The thermodynamic properties and thermolysis characteristics of 2,5-dimethyl-2,5-di-(m-carboranoylperoxy)-3-hexine and 1,1-dimethyl-2-propine-1- yl diperoxy ester of m-carborane-1,7-dicarboxylic acid

Article abstract of DOI:10.1134/S0036024406010055

The standard enthalpies of combustion Δ_c H°_298.15 and formation Δ_f H° _298.15 of 2,5-dimethyl-2,5-di-(m-carboranoylperoxy)-3-hexine and 1,1-dimethyl-2-propine-1-yl diperoxy ester of m-carborane-1,7-dicarboxylic a

Full text of DOI:10.1134/S0036024406010055

ISSN 0036-0244, Russian Journal of Physical Chemistry, 2006, Vol. 80, No. 1, pp. 42–46. © Pleiades Publishing, Inc., 2006.
Original Russian Text © V.N. Dibrivnyi, N.A. Butylina, V.V. Kochubei, Yu.Ya. Van-Chin-Syan, A.P. Yuvchenko, 2006, published in Zhurnal Fizicheskoi Khimii, 2006, Vol. 80, No. 1,
pp. 50–54.
CHEMICAL THERMODYNAMICS
AND THERMOCHEMISTRY
The Thermodynamic Properties and Thermolysis Characteristics
of 2,5-Dimethyl-2,5-di-(m-carboranoylperoxy)-3-hexine
and 1,1-Dimethyl-2-propine-1-yl Diperoxy Ester
of m-Carborane-1,7-dicarboxylic Acid
V. N. Dibrivnyi*, N. A. Butylina*, V. V. Kochubei*,
Yu. Ya. Van-Chin-Syan*, and A. P. Yuvchenko**
*Lviv Politechnic National University, Lviv, Ukraine
**Institute of Physicoorganic Chemistry, Belarussian Academy of Sciences, Minsk, 220072 Belarus
Received January 13, 2005
°
°
Abstract—The standard enthalpies of combustion ∆cH298.15 and formation ∆fH298.15 of 2,5-dimethyl-2,5-di-
(m-carboranoylperoxy)-3-hexine and 1,1-dimethyl-2-propine-1-yl diperoxy ester of m-carborane-1,7-dicar-
boxylic acid and the effective activation energy Eeff of their thermolysis were determined for the first time.
DOI: 10.1134/S0036024406010055
INTRODUCTION
The enthalpies of combustion of the compounds
were determined using the technique with incomplete
combustion developed at the Laboratory of Thermo-
chemistry (Moscow State University) [7]. The design
of the bomb was slightly modified, and a nontraditional
method for data processing was used [8]. To increase
the completeness of combustion, the substances were
burned on a platinum net, and the electrodes were pro-
tected by platinum screens. The procedure used
ensured the reproducibility of the qualitative composi-
tion of bomb combustion products. The combustion of
the compounds is described by the general equation
The use of carborane nuclei as radical polymeriza-
tion initiators increases the thermal stability of the
polymers synthesized this way [1], which find applica-
tion as thermally stable heat-insulating materials, glu-
ing compositions, and antifriction plastics [1]. The
introduction of peroxy-containing carboranes into
polymeric chains increases their stability not only to
thermooxidative destruction but also to UV and gamma
irradiation [2–4]. At the same time, data on the thermo-
dynamic properties of peroxy-containing carboranes
are almost entirely absent, which complicates develop-
ing technologies for the preparation of new polymeric
materials with peroxycarborane chain fragments.
ë‡ÇbHcOd(cr)
+ (a + c/4 + 3/4b – d/2)O2
(1)
= aCO2 + ((c – 3b)/2)H2O(l) + bH3BO3(cr).
In this work, we for the first time experimentally
determined the thermodynamic properties and
kinetic characteristics of the thermolysis of two crys-
talline peroxy-containing carborane-12 derivatives,
çëÇ10ç10ëë(é)ééë(ëç3)2ë≡ëë(ëç3)2ééë(é)–
ëÇ10ç10ëç (I) and çë≡ë(ëç3)2ëéé(é)ëë–
Ç10ç10ëë(é)ééë(CH3)2C≡CH (II).
In addition to the substances specified in the equa-
tion, combustion products contained a saturated aque-
ous solution of H3BO3 (~1 ml) and small amounts of
boron, carbon, and boron carbide. When combustion
was performed, the bomb volume was filled with boron
oxide and water vapor formed in the reaction. As a
result of an explosion, these products fairly uniformly
settled down on the inside surface of the bomb. Prior to
measurements, water (1 ml) was introduced into the
bomb; part of boric acid formed was therefore dis-
solved in excess water. Because of the low solubility of
ç3Çé3, a saturated solution of the acid was formed.
Moreover, the formation of boric acid from I according
to (1) required an additional amount of water. This
amount was taken into account by subtracting it from
the amount of water (1 ml) introduced beforehand.
EXPERIMENTAL
The methods for synthesizing these compounds and
data on their purification and thermal stability were pre-
sented in [5, 6]. The samples were purified by low-tem-
perature recrystallization from pentane. The structure
of the compounds was characterized by elemental anal-
yses for carbon, boron, and active oxygen and IR spec-
troscopically, and their individual character was proved
by thin-layer chromatography.
The explosive character of the combustion of the
carborane nucleus and peroxide group was used as a
42

THE THERMODYNAMIC PROPERTIES AND THERMOLYSIS CHARACTERISTICS
43
favorable factor. Crystalline substances were prepared The calculations were performed with corrections for
by grinding in a chalcedony mortar, sifted through a the combustion of the Terylene ampule (qTer) and cotton
sieve, and then encapsulated in Terylene disks. A disk
was placed on a platinum net with a gauze strip for
simultaneously igniting the whole sample. Finely
divided powder particles managed to burn in the bomb
volume before they could reach the cold walls of the
bomb.
gauze with a thread (qgauze), the formation of a solution
of nitric acid in the bomb (qHNO ) , partial solution of
3
boric acid (qH BO ) , the combustion of free boron to
3
3
boric acid (qB), and the combustion of carbon (graphite)
to carbon dioxide (qC). The Washburn correction (∆Uw)
was also introduced. We used the following heats of
combustion (J/g) under bomb conditions: 22944.2 for
the combustion of Terylene [10], 16704.2 for cotton
gauze and thread [11], 61379 for boron (to ç3Çé3 (cr))
[7], and 32763 for carbon (to ëé2 (g)). The heats of
formation of nitric acid and a saturated solution of boric
acid were taken to be 59 kJ/mol [12] and –21836 J/mol
[13], respectively. The Washburn corrections (5.0 and
3.9 J/g for I and II, respectively) were calculated
according to [12, 14]. The amounts of carbon dioxide
formed in the combustion of Terylene (1 g) and cotton
thread (1 g) were taken to be 2.2872 and 1.6284 g,
respectively.
The enthalpies of combustion of the peroxides were
measured on a V-06 M calorimeter equipped with an
isothermic ( 0.003 K) shell. The energy equivalent of
the calorimetric system (W) was determined by mea-
suring the enthalpy of combustion of reference benzoic
acid, K-1 brand (the content of the major component
was 99.995 mol %, and the heat of combustion was
−26426.9 J/g taking into account the Jessup factor). For
this purpose, a series of eight experiments were per-
formed, which gave W = 14835 13 J/V. The initial
oxygen pressure purified from combustible impurities,
carbon dioxide, and water was 2.94 × 106 Pa. The initial
temperature of the main period was 298.15 K in all
experiments, and the duration of the main period was
35 min. In 35 min, boron oxide hydration and boric acid
solution were complete. This followed from the coinci-
dence of temperature changes during the final periods
of carborane and benzoic acid combustion.
RESULTS AND DISCUSSION
The results obtained in determining the energies of
combustion ∆U of I and II are listed in Table 1. In this
table, m is the sample weight, ∆T is the true temperature
rise during measurements, QΣ is the total amount of
energy released, and B and C are the completeness of
combustion for boron and carbon, respectively (the
other denotations were specified above).
An analysis of the results showed that the energy of
combustion was related to combustion completeness.
We explain this by the presence of boron carbide in
combustion products; the amount of this substance is
virtually impossible to determine. The neglect of cor-
rections for the formation of boron carbide automati-
cally leads to exaggerated corrections for the formation
of free boron and carbon and, as a consequence, exag-
gerated energies of combustion. The approximation of
the dependence of the energy of combustion of the sub-
stances on the incompleteness of their combustion with
respect to carbon (100 – C) by the straight line equation
∆U° = a + b(100 – C) gives satisfactory results (the cor-
relation coefficient ρ is 99.16 and 97.25% for I and II,
respectively). The a value in the equation is the energy
of combustion of the substance by 100% with respect to
Each combustion experiment was followed by a
quantitative analysis of the products for carbon dioxide
and boric and nitric acids. Nitric acid was formed
because of the presence of some amount of nitrogen in
the oxygen that we used. The amount of carbon dioxide
produced was determined by the Rossini method [9] to
within 1 × 10–4 g. The reliability of gas analyses was
substantiated in a series of experiments with the com-
bustion of standard benzoic acid. The content of carbon
monoxide was controlled in separate experiments using
indicator tubes to within 1 × 10–6 g. The content of
nitric acid was determined by potentiometric titration,
and the content of boric acid, by titration with alkali in
the presence of mannitol.
The liquid decomposition products were determined
chromatographically using an LKhM-72 chromato-
graph with a flame ionization detector and Chromaton
N-AW-DMCS (15%) deposited on Apieson-L + 5%
PEG-2000 as a stationary phase. The column was 3 m
long and 2 mm in diameter, the temperature of the col-
umn was 80°ë, the temperature of the vaporizer was
150°C, and the carrier gas was helium. Gaseous decom-
position products were analyzed on an LKhM-72 chro-
matograph. The column 3 m long and 4 mm in diameter
was packed with triethylene glycol butyrate (20 wt %)
and ethylene glycol (3 wt %) on chromaton-N.
°
carbon, ∆U100 . The coefficients of the straight line
equations were determined by the method of least
squares (Table 1). The standard deviations of the energy
of combustion from the straight-line dependences were
calculated with the Student test value for a 0.05 signif-
icance level. Good agreement between the earlier data
on o- and m-carboranes obtained using straight line
equations [8] and the procedure described in [7] is evi-
dence of the acceptability of this approach. This allows
us to use the results of experiments with relatively low
combustion completeness.
The energy of combustion of the substances (J/g)
was calculated by the equation
–∆U° = (QΣ – qTer – qgauze – qHNO
3
(2)
+ qH BO + qB + qC – ∆Uw )/m.
3
3
RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY Vol. 80 No. 1 2006

44
DIBRIVNYI et al.
Table 1. Data obtained in experimentally determining the energies of combustion
qH BO , J qHNO , J
m, g
∆T, V QΣ, J
qgauze, J
qTer, J
qB, J
qC, J
B, %
C, % –∆U°, J/g
3
3
3
0.09314 0.3288 4878.1 127.6
0.09101 0.3096 4592.7 116.9
0.09031 0.3200 4746.7 140.3
0.10236 0.3581 5312.8 110.8
0.11344 0.3869 5740.4 108.2
0.08297 0.2970 4406.6 123.1
611.5
450.3
606.9
663.4
598.1
596.6
21.1
33.8
44.0
131.5
29.6
66.9
3.0
9.8
15.6
15.6
15.6
15.5
15.4
15.6
3.1
99.12
98.56
98.11
95.02
98.99
96.87
99.70
98.99
98.60
95.62
99.55
97.01
44779
44817
45021
46181
44760
45669
0.9
1.7
1.5
2.0
2.0
13.5
48.0
5.5
26.5
°
–∆U100 = 44567 54 J/g
Compound I
–∆U° = (44567 54) + (363 24)(100 – C)
ρ = 99.16%
0.11168 0.3302 4898.0 123.11
0.07845 0.2399 3558.9 107.7
0.09750 0.2914 4322.3 127.8
0.08631 0.2639 3914.4 135.0
0.09720 0.2948 4373.9 126.9
0.11389 0.3386 5023.2 108.2
0.11145 0.3312 4913.3 129.7
596.5
516.9
554.2
559.7
624.8
662.0
629.5
53.8
22.5
54.2
44.6
21.3
78.7
54.5
36.0
16.7
36.7
28.9
10.8
57.0
37.5
16.0
16.1
16.1
16.1
16.1
16.0
16.0
1.7
1.2
2.0
1.4
1.8
2.0
1.9
97.12
98.29
96.68
96.91
98.69
95.87
97.08
97.68
98.47
97.29
97.59
99.20
96.45
97.58
38311
38043
38373
38280
37703
38623
38190
°
–∆U100 = 37490 66 J/g
Compound II
–∆U° = (37490 66) + (323 28)(100 – C)
ρ = 97.25%
created by one scheme signal was 10 K, and the signal
duration was 2–3 min.
Attempts at determining the temperature depen-
dence of saturated vapor pressures of I and II by the
Knudsen integral effusion method gave the following
results:
°
The standard enthalpies of combustion ∆cH298.15 of
I and II were calculated from the heats of combustion
with corrections for the work of expansion ∆nRT. The
standard enthalpies of formation ∆f H298.15 of the com-
°
pounds in the condensed state were calculated using the
°
following ∆f H298.15 (kJ/mol) key values: –285.830
(1) The substances were not volatile in the crystal-
line state up to their melting points. The weight of the
effusion cell with substances I and II remained
unchanged after heating at 338 K for 10 h and at 333 K
for 7 h, respectively.
(2) Noticeable sample weight loss was only detected
at temperatures exceeding the melting points of I and II.
0.042 for H2O(l), –393.514 0.046 for CO2(g) [15],
and −1094.99 1.3 for H3BO3(cr) [16]. The standard
energies of combustion, enthalpies of combustion, and
enthalpies of formation and corrections for the work of
expansion are listed in Table 2.
The temperatures of fusion Tfus (343 and 338 K) and
the enthalpies of fusion ∆fusH (18.7 and 30.2 kJ/mol) of
I and II, respectively, at atmospheric pressure were
determined on a Perkin-Elmer DSC-1B differential
scanning calorimeter. The temperature range of calo-
rimeter operation was 315–450 K, the rate of scanning
temperature was 4 K/min, the mean temperature rise
(3) The color of the substances in the cell changed
after effusion experiments.
The IR spectra of the residues showed the disap-
pearance of peroxide groups in the decomposition
products (the absence of C–O (1000 cm–1) and peroxide
bridge (850 cm–1) absorption bands), whereas the car-
borane nucleus remained intact (the absorption bands at
2615, 735, and 3068 cm–1 corresponding to B–H, B–B,
and C–H stretching vibrations in the carborane nucleus,
respectively, remained unchanged). The shift of the
C=O group vibration band to the lower frequencies,
from 1800 to 1720 cm–1, is evidence of the presence of
ketones in the decomposition products.
Table 2. Standard enthalpies of combustion and formation
of the substances studied (kJ/mol)
Com-
pound
° °
–∆nRT –∆c H298.15 –∆f H298.15
∆U°
To conclusively substantiate the occurrence of ther-
molysis, compound II was sealed and held at 353 K for
70 h, which corresponded to the time and temperature
conditions of effusion experiments. The content of the
ampule was then analyzed chromatographically.
I
22936 28
14863 26
51
26
22987 28 706 28
14889 26 713 26
II
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THE THERMODYNAMIC PROPERTIES AND THERMOLYSIS CHARACTERISTICS
45
Table 3. Data obtained in experimentally determining the temperature dependence of saturated vapor pressures
t × 10–3, s
∆m × 106, kg
T, K
ν × 1011, kg/s
Compound I
25.202
25.202
25.202
25.200
25.202
25.202
0.750
0.950
1.400
2.250
2.400
8.131
345.4
348.4
352.3
358.2
358.4
372.0
2.976
3.769
5.556
8.929
9.523
32.264
Compound II
7.202
7.203
7.202
7.201
7.201
7.201
7.201
7.201
7.202
0.590
0.575
0.580
0.850
0.820
1.010
1.000
1.540
1.550
345.2
345.2
345.2
349.2
349.2
351.0
351.0
356.2
356.2
8.192
7.982
8.052
11.801
11.390
14.032
13.890
21.391
21.523
The thermolysis products were found to contain allowed us to suggest the following thermolysis
ëé2 and acetone. The results of chromatographing scheme:
t
HC≡CC(CH3)2OO(CO)CB10H10C(CO)(CH3)2CC≡CH
CO2
·
·
+ HC≡CC(CH3)2O + CB10 H10C(CO)(CH3)2CC≡CH,
P
·
·
·
HC≡CC(CH3)2O
HC≡C + (CH3)2CO, HC≡C
HC≡CH,
P
·
CB10 H10C(CO)(CH3)2CC≡CH
HCB10H10C(CO)(CH3)2CC≡CH
t
·
·
CO2 + HC≡CC(CH3)2O + HCB10H10C ,
where P stands for peroxides.
line ensured evacuation to 0.1 Pa in 35 5 s. The accu-
racy of maintaining temperature and of temperature and
time measurements was 0.1 and 0.05 K and 0.5 s,
respectively. The weight of the substance effused ∆m
was determined from the difference in effusion cell
weights before and after measurements with an accu-
racy of 5 × 10–6 g. The effective effusion duration (the
calculated effusion time under stationary conditions at
which the effused substance weight equaled that under
nonstationary conditions) was taken to be zero because
of the long duration of experiments (2 and 7 h for I and
II, respectively).
As decomposition occurs in the absence of a sol-
vent, it is considerably complicated by induced decom-
position, especially as unsaturated peroxy esters are
more likely to experience induced decomposition than
are peroxy esters of saturated carboxylic acids [17].
The analyses performed led us to conclude that,
instead of the expected temperature dependences of sat-
urated vapor pressures, the temperature dependences of
compound decomposition rates v were measured.
These dependences were used to determine the kinetic
characteristics of thermolysis. The temperature depen-
dences of the weight loss rates for liquid I and II were
The primary results of effusion measurements
determined over the temperature ranges 345–372 and (weight loss ∆m, temperature of measurements T, and
345–356 K, respectively. The design of the unit, the effusion time t) are listed in Table 3. The measurement
special technology for manufacturing the cell and results were processed using the method of least
membrane, and the procedure for performing measure- squares for a 95% confidence interval according to the
ments were selected according to [18, 19]. The vacuum Student test value and were represented in the form of
RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY Vol. 80 No. 1 2006

46
DIBRIVNYI et al.
Table 4. Linear equation coefficients for describing the temperature dependence of the weight loss rate and the effective ac-
tivation energies of thermolysis (Eeff, kJ/mol)
Compound
∆T, K
A
–B × 10–3, K
ρ, %
Eeff
I
II
345–372
345–356
9.17 0.63
8.29 0.48
11.55 0.22
10.88 0.17
99.91
99.92
96.0 6.7
90.5 5.1
7. G. A. Gal’chenko, in Chemical Thermodynamics, Ed. by
Ya. I. Gerasimov and P. A. Akishin (Mosk. Gos. Univ.,
Moscow, 1984) [in Russian].
8. V. N. Dibrivnyœ, Z. E. Pistun, T. D. Zvereva, et al.,
Zh. Fiz. Khim. 71, 1581 (1997) [Russ. J. Phys. Chem.
71, 1421 (1997)].
9. F. D. Rossini, J. Res. Natl. Bur. Stand. 6, 37 (1931).
10. S. M. Pimenova, Extended Abstract of Candidate’s Dis-
sertation in Chemistry (Moscow, 1981).
linear equations lnv = A – B/T. The A and B constants,
correlation coefficients ρ, and effective activation ener-
gies Eeff averaged over the temperature range of mea-
surements are listed in Table 4.
The available data on the enthalpies of vaporization
of carboranes [7, 20] and organic peroxides [21] allow
us to estimate these values for the compounds under
consideration (165–168 kJ/mol). A comparison of these
values with the activation energies (91 and 96 kJ/mol)
shows that the enthalpies of vaporization of the sub-
stances cannot in principle be determined experimen-
tally, because the energy barriers to the dissociation of
the molecules at the peroxy bond are substantially
lower than the energy barriers to overcoming intermo-
lecular forces during vaporization.
The data on thermolysis obtained in this work are of
importance for applications because they can be used to
estimate the degree of the decomposition of the sub-
stances under consideration (active oxygen loss) during
a certain time at the temperature of their storage.
11. G. V. Mel’nik, Extended Abstract of Candidate’s Disser-
tation in Chemistry (St. Petersburg, 2000).
12. Experimental Thermochemistry, Ed. by F. D. Rossini
(Interscience, New York, 1956).
13. G. L. Gal’chenko and R. M. Varushchenko, Zh. Fiz.
Khim. 37, 2513 (1963).
14. Experimental Chemical Thermodynamics, Vol. 1: Com-
bustion Calorimetry, Ed. by S. Sunner and M. Mansson
(Pergamon, New York, 1979).
15. “CODATA Recommended Key Values for Thermody-
namics 1977,” J. Chem. Thermodyn. 10 (10), 903
(1978).
16. J. K. Johnson and W. N. Hubbard, J. Chem. Thermodyn.
1, 495 (1969).
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