Preparation of fluorinated esters of abietic acid

Article abstract of DOI:10.1134/S1070427208120276

The reaction of abietic acid chloride with sodium salts of 1H,1H-dihydrotrifluoroethanol, 1H,1H,3H-trihydrotetrafluoropropanol, 1H,1H,5H-trihydrooctafluoropentanol, and pentafluorophenol was studied. The main reaction products are the corresponding fluorinated alkyl (aryl) abietates.

Full text of DOI:10.1134/S1070427208120276

ISSN 1070-4272, Russian Journal of Applied Chemistry, 2008, Vol. 81, No. 12, pp. 2175–2177. © Pleiades Publishing, Ltd., 2008.
Original Russian Text © I.N. Gaidukov, L.M. Popova, 2008, published in Zhurnal Prikladnoi Khimii, 2008, Vol. 81, No. 12, pp. 2065–2067.
BRIEF
COMMUNICATIONS
Preparation of Fluorinated Esters of Abietic Acid
I. N. Gaidukov and L. M. Popova
St. Petersburg State Technological University of Vegetable Polymers, St. Petersburg, Russia
Received July 28, 2008
Abstract—The reaction of abietic acid chloride with sodium salts of 1H,1H-dihydrotrifluoroethanol,
1H,1H,3H-trihydrotetrafluoropropanol, 1H,1H,5H-trihydrooctafluoropentanol, and pentafluorophenol was
studied. The main reaction products are the corresponding fluorinated alkyl (aryl) abietates.
DOI: 10.1134/S1070427208120276
One of the ways to modify rosin is its esterifica-
tion. The resulting products, depending on the kind of
the rosin and alcohol used, show promise in production
of synthetic resins, ester plasticizers, hot-melt adhe-
sives, varnishes, paints, adhesives for food package,
etc., meeting the most stringent environmental require-
ments. As compounds with long-chain fluoroalkyl
group exhibit surface activity [1], esters of rosin and
fluorinated alcohols can be valuable hydro- and oleo-
phobizing agents for fibrous composite materials.
Therefore, development of procedures for preparing
such esters is a topical problem.
tion of resin acids with alcohols in the presence of acid
catalysts is an extremely inefficient route to esters.
In some reports, alternative procedures for prepar-
ing resin acid esters have been suggested. For example,
it is recommended to prepare methyl abietate by the
reaction of abietic acid with diazomethane [6] or of
silver abietate with methyl iodide on heating [7]. Hal-
brook and Lawrence [8] prepared rosin monoesters of
ethylene or 1,3-propylene glycol by the reaction of
rosin with ethylene or propylene oxide at elevated tem-
peratures. The reactions of alkali metal resinates with
alkyl halides also yield esters; by this route, Zander-
sons and Tardenaka [9] prepared glycidyl abietate. As
reported by Bardyshev [4], methyl, ethyl, and phenyl
abietates are formed by reactions of the corresponding
alcohols with abietic anhydride. It was also noted that
these reactions occur at elevated temperatures in the
presence of a catalyst. Johnston [10] prepared ethyl
abietate by the reaction of abietic acid chloride with
ethanol.
This work continues our studies devoted to devel-
opment of new fluorinated surfactants [2, 3] and is
aimed to devise of a procedure for preparing previ-
ously unknown esters of abietic acid (model compound
of oleoresin rosin) and fluorinated alcohols: 1H,1H-di-
hydrotrifluoroethanol, 1H,1H,3H-trihydrotetrafluoro-
propanol, 1H,1H,5H-trihydrooctafluoropentanol, and
pentafluorophenol.
Kryachko et al. [3] reported that esterification of
abietic acid with 1H,1H,5H-trihydrooctafluoropentanol in
the presence of p-toluenesulfonic acid yields 1H,1H,5H-
trihydrooctafluoropentyl dehydroabietate, i.e., the es-
terification is accompanied by disproportionation of
abietic acid. The same ester has been prepared by es-
terification of dehydroabietic acid with concentrated
H2SO4 as catalyst [2].
Esterification of resin acids, the major component
of rosin, is complicated by the steric shielding of the
carboxy group located at the tertiary carbon atom [4]
and by the low acidity (pKa 6.4) [5] of compounds of
this class. This results in a decrease in the rate of esteri-
fication of resin acids in the presence of common acid
catalysts (H2SO4, H3PO4, etc.). Performing the ester-
ification under harsh conditions (in the presence of
aggressive acid agents and at elevated temperatures)
gives rise to undesirable side reactions, such as dimeri-
zation of abietic-type acids and their disproportiona-
tion, which diminishes the yield of the target product
and complicates its isolation [3]. Therefore, the reac-
In the present study, esters of abietic acid and
fluorinated alcohols were prepared by reactions of so-
dium salts of the corresponding alcohols and abietic
acid chloride synthesized as described in [4, 11–14].
The reactions between the alcoholates and acid chlo-
2175

2176
GAIDUKOV, POPOVA
Analytical and NMR data for products of reactions of abietic acid chlorides with sodium salts of 1H,1H-dihydro-
trifluoroethanol, 1H,1H,3H-trihydrotetrafluoropropanol, 1H,1H,5H-trihydrooctafluoropentanol, and pentafluorophenol
(products I–IV, respectively)
Iodine
number,
g I2/g
Acid
number,
mg KOH/g
NMR spectrum, δ, ppm
Prod- Reaction Product
uct time, h yield, %
Rf
1H
19F
3
6
90
85
0.86 0.87, 1.02, 1.22, 1.26, 1.33, 2.75, –72.26 (s)
4.46, 5.37, 5.78
154
1.5
I
0.85 0.86, 0.92, 1.01, 1.22, 1.26, 1.33, –123.6 (s), –136.4 (d)
2.87, 4.59, 4.9, 5.25–5.6, 5.78,
168
35
II
6.37 (t.t, 2JHF 52.7 Hz)
6
6
65
60
0.89 0.87, 1.02, 1.22, 1.26, 1.33, 2.75, –119.5 (s), –124 (s),
150
168
30
21
III
IV
4.75, 5.25–5.6, 5.78, 6.73
–131 (s), –138, –137.3 (d)
(t.t, 2JHF 52.7 Hz)
0.79 0.85, 0.91, 1.03, 1.20, 1.21, 1.26, –170.8 (t), –165.1 (t),
2.85, 4.90, 5.37, 5.78 –161.9 (d)
ride were performed in toluene in the course of 3–6 h,
at the reactant molar ratio of 1: 1.25. The choice of the
alcoholate instead of the corresponding alcohol was
governed by the facts that the reaction in this case is
faster and that the second product is sodium chloride,
which is insoluble in toluene and can be readily re-
moved from the reaction mixture, i.e., isolation of the
desired product is simplified. The products obtained
were yellow-brown resinous noncrystallizing sub-
(5.5 mmol) of PCl3 was slowly added at room tempera-
ture with stirring. The reaction mixture was stirred for
20 h, after which H3PO3 was filtered off. Abietic acid
chloride was used immediately after preparation, with-
out isolation.
Reaction of abietic acid chloride with sodium
1H,1H-trifluoroethylate. To 5.30 g (16.5 mmol) of
abietic acid chloride in 100 ml of toluene, a suspension
of 2.51 g (20.6 mmol) of sodium 1Н,1Н-dihydro-
trifluoroethylate was added with vigorous stirring at
room temperature. The mixture was stirred for 3 h,
after which the NaCl precipitate was filtered off, the tolu-
ene solution was washed with water and dried over cal-
cined MgSO4, and the solvent was separated. The tarry
residue was dried in a vacuum over P2O5. The yield of
the product (I) was 90%.
EXPERIMENTAL
The 1H and 19F NMR spectra of the products were
recorded on a Bruker WH-400 spectrometer (400 MHz)
from 5% solutions in acetone-d6. The chemical shifts
were determined relative to internal TMS (1H NMR)
and trifluoroacetic acid (19F NMR).
1Н,1Н,3Н-Trihydrotetrafluoropropyl (product II),
1Н,1Н,5Н-trihydrooctafluoropentyl (product III), and
pentafluorophenyl (product IV) esters of abietic acid
were prepared similarly from 5.30 g (16.5 mmol) of
abietic acid chloride and 3.17 g of sodium 1Н,1Н,3Н-tri-
hydrotetrafluoropropylate, 5.23 g of sodium 1Н,1Н,5Н-
trihydrooctafluoropentylate, and 4.24 g of sodium pen-
tafluorophenolate, respectively; the reaction time was
6 h. The yields of fluorinated alkyl (aryl) abietates II–
IV, evaluated by 1H NMR, were 60–85% (see table).
To evaluate the purity of the initial abietic acid
and monitor the reaction progress, we used TLC on
Silufol UV 254 plates (eluent hexane–methylene chlo-
ride–acetone, 1 : 1 : 0.5).
Abietic acid was isolated from oleoresin rosin of
the Wg brand according to [6]. The solvents were puri-
fied by the standard procedures [15].
Sodium alcoholates were prepared by reactions of
the corresponding fluorinated alcohols with sodium
metal in ether or toluene, following the procedures de-
scribed in [16–19].
The TLC data suggest the presence of a minor
impurity of abietic acid in all the reaction mixtures.
The formation of esters is also confirmed by the acid and
iodine numbers of the resulting products (see table).
Abietic acid chloride. To a solution of 5.00 g
(16.5 mmol) of abietic acid in 100 ml of toluene, 0.74 g
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 81 No. 12 2008

PREPARATION OF FLUORINATED ESTERS OF ABIETIC ACID
2177
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trihydrooctafluoropentanol, and pentafluorophenol under
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ACKNOWLEDGMENTS
The study was financially supported by the St. Pe-
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