Retention Indices and Enthalpies of Sorption of Esters of Neopentyl Glycol on DB-1 Stationary Phase

Article abstract of DOI:10.1134/S0036024420030188

Abstract: The logarithmic retention indices and the enthalpies of sorption at the average temperature of an experiment and 298.2 K are determined via gas–liquid chromatography using DB-1 stationary phase for esters of neopentyl glycol and С₂–С<

Full text of DOI:10.1134/S0036024420030188

ISSN 0036-0244, Russian Journal of Physical Chemistry A, 2020, Vol. 94, No. 3, pp. 659–661. © Pleiades Publishing, Ltd., 2020.
Russian Text © The Author(s), 2020, published in Zhurnal Fizicheskoi Khimii, 2020, Vol. 94, No. 3, pp. 478–480.
SHORT
COMMUNICATIONS
Retention Indices and Enthalpies of Sorption of Esters
of Neopentyl Glycol on DB-1 Stationary Phase
O. D. Lukinaa, E. L. Krasnykha,*, S. V. Portnovaa, and S. V. Levanovaa
aSamara State Technical University, Samara, 443001 Russia
*е-mail: kinterm@samgtu.ru
Received April 18, 2019; revised April 18, 2019; accepted September 10, 2019
Abstract—The logarithmic retention indices and the enthalpies of sorption at the average temperature of an
experiment and 298.2 K are determined via gas–liquid chromatography using DB-1 stationary phase for
esters of neopentyl glycol and С2–С6 monobasic carboxylic acids of linear and branched structure at 423.2–
523.2 K. The temperature dependences of the studied compounds’ retention indices are obtained, and the
linearity of these dependences in the investigated range of temperatures is demonstrated. The values obtained
for the enthalpies of sorption are analyzed.
Keywords: esters, neopentyl glycol, retention times, logarithmic retention indices, enthalpy of sorption
DOI: 10.1134/S0036024420030188
INTRODUCTION
gas–liquid chromatography on DB-1 nonpolar
phase [2–4].
Esters of neopentyl glycol and carboxylic acids are
characterized by reduced oxidation and hydrolysis
potential, compared to natural esters. They can be
used as plasticizers and viscosity modifiers for poly-
mers. The special interest in these compounds is due
to the possibility of using them as the basis for syn-
thetic lubricants [1].
EXPERIMENTAL
Esters of neopentyl glycol were obtained via azeo-
tropic esterification. Carboxylic acids of linear and
branched structure containing 2–6 carbon atoms per
molecule were used as precursors. The neopentyl gly-
col : acid molar ratio was 1 : 4. Synthesis was per-
formed in the presence of benzene (for the esters of
This work continues a series of studies on the
sorption of esters of carboxylic acids and poly- C2–C5 acids) or toluene (for the esters of С6–С7
atomic alcohols characterized by different contents
of ester and hydroxyl groups under conditions of added as a catalyst.
acids); 1 wt % of orthophosphoric acid (72.5%) was
O
C
CH3
O
R
OH
OH
HO CH2
C
CH2
O
C R + H2O
CH3
CH3
HO CH2
C
CH2 OH
+
Neopentyl glycol monoesters
CH3
CH3
Neopentyl glycol
O
C
O
C
2R
R
C
O
O CH2
C
CH2
CH3
Neopentyl glycol diesters
O
R + 2H2O
where R = CH3, C2H5, n-C3H7, n-C4H9, n-C5H11, the mixture was neutralized with an aqueous solution
n-C6H13, iso-C3H7, iso-C4H9, tert-C4H9.
Excess acid was removed from the reaction mixture
via distillation using a water-jet vacuum pump, and cation under vacuum to isolate the target ester.
of sodium bicarbonate. Once purified of the residues
of acid, the reaction mixture was separated via rectifi-
659

660
LUKINA et al.
Table 1. Experimental values of the retention indices and coefficients of temperature dependences for the esters of neopen-
tyl glycol (I = aTc + b, where Tc is temperature of column)
R2
R
I, arb. units
ΔI/ΔT
a
b
Neopentyl glycol monoesters
423.2 К
1015.4 0.1
1108.1 0.1
453.2 К
433.2 К
443.2 К
1019.4 0.1
1112.5 0.1
473.2 К
453.2 К
1021.7 0.1
1114.7 0.1
483.2 К
CH3–
C2H5–
1017.7 0.1
1110.3 0.1
463.2 К
2.1
2.2
0.206
0.219
984.5
1075.2
0.997
0.999
n-C3H7–
1204.4 0.1
473.2 К
1206.7 0.4
483.2 К
1209.0 0.1
493.2 К
1211.5 0.1
503.2 К
2.4
0.237
1161.7
0.998
n-C4H9–
iso-C4H9–
1305.9 0.1
1262.3 0.1
493.2 К
1308.6 0.1
1265.1 0.1
503.2 К
1311.4 0.1
1268.0 0.1
513.2 К
1314.1 0.1
1271.1 0.1
523.2 К
2.7
2.9
0.272
0.292
1251.5
1203.9
0.999
0.999
n-C5H11–
n-C6H13–
tert-C4H9–
1408.9 0.1
1511.2 0.1
1207.7 0.1
463.2 К
1412.0 0.1
1514.4 0.2
1211.2 0.1
473.2 К
1415.0 0.1
1518.1 0.2
1214.6 0.1
483.2 К
1418.3 0.1
1521.8 0.4
1218.4 0.1
493.2 К
3.1
3.5
3.6
0.313
0.356
0.223
1340.1
1129.3
1125.6
0.999
0.999
0.998
iso-C3H7–
1168.0 0.1
1170.1 0.1
1172.2 0.1
1174.7 0.1
2.2
Neopentyl glycol diesters
423.2 K
1138.8 0.1
1318.0 0.1
453.2 K
433.2 К
1139.2 0.1
1318.5 0.1
463.2 К
443.2 К
1139.6 0.1
1319.0 0.1
473.2 К
453.2 К
CH3–
C2H5–
1140.0 0.1
1319.6 0.1
483.2 К
0.4
0.5
0.041
0.053
1132.7
1310.1
0.996
0.998
n-C3H7–
1490.7 0.1
473.2 K
1491.7 0.1
483.2 К
1492.5 0.1
493.2 К
1493.4 0.1
503.2 К
0.9
0.089
1474.8
0.999
n-C4H9–
iso-C4H9–
1678.2 0.1
1591.3 0.1
493.2 K
1679.4 0.1
1592.4 0.1
503.2 К
1680.7 0.5
1593.7 0.1
513.2 К
1681.7 0.1
1595.0 0.1
523.2 К
1.2
1.2
0.119
0.122
1654.2
1566.9
0.997
0.997
n-C5H11–
tert-C4H9–
n-C6H13–
1868.1 0.1
1471.2 0.2
2057.7 0.1
463.2 K
1869.7 0.1
1473.5 0.1
2059.4 0.1
473.2 К
1871.2 0.1
1475.9 0.1
2061 0.1
483.2 К
1872.9 0.1
1478.4 0.1
2062.2 0.1
493.2 К
1.6
2.4
1.7
0.159
0.241
0.169
1832.9
1418.1
2020.6
0.999
0.999
0.999
iso-C3H7–
1412.3 0.1
1413.3 0.3
1414.2 0.2
1415.4 0.1
1.0
0.101
1393.1
0.997
The retention times were determined using a
Kristall-2000M gas chromatograph in the isothermal
mode; the Khromatek-Analitik software was used.
The chromatograph was equipped with a flame ion-
ization detector and a capillary column (100 m ×
0.2 mm × 0.5 μm) with DB-1 grafted stationary liquid
phase (dimethylpolysiloxane). The experimental con-
ditions were an injector temperature of 623.2 K; a
detector temperature of 573.2 K; and a column tem-
perature of 423.2–523.2 K. Helium was used as the
carrier gas. The flow rate was 0.7 mL/min, and the
split ratio was 1/100. The sample volume was 0.2 μL.
RESULTS AND DISCUSSION
The obtained values of the retention indices and
the coefficients of their temperature dependences are
given in Table 1. All dependences are linear, showing
there was no interaction between the molecules of the
substance in the sorbent. With monoesters the
increase in indices by 10° (∆I/10) varies from 2 to
4 arb. units; with diesters, this value varies from 0.4 to
2.4 arb. units. The dependences of the retention indi-
ces on the number of carbon atoms in the alkyl substit-
uent of the esters are described for monoesters and
diesters, respectively, by the equations
The experimental technique, the procedure for
extrapolating the enthalpy of sorption to 298.2 K, and
the way of calculating the retention indices, the reten-
I220 = 96.00nC + 834.4, R2 = 0.999,
I220 = 182.9nC + 770.7, R2 = 0.999.
(1)
(2)
tion factor, and enthalpy of sorption
(kJ/mol)
sorpH
Δ
The results from calculating enthalpies of sorption
at the average experimental temperature were
described in detail in [2–4].
and (298.2 K) of esters of neopentyl
ΔsorpH°
Δ
sorpH
RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A
Vol. 94
No. 3
2020

RETENTION INDICES AND ENTHALPIES OF SORPTION OF ESTERS
661
glycol are given in Table 2. It is seen that the values of enthalpy of sorption, calculated per one СН2 group of
enthalpies of sorption depend linearly on the number
of carbon atoms in the alkyl substituent for mono- and
monoesters, is 5.7 kJ/mol. This is higher than the
value obtained for esters of glycolic and lactic acids
diesters of neopentyl glycol. The increase in the (4.4 kJ/mol) [4] characterized by similar structure.
CH3
O
O
C
O
C
HO CH2
C
CH2
O
C R
HO CH2
O
R
HO CH
CH3
O R
CH3
Neopentyl glycol monoesters
Glycolic acid esters
Lactic acid esters
The enthalpies of sorption of С10–С16 linear neopentyl glycol and esters of glycolic and lactic acids
shows that the enthalpy of sorption depends on the
ratio between the hydroxyl and ester groups, and the
alkyl component of the molecule. An increase in the
alkanes used to calculate the retention indices
(Table 2) were determined to explain such behavior.
The change on the enthalpy of sorption, calculated for
one СН2 group of the studied normal alkanes, is
5.4 kJ/mol. This agrees with the increase in the
enthalpy in monoesters of neopentyl glycol within the
margin of error. Analysis of structure of monoesters of
number of methyl groups raises
(298.2 K),
sorpH°
Δ
which tends toward the values typical of n-alkanes.
With diesters of neopentyl glycol, the increase in
the enthalpy of sorption, calculated per one СН2
group, is 4.3 kJ/mol. This means the presence of ester
groups (–СOO–) lowers the value of the enthalpy of
sorption, as compared to normal alkanes. A similar
dependence was recorded for trimethylolpropane tri-
esters containing three ester groups; here, the contri-
bution to the enthalpy of sorption per one СН2 group
is 3.8 kJ/mol [3].
Table 2. Results from calculating enthalpies of sorption
(kJ/mol)
−Δпl Сp° [6],
J/(mol K)
−ΔsorpH°
(298.2 K)
−ΔsorpH
(Тav)
Тav, K
Compound
Neopentyl glycol monoesters
CH3–
C2H5–
110.8
117.9
125.1
132.2
139.4
122.6
130.1
125.9
146.5
438.2 44.2 0.1
438.2 47.9 0.1
468.2 49.8 0.3
488.2 50.9 0.1
508.2 53.0 0.1
478.2 47.0 0.2
488.2 49.6 0.1
508.2 46.9 0.1
518.2 55.3 0.2
59.7
64.4
71.0
76.0
82.3
69.1
74.3
73.3
87.7
FUNDING
n-C3H7–
n-C4H9–
n-C5H11–
iso-C3H7–
iso-C4H9–
tert-C4H9–
n-C6H13–
This work was supported by the Russian Foundation for
Basic Research, project no. 19-08-00928 A.
CONFLICT OF INTEREST
The authors have no conflict of interest to declare.
Neopentyl glycol diesters
CH3–
C2H5–
102.9
112.6
123.3
134.6
146.4
118.9
130.8
123.4
158.6
438.2 49.8 0.1
438.2 56.2 0.1
468.2 60.0 0.1
488.2 63.9 0.1
508.2 68.2 0.1
478.2 55.9 0.1
488.2 61.2 0.1
508.2 55.5 0.1
518.2 72.9 0.2
64.2
71.9
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n-C3H7–
n-C4H9–
n-C5H11–
iso-C3H7–
iso-C4H9–
tert-C4H9–
n-C6H13–
80.9
89.4
98.9
77.3
86.1
81.4
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Russ. J. Phys. Chem. A 93, 577 (2019).
Alkanes
С10
С11
С12
С13
С14
С15
81.7
88.9
96.0
103.1
110.2
117.4
438.2 45.1 0.1
438.2 48.5 0.1
438.2 51.9 0.1
468.2 54.4 0.2
508.2 54.7 0.1
508.2 57.8 0.1
56.5
60.9
65.4
71.9
77.8
82.4
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Translated by P. Vlasov
RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A Vol. 94 No. 3 2020