Synthesis and GC-MS study of fluorinated esters derived from thrimethylolpropane

Article abstract of DOI:10.1134/S1070363208090107

Zol-gel process was used to synthesize equilibrium mixtures of mono-, di-, and trimester derived from trimethylolpropane and perfluorocarboxylic acids. The elution order of the components of the mixtures from a weakly polar HP-5 column was established. The mass spectra of the synthesized compounds were studied. The GC-MS parameters of the products were compared with the respective parameters of their nonfluorinated analogs. The characteristics of the fluorinated esters have features determined by the esterification degree and the nature of the perfluoroalkyl groups, due to which these compounds can be identified in mixtures.

Full text of DOI:10.1134/S1070363208090107

ISSN 1070-3632, Russian Journal of General Chemistry, 2008, Vol. 78, No. 9, pp. 1701–1706. © Pleiades Publishing, Ltd., 2008.
Original Russian Text © M.G. Pervova, V.E. Kirichenko, T.I. Gorbunova, A.Ya. Zapevalov, V.I. Saloutin, 2008, published in Zhurnal Obshchei Khimii,
2008, Vol. 78, No. 9, pp. 1469–1474.
Synthesis and GC–MS Study of Fluorinated Esters
Derived from Thrimethylolpropane
M. G. Pervova, V. E. Kirichenko, T. I. Gorbunova, A. Ya. Zapevalov, and V. I. Saloutin
Postovskii Institute of Organic Synthesis, Ural Branch, Russian Akademy of Scinces,
ul. S. Kovalevskoi 22, Ekaterinburg, 620041 Russia
e-mail: pervova@ios.uran.ru
Received April 4, 2008
Abstract―Zol–gel process was used to synthesize equilibrium mixtures of mono-, di-, and trimester derived
from trimethylolpropane and perfluorocarboxylic acids. The elution order of the components of the mixtures
from a weakly polar НР-5 column was established. The mass spectra of the synthesized compounds were
studied. The GC–MS parameters of the products were compared with the respective parameters of their
nonfluorinated analogs. The characteristics of the fluorinated esters have features determined by the
esterification degree and the nature of the perfluoroalkyl groups, due to which these compounds can be
identified in mixtures.
DOI: 10.1134/S1070363208090107
Previously we studied the structural effects of
complete esters derived from polyfluorocarboxylic
esters and polyols (pentaerythritol, trimethylolpropane,
and neopentyl glycol) on their termooxidative stability
and established that such esters are thermally more
stable than their nonfluorinated analogs [1]. The
structures of all the compounds synthesized in [1] were
confirmed by elemental analysis and IR and 1H and 19F
NMR spectroscopy.
A feature of the present work is that we have
developed a one-stage synthesis of all possible tri-
methylolpropane esters by esterification of perfluoro-
carboxylic acid. The known procedure of esterification
of perfluorocarboxylic acid with trimethylolpropane,
catalyzed by mineral acids [1]1 cannot provide the
required mixtures of mono-, di-, and triesters (see
scheme, conditions А).
The compositions of products Iа–If, IIa–IIf, and
IIIa–IIIf are presented in Table 1. As seen from the
table, under mineral acid–catalyzed conditions, even at
shortened contact times monoesters Ib–If in amounts
sufficient for further studies cannot be obtained. An
exception is trifluoroacetic acid: In this case, the
fractions of esters Iа–IIIа in the resulting mixtures are
quite considerable.
The complete esters we described in [1] possess a
number of useful properties characteristic of ester oils.
One the other hand, they have certain drawbacks, such
as poor solubility (insolubility) in hydrocarbon oils and
weak adhesion to various surfaces. These features
prevent application of complete fluorinated esters both
as oil lubricants and as antifriction greases and oils.
The problem of synthesizing equilibrium mixtures
of Ib–If, IIb–IIf, and IIIb–IIIf with quantitative
characteristics suitable for analysis is solved by means
of a zol–gel process that occurs in solutions and makes
it possible to controls the reactivity of reaction
participants.
The use in technics of incomplete fluorinated
polyol esters or their mixtures with complete
fluorinated esters allows one to overcome the above
drawbacks. However, components of such mixtures are
much more difficult to identify. This complex task can
be solved by means of gas chromatography (GC) and
gas chromatography–mass spectrometry (GC–MS).
The best studied in the zol–gel process with tetra-
alkoxysilanes [2]. Due to the use in the esterification
The aim of the present study was to synthesize
fluorine-containing mono-, di-, and triesters derived
from trimethylolpropane.
1
The reaction time of trimethylolpropane with perfluoro-
carboxylic acids was reduced by a factor of 3 compared with that
in [1].
1701

1702
PERVOVA et al.
CH2OC(O)R
C2H5C(CH2OH)2 + C2H5CCH2OH + C2H5CCH2OC(O)R
CH2OC(O)R
A/B
−Η2Ο
C2H5C(CH2OH)3 + RCOOH
CH2OC(O)R
CH2OC(O)R
CH2OC(O)R
Iа−Ii
IIа−IIi
IIIа−IIIi
А: Н+, t°, 1 h; B: Si(OEt)4, t°, 3 h; R = CF3 (Iа–IIIа), C2F5 (Ib–IIIb), C3F7 (Ic–IIIc), C4F9 (Id–IIId), C6F13 (Ie–IIIe), C8F17
(If–IIIf), СН3 (Ig–IIIg), С3Н7 (Ih–IIIh), С7Н15 (Ii–IIIi).
While having high molecular weights, compounds
Ia–If, IIa–IIf, and IIIa–IIIf containing perfluoroalkyl
groups feature much shorter retention times than their
respective nonfluorinated analogs. The elution order of
fluorinated esters Ia–Ic, IIa–IIc, and IIIa–IIIc with a
С2–С4 acyl chain length is reverse to that of the
nonfluorinated analogs: Triesters IIIa–IIIc are eluted
first, diesters IIa–IIc second, and monoesters Ia–IIc
last.
reaction of the zol–gel process involving tetra-
ethoxysilane, we could synthesize equilibrium
mixtures of fluorinated mono-, di-, and triesters Ia–If,
IIa–IIf, and IIIa–IIIе, respectively (see scheme,
conditions B). The compositions of the resulting
mixtures are presented in Table 1, and the synthesis
and analysis procedures are given in the Experimental
section.
For
objective
assessment
of
GC–MS
characteristics, we synthesized mixtures of non-
fluorinated mono-, di-, and trimesters Ig–Ii, IIg–IIi,
and IIIg–IIIi, respectively.
The elution order of esters Id–IIId with a C5 acyl
chain length is more intricate: Triester IIId is followed
by monoester Id, and diester IId is eluted last. The
elution order of esters Ie–IIIe with a C7 acyl chain
length changes again: Ie, IIIe, and IIe.
By combined analysis of the GC and MS data for
mixtures of esters Ig–Ii, IIg–IIi, and IIIg–IIIi we
established that the monoesters are eluted first from a
weakly polar HP-5 column, and then the diesters are
eluted, and the triesters are eluted last. Table 2 lists the
retention times of all the esters synthesized in this
work.
Only esters If–IIIf (acyl chain length С9) are
eluted in the same order as their nonfluorinated
analogs.
The shorter retention times of fluorinated
compounds compared with nonfluorinated on weakly
polar columns are explained by enhanced volatility of
the former [3]. This feature of fluorinated compounds
With fluorinated esters Ia–If, IIa–IIf, and IIIa–
IIIf, the above elution order undergoes radical
changes.
Table 1. Compositions of trimethylolpropane ester mixtures
Table 2. Retention times of trimethylolpropane esters Ia–Ii,
IIa–IIi, and IIIa–IIIi
synthesized by two proceduresa
Retention time, min
Contents of esters, %
monoesters
diester
triesters
Compound
R
monoester
diesters
triesters
Acid
Ia–If
IIa–IIf
IIIa–IIIf
Ia–Ii
IIa–IIi
IIIa–IIIi
Аb
Bc
А
B
А
B
CF3
10.00
10.26
10.81
11.40
12.57
13.74
10.96
14.05
21.18
9.39
9.75
7.96
8.29
Ia–IIIa
Ib–IIIb
Ic–IIIc
Id–IIId
Ie–IIIe
If–IIIf
Ig–IIIg
Ih–IIIh
Ii–IIIi
CF3COOH
C2F5COOH
C3F7COOH
C4F9COOH
C6F13COOH
C8F17COOH
13.4
0
14.3
14.7
25.5
26.6
6.2
47.4
20.8
17.6
27.7
3.8
58.4
63.1
55.3
54.6
64.4
44.8
37.4
79.1
80.5
67.1
86.6
93.6
26.0
22.1
18.1
17.3
29.4
22.0
C2F5
C3F7
C4F9
C6F13
C8F17
CH3
10.67
11.65
13.58
15.40
13.26
17.20
24.00
9.52
0.8
0.9
0
10.85
13.42
15.76
14.42
19.51
29.00
0.1
29.9
6.3
a
The compositions were determined by GLC by the internal
C3H7
C7H15
normalization procedure. (A) Mineral acid catalysis. c (B) zol–
b
gel process.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 78 No. 9 2008

SYNTHESIS AND GC–MS STUDY OF FLUORINATED ESTERS
1703
is a consequence of their poor solubility in the column
phase. In this connection fluoroacyl derivatives are
frequently used for improving GC characteristics of
hydroxyl-containing compounds.
Molecular ions [М]+ are absent in all the cases. The
[М]+ ion masses for compounds IIIe and IIIf are
beyond the scan range of the mass spectrometer.
However, these compounds are unlikely to give
molecular ions.
In trimethylolpropane derivatives Ia–If, IIa–IIf,
and IIIa–IIIf, the hydrocarbon part is strongly
screened by fluoroalkyl groups, and the stronger
screening, the weaker the compounds are adsorbed on
the column. As a result, triesters are eluted first,
diesters second, and monoesters last. This order is
observed with mixtures of Ia–Ic, IIa–IIc, and IIIa–
IIIc. As the size of the perfluronated group increases,
the saturated vapor pressure of a compound on GC
analysis decreases, and the elution order of esters Id–
If, IId–IIf, and IIId–IIIf gets to be primarily
determined by the molecular weight.
The highest mass ions for triesters IIIa–IIIf
correspond to the [M–R]+ fragment, for diesters IIa–
IIf, to [M–RСО2]+, and for monoesters Ia–If, to [M –
СН2OH–OH]+. The greatest number of ions formed on
cleavage of fluorine-containing fragments is
characteristic of triesters IIIa–IIIf. Their characteristic
ions are low-intensity ions [M – RСО2]+ and [M–
RСО2СН2]+. More stable ions are [M – 2RСО2H]+ and
[M–RСО2H–RСО2СН2]+. The prevailing fragmenta-
tion pathway involes cleavage of perfluoroacyl groups
to form a base ion at m/z 81 (С6Н9). The fragmentation
of perfluoroacyl groups gives rise to R+ and other
fluorine-containing fragments, and their assortment is
the larger, the longer is R.
Thus we established that the retention
characterstics of fluorinated esters Ia–If, IIa–IIf, and
IIIa–IIIf on a weakly polar НР-5 column differ from
those of compounds Ig–Ii, IIg–IIi, and IIIg–IIIi and
depend on the acyl chain length.
The base ion for monoesters Ia–If and diesters
IIa–IIf is m/z 68 (brutto formula С5Н8). Along with
this ion, the spectra of diesters IIa–IIf contain an m/z
99 ion (brutto formula С9Н11О), corresponding to the
fragment [M–RСО2H–RСО2]+ (I 5-10%). The
characteristic peak at m/z 31 ([СН2ОН]+) is observed
in the mass spectra of all monoesters Ia–If (I 10-15%)
and diesters IIa–IIf (I 4–8%), and, naturally, are absent
from the spectra of triesters IIIa–IIIf. The [RC(OH)2]+
ion peaks are very weak, especially in the case of
triesters IIIa–IIIf.
There is scarce information in the literature,
concerning mass-spectral fragmentation of compounds
Ia–If, IIa–IIf, and IIIa–IIIf.
In the present work we have analyzed the
fragmentation patterns of perflurinated mono-, di-, and
triesters of trimethylolpropane under electron impact
(Tables 3–5). As an example, we show in Figs. 1–3
the mass spectra of esters Ic–IIIc. Homologs Ia–If, IIa–
IIf, and IIIa–IIIf have similar fragmentation patterns.
Table 3. Mass spectral data for fluorinated monoesters Ia–If
R
Fragment
CF3
C2F5
C3F7
C4F9
I, %
C6F13
I, %
C8F17
I, %
m/z
I, %
m/z
I, %
m/z
I, %
m/z
m/z
m/z
M
230
182
115
113
97
–
280
232
165
163
147
119
86
–
330
282
215
213
197
169
86
–
380
332
265
263
247
219
86
–
480
432
365
363
347
319
86
–
580
532
465
463
447
419
86
–
M–CH2OH–OH
RCO2H2
RCO2
3.4
2.2
1.6
1.2
1.1
0.2
0.1
4.2
1.5
0.8
1.3
1.7
0.9
1.3
0.1
1.4
0.1
1.6
0.1
–
–
RCO
2.3
1.9
0.8
–
R
69
36.7
21.2
2.8
20.4
22.2
4.9
13.7
22.9
6.3
1.4
0.6
С5Н10О
C6H9
86
24.9
7.6
27.6
10.0
28.7
12.5
81
81
81
81
81
81
C5H9
68
68
68
68
68
68
100
14.5
100
15.1
100
13.1
100
13.4
100
11.7
100
10.8
CH2OH
31
31
31
31
31
31
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 78 No. 9 2008

1704
PERVOVA et al.
Table 4. Mass spectral data for fluorinated diesters IIa–IIf
R
Fragment
CF3
C2F5
C3F7
C4F9
I, %
C6F13
I, %
C8F17
I, %
m/z
I, %
m/z
I, %
m/z
I, %
m/z
m/z
m/z
M
326
257
213
194
182
115
113
97
–
426
307
263
244
232
165
163
147
119
99
–
526
357
313
294
282
215
213
197
169
99
–
626
407
–
726
507
463
444
432
365
363
347
319
99
–
826
607
563
544
532
465
463
447
419
99
–
–
M–R
<0.1
<0.1
0.1
0.3
2.4
1.3
0.4
3.4
30.1
9.6
12.2
100
6.8
<0.1
<0.1
0.3
0.4
1.9
1.9
0.4
0.3
7.7
17.9
15.0
100
5.1
<0.1
M–RCO2
M–RCO2H–Н2О
M–RCO2CH2–Н2О
RCO2H2
RCO2
–
0.1 363
0.4 344
2.3 332
1.8 265
0.4 263
1.5 247
22.5 219
0.6
0.4
0.3
1.7
2.0
0.2
0.2
2.7
1.3
0.9
3.5
0.6
1.9
2.2
0.4
RCO
–
–
R
69
37.1
5.2
2.2
0.5
С6Н11О
C6H9
99
12.7
13.6
99
81
68
31
23.8
15.8
26.2
14.8
81
7.8
81
81
81
81
C5H9
68
68
68
68
68
100
7.2
100
6.0
100
3.9
100
3.4
CH2OH
31
31
31
31
31
For comparison we used the MS characteristics of
complete esters of trimethylolpropane and non-
fluorinated carboxylic acids with a С2–С10 acyl chain
length, reported in [4, 5]. Our data on the
fragmentation of compounds IIIg–IIIi are nicely
consistent with published data. We also studied the
mass spectra of monoesters Ig–Ii and diesters IIg–IIi.
Homologous nonfluorinated esters, too, have similar
fragmentation patterns.
The fragmentation of fluorinated esters Ia–If, IIa–
IIf, and IIIa–IIIf and nonfluorinated esters Ig–Ii, IIg–
IIi, and IIIg–IIIi occurs along several pathways. The
fragmentation patterns are coinciding in part, but there
are certain differences.
The most characteristic difference consists in that
the base ion for nonfluorinated compounds Ig–Ii, IIg–
IIi, and IIIg–IIIi is [RCO]+, and the corresponding ion
I, %
I, %
68
68
100
100
57
50
50
41
86
31
0
0
0
80 160 240 320 400 480 560 640 720
m/z
0
80 160 240 320 400 480 560 640 720
m/z
Fig. 1. Mass spectrum of monoester Ic.
Fig. 2. Mass spectrum of diester IIc.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 78 No. 9 2008

SYNTHESIS AND GC–MS STUDY OF FLUORINATED ESTERS
Table 5. Mass spectral data for fluorinated triesters IIIa–IIIf
1705
R
Fragment
CF3
C2F5
I, %
C3F7
I, %
C4F9
I, %
C6F13
I, %
C8F17
I, %
m/z
I, %
m/z
m/z
m/z
m/z
m/z
M
422
353
309
295
194
181
167
115
113
97
–
572
453
409
395
244
231
217
165
163
147
119
81
–
722
553
509
495
294
281
267
215
213
197
169
81
–
872
–
1172
853
809
795
444
431
417
365
363
347
319
81
–
1472
–
M–R
0.1
0.2
2.0
6.3
0.1 653
1.8 609
3.4 595
<0.1
1.9
<0.1 1053
0.7 1009
–
M–RCO2
M–RCO2CH2
M–2RCO2H
M–RCO2H–RCO2CH2
M–2RCO2CH2
RCO2H2
0.6
5.8
–
1.6
0.5
8.6
9.4
2.1
0.1
0.6
0.1
4.6
995
544
531
517
465
463
447
419
81
<0.1
6.4
7.0
1.2
–
12.6
35.6
3.1
15.4
28.8
3.7
13.5 344
20.2 331
3.5 317
0.3 265
0.9 263
5.1 247
52.4 219
11.3
15.2
2.9
1.7
0.5
0.2
RCO2
1.8
1.2
0.8
0.5
–
RCO
18.2
80.0
72.2
13.0
78.6
1.2
R
69
18.3
100
43.8
1.1
C6H9
81
81
67
100
72.8
100
52.7
100
35.3
100
31.8
C5H8
67
67
67
67
67
100
for fluorinated esters Ia–If, IIa–IIf, and IIIa–IIIf has
a low intensity and is getting weaker with increasing
R. Furthermore, the [RC(OH)2]+ ion peaks for non-
fluorinated esters Ig–Ii, IIg–IIi, and IIIg–IIIi more
intense that for their fluorinated analogs.
Injector temperature 250°С. Carrier gas helium, split
ratio 1:50. Ionization energy 70 eV. Mass range 30–
1000 amu. Injection volume 0.2 μl.
Solutions of mixtures of Ia–Ii, IIa–IIi, and IIIa–
IIIi in acetone (concentration 5 mg ml–1) were used for
analysis.
As relatively intense characteristic ions of
nonfluorinated esters Ig–Ii, IIg–IIi, and IIIg–IIIi we
can mention [M–СН2–OH]+ for monoesters Ig–Ii,
[M–СН2OCOR–OH]+ for diesters IIg–IIi, and [M–
СН2OCOR–СО2R]+ for triesters IIIg–IIIi.
Synthesis of esters Ia–If, IIa–IIf, and IIIa–IIIf.
Tetraethoxysilane, 0.31 g, water, 0.5 ml, and 50 μl of
sulfuric acid were added to 6.70 g of trimethyl-
olpropane heated to the melting point. The reaction
Thus, we have developed a procedure for preparing
mixtures of fluorinated trimethylolpropane mono-, di-,
and triesters, based on a zol–gel process involving
tetraethoxysilane. Analysis of the resulting mixtures
was performed by GC and GC–MS. The analytic
characteristics of trimethylolpropane mono-, di-, and
triesters Ia–If, IIa–IIf, and IIIa–IIIf have features
determined by the degree of esterification and the
nature of the perfluoroalkyl group, due to which these
compounds can be identified in mixtures.
I, %
81
100
67
169
50
EXPERIMENTAL
Gas chromatography-mass spectrometry was
performed on an Agilent 7890A MS 5975C Inert XL
instrument, using an HP5–MS quartz capillary column
(30 m × 0.25 mm × 0.25 μm). Temperature program:
initial temperature 60°С (hold 2 min), ramp rate
10°С/min, final temperature 290°С (hold 20 min).
309
0
0
80 160 240 320 400 480 560 640 720
m/z
Fig. 3. Mass spectrum of triester IIIc.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 78 No. 9 2008

1706
PERVOVA et al.
mixture was heated on a boiling water bath and stirred
until a gel-like material formed. Perfluorobutyric acid,
32.10 g, was then added, and stirring was continued for
3 h. The reaction mixture was cooled and diluted with
water. The organic layer was washed with water, a
soda solution, and water, and dried over calcium
chloride.
REFERENCES
1.Gorbunova, T.I., Sorokina, S.M., Zapevalov, A.Ya., and
Saloutin, V.I., Zh. Org. Khim., 2006, vol. 76, no. 11,
p. 1879.
2.Shabanova, N.A. and Sarkisov, P.D., Osnovy zol'-gel'
tehnologii nanodispersnogo kremnezema (Basics of Zol–
Gel Technology of Nanodispersed Silica), Moscow:
Akademkniga, 2004.
3.Zaikin, V.G. and Mikaya, A.I., Khimicheskie metody v
mass-spektrometrii organicheskikh soedinenii (Chemical
Methods in Organic Mass Spectrometry), Moscow:
Nauka, 1987.
4.Von Zeman, A., Bartl, P., and Schaaff, A., Fette Seifen
Anstrichmittel., 1978, vol. 80, no. 7, p. 278.
ACKNOWLEDGMENTS
The work was financially supported by the Ministry
for Industry, Energy, and Science of the Sverdlovsk
Region (contract no. RF-26/07) and the Russian
Foundation for Basic Research (project no. 07-03-
97631-r_ofi).
5.Black, K.D. and Gunstone, F.D., Chem. Phys. Lipids,
1990, vol. 56, p. 169.
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