Chloroacetoxylation of oleic acid - a kinetic study

Article abstract of DOI:10.1007/s11746-000-0039-z

The kinetics of the addition reaction of chloroacetic acid to oleic acid (chloroacetoxylation) in the presence of sulfuric acid as a catalyst were investigated. The reactions were carried out at the same concentration of both reactants at various temperatures and catalyst content. The reaction time ranged from 30 min up to 12 h, and the reaction course was observed by determining mainly iodine value, and chlorine content of the oil samples at 30-min intervals. The experimental data fitted the reversible second-first order rate equation for bi-molecular-unimolecular type reactions. The reaction constants of the forward and reverse reactions were obtained at temperatures 70 and 80 °C. The effect of sulfuric acid content on the reaction constant was investigated at 70 and 80 °C.

Full text of DOI:10.1007/s11746-000-0039-z

Chloroacetoxylation of Oleic Acid—A Kinetic Study
Danae Doulia*, Fotis Rigas, and Kostantinos Gimouhopoulos
Chemical Engineering Department, National Technical University of Athens, Zografou Campus, GR-157 80, Athens, Greece
ABSTRACT: The kinetics of the addition reaction of chloro- balance (HLB) ratio of surfactants based on oleic acid (9).
acetic acid to oleic acid (chloroacetoxylation) in the presence
of sulfuric acid as a catalyst were investigated. The reactions
were carried out at the same concentration of both reactants at
various temperatures and catalyst content. The reaction time
ranged from 30 min up to 12 h, and the reaction course was ob-
served by determining mainly iodine value, and chlorine con-
tent of the oil samples at 30-min intervals. The experimental
data fitted the reversible second-first order rate equation for bi-
molecular-unimolecular type reactions. The reaction constants
of the forward and reverse reactions were obtained at tempera-
tures 70 and 80°C. The effect of sulfuric acid content on the re-
action constant was investigated at 70 and 80°C.
The synthesis of monohydroxystearic acids from oleic acid
has been achieved chemically by different reactions includ-
ing mainly hydroboration of methyl oleate, formoxylation, or
acetoxylation as well as enzymatically (2,3,6). We have al-
ready studied, under different conditions, the addition of
chloroacetic acid to the double bond of oleic acid and
methanolysis of the addition product to methyl monohydrox-
ystearates (10). So far, kinetic studies on the chloroacetoxyla-
tion of oleic acid or other unsaturated fatty acids do not exist.
In the present work, the kinetics of the chloroacetoxyla-
tion reaction of oleic acid was investigated. Reactions were
carried out in stoichiometric proportions of reactants in the
presence of catalyst (sulfuric acid) at temperatures of 70 and
80°C to determine the order of reaction. The effect of sulfuric
acid content were also examined. The recovery of unreacted
chloroacetic acid was achieved by precipitation in petroleum
ether at 0°C, and this separation method is suggested as an al-
Paper no. J9225 in JAOCS 77, 239–242 (March 2000).
KEY WORDS: Chloroacetic acid, chloroacetoxylation, kinet-
ics, oleic acid, reaction constants.
Vegetable oils and their component fatty acids represent an ternative solution to the expensive process of production of
attractive renewable source for the production of useful anhydrous low molecular weight acids (formic and acetic
chemicals. Their reactivity needs to be enhanced by introduc- acids). Extraction with water and distillation are generally ap-
ing additional functionalities into the fatty acid molecules plied for the separation of the components of these reaction
(1,2). So far, a variety of chemical and biochemical reactions mixtures (11).
have been used for conversion to value-added products such
as hydroxystearic fatty acids and their derivatives (3–5).
These compounds are used in greases, lubricants, detergents,
MATERIALS AND METHODS
and chemical additives. A good review of the literature con- Materials. Oleic acid (pure; Merck, Darmstadt, Germany,
cerning the production, properties, and uses of the above Art. 471 with an acid value of 199 and an iodine value of 90,
acids is given by Lower (6).
mean oleic acid content 85%), chloroacetic acid (Merck, Art.
This work is part of a research project aimed at the pro- 412, 99%), sulfuric acid (Merck, 96–98%), petroleum ether
duction of methyl monohydroxystearates and their derivatives (Merck, 40–70°C), and additional reagents (such as Na2SO4,
from oleic acid through chloroacetoxylation reaction fol- NaHCO3) were of very pure grade. The reagents used in ana-
lowed by methanolysis of the addition product. Methyl mono- lytical tests are described in the relevant literature.
hydroxystearates are important as intermediate chemical
Experimental setup. Chloroacetoxylation reaction was per-
products, and one of their most interesting applications is in formed in a spherical three-necked flask equipped with a me-
the production of surface-active agents from natural products, chanical stirring system, a thermometer, and a condenser. The
such as sucrose esters (7). In addition, 9- or 10-monohydroxy- flask system was placed in a constant-temperature water bath
stearic acids could be used as substitutes for 12-hydroxy- (±0.5°C). Schoeniger apparatus was used for chlorine analy-
stearic acid, derived from castor oil, which is an important sis (12,13).
high-temperature lubricant (8). The introduction of a hy-
Chloroacetoxylation of oleic acid. Chloroacetoxylation re-
drophilic group, such as a hydroxyl group, into the middle of action of oleic acid with chloroacetic acid was carried out as
the hydrocarbon chain of the oleic acid molecule reduces its follows: A solution of oleic acid, chloroacetic acid, and sul-
hydrophobicity and can improve the hydrophilic–lipophilic furic acid (catalyst) was heated at 70 or 80°C with continuous
stirring for 0 min to 12 h. The reaction yield in addition prod-
*To whom correspondence should be addressed.
uct was studied at equimolar concentration of reactants and
E-mail: ddoulia@orfeas.chemeng.ntua.gr
Copyright © 2000 by AOCS Press
239
JAOCS, Vol. 77, no. 3 (2000)

240
D. DOULIA ET AL.
with different catalyst content [1.82, 3.64, and 5.46% (w/w) measure of the unsaturation of oleic acid, decreases continu-
based on oleic acid]. The hot reaction mixture was poured ously with time and reveals that as the concentration of oleic
into petroleum ether and cooled at 0°C to crystallize the unre- acid decreases the addition product yield increases. The addi-
acted chloroacetic acid, which eventually was removed by fil- tion to the double bond in oleic acid was also measured by
tration. Then, the organic filtrate was washed thoroughly with saponification value determination (a direct measure of the
distilled water to remove the catalyst, it was dried using an- number of chloroacetoxy groups added) and led to similar re-
hydrous sodium sulfate, and finally it was distilled to remove sults. In this case, an increase in saponification value was ob-
the solvent. The total yield of addition product (chloroace- served during the reaction.
toxylated stearic acid) was determined mainly by Wijs
The effect of catalyst content on the rate of reaction at
method (iodine value) (14) and by chlorine analysis using 80°C is illustrated in Figure 2. It was observed that an in-
Schoeniger method. Supplementary analysis of the reaction crease in catalyst content had a positive effect on the rate of
product included saponification value according to AOCS conversion of oleic acid. The effect of reaction time was more
methods (14). Each experiment was carried out twice to check pronounced in the first 2 h. The increase of reaction tempera-
the reproducibility of the results.
ture from 70 to 80°C had a positive effect on the rate of reac-
tion. The experimental results were based mainly on the
change of unsaturation expressed by iodine value or saponifi-
cation value. Chlorine analysis gave similar conversion val-
ues with mean deviation ±2%.
RESULTS AND DISCUSSION
The chloroacetoxylation reaction is the following:
Chloroacetoxylation of oleic acid by chloroacetic acid was
oleic acid + chloroacetic acid
or in abbreviated form
A + B
chloroacetoxystearic acid [1] assumed to be a reversible bimolecular-unimolecular second-
W
first order reaction under the applied conditions, since it was
observed that the experimental data could be described suc-
cessfully by the relative equations. The results did not permit
[2] application of the integrated forms of rate equations for half-,
first-, and second-order reactions. In this case, the following
k1
C
W
k2
where A, B, and C correspond to oleic, chloroacetic, and equations can be used for the calculation of the rate constants
chloroacetoxylated acid, respectively.
k1 and k2 for the forward and opposing reaction (15,16).
The progress of converting oleic acid to chloroacetoxy-
stearic acid at 70°C with 3.64% catalyst content is shown in
Figure 1. Similar curves were obtained at different catalyst
content and at different temperatures. The iodine value, a
CAo 1− x2
k t
1
1− xA × xAe × x
Ae
(
)
(
)
[
]
Ae
[3]
ln
=
xAe − xA
xAe
FIG. 1. Iodine value (IV) and conversion (x) (%) of oleic acid during chloroacetoxylation reaction at 70°C and
3.64% catalyst content.
JAOCS, Vol. 77, no. 3 (2000)

CHLOROACETOXYLATION OF OLEIC ACID
241
FIG. 4. Plots of the quantity ln 1 − xA · xAe
tion time at 80°C and in the presence of various catalyst contents. See
Equation 3.
x
x
− xA vs. reac-
{[
(
)]
(
)}
Ae
Ae
/
FIG. 2. Effect of catalyst content (% w/w based on oleic acid) on
chloroacetoxylation reaction at 80°C.
CCe
C
Ao − CAe k1
K =
=
=
[4]
CA2e
CAe × CBe
k2
where xA and xAe are the molar fraction of reactant A con-
verted into product at any time t and at equilibrium; respec-
tively, CAe, CBe, and CCe (mol/L) are the concentrations of
the reactants and the product, respectively, at equilibrium,
CAo is the initial concentration of reactant A (oleic acid) and
K is the equilibrium constant of the reaction.
Thus, the integral method was applied to correlate the ex-
perimental data and to test the second-first order kinetics by
plotting ln 1 − x × x
× x
xAe − xA vs. reaction time.
{[
(
Ae)]
}
A
Ae
/
In Figures 3 and 4 these plots are presented. In all cases, the
plots were linear, with the slopes giving the values of the
quantity C 1 − x2 k x
.
]
[
(
)
Ao
Ae
1
Ae
/
TABLE 1
Rate Constants in the Kinetic Study of Chloroacetoxylation
of Oleic Acid
Temperature
(°C)
H2SO4
(%)
k1 × 105
k2 × 103
(L mol−1s−1
)
r2
(s−1)
70
70
70
80
80
80
1.82
3.64
5.46
1.82
3.64
5.46
2.520
5.041
7.858
5.619
11.530
17.370
99.3
99.9
99.6
99.2
99.2
99.4
2.540
5.082
7.921
2.722
5.586
8.416
FIG. 3. Plots of the quantity ln 1 − xA · xAe
tion time at 70°C and in the presence of various catalyst content. See
Equation 3.
x
x
− xA vs. reac-
Ae
{[
(
)]
(
)}
Ae
/
JAOCS, Vol. 77, no. 3 (2000)

242
D. DOULIA ET AL.
7. Ismail, R.M., and H. Simonis, Fettesäurezuckerester mit
For the determination of the reaction order with respect to
Schwach Hydrophilen Gruppen im Fettrest, Fette Seifen
Anstrichm. 66:214–215 (1964).
8. Naughton F.C., Production, Chemistry, and Commercial Appli-
cations of Various Chemicals from Castor Oil, J. Am. Oil Chem.
Soc. 51: 65–67 (1974).
9. Bertsch H., F. Püschel, and E. Ulsperger, Herstellung and Ver-
wendung von Fettsäurezuckerestern, Tenside 2:399–404 (1965).
10. Doulia, D., and G. Valkanas, Production of Methyl Monohy-
droxystearates from Oleic Acid by the Method of Chloroace-
toxylation-Methanolysis, Riv. Ital. Sostanze Grasse 76:411–418
(1999).
oleic acid, the values of k1 were obtained at three different
contents of the catalyst (namely 1.82, 3.64, and 5.46 g/100 g)
at temperatures of 70 and 80°C. The quality of the fit was
judged sufficient based on the values of the correlation coef-
ficient (r2). The values for the rate constants k1 and k2 for the
forward and opposing reactions are given in Table 1. The cal-
culated values of the equilibrium constants at 70 and 80°C
were 0.992 and 2.064 L mol−1, respectively.
11. Munns W.O., S. Kairys, and D.A. Manion, The Preparation of
Hydroxystearic Acids from Red Oil (commercial oleic acid), J.
Am. Oil Chem. Soc. 40:22–24 (1963).
12. Schoeniger, W., Rapid Microanalytical Determination of Halo-
gen in Organic Compounds, Mikrochim. Acta:123–129 (1955).
13. Schoeniger, W., The Rapid Microanalytical Determination of
Halogens and Sulfur in Organic Substances, Ibid.:869–876
(1956).
14. Association of Official Analytical Chemists, Official Methods
of Analysis, 14th edn., edited by S. Williams, AOAC, Arlington,
1984, 28023 (iodine number), 28028 (saponification number).
15. Levenspiel, O., Chemical Reaction Engineering, 2nd edn., John
Wiley & Sons, New York, 1972, pp. 41–92.
16. Chandrinos, J., Elements-Principles of Chemical Kinetics, 3rd
edn., National Technical University of Athens, Athens, 1997,
pp. 41–47.
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[Received April 29, 1999; accepted November 30, 1999]
JAOCS, Vol. 77, no. 3 (2000)