.6
9.2
8.5
8.8
9.0
9.0
9.0
2.0
10.6
9.0
12.5
15.7
17.8
21.1
27.5
2.0
0.4
1.5
1.8
2.2
2.8
0.3
4.0
1.5
1.3
1.9
1.9
1.9
1.8
0.2
3.0
1.9
3.6
4.5
5.7
7.5
10.5
0.5
9.4
5.1
2.5
2.7
2.9
3.0
3.2
30.3
35.1
39.1
44.7
54.8
5.0
1.5
2
3
1
95.0
7.0
1
24.7
16.0
4.0
2.8
55.7
36.3
1
38.2
Bromoacetic acid
1 : 1
1 : 1
1 : 1
1 : 1
70
70
70
70
0.5
1
71.0
65.0
56.0
48.8
9.4
9.0
10.5
10.3
6.7
8.5
10.1
12.1
0.4
1.3
1.5
1.7
1.7
2.0
2.5
2.7
3.1
2.5
2.7
2.9
3.0
22.3
24.8
28.5
30.8
0.6
0.6
0.6
2
4
Trichloroacetic acid
1 : 1
1 : 1
1 : 1
1 : 1
2 : 1
1 : 1*
1 : 1*
70
70
70
70
70
70
90
0.5
1
12.7
10.5
8.0
14.1
14.4
14.0
14.4
14.0
14.0
13.5
27.5
25.2
23.0
16.6
12.5
12.1
6.0
0.4
3.1
2.5
2.0
1.0
1.3
9.8
9.2
9.6
8.0
8.4
6.5
3.0
2.5
2.4
2.7
3.0
2.4
2.9
3.0
57.4
54.1
51.5
43.0
47.0
35.5
25.5
0.4
0.2
2
4
6.6
1
25.2
1.5
0.4
1
1
Reaction mixture composition, wt %
addition products (esters of indicated monoterpene alcohols)
Pinene : acid
molar ratio
T,
, h
C
Polyterpenes
fenchol
borneol
Chloroacetic acid
8.3
8.9
9.4
9.6
9.0
isoborneol
-terpineol
total
1 : 1
1 : 1
1 : 1
1 : 1
1 : 1
1 : 1
1 : 1
2 : 1
70
70
70
70
70
50
90
70
0.5
1
3.6
3.8
3.9
3.8
4.0
23.0
22.7
22.9
23.3
23.0
34.9
35.4
36.1
36.7
36.0
1.5
2
3
1
1
5.8
4.0
14.0
7.5
17.5
14.0
37.3
25.5
1
Bromoacetic acid
1 : 1
1 : 1
1 : 1
1 : 1
70
70
70
70
0.5
1
2.1
3.8
5.7
6.0
4.6
6.4
6.7
10.2
15.5
20.4
2
9.8
4
2.4
12.0
Trichloroacetic acid
1 : 1
1 : 1
1 : 1
1 : 1
2 : 1
1 : 1*
1 : 1*
70
70
70
70
70
70
90
0.5
1
1.4
2.1
2.2
3.3
1.2
1.8
1.7
7.6
8.6
0.2
0.9
1.1
1.9
0.2
0.4
0.5
20.7
21.3
22.3
23.0
19.4
19.0
21.3
29.9
32.9
34.5
38.4
27.8
28.0
32.5
2.5
6.0
2
8.9
4
10.2
7.0
6.8
9.0
12.0
1
1
35.0
42.0
1
*
The reaction was performed without preliminary cooling of the reactants.
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REACTION OF -PINENE WITH HALOACETIC ACIDS
313
As already mentioned, the reaction products formed
from -pinene contain both mono- and bicyclic ter-
penoids. Terpenoids with various structures of the
carbon skeleton are present both in isomerization
products and in the esters. Our results are well consis-
tent with the well-known and generally accepted car-
bocation mechanism of -pinene isomerization in the
presence of acid catalysts [4] (see scheme).
Scheme of -pinene transformations in the presence of -haloacetic acids.
(II) Camphene, (III) dipentene, (IV) -terpinene, (V) -terpinene, (VI) terpinolene, (VII) fenchene, (VIII) pinyl cation,
(IX) bornyl cation, (X) fenchyl cation, (XI) isocamphyl cation, (XII) terpenyl cation, (XIII) isomeric terpenyl cation,
(XIV) terpineol ester, (XV) borneol ester, and (XVI) fenchol ester.
Protonation of -pinene gives pinyl cation VIII,
which undergoes Wagner Meerwein rearrangement to
give carbocations IX XI, subsequently transforming
into bicyclic terpenoids of the bornane, fenchane, and
camphane series. Namely, deprotonation yields hydro-
carbons (camphene, II; fenchene, VII), and addition
of the acid anion to carbocations IX and X gives the
corresponding bornyl and fenchyl haloacetates.
It should be noted that, when studying the reactions
of -pinene with chloro- and trichloroacetic acids
under similar conditions Markevich et al. [6], have
not detected the corresponding -terpineol esters. This
could be due to inefficient GLC procedure used in [6]
for identification of terpenoids. A packed GLC col-
umn with tricresyl phosphate as liquid phase does not
provide separation of borneol and -terpineol esters
of haloacetic acids, as shown by our experiments with
the corresponding reference compounds under the
similar conditions. Therefore, we chose conditions for
more efficient GLC analysis.
Monocyclic terpenoids, such as dipentene III and
terpinolene VI, are formed via terpenyl cation XII,
which is, in turn, formed by ring opening in pinyl
cation VIII; - and -terpinenes are formed via carbo-
cation XIII.
To confirm the formation of -terpineol esters of
haloacetic acids, the products of the reactions of
-pinene with chloro- and trichloroacetic acids were
treated with a 10% solution of NaOH in ethanol. In
the resulting mixture, we detected, along with fenchol
and borneol formed by saponification of the corre-
sponding haloacetates, also -terpineol, and the ratio
of the alcohols fully coincided with the ratio of the cor-
responding esters in the initial mixture. All the alco-
hols were also identified by GLC using the reference
compounds. Thus, we can conclude with certainty that
-terpineol haloacetates are major products of the re-
actions of -pinene with haloacetic acids.
Transformations occurring in the presence of tri-
chloroacetic acid yield, along with isomeric terpene
hydrocarbons and terpene esters (via carbocations
VIII, XII, and XIII), also oligoterpenes.
The ratio between the products of -pinene isomer-
ization and addition of haloacetic acids, and also the
ratio between the mono- and bicyclic terpenoids, gov-
erned by the rates of the competing isomerization and
addition reactions, depend on the reaction conditions
and particular haloacetic acid.
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314
RADBIL’ et al.
3 m; stationary phase tricresyl phosphate; column
EXPERIMENTAL
temperature 110 180 C; vaporizer temperature 250 C;
carrier gas nitrogen, flow rate 60 ml min . Tridecane
1
-Pinene and haloacetic acid were cooled to 5 C
and then carefully mixed, with warming up avoided,
and transferred to a temperature-controlled reactor
equipped with a heated jacket, a stirrer, and a reflux
was added as internal reference. The products were
identified by comparison with the corresponding ref-
erence compounds or by using data on relative reten-
condenser. The temperature in the reactor was main- tion of terpenoids [4]. The relative error of single
tained constant to within 0.5 C. The stirrer rotation analysis at a confidence level of 0.95 was within 2%.
rate was controlled with a tachometer. After a certain With each sample, five chromatograms were recorded,
time, the mixture was rapidly cooled, the reaction
products were washed with water, excess acid was
neutralized with 10% aqueous Na2CO3, and the mix-
ture was again washed with water to pH 7 and dried
over MgSO4, after which the products were analyzed
by GLC. In experiments without preliminary cooling
of the reactants, the acid was charged into the reactor
and heated with stirring to a certain temperature, after
which -pinene was added, which was regarded as
the start of the reaction.
and the results were averaged.
CONCLUSION
Reactions of -pinene with chloro-, bromo-, and
trichloroacetic acids yield terpene alcohols and esters,
which can be used as components or intermediates in
syntheses of active substances.
REFERENCES
Sodium hydroxide treatment of the product mix-
tures from reactions of -pinene with chloro- and
trichloroacetic acids was performed as follows. After
washing with water to pH 7 and drying over MgSO4,
the mixture was charged into a reactor. A twofold ex-
cess amount (by volume) of a 10% solution of NaOH
in ethanol was added. The mixture was refluxed for
2 h and cooled; the reaction products were extracted
with two portions of hexane. The combined extract
was washed with water to pH 7 and dried over
MgSO4. The solvent was removed, and the products
were analyzed by GLC.
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The chromatographic analysis was performed on a
Chrom-5 chromatograph (flame ionization detector;
3-m stainless steel column; stationary phase 15%
PFMS-4 silicone oil on Chromaton N-AW-DMSC,
0.20 0.25 mm; column temperature 110 180 C;
vaporizer temperature 250 C; carrier gas nitrogen,
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1
flow rate 60 ml min ). Also, we performed analysis
under the same conditions as in [6]: column length
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 75 No. 2 2002