STANDARD FORMATION ENTHALPIES OF METHYLADAMANTANES
Apendina А.К., Saginaev А.Т., Tastanova L.K.
Aktobe Regional State University after K.Zhubanov,
Atyrau Oil and Gas Institute, Kazakhstan.
K.Ajnagul@mail.ru
Methyladamantanes are of great interest both for use as artificial field of calculations
and for determination of deformation energy inside this system. Schleyer with colleagues
calculated deformation energy for adamantane and 1,3,5,7- tetramethyladamantane - 6.9
kcal/mole and 5.0 kcal/mole respectively [1]. Data on exact standard formation enthalpies of
these compounds play crucial role in assessment of calculations methods.
Thermodynamic stabilities of some alkyladamantanes are determined experimentally
and calculated and then compared with each other [2].
In order to minimize errors 1- and 2- methyladamantanes, 2,2 – dimethyladamantane,
1,3,5- trimethyladamantane were purified by standard methods (recrystallization, vacuum
sublimation, multiplied affinage) before burning in calorimeter and 1,3- dimethyladamantane
was purified by repetitive fractional distillation under low pressure. was used. 1 cm3 of water
was placed into the calorimetric bomb of internal volume 0.1 dm3 with calibration and
additional equipment and then oxygen pressure up to 30 atmospheres at 298.15 К was
established.
Vapor pressures of all solid compounds are measured by Bourdon barometer and
calculated using the following equation:
Logo10 (p/Torr) = A/T + B
Enthalpy of sublimation is calculated by the equation:
∆H sub = - R A ln 10
Vapor pressure of 1,3- dimethyladamantane is determined by semimicroebuliometric
method.
Results of determination are presented in table 1.
Table 1- Results of experiments on typical calorimetry at 298.15 К
Property
m(substance)/g
m(polyethylene)/
g
m(cotton)/g
m(H2O)/mole
∆ R/ 
-∆RE (color)/kJ
-∆RE (cont)/kJ6
-∆Ew/ kJ
-∆E(ign)/ kJ
-∆ес(substance)/
kJ g-1
1- methyl- 2- methyl- 1,3adamantane adamantane dimethyladamantane
0,052167
0,054328
0,052458
0,016427
0,017204
0,017284
2,2dimethyladamantane
0,050126
0,016824
1,3,5trimethyladamantane
0,052339
0,016424
1,3,5,7tetramethyladamantane
0,053385
0,015484
0,002794
0,05551
1, 2996
-3,1010
-0,0156
0,0012
0,0008
44,2387
0,002079
0,05551
1,2703
-3,0309
-0,0153
0,0010
0,0012
44, 4975
0,002061
0,05551
1,3001
-3,1020
-0,0160
0,0016
0,0009
44,3417
0,002000
0,05551
1,3020
-3,1066
-0,0170
0,0018
0,0012
44,4024
0,002542
0,05551
1,3555
-3,2342
-0,0163
0,0012
0,0016
44,3424
0,002248
0,05551
1,3202
-3,1500
-0,0157
0,0013
0,0012
44, 3326
Reaction of burning is presented by the equation:
CaHb + (a+b/4)O2 = aCO2 +1/2 b H2O
Derivatives from standard molar energy of burning ∆Eb˚, standard molar enthalpy of
burning ∆Нb˚ and standard molar enthalpy of formation ∆Нf˚ of compounds are presented in
table 2.
Table 2- Oscillating molar energies of condense state at 298.15 К
Compounds
1- Methyladamantane
2- Methyladamantane
2,2- Dimethyladamantane
1,3- Dimethyladamantane
1,3,5- Trimethyladamantane
1,3,5,7- Tetramethyladamantane
-∆Eb˚, kJ/mole
-∆Нb˚, kJ/mole
-∆Нf˚, kJ/mole
6647,1±0,4
6665,1±0,4
7311,5±0,6
7281,4±0,6
7913,6±1,0
8545,4±0,9
6658,4±0,4
6676,4±0,4
7324,1±0,6
7293,9±0,6
7927,4±1,0
8560,5±0,9
242,7±0,4
224,7±0,4
256,5±0,6
286,6±0,6
332,6±1,0
378,6±0,9
Derivatives from sublimation enthalpies of methyladamantanes are presented in table
3. Values of Тm are taken from before studied middle temperatures. Standard sublimation
enthalpies, ∆Hs˚ (298.15К), are determined from the equation:
∆Hs˚(298.15К) = ∆Hs˚(Тm ) +(298.15 К – Тm ) (Сp˚(gas)- Сp˚(solid))
Table 3 – Sublimation enthalpies of methyladamantanes
Compounds
∆Hs˚(Тm)/ kJ/mole
Т/К
1- Methyladamantane
2- Methyladamantane
2,2- Dimethyladamantane
1,3- Dimethyladamantane
1,3,5- Trimethyladamantane
1,3,5,7- Tetramethyladamantane
16,0±0,2
16,1±0,2
17,2±0,2
16,2±0,2
18,2±0,2
19,5±0,2
300-340
300-340
300-360
-----300-360
310-350
∆Hs ˚(298.15К)/
kJ/mole
16,2±0,3
16,3±0,3
17,6±0,3
16,2±0,3
18,6±0,3
20,0±0,3
Substitution of methyl groups in tertiary positions of adamantanes nuclei increases
thermochemical stability.
Literature
1.
Engler E.M., Andose J.D., Schleyer P.v.R.// J.Am. Chem. Soc. 1993, 125, 8005
2.
Сагинаев А.Т., Апендина А.К. // Вестник Атырауского Института Нефти
и Газа , 2006, № 10, с. 125-129