Features of reactions of phthalic anhydride with polyfluorinated alcohols

Article abstract of DOI:10.1134/S107036321107019X

Polyifluoroalkyl mono- and diesters of phthalic acid were obtained by the reaction of phthalic anhydride with polyfluorinated alcohols. The structure of the polyfluoroalkyl phthalates was studied using IR and ¹H, ¹³C NMR spectroscopy. The nature of the associative interactions between cyclohexanone and polyfluorinated alcohols was revealed. Pleiades Publishing, Ltd., 2011.

Full text of DOI:10.1134/S107036321107019X

ISSN 1070-3632, Russian Journal of General Chemistry, 2011, Vol. 81, No. 7, pp. 1529–1534. © Pleiades Publishing, Ltd., 2011.
Original Russian Text © N.A. Rakhimova, S.V. Kudashev, 2011, published in Zhurnal Obshchei Khimii, 2011, Vol. 81, No. 7, pp. 1181–1186.
Features of Reactions of Phthalic Anhydride
with Polyfluorinated Alcohols
N. A. Rakhimova and S. V. Kudashev
Volgograd State Technical University, pr. Lenina 28, Volgograd, 400131 Russia
e-mail: organic@vstu.ru
Received June 22, 2010
Abstract—Polyifluoroalkyl mono- and diesters of phthalic acid were obtained by the reaction of phthalic
anhydride with polyfluorinated alcohols. The structure of the polyfluoroalkyl phthalates was studied using IR
1
and H, 13C NMR spectroscopy. The nature of the associative interactions between cyclohexanone and
polyfluorinated alcohols was revealed.
DOI: 10.1134/S107036321107019X
Phthalic anhydride is an important starting material
for the production of various derivatives of phthalic
acid, which are used in manufacturing paints, rubber
products, plasticizers, etc. [1]. The introduction of
various substituents in the benzene ring and in the
chain component of the ester fragment gives rise to
specific design of structures potentially appropriate for
development of materials with different combinations
of physical, mechanical and operational characteristics
[2].
light, heat and wear, and other useful properties inerent
in polymeric materials due to the unique nature of
polyfluorinated and perfluorinated groups [5–8].
The acylation by phthalic anhydride of poly-
fluorinated telomeric alcohols of the H(CF2CF2)n·
CH2OH type with a degree of telomerization n = 2, 3 is
unexplored because of the difficulty of formation of
such esters in the classical esterification reaction, and
therefore, it requires activating reagents [ 9].
The aim of this work was to study the regularities at
the obtaining phthalic esters with polyfluorinated
alcohols in the medium of cyclohexanone, and the
effect of the latter on the nature of associative
interactions with polyfluorinated alcohols.
For introducing fluorine atoms in the benzene ring
to obtain the corresponding derivatives of phthalic
anhydride are known several methods [2–4]. However,
it is interesting to obtain a phthalic acid ester conaining
a polyfluorine fragment. The use of polyfluorinated
compounds is very promising because they show
enhanced hydrolytic stability, as well as the stability to
Synthesis of mono- and dipolyfluoroalkyl phthalates
was performed according to the following reaction:
O
O
CH2(CF2CF2)nH
OH
O
O
O
H(CF2CF2)nCH2OH
O
n = 2, 3
O
O
CH2(CF2CF2)nH
CH2(CF2CF2)nH
O
O
1529

1530
RAKHIMOVA, KUDASHEV
We found that phthalic anhydride does not react
tions for dissolving phthalic anhydride and ensuring
the homogeneity of the esterifocation. The choice of
cyclohexanone as a solvent is explained by the techno-
logical features of the acylation reaction: the cyclo-
hexanone boiling point is 156.5°C [10], which allows
to perform the esterification at an elevated tem-
perature. Therewith, the structural features of the poly-
fluorinated alcohol, namely, the presence of proton-
donor HCF2 and HO groups, suggest a possibility
of formation of its associates with cyclohexanone
[11, 12]:
with a polyfluorinated alcohol to form ester in the
temperature range 100–230°C for 2–6 h. This fact
shows the low reactivity of the polyfluorinated alcohol
in the reaction with phthalic anhydride because of their
high acidity due to the presence of fluorine atoms
possessing –I effect. In addition, phthalic anhydride is
practically insoluble in polyfluorinated alcohols even
at elevated temperatures.
Cyclohexanone, used as a medium for the acylation
of polyfluorinated alcohols, provides favorable condi-
_δ
O
F2
C
H2
C
F2
C
_δ
O
_δ
O
H
+δ
+δ
+δ
+δ
C
C
H
C
C
H
C
OH
H2
F2
n
F2
n
I
II
The electron density distribution in the appearing
associate (I) contributes to the magnitude of the
negative charge on the oxygen atom of the hydroxy
groups of polyfluorinated alcohol and to an increase in
its nucleophilic properties. Finally, this promotes
attack of the electrophilic carbon atom of the carboxy
group by the lone electron pair of the oxygen atom of
the hydroxy group of the telomeric alcohol.
phthalic anhydride in the cyclohexanone and a
decrease in the conversion of the reactants. It is
important that raising the temperature of esterification
to 150–200°C promotes intensive dehydrofluorination
of perfluorinated chain and, consequently, the forma-
tion of resinous compounds, complicating isolation
and purification of the reaction product.
We studied the possible associative interaction of
polyfluorinated alcohol with the molecules of cyclo-
hexanone and their influence on the strength of the
hydrogen bonds in the associates formed in dilute
solutions of carbon tetrachloride and chloroform by the
methods of IR and 1H NMR spectroscopy. In [15–17] a
possibility has been considered of association of
polyfluorinated alcohols with proton-acceptor amide
groups in polycaprylamide, with acetone and with
tertiary nitrogen atom of triethylamine.
Thus, the role of cyclohexanone in the reaction of
formation of polyfluoroalkyl phthalates consists not
only in dissolving phthalic anhydride but also in the
redistribution of electron density in the telomeric
alcohol molecule through an associative interaction
between the cyclohexanone and the polyfluorinated
alcohol.
We found that with the increase in the length of
perfluoroalkyl chain of the telomeric alcohol a regular
almost twice decrease occurs in the degree of
conversion of the initial reagents. As a rule, mono-
polyfluoroalkyl esters are formed in higher yields and
degree of conversion of the initial reagents, due,
apparently, to steric hindrance to the esterification of
the second carboxy group and low reactivity of the
polyfluorinated alcohol. Interestingly, the lengthening
of the polyfluorinated chain leads to a decrease in
melting temperature of the formed ester, which is
consistent with the data of a number of studies [13, 14].
In the IR spectra of polyfluorinated alcohols there
are the bands of stretching vibrations νOH characteristic
of the “free,” that is, unbound hydroxy groups
(monomers) and of those self-associated through
intermolecular hydrogen bonds [17–19]. In the spectra
of associates with cyclohexanone the absorption bands
appeared characteristic of HO groups involved into the
hydrogen bonding. It is interesting that the addition of
cyclohexanone sharply increases the intensity of the
polymer band and shifts it to lower wavenumbers. The
data of IR spectroscopy of the non-associated
telomeric alcohols and associated with cyclohexanone
are given in Table 1. The value of Δν shown in Table 1
is the difference between the frequencies of the
Carrying out the reaction of acylation of
polyfluorinated alcohols with phthalic anhydride in
cyclohexanone medium at a temperature below 130°C
leads to a significant decrease in the solubility of
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 81 No. 7 2011

FEATURES OF REACTIONS OF PHTHALIC ANHYDRIDE
1531
Table 1. Position of absorption band of the polyfluoroalcohol hydroxy group νOH in the IR spectra of monomers, poly-
associates, and associates with cyclohexanone
Position νОН, cm–1
In associaes with
System
Solvent
CCl4
Concentration, M
Δν, cm–1
cyclohexanone
monomer
3608
polyassociation
3460
0.1092
0.0642
0.1234
0.0824
–
–
148
168
175
184
254
III
CHCl3
3604
3582
3574
–
3436
3407
3390
–
CCl4
–
IV
CHCl3
CCl4
–
III–
0.0876 (III) 0.0831
(cyclohexanone)
0.0898 (III) 0.0849
(cyclohexanone)
0.0972 (IV) 0.0864
(cyclohexanone)
0.0996 (IV) 0.0888
(cyclohexanone)
3354
cyclohexanone
CHCl3
CCl4
–
–
–
–
–
–
3315
3316
3264
289
292
310
IV–
cyclohexanone
CHCl3
stretching vibrations of hydroxy groups in the
monomer (the wavenumbers were obtained at the
minimum allowable concentration of polyfluorinated
alcohol in carbon tetrachlloride and chloroform) and
the HO groups in the self-associates and associates
with cyclohexanone.
chemical shifts of functional groups before and after
adding the proton-acceptor cyclohexanone describes
the ability to association of various proton-containing
structural fragments of molecules, as well as the
stability of the formed associates.
As show the data in Table 2, at a change in
concentration from 0.177 to 0.354 mol l–1 the signal of
the H(CF2CF2)n proton (n = 2,3) of the polyfluorinated
alcohol does not undergo a shift to the strong or weak
field. It appears as a triplet of triplets with charac-
teristic chemical shift δ and the corresponding spin-
spin coupling constants (2J = 52 Hz, 3J = 6 Hz) [19].
As the data in Table 1 show, the solvent polarity
plays an important role, and in more polar chloroform
the formed hydrogen bonds are the most stable. The
increase in the length of the perfluoroalkyl chain
increases the strength of the polyfluorinated alcohol–
cyclohexanone associates. These associates are more
stable than, for example, the system of polyfluorinated
alcohol–carboxylic acid amide, which indicates the
possible additional associative interactions between
fluorine and hydrogen atoms of the polyfluorinated
alcohol with the cyclohexanone six-membered ring
[11, 12, 17].
1
The data obtained by analysis of H NMR spectra
indicate a different associative ability of the proton of
perfluoroalkyl chain of the telomeric alcohols to poly-
association. The increase in the number of fluorine
atoms in the polyfluorinated alcohol molecule leads to
reduced 1.2 times activity of polyassociate formation
that is seen from the comparison of the Δδ for the
singlet proton signal of HO groups at varying the
polyfluorinated alcohol concentration in carbon
tetrachloride. Probably, this result is associated with an
increase in the size of the polyfluorinated alcohol
molecule and steric barriers to these interactions.
We studied
a
possibility of polyassociative
interaction of polyfluorinated alcohol dissolved in
carbon tetrachloride, as well as features of the associa-
tion between the carbonyl group of cyclohexanone and
protons of the telomereic alcohols by the method of 1H
NMR spectroscopy. For this purpose, the minimum
allowable concentration of polyfluorinated alcohol in
the carbon tetrachloride was determined, which
allowed the comparison of the proton-donor activity of
H(CF2CF2)n groups at various degrees of telomeriza-
tion. The value of Δδ equal to the difference of proton
Adding the proton-acceptor cyclohexanone in an
appropriate quantity to the solution of polyfluorinated
alcohol in carbon tetrachloride shifts the signals of the
difluoromethyl group proton of the perfluoroalkyl
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 81 No. 7 2011

1532
RAKHIMOVA, KUDASHEV
1
Table 2. Chemical shifts of the protons of H(CF2CF2)n and HO groups in the H NMR spectra of polyfluorinated alcohol
associates
Associates through HCF2CF2 and HO groups of the
Polyassociates of polyfluorinated alcohol (CCl4)
a
polyfluorinated alcohols in CCl4
Concentration,
Alcohol
НО
HCF2CF2
НО
M
HCF2CF2,
δ, ppm
δ, ppm
Δδ, ppm
δ, ppm
Δδ, ppm
δ, ppm
Δδ, ppm
0.177
0.354
0.177
0.354
5.88
5.88
5.89
5.89
2.16
0.25
6.03
0.15
4.06
1.9
III
IV
2.41
1.92
2.13
0.21
5.95
0.06
3.98
2.06
a Cyclohexanone concentration 0.0632 M.
chain and the HO group of the polyfluorinated alcohol
downfield. It becomes possible to compare the
proportion of associates I and II. Adding 0.0632 M of
cyclohexanone reduces the proportion of the
associative interaction of the H(CF2CF2)n proton 2.5-
fold on going from the polyfluorinated alcohol with
n = 2 to that with n = 3. Therewith, the proportion of
associative interactions corresponding to the proton of
HO group of the telomeric alcohol increases 1.1-fold.
It is noteworthy that the strength of the associates of
polyfluorinated alcohols with acetone is in fact 2-fold
lower compared with the system of polyfluorinated
alcohol-cyclohexanone [20], which is probably due to
the molecular conformation of cyclohexanone
providing more opportunity for the stabilization of the
associative complexes of cyclohexanone-polyfluo-
rinated alcohol through the formation of hydrogen
bonds between hydrogen and fluorine atoms in the
molecules of cyclohexanone and polyfluorinated
alcohol, respectively. This conclusion is consistent
with the above IR spectral features of these systems.
300 instrument at the operating frequency 300 MHz,
internal reference tetramethylsilane. Individuality of
the compounds obtained was confirmed by thin layer
chromatography on the Sorbfil plates, eluent a mixture
of diethyl ether and ethanol, 1:0.05. Development of
the plates was performed using UV light. The melting
points were determined on a Mettler Toledo instrument
MP50 at a heating rate of 2°C min–1. The IR spectra in
the study of the associative interactions were taken
from the solutions in chloroform and carbon tetra-
chloride in 0.4 mm cells of sodium chloride. The
suspensions of phthalic anhydride and polyfluorinated
alcohols in cyclohexanone were homogenized using a
Prolabo ultrasonic bath at a frequency of 40 kHz.
Monopolyfluoroalkyl phthalates. Equimolar
amounts of phthalic anhydride and polyfluorinated
alcohol were preliminary dispersed in cyclohexanone
in an ultrasonic field at a frequency of 40 kHz for 2 h
at 70°C. Then the homogenized reaction mixture was
maintained at 130°C for 2 h to complete transition of
phthalic anhydride into the solution. The amount of the
telomeric alcohol entered into reaction was evaluated
by distilling off the unreacted polyfluorinated alcohol
and cyclohexanone in a vacuum. Then the reaction
mixture was washed with distilled water (50°C) to
separate phthalic anhydride from the reaction product.
The monoesters formed were purified by titration with
0.1 N sodium hydroxide solution until the transition of
the monoesters in solution, and subsequent
acidification with 0.1 N hydrochloric acid until the
cessation of precipitation of the monoester crystals.
The precipitated product was filtered off, washed with
cold water and recrystallized from glacial acetic acid.
The product was dried over magnesium sulfate.
Thus, in dilute solutions of polyfluorinated alcohol
and cyclohexanone the most favorable is the formation
of associates with structure I, in which electron density
distribution enhances nucleophility of the oxygen atom
of HO group of the polyfluorinated alcohol and the
possibility of acylation of the telomeric alcohol by
phthalic anhydride.
EXPERIMENTAL
The IR spectra of the reaction products were
1
recorded on a Specord-M82 device. The H and 13C
NMR spectra were recorded at 25°C from solutions in
deuterated dimethyl sulfoxide on a Varian Mercury-
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 81 No. 7 2011

FEATURES OF REACTIONS OF PHTHALIC ANHYDRIDE
1533
1,1,5-Trihydroperfluoropentyl hydrogen phtha-
late. Colorless crystals. Yield 48.4%. Degree of the
reactants conversions: phthalic anhydride 51%, poly-
fluorinated alcohol (n = 2) 67%, mp 101–103°C, Rf
0.81. IR spectrum, ν, cm–1 : 3598 (O–H), 2980–2914
(C–H), 1780 (C=O), 1684–1570 (Car–Car), 1216–1198
(CF). 1H NMR spectrum (DMSO-d6), δ, ppm: 4.938 m
(1H, CH2–CF2, J = 14.1 Hz), 7,373 cyclohexanone
(1H, CHF2, 2J = 50.1 Hz, 3J = 5.7 Hz), 7.538–8.026 m
(4H, C6H4), 12.778 (1H, COO H). 13C NMR spectrum
(DMSO-d6), δ, ppm: 166.439 (1C, COOH), 128.847–
133.963 (6C, C6H4), 62.034 (1C, CH2CF2), 113.824–
124.725 (4C, CF2 ). Found, %: C 39.69, F 40.21.
C13H8O4F8. Calculated, %: C 41.05, F 40.00
1648–1528 (Car–Car), 1210–1150 (CF). 1H NMR
spectrum (DMSO-d6), δ, ppm: 4.930 m (4H, CH2CF2,
2
J = 14.7 Hz), 7,384 cyclohexanone (2H, CHF2, J =
3
50.1 Hz, J = 5.6 Hz), 7.522–8.022 m (4H, C6H4). 13C
NMR spectrum (DMSO-d6), δ, ppm: 175.239 (2C,
C=O), 134.841–132.867 (6C, C6H4), 60.198 (2C,
CH2CF2), 112.842–127.354 (8C, CF2). Found, %: C
35.77, F 50.92. C18 H10O4F16. Calculated, %: C 36.36,
F 51.18.
Di(1,1,7-trihydroperfluorogeptyl)
phthalate.
Colorless crystals. Yield 24.5%. Degree of conversion
of the reactants: phthalic anhydride 23%, poly-
fluorinated alcohol (n = 3) 31%, mp 64–66°C, Rf 0.75.
IR spectrum, ν, cm–1: 2968–2920 (C–H), 1792 (C=O),
1651–1518 (Car–Car), 1219–1157 (CF). 1H NMR spec-
trum (DMSO-d6), δ, ppm: 4.939 m (2H, C H2CF2, J =
14.7 Hz), 7.464 cyclohexanone (2H, CHF2, 2J = 50.1 Hz,
3J = 5.4 Hz), 7.541–8.012 m (4H, C6H4). 13C NMR
spectrum (DMSO-d6), δ, ppm: 169.941 (2C, C=O),
133.811–132.823 (6C, C6H4), 62.338 (2C, CH2CF2),
111.892–126.684 (12C, CF2). Found, %: C 33.37, F
57.09. C22H10O4F24. Calculated, %: C 33.25, F 57.43.
1,7,7-Trihydroperfluoroheptyl hydrogen phtha-
late. Colorless crystals. Yield 32.2%. Degree of con-
version of the reactants: phthalic anhydride 42%,
polyfluorinated alcohol (n = 3) 51%, mp 87–89°C, Rf
0.72. IR spectrum, ν, cm–1: 3620 (O–H), 2982–2912
(C–H), 1785 (C=O), 1687–1572 (Car–Car), 1212–1200
(CF) . 1H NMR spectrum (DMSO-d6), δ, ppm: 4.961 m
(1H, CH2–CF2, J = 14.1 Hz), 7.250 t.t (1H, CHF2, 2J =
3
50.4 Hz, J = 5.4 Hz), 7.534–8.029 m (4H, C6H4),
12.431 (1H, COO H). 13C NMR spectrum (DMSO-d6),
δ, ppm: 167.249 (1C, COOH), 127.621–133,113 (6C,
C6H4), 62.047 (1C, CH2CF2), 113.711–125.174 (6C,
CF2). Found, %: C 37.02, F 46.52. C15H8O4F12.
Calculated, %: C 37.5, F 47.5.
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