Thermodynamic properties for 2-(1′-hydroxycyclohexyl)cyclohexanone and equilibrium of dimerization of cyclohexanone

Article abstract of DOI:10.1021/je0501078

Thermodynamic properties of 2-(1′-hydroxycyclohexyl)cyclohexanone (ketol) are reported. The investigated compound is a byproduct from the caprolactam manufacture. The heat capacity of ketol was measured by vacuum adiabatic calorimetry (T = 5 K to T = 310 K) and by differential scanning calorimetry (T = 294 K to T = 370 K). The fusion temperature T_fus = 306.75 K and the mole fraction of the ketol sample (x = 0.9982) were found by fractional melting analysis. The molar enthalpy of fusion Δ _fusH_m^o = (20.81 ± 0.02) kJ·mol^-1 was determined in the adiabatic calorimeter. The standard molar thermodynamic functions of ketol in the condensed state were obtained with the use of these calorimetric measurements. The standard molar enthalpy of combustion of ketol Δ_cH_m^o(cr, 298.15 K) = -(6963.0 ± 1.8) kJ·mol^-1 was found by bomb calorimetry, and the standard molar enthalpy of formation Δ _fH_m^o(cr, 298.15 K) = -(597.6 ± 2.4) kJ·mol^-1 was derived. The equilibrium of dimerization of cyclohexanone with ketol formation was investigated in the temperature range 294 K to 367 K. The equilibrium constants (K_a) were obtained at five temperatures, and the enthalpy of the reaction at the average temperature Δ_rH_m(330.5 K) = -(34.4 ± 3.3) kJ·mol^-1 was derived.

Full text of DOI:10.1021/je0501078

40
J. Chem. Eng. Data 2006, 51, 40-45
Thermodynamic Properties for 2-(1′-Hydroxycyclohexyl)cyclohexanone and
Equilibrium of Dimerization of Cyclohexanone
Marina P. Shevelyova,† Gennady J. Kabo,*,† Andrey V. Blokhin,† Andrey G. Kabo,† Joseph A. Jursha,‡ and
Anna A. Rajko‡
Chemical Department, Belarusian State University, Leningradskaya 14, Minsk 220050, Belarus, and “Grodno Azot”,
Kosmonavtov av. 100, Grodno 230013, Belarus
Thermodynamic properties of 2-(1′-hydroxycyclohexyl)cyclohexanone (ketol) are reported. The investigated
compound is a byproduct from the caprolactam manufacture. The heat capacity of ketol was measured by vacuum
adiabatic calorimetry (T ) 5 K to T ) 310 K) and by differential scanning calorimetry (T ) 294 K to T ) 370
K). The fusion temperature Tfus ) 306.75 K and the mole fraction of the ketol sample (x ) 0.9982) were found
by fractional melting analysis. The molar enthalpy of fusion ∆fusHom ) (20.81 ( 0.02) kJ‚mol-1 was determined
in the adiabatic calorimeter. The standard molar thermodynamic functions of ketol in the condensed state were
obtained with the use of these calorimetric measurements. The standard molar enthalpy of combustion of ketol
∆cHom(cr, 298.15 K) ) -(6963.0 ( 1.8) kJ‚mol-1 was found by bomb calorimetry, and the standard molar
enthalpy of formation ∆fHom(cr, 298.15 K) ) -(597.6 ( 2.4) kJ‚mol-1 was derived. The equilibrium of
dimerization of cyclohexanone with ketol formation was investigated in the temperature range 294 K to 367 K.
The equilibrium constants (Ka) were obtained at five temperatures, and the enthalpy of the reaction at the average
temperature ∆rHm(330.5 K) ) -(34.4 ( 3.3) kJ‚mol-1 was derived.
With the purpose of thermodynamic investigation of reaction
1, the heat-capacity of 2-(1′-hydroxycyclohexyl)cyclohexanone
was measured in the temperature range (5 to 370) K, and the
thermodynamic properties of ketol in the condensed state were
calculated. The enthalpy of formation for ketol was determined
by bomb calorimetry. The equilibrium of reaction 1 with
aqueous alkali solution as a catalyst was investigated. The
enthalpy of reaction 1 was obtained and compared with the
calorimetric data.
Introduction
2-(1′-Hydroxycyclohexyl)cyclohexanone (ketol) is one of the
byproducts of caprolactam production, and it is formed during
cyclohexane oxidation and cyclohexanol dehydrogenation to
cyclohexanone (reaction ):
Experimental Section
Chemicals. A sample of 2-(1′-hydroxycyclohexyl)cyclohex-
anone was prepared by the procedure described in ref 1 and
was purified by thrice-repeated recrystallization from petroleum
ether (fraction with Tboil ) (323 to 333) K). Thereafter, it was
sublimated from the melt and crystallized on a glass trap at T
) (313 to 318) K and p ) 267 Pa. The final mole fraction
purity of the sample was 0.9982, determined as described below.
Apparatus and Procedure. The low-temperature heat capaci-
ties in the temperature range (5 to 310) K and the enthalpy of
fusion of ketol were measured in the vacuum adiabatic
calorimeter (AC) TAU-1 constructed by VNIIFTRI (Moscow)
as previously described.3-5 The crystalline sample (m ) 0.9378
g) was loaded into a stainless steel container of 1.0 cm3 volume.
The container headspace was filled with helium to the pressure
about 6 kPa to improve the heat exchange. The container was
sealed with an indium ring. The temperature was measured with
an iron-rhodium resistance thermometer (R0 ) 101.83 Ω)
located on the inner surface of the adiabatic shield and calibrated
for ITS-90 by VNIIFTRI (Moscow). Adiabatic conditions within
( 0.001 K were maintained with a four-junction differential
thermocouple {(Cu (mole fraction 0.999) + Fe (mole fraction
0.001))-to-chromel} that indicated of the temperature difference
between the shield and the calorimetric cell.
The reaction is an initial stage of the other bicyclic ketones1
formation influencing the economics of caprolactam production.
Ketol is dehydrated easily at temperatures above 373 K with
the formation of bicyclic ketones. Efimova et al.2 investigated
the equilibrium of reaction 1 in the presence of alkali solution
with butan-1-ol as the solvent in the temperature range (303.15
to 343.15) K, but they did not give information about the
equilibrium concentrations of the reagents and the method used
to calculate the equilibrium constants. The enthalpy of reaction
1
∆rHo (323.15 K) ) -47.8 kJ‚mol-1
adduced in ref 2 does not correspond with the value
∆rHo (323.15 K) ) -(26.6 ( 7.7) kJ‚mol-1
derived from the equilibrium constants that are presented in the
article.
* Corresponding author. E-mail: kabo@bsu.by.
† Belarusian State University.
‡ “Grodno Azot”.
10.1021/je0501078 CCC: $33.50 © 2006 American Chemical Society
Published on Web 12/09/2005

Journal of Chemical and Engineering Data, Vol. 51, No. 1, 2006 41
The reliability of the heat capacity measurements had been
verified previously with benzoic acid6,7 (K-1 grade, mass fraction
g 0.99995) and high-purity copper8 (mass fraction g 0.99995).
The estimated uncertainty of the molar heat capacity measure-
ments was ( 0.4 % in the temperature range (40 to 320) K.
The uncertainty increased at T < 40 K and finally reached ( 2
% in the temperature range (5 to 10) K. The difference between
the values of Cs,m and Cp,m was considered to be negligible
because of the low vapor pressure of ketol.
The heat capacity of ketol in the temperature range (294 to
370) K was measured using an improved automatic scanning
calorimeter of the heat bridge type9 (DSC). The calorimeter was
calibrated with high-purity copper (mass fraction g 0.99995).
The expanded uncertainty of the heat capacity measurements
was estimated to be ( 2 %. The container with the sample (m
) 0.9991 g) was hermetically sealed in a vacuum. The values
of the heat capacity were obtained with temperature steps from
Figure 1. Experimental heat capacity (Cs,m) of 2-(1′-hydroxycyclohexyl)-
cyclohexanone in the condensed state in the range (5 to 370) K. AC is the
range of adiabatic calorimetry; DSC is the range of differential scanning
calorimetry. Inset: experimental heat capacity measured by differential
scanning calorimetry
(0.05 to 0.1) K. The average heating rate was 0.8 K‚min-1
.
The enthalpy of combustion for ketol was determined by the
procedure described earlier.4 Three isoperibolic calorimeters (A,
B, and C) with isothermal water shields and static bombs were
used for the measurements. The temperatures of the shields were
kept constant within ( 0.01 K. The reproducibility of the
measurements of the combustion energy was ( 0.02 %.4
Reference benzoic acid (K-1, VNIIM, St-Petersburg) was used
for calibration of the calorimeters; its specific energy of
combustion was
0.25 K. The relative content of ketol and cyclohexanone in
organic phase was determined by gas chromatography (TSVET-
100 using N2 as carrier gas and a flame ionization detector).
Samples of the organic phase for chromatography were taken
with a microsyringe in fixed time intervals. The mixtures were
analyzed on a 0.4 m glass column, filled with 15 % Reoplex
on chromatron N-AW-HMDS. Temperature of the evaporator
and the column was 403 K. The relation of molar concentrations
of cyclohexanone and ketol in the organic phase was determined
using a calibration factor for calculation of composition ac-
cording to the areas of the chromatographic peaks. Equilibrium
was assumed when the ratio of ketol peak areas to cyclohex-
anone peak areas with time remained constant.
∆cUoBA ) -(26434.4 ( 0.6) J‚g-1
based on mass in a vacuum and combusted under certificated
conditions. The energy equivalents of the calorimeters were
WA ) (14890.0 ( 2.2) J‚K-1
WB ) (14939.4 ( 3.0) J‚K-1
WC ) (14709.9 ( 2.3) J‚K-1
Results and Discussion
The measured molar heat capacities of ketol in the range (5
to 370 K) are shown in Figure 1. The values obtained by
adiabatic calorimetry are presented in Table 1. The temperature
intervals of the values of Cs,m are close to the difference between
the mean temperatures of two successive experiments in the
series of measurements.
Only one anomaly attributed to melting was found in the
curve Cs,m ) f(T). To obtain a completely crystalline sample in
the calorimeter, a liquid sample was cooled from 310 K to 100
K, and then it was heated from 100 K to about 290 K and was
kept at this temperature for (8 to 10) h until the spontaneous
heat evolution due to crystallization had stopped. The temper-
ature interval of fusion of the sample was (294 to 308) K in the
adiabatic calorimeter and (303 to 359) K in the differential
scanning calorimeter.
Measurements on two samples were made with a terylene
ampule. The energy of combustion of terylene (C10H8O4, F )
1.38 g‚cm-3) was determined in five individual experiments:
∆cUoter ) -(22879.7 ( 11.1) J‚g-1
Sums of the Washburn corrections for conversion of the
energy of combustion to the standard state were calculated as
previously described.10 Correction for ignition was 2.0 J in each
experiment.
The experimental heat capacities of the phases were fitted
by the polynomials:
The samples were weighed on a Mettler Toledo AG 245
balance. The uncertainty of the weighing was ( 5‚10-5 g. The
masses of the samples were converted to the vacuum masses;
the density of crystalline ketol (Fcr ) 1.14 g‚cm-3) at 292 K
was determined with a pycnometer, with a saturated aqueous
solution of ketol being used as a working liquid.
Cp,m(cr)/(J‚K-1‚mol-1) ) 227.32 - 1.0032(T/K) +
3.9432‚10-3(T/K)2 (1)
Reaction 1 takes place on the interface between an alkali
solution (as catalyst) and an organic phase. The equilibrium of
reaction 1 was studied in the range (294 to 367) K, with the
choice of the temperature range determined by the instability
of ketol at higher temperatures and long duration of equilibrium
establishment at lower temperatures. Cyclohexanone (or its
mixtures with ketol with higher mole fractions of ketol than
the equilibrium ones) and aqueous solution of KOH (mass
fraction 5 %) were loaded in a vessel in the volume ratio of 1
to 2.1 The uncertainty of the temperature measurement was (
Cp,m(liq)/(J‚K-1‚mol-1) ) 657.79 - 2.6379(T/K) +
5.3279‚10-3(T/K)2 (2)
obtained in the temperature ranges (251 to 294) K for the
crystalline state and (308 to 312) K (results of adiabatic
calorimetry) and (359 to 370) K (results of differential scanning
calorimetry) for the liquid state. The difference between the
values of the molar heat capacity in the range (294 to 303) K
obtained by differential scanning calorimetry and the values of

42 Journal of Chemical and Engineering Data, Vol. 51, No. 1, 2006
Table 1. Experimental Molar Heat Capacities (Cs,m) at
Vapor-Saturation Pressure for
2-(1′-Hydroxycyclohexyl)cyclohexanone (R ) 8.31447 J‚K-1‚mol-1
)
Cs,m
R
a
a
a
a
T
Cs,m
R
T
Cs,m
R
T
Cs,m
R
T
K
K
K
K
Series 1: Crystal
99.86 12.10
101.89 12.29
103.96 12.50
106.00 12.69
108.09 12.89
110.22 13.08
112.32 13.27
114.47 13.49
116.67 13.68
118.84 13.90
120.97 14.07
123.07 14.28
125.14 14.48
127.19 14.68
129.21 14.87
131.21 15.06
133.17 15.24
135.12 15.42
137.05 15.59
138.96 15.79
141.00 15.97
143.17 16.16
145.31 16.38
147.42 16.56
149.52 16.77
149.69 16.78
151.77 17.00
153.83 17.17
155.94 17.40
158.11 17.58
160.26 17.81
162.40 17.99
164.58 18.22
166.82 18.41
169.05 18.62
171.25 18.85
173.43 19.07
175.59 19.26
177.74 19.48
179.87 19.70
181.98 19.89
184.22 20.13
186.58 20.34 239.45 25.74
188.92 20.59 242.37 26.01
191.24 20.79 245.30 26.33
193.62 21.04 248.20 26.66
196.06 21.24 251.09 26.94
198.49 21.53 253.97 27.32
200.89 21.75 256.81 27.61
203.28 21.97 259.61 27.99
205.65 22.23 262.37 28.29
208.08 22.45 265.10 28.72
210.57 22.68 267.80 29.04
213.04 22.97 270.46 29.36
215.63 23.20 273.22 29.82
218.36 23.46 276.10 30.16
220.54 23.71 278.95 30.59
223.28 23.98 281.77 31.01
226.00 24.24 284.57 31.44
228.71 24.51 287.35 31.78
231.37 24.80 290.11 32.30
234.03 25.16 292.83 32.64
236.67 25.35 295.66 33.11
Figure 2. Results of the fractional-melting experiments; O, results of series
1; 0, results of series 2; b, completely melted ketol sample; T1, fusion
temperature of the ketol sample used (mole fraction 0.9982); T0, fusion
temperature of the pure substance.
Table 3. Determination of the Molar Enthalpy of Fusion for
2-(1′-Hydroxycyclohexyl)cyclohexanone
Tstart/K
Tend/K
Qa/J
∆
fusHom/J‚mol-1
293.16
293.35
293.85
293.04
309.47
309.85
309.66
308.80
124.366
124.910
123.787
123.308
20807
20837
20809
20792
Series 1: Liquid
308.34 42.21
306.72 50.88
310.04 42.28 311.73 42.51
∆
fusH°m ) (20812 ( 29)b
Series 2: Crystal
282.51 31.08
285.02 31.51
274.83 29.97
277.41 30.36
279.97 30.76
287.51 31.86 292.40 32.65
289.97 32.19 294.18 32.89
a Q is the energy needed for heating the sample from Tstart to Tend
.
b Average value.
Series 3: Crystal
5.156 0.06411 13.09 0.9042 29.78 3.874 63.72 8.414
5.413 0.07408 13.65 0.9946 31.31 4.121 65.71 8.599
after subtraction of the regular part of the heat capacity. The
experimental values were fitted by the van’t Hoff equation:
5.681 0.08589 14.26 1.093
5.967 0.09841 14.87 1.190
32.81 4.360 67.67 8.841
34.25 4.605 69.76 9.063
35.69 4.813 72.08 9.302
37.25 5.057 74.55 9.565
38.95 5.326 76.99 9.804
40.79 5.576 79.43 10.05
42.67 5.860 81.9 10.30
44.41 6.084 84.37 10.56
46.25 6.347 86.86 10.80
48.19 6.575 89.34 11.07
50.08 6.811 91.79 11.29
51.93 7.031 94.27 11.55
53.83 7.296 96.74 11.78
55.82 7.536 99.23 12.06
57.81 7.744 101.72 12.28
59.76 7.963 104.22 12.52
61.73 8.182
2
6.289 0.1165
6.618 0.1368
6.939 0.1608
7.272 0.1881
7.692 0.2224
8.087 0.2605
8.514 0.3036
8.974 0.3491
9.402 0.3977
9.859 0.4527
15.47 1.288
16.12 1.402
16.79 1.523
17.47 1.643
18.17 1.771
18.86 1.900
19.61 2.029
20.52 2.194
21.52 2.383
22.54 2.569
23.56 2.763
24.68 2.967
25.89 3.197
27.12 3.408
28.37 3.626
RTfus
1
T ) Tfus
-
o (1 - x) ) (306.75 ( 0.01) - (0.0683 (
{
}
f
∆fusHm
1
f
0.0037) (3)
The temperature of fusion by differential scanning calorimetry
was considered to be the value obtained by the intersection of
curve Cs,m (ketol,cr) ) f(T) and the tangent to the rising branch
of the melting peak. The value obtained Tfus ) (306.9 ( 0.2) K
is in good agreement with the results of adiabatic calorimetry.
10.32
10.80
11.34
11.91
12.50
0.5108
0.5707
0.6478
0.7310
0.8158
The enthalpy of fusion by adiabatic calorimetry ∆fusH°m
)
(20.81 ( 0.02) kJ‚mol-1 was obtained by averaging the results
of four independent single-step experiments presented in Table
3. In each experiment the sample was heated from a temperature
≈ 13 K below the melting point to a temperature of 3 K above
the melting point. The enthalpy of fusion was calculated by the
equation:
a Average heat capacity at the mean temperature of an experiment T .
Table 2. Melted Fraction ( f ) as a Function of Temperature
Series 1
T/K
Series 2
T/K
T/K
f
f
T/K
f
f
306.44 0.2250 306.64 0.6120 306.44 0.2174 306.64 0.5914
306.55 0.3157 306.65 0.7326 306.53 0.3050 306.65 0.7077
306.58 0.4082 306.67 0.8540 306.58 0.3943 306.68 0.8251
Tfus
Tend
Q
∆fusHom ) M -
m
Cp,m(cr) dT -
Cp,m(liq) dT (4)
∫
∫
Tstart
Tfus
306.62 0.5102
306.62 0.4929
where Cp,m(cr) and Cp,m(liq) are the molar heat capacities of
crystal and liquid (eqs 1 and 2), Q is the energy needed for
heating the sample from Tstart to Tend, m is the mass of the
sample, and M is the molar mass of ketol.
The enthalpy of fusion ∆fusH° ) (20.69 ( 0.41) kJ‚mol-1
by differential scanning calorimetmry was determined by integra-
tion of the excess heat capacity over the fusion area. The values
of the enthalpy of fusion obtained by both the methods agree
within their respective uncertainties.
adiabatic calorimetry extrapolated by polynomial (1) did not
exceed 1.3 %.
The temperature of fusion Tfus ) (306.75 ( 0.01) K and the
mole fraction purity x ) (0.9982 ( 0.0001) of ketol were
obtained from the fractional melting experiments. The results
are presented in Table 2. The plot of the equilibrium temperature
as a function of 1/f ( f is the melted fraction at the temperature
T) is shown in Figure 2. The melted fractions were determined

Journal of Chemical and Engineering Data, Vol. 51, No. 1, 2006 43
C12H20O2(cr) + 16O2(g) ) 12CO2(g) + 10H2O(l)
Table 4. Molar Thermodynamic Functions for
2-(1′-Hydroxycyclohexyl)cyclohexanone (R ) 8.31447 J‚K-1‚mol-1
)
The molar mass of ketol M ) 196.286 g‚mol-1 was calculated
using recommended atomic masses of the elements.11
The standard enthalpy of formation of crystalline ketol
T/K
C
p,m/R
∆T0Hom/RT
∆T0Som/R
Φom a/R
Crystal
0.0149
0.1203
0.3549
0.6792
1.056
1.459
1.867
2.271
2.665
3.048
3.775
4.456
5.100
5.713
6.303
6.874
7.429
7.971
8.502
9.025
9.541
10.05
10.56
11.07
11.57
12.08
12.58
13.08
13.59
14.10
14.61
15.13
15.66
16.21
16.77
17.16
5
10
15
20
25
30
35
40
45
50
60
70
80
90
0.0597
0.4701
1.212
2.102
3.027
3.907
4.712
5.472
6.164
6.805
7.994
9.087
10.12
11.11
12.11
13.06
14.00
14.94
15.88
16.82
17.77
18.74
19.71
20.68
21.65
22.64
23.65
24.67
25.73
26.85
28.05
29.34
30.73
32.23
33.86b
35.04b
0.0200
0.1602
0.4842
0.9533
1.522
2.152
2.816
3.495
4.180
4.863
6.211
7.526
8.807
10.06
11.28
12.48
13.66
14.81
15.95
17.08
18.20
19.30
20.40
21.49
22.58
23.66
24.73
25.81
26.88
27.95
29.03
30.11
31.20
32.31
33.43
34.19
0.00505
0.0399
0.1293
0.2741
0.4655
0.6934
0.9490
1.225
1.515
1.816
2.436
3.070
3.707
4.343
4.976
5.604
6.226
6.842
7.452
8.057
8.656
9.250
9.839
10.42
11.00
11.58
12.15
12.72
13.29
13.86
14.42
14.98
15.54
16.10
16.66
17.04
∆fHom(cr, 298.15 K) ) -(597.6 ( 2.4) kJ‚mol-1
was calculated from the standard enthalpy of combustion of
ketol and the enthalpies of formation of CO2(g) and H2O(l):12
∆fHom(CO2, g, 298.15 K) ) -(393.51 ( 0.13) kJ‚mol-1
∆fHom(H2O, l, 298.15 K) ) -(285.83 ( 0.04) kJ‚mol-1
The standard enthalpy of formation of liquid ketol
∆fHom(ketol, 298.15 K) ) -(577.3 ( 2.4) kJ‚mol-1
was calculated using the enthalpy of fusion
100
110
120
130
140
150
160
170
180
190
200
210
220
230
240
250
260
270
280
290
300
306.75
∆fusHom(306.75 K) ) (20.81 ( 0.02) kJ‚mol-1
converted to T ) 298.15 K with the use of the heat capacities
of the crystalline and liquid ketol (eqs 1 and 2):
∆fusHom(298.15 K) ) (20.32 ( 0.03) kJ‚mol-1
Condensation Equilibrium of Cyclohexanone. The equilib-
rium mole fractions of ketol and cyclohexanone in the temper-
ature range (294 to 367) K are summarized in Table 6. Since
the number of moles changes during the reaction, it is necessary
to calculate the composition of the components (ketol, cyclo-
hexanone, water, and KOH) in the organic phase in order to
determine the equilibrium constant of reaction 1. For the
calculations, the solubility of water in mixtures of ketol and
cyclohexanone was measured by means of visual-polythermic
method. The homogenization temperatures and the clouds
temperatures were determined by sight at the heating and
cooling, respectively, for the three mixtures of ketol and
cyclohexanone with water. The average value of the tempera-
tures was recognized as the temperature of saturation of each
mixture. The average heating and cooling rate did not exceed
0.5 K‚min-1. Near the saturation temperatures system was
maintained during 30 min at each change of temperature for
0.5 K. The results are summarized in Table 7 and shown in
Figure 3. The solubility of water as a function of temperature
was fitted by the polynomials:
Liquid
25.32
25.50
26.03
26.57
27.10
27.64
28.19
28.74
306.75
310
320
330
340
350
360
370
42.09b
42.34c
43.21c
44.20c
45.32c
46.57c
47.95
42.35
42.80
44.16
45.50
46.84
48.17
49.50
50.83
17.04
17.30
18.12
18.93
19.73
20.53
21.31
22.09
49.45
a Φom is Φom ) - Gom(T) - Hmo (0)/T ) ∆0TSmo - ∆T0Hmo T. b Extrapolated
values. c Interpolated values.
The thermodynamic functions for ketol are presented in Table
4. The value of the enthalpy of fusion by adiabatic calorimetry
was used in the calculations.
Energy of combustion measurements for ketol are sum-
marized in Table 5. Measurements on samples 4 and 5
compacted in air were made with a terylene ampule. The
standard enthalpy of combustion of crystalline ketol
x2(x1 ) 0.0121) ) (-1.071 ( 0.426) +
(4.05 ( 1.28)‚10-3 T/K (5)
x2(x1 ) 0.0326) ) (-1.056 ( 0.633) +
(3.97 ( 1.89)‚10-3 T/K (6)
∆cHom ) -(6963.0 ( 1.8) kJ·mol-1
was calculated from the measured energy of combustion
∆cUo ) -(6972.9 ( 1.8) kJ·mol-1
using the equation:
x2(x1 ) 0.1346) ) (-0.9982 ( 0.7094) +
(3.67 ( 2.18)‚10-3 T/K (7)
where x1 is the mole fraction of ketol in the parent organic
mixture and x2 is the mole fraction of water in the saturated
solution.
These polynomials were used for the calculation of the
equilibrium compositions of the organic phase. For the calcula-
tion of the values outside the limits of the direct measurements,
the solubility of water in mixtures of cyclohexanone and ketol
∆cHo ) ∆cUo + ∆nRT
where ∆n is the change of the number of moles of the gaseous
products during the reaction under standard conditions:

44 Journal of Chemical and Engineering Data, Vol. 51, No. 1, 2006
Table 5. Determination of the Combustion Energy for 2-(1′-Hydroxycyclohexyl)cyclohexanonea
m
mterylene
K‚103
min-1
∆T
q(HNO3)
qterylene
∑q
-∆cUo
J‚g-1
expt no.
g
g
calorimeter
K
J
J
J
1
2
0.54031
0.51576
Ab
Ab
2.05
2.03
1.2899
1.2310
4.2
3.6
7.6
7.1
35527.7
35519.7
3
4
5
0.50816
0.34410
0.34872
Bb
Bb
Bb
2.12
2.02
2.10
1.2093
0.8628
0.8704
4.2
2.4
2.1
7.0
4.9
5.0
35527.2
35521.7
35515.3
0.02872
0.02663
657.1
609.3
6
7
8
9
10
0.50776
0.32620
0.33072
0.34655
0.35444
C
C
C
C
C
2.14
2.11
2.03
2.14
2.13
1.2275
0.7880
0.7986
0.8372
0.8566
6.3
3.5
2.4
2.4
2.4
7.7
4.4
4.7
5.0
5.1
35542.0
35517.8
35508.4
35522.4
35538.1
35524.0 ( 9.2
-∆cUo
)
a m, mass of the sample; mterylene, mass of terylene; q(HNO3), correction for nitric acid formation; qterylene, correction for the heat of combustion of
terylene; K, cooling constant of the calorimeter; ∆T, corrected temperature rise; Σq, sum of the Washburn corrections; ∆cUo, energy of combustion. b These
results were obtained by Yury V. Maksimuk. The authors express their thanks to him. Samples 4 and 5 were combusted in terylene ampules.
Table 6. Equilibrium Mole Fractions of
2-(1′-Hydroxycyclohexyl)cyclohexanone (1) and Cyclohexanone (2) in
the Liquid Phasea
T
mole fraction, xi
parent
no. of
K
substance expts
x1
x2
102 x1
293.6
313.2
333.2
352.9
367.4
a
b
a
b
a
b
a
b
a
b
5
4
7
5
7
10
4
5
4
3
13.27 ( 0.09 86.73 ( 0.09 13.46 ( 0.05
13.64 ( 0.01 86.36 ( 0.01
6.29 ( 0.02 93.71 ( 0.02
6.29 ( 0.18 93.71 ( 0.02
3.29 ( 0.05 96.71 ( 0.05
3.24 ( 0.05 96.76 ( 0.05
1.61 ( 0.03 98.39 ( 0.03
1.60 ( 0.03 98.40 ( 0.03
1.23 ( 0.05 98.77 ( 0.05
1.19 ( 0.02 98.81 ( 0.02
6.29 ( 0.09
3.26 ( 0.04
1.60 ( 0.02
1.21 ( 0.03
a Key: a, cyclohexanone and aqueous solution of KOH (5 %). b, solutions
of ketol and cyclohexanone with higher mole fractions of ketol than the
equilibrium ones and aqueous solution of KOH (5 %). x1, mole fraction of
ketol measured by gas-liquid chromatography. x2, mole fraction of
cyclohexanone measured by gas-liquid chromatography.
Figure 3. Solubility of water (1) in the cyclohexanone + 2-(1′-hydroxy-
cyclohexyl)cyclohexanone system depending on temperature and mole
fraction of ketol (2); x1, mole fraction of water in the saturated solution; x2
) 0.0121; x2 ) 0.0326; x2 ) 0.1344.
ketol: C12H20O2 ) [8CH2, CH, C, CH2CO, OH]
cyclohexanone: C6H10O ) [4CH2, CH2CO]
Table 7. Solubility of Water (3) in the
2-(1′-Hydroxycyclohexyl)cyclohexanone (1) + Cyclohexanone (2)
Systema
102x1
x3
T1/K
T2/K
T /K
and
1.21
0.249
0.253
0.264
0.284
0.312
326.7
327.3
329.7
332.7
342.4
326.2
327.7
327.7
332.7
341.4
326.4
327.5
328.7
332.7
341.9
water: [H2O]
described earlier.14 The results are summarized in Table 8.
Since the activity coefficients depend on temperature and
composition of the mixture, the sum of the components activities
(Σai) is not constant with the change of temperature. Thus, a
normalized equilibrium constant was calculated as
3.26
0.245
0.260
0.280
0.307
328.2
331.0
334.7
344.95
328.2
331.4
334.7
342.2
328.2
331.2
334.7
343.6
13.46
0.082
0.230
0.263
294.7
334.0
346.0
295.2
333.2
344.1
294.9
333.6
345.0
a1
x1γ1
a x1, mole fraction of ketol in a parent mixture of ketol and cyclohex-
anone. x3, mole fraction of water in the saturated solution. T1, homogeniza-
tion temperature. T2, clouds temperature. T , temperature of saturation.
a
x γ
(
)
(
)
∑
i
∑
i
i
i
T
i
T
Ka(T) )
)
(8)
2
2
a2
x2γ2
was extrapolated. It was assumed that content of KOH in organic
phase was much less than the uncertaities in the gas-liquid
chromatography measuremens of concentrations of ketol and
cyclohexanone. Therefore, the content of KOH was not taken
into account.
a
x γ
(
)
(
)
∑
i
∑
i
i
i
T
i
T
where a1, x1, γ1, a2, x2, and γ2 are activities, mole fractions,
and activity coefficients of ketol and cyclohexanone in an
equilibrium mixture, respectively. The equilibrium compositions
of the reaction system, the activity coefficients, and the
equilibrium constants are presented in Table 8.
For calculation of Ka, the activity coefficients of the com-
ponents were evaluated by the UNIFAC group contributions
scheme using the program unifac.exe13 and the next groups:

Journal of Chemical and Engineering Data, Vol. 51, No. 1, 2006 45
Table 8. Equilibrium Contents of the Reacting System 2-(1′-Hydroxycyclohexyl)cyclohexanone (1) + Cyclohexanone (2) + Water (3) in the
Liquid Phasea
T
102 xi
102 xi,equil
γi
102 ai
K
x1
x2
x1
x2
x3
γ1
γ2
γ3
a1
a2
a3
102 Ka
293.6
313.2
333.2
352.9
367.4
330.5
13.46
6.29
3.26
1.60
1.21
86.56
93.71
96.74
98.40
98.79
12.38
5.18
2.39
1.03
0.71
79.71
77.15
70.79
63.40
57.64
7.91
17.67
26.83
35.57
41.65
0.87
0.74
0.68
0.67
0.71
1.05
1.12
1.21
1.35
1.48
8.04
6.18
4.77
3.78
3.24
10.77
3.83
1.63
0.69
0.50
∆
83.70
86.41
85.66
85.59
85.31
63.60
109.20
127.98
134.45
134.95
24.30
10.23
4.78
2.08
1.52
r(1)Hom ) -(34.4 ( 3.3) kJ‚mol-1
a xi, ratios of the mole fractions of ketol and cyclohexanone (measured by gas-liquid chromatography). xi,equil, mole fractions of ketol, cyclohexanone,
and water (calculated with the use of the solubility data). γi, activity coefficients of ketol, cyclohexanone, and water. ai, activities of ketol, cyclohexanone,
and water. Ka, equilibrium constants.
with the value ∆r(1)Hom, obtained from equilibrium data (Table
8), within the uncertainties of the measurements of both the
values.
Conclusions
(1) Enthalpy of formation and entropy of 2-(1′-hydroxycy-
clohexyl)cyclohexanone were determined by calorimetric in-
vestigations. Thermodynamic properties of dimerization of
cyclohexanone were calculated.
(2) The equilibrium of dimerization of cyclohexanone was
investigated at (294 to 367) K. Thermodynamic properties of
the reaction were calculated using the equilibrium constants.
(3) The two values of the enthalpies of dimerization satisfac-
tory fit within their respective uncertainties.
Literature Cited
Figure 4. Temperature dependence of the normalized equilibrium constant
(1) Iogansen, A. V.; Kurkchi, G. A.; Baeva, V. P. Aldol condensation of
cyclohexanone. Zh. Org. Khim. 1971, 7, 2509-2511 (in Russian).
(2) Efimova, G. A.; Shutova, I. V.; Shapiro, Yu. E. Autocondensation of
cyclohexanone. Zh. Org. Khim. 1989, 25, 1201-1204 (in Russian).
(3) Kosov, V. I.; Malyshev, V. M.; Milner, G. A.; Sorkin, E. L.; Shibakin,
V. F. Multi-purpose set-up for thermophysical measurements controlled
with a microcomputer. Izmer. Tekh. 1985, 11, 56-58 (in Russian).
(4) Kabo, G. J.; Blokhin, A. V.; Kabo, A. G. Investigation of thermody-
namic properties of organic substances. Chem. Probl. DeV. New Mater.
Technol. 2003, 1, 176-193.
ln Ka.
The temperature dependence of the equilibrium constant of
reaction 1 was fitted by the polynomial and shown in Figure 4:
ln Ka ) (-15.49 ( 1.22) + (-41.35 ( 4.00)102‚1/(T/K)
(9)
(5) Pavese, F.; Malyshev, V. M. Routine measurements of specific heat
capacity and thermal conductivity of high-Tc superconducting materials
in the range 4-300 K using modular equipment. AdV. Cryog. Eng.
1994, 40, 119-124.
The enthalpy of reaction 1 at the average temperature is
∆
r(1)Hm(330.5 K) ) -(34.4 ( 3.3) kJ‚mol-1
(6) Furukawa, G. T.; McCoskey, R. E.; King, G. J. Calorimetric properties
of benzoic acid from 0 to 410 K. J. Res. Natl. Bureau Stand. 1951,
47, 256-261.
The enthalpy of reaction 1 was also calculated at 298.15 K using
the calorimetric data:
(7) Vasiliev, I. A.; Petrov, V. M. Thermodynamic Properties of Oxygen-
Containing Organic Compounds; Khimiya: Leningrad, 1984 (in
Russian).
(8) White, G. K.; Collocott, S. J. Heat-capacity of reference materials:
Cu and W. J. Phys. Chem. Ref. Data 1984, 13, 1251-1257.
(9) Kabo, A. G.; Diky, V. V. Detailes of calibration of a scanning
calorimeter of the triple heat bridge type. Thermochim. Acta 2000,
347, 79-84.
(10) Hubbard, W. N.; Scott, D. W.; Waddington, G. Standard states and
corrections for combustions in a bomb at constant volume. In
Experimental Thermochemistry; Rossini, F. D., Ed.; Interscience: New
York, 1956; Chapter 5.
(11) Atomic weights of the elements 2001 (IUPAC Technical Report). Pure
Appl. Chem. 2003, 75, 1107-1122.
∆fHom(ketol, l, 298.15 K) ) -(577.3 ( 2.4) kJ‚mol-1
∆fHom(cyclohexanone, l, 298.15 K) ) -(272.6 (
1.8) kJ‚mol-1 15
∆
r(1)Hom(298.15 K) ) ∆fHmo (ketol, l, 298.15 K) -2∆fHmo
(Chon, l, 298.15 K) ) -(32.1 ( 4.3) kJ‚mol-1
(12) Cox, J. D.; Wagman, D. D.; Medvedev, V. A. CODATA Key Values
for Thermodynamics; Hemisphere Publishing Corp.: New York, 1989.
(13) www.che.udel.edu/thermo/basicprograms.htm#UNIFAC.
(14) Sandler, S. I. Chemical and Engineering Thermodynamics; John Wiley
& Sons: New York, 1999.
and was reduced to the average temperature of the measure-
ments:
(15) Wolf, G. Thermochemical investigation of some cyclic ketones. HelV.
∆
r(1)Hom(330.5 K) ) -(30.9 ( 4.4) kJ‚mol-1
Chim. Acta 1972, 55, 1446-1459 (in German).
Received for review March 19, 2005. Accepted September 28, 2005.
JE0501078
from the temperature dependence of the heat capacities of ketol
(Table 4) and cyclohexanone.7 This value is in good agreement