Kinetics of the n-Decanol Oxyethylation Reaction with Allowance for Association

Article abstract of DOI:10.1134/S0036024416040282

The kinetics of n-decanol oxyethylation in the temperature range of 60-150°C at a pressure of 1.4MPa is investigated under conditions of base catalysis and an excess of alcohol in the initial step of the reaction (initial concentration of ethylene oxide in the reaction mixture, approximately 1 mol/L; that of the catalyst, 10^-1 to 10^-3 mol/L). The experimental results are satisfactorily described by a kinetic equation that allows for the association of alcohol molecules and is first order with respect to the concentration of alcohol associates. Based on kinetic studies and thermogravimetry, it is concluded that the structural rearrangement of liquid decanol occurs at a temperature of around 87.5°C.

Full text of DOI:10.1134/S0036024416040282

ISSN 0036-0244, Russian Journal of Physical Chemistry A, 2016, Vol. 90, No. 4, pp. 754–760. © Pleiades Publishing, Ltd., 2016.
Original Russian Text © B.Ya. Stul’, 2016, published in Zhurnal Fizicheskoi Khimii, 2016, Vol. 90, No. 4, pp. 532–538.
CHEMICAL KINETICS
AND CATALYSIS
Kinetics of the n-Decanol Oxyethylation Reaction
with Allowance for Association
B. Ya. Stul’
SINTEZ Scientific Research Institute, Moscow, 109088 Russia
e-mail: b.st@mail.ru
Received March 10, 2015
Abstract—The kinetics of n-decanol oxyethylation in the temperature range of 60–150°С at a pressure of
1.4 MPa is investigated under conditions of base catalysis and an excess of alcohol in the initial step of the
reaction (initial concentration of ethylene oxide in the reaction mixture, approximately 1 mol/L; that of the
catalyst, 10−1 to 10−3 mol/L). The experimental results are satisfactorily described by a kinetic equation that
allows for the association of alcohol molecules and is first order with respect to the concentration of alcohol
associates. Based on kinetic studies and thermogravimetry, it is concluded that the structural rearrangement
of liquid decanol occurs at a temperature of around 87.5°С.
Keywords: oxyethylation reaction, n-decanol, ethylene oxide, kinetic studies, thermogravimetry.
DOI: 10.1134/S0036024416040282
INTRODUCTION
The kinetics of alcohol oxyethylation are generally
described by the scheme
trations and conversions, the experimental results in a
flow reactor when the impact of the second step of the
reaction on the rate of EO consumption was negligible
were satisfactorily described by the equation
C2H4O
ROH ⎯⎯⎯→ ROC2H4OH
ko, obs.
0
W = (co0 − co)/τ = ko,obs.ccco(ca − nc1)
,
(1)
C2H4O
k1, obs.
C2H4O
⎯⎯⎯→ RO(C2H4O)2H ⎯⎯⎯→ etc.
k2, obs.
where W is the reaction rate determined from EO con-
The kinetics of this irreversible sequential reaction for
0
alcohol has been investigated in a number of studies sumption;
and are the concentrations of EO in
co
co
[1]. It is shown in this work that under conditions of the initial mixture and in the reactor, respectively; τ is
base catalysis, the reaction rate in the initial stage with the length of time the reaction mixture is in the reac-
an excess of alcohol follows first order kinetics with tor; kо, obs. is the observed reaction rate constant of the
respect to the concentrations of ethylene oxide (EO)
and catalyst, and exhibits a complex dependence with
respect to alcohol concentration. It has been suggested
[1] that deviations from first order kinetics with
respect to alcohol concentration are due to the associ-
ation of alcohol molecules as a result of the formation
of hydrogen bonds. Both the reaction rate and degree
of association depend on the alcohol concentration
and the overlapping of these phenomena complicates
the general picture.
In [2], we proposed a kinetic model and corre-
sponding equation that satisfactorily described the
kinetics of this reaction. This model considered the
association of alcohol molecules via the formation of
hydrogen bonds and suggested that a monomeric form
of the alcohol molecule participated in this reaction
not as a kinetically independent unit but rather as a
linear chain associate (neither closed nor branched)
that consisted of n molecules of alcohol on average.
first reaction stage; сc and с1 are the concentrations of
the catalyst and the first product in the reactor,
0
respectively; is the concentration of alcohol in ini-
ca
tial mixture; and n is the average number of alcohol
molecules in the alcohol associate.
Since n > 1, the calculated concentration of alcohol
in this equation, which reflects the reaction rate (the
expression in parentheses of the right part of the equa-
tion), falls much faster than follows from the stoichi-
ometry. From the viewpoint of chemical kinetics,
parameter n is a quantitative measure of the deviation
of the observed first order kinetics with respect to
alcohol concentration. The higher n, the greater the
deviation. When n = 1 (no association), Eq. (1) is
transformed into a general first order equation with
0
respect to alcohol concentration, since
– c1 ≈ ca.
ca
Use of Eq. (1) is limited to the range of concentrations
0
It was shown that in the investigated range of concen- and conversions for which condition
is valid.
ca > c1n
754

KINETICS OF THE n-DECANOL OXYETHYLATION REACTION
755
To substantiate the proposed kinetic model, the in [5] with mass spectrometry that methanol associ-
following conditions must be met [2]:
ates of (CH3OH)n composition with n = 5–20 have
lifetimes in gaseous phase on an order of 10−4 to 10−5 s.
The lifetime of an associate should increase by 1–
1. Alcohol molecules are bound via hydrogen
bonds forming linear chain associates with n average
number of molecules.
2 orders of magnitude and be no shorter than 10−3
s
upon transitioning to the liquid phase, which is suffi-
cient for participation in an elementary chemical act.
Considering the results obtained in [6], we may
assume that the lifetime of such associates can be
much longer.
The results from experiments on the oxyethylation
of the normal primary alcohols of С4–С7 composition
inclusive in the temperature range of 80–180°C are
presented in [2], along with the results from processing
these data with Eq. (1). The reaction rate constants,
activation energies, and the values of parameter n and
its dependence on temperature were determined. It
should be noted that the obtained kinetic parameters
and parameters of association are in reasonable agree-
ment with the literature data.
2. Only one of two terminal alcohol molecules in a
chain associate participates in the reaction with its
hydrogen atom of the hydroxyl group not participating
in hydrogen bond formation.
3. The corresponding molecule of ethylene glycol
monoester formed in the reaction remains in the com-
position of the associate and, being less reactive, it
closes this associate.
It should be noted that point 3 is required in order
to fix the associate as a kinetically independent unit. If
this point is not met and the molecule of the formed
ethylene glycol monoester does not form a complex
with the terminal molecule of the alcohol associate,
the above model is not valid, and association parame-
ter n cannot be determined from it. Fulfillment of
condition 3 is indirectly confirmed by IR spectroscopy
data [3] showing that, unlike alcohol molecules, the
molecules of ethylene glycol monoesters are prone to
forming intramolecular hydrogen bonds when the
hydrogen atoms of hydroxyl groups bond to the ester
oxygen atoms of the same molecules. This causes the
hydroxyl groups of the ethylene glycol monoester mol-
ecules to become monofunctional with regard to the
formation of intermolecular hydrogen bonds, while
the hydroxyl groups of alcohol are from this point of
In this work, the kinetics of the oxyethylation of С10
alcohol were investigated in a similar manner. This
was done with the aim of extending the series of the
considered alcohols and comparing the obtained
results to those for С4–С7 alcohols obtained earlier.
EXPERIMENTAL
The method employed for С4–С7 alcohols in [2]
view bifunctional. It follows that a monoester mole- was used to investigate the kinetics of С10 alcohol
cule in an alcohol solution cannot be located inside
the alcohol chain but can only be at its terminus.
If points 1–3 are fulfilled, Eq. (1) can be inter-
preted as a first order equation with respect to alcohol
associate concentration. By factoring out term n in the
right part of Eq. (1), an equation identical to it is pro-
duced:
oxyethylation. Our experiments were conducted in a
flow system made of titanium in a mixing reactor at
temperatures in the range of 60–150°C and a pressure
of 1.4 MPa. The preset temperature in the reactor was
maintained with an accuracy of 0.5°C. The reactor
was a hollow cylinder with a volume of 15 cm3,
equipped with a magnetic stirrer and all of the neces-
sary connectors. A reaction mixture at a given tem-
perature, pressure, and volume rate was pumped
through the reactor and then passed through a con-
denser, reaching a collector from which cooled sam-
ples could be taken for analysis. The reaction mixtures
were analyzed by means of GLC. The reactor reached
the steady state mode after no fewer than 6 reactor vol-
umes of the reaction mixture were passed through it.
Both the preliminary calculations and our experi-
ments showed that the pressure we used was sufficient
to prevent the EO state changing from liquid to vapor,
the volume of which in our setup was minimal. Errors
in the mass balance for EO in our experiments was
5% or less. In most cases, errors in determining
parameters kо,obs. and n did not exceed 10 rel. %.
0
W = (co0 − co)/τ = ko,obs.ncaco(ca /n − c1)
,
(2)
where the expression in parentheses in the right part of
the equation represents the concentration of unre-
acted alcohol associates in a reactor, since according
0
to the accepted model,
is the concentration of
ca /n
alcohol associates in the initial mixture; с1 is the con-
centration of reacted alcohol associates, which is equal
to the concentration of the first reaction product; and
product (
) is the reaction rate constant in the
ko,obs.n
new scale of alcohol concentration. It follows that the
widely accepted physicochemical concept of first
order kinetics is preserved in this case, but it applies to
the concentration of alcohol associates, rather than
the total alcohol concentration.
Commercial n-decanol was used with a main com-
Since the lifetime of a single hydrogen bond is very
ponent content of no less than 99 wt %. It was desic-
short (on the order of 10−13 s [4]), the lifetime of an cated prior to use over molecular sieves. The water
alcohol associate becomes a key parameter for inter- content in the n-decanol after drying was 0.016 wt %.
preting this mechanism. It was shown experimentally Sodium n-decycloxide was used as a catalyst.
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756
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Table 1. Results from experiments on decanol-1 oxyethylation at different temperatures
Concentration, mol/L
kо, obs. × 103,
L2/(mol2 s) at
cc × 102
cо0
ca0
cо
ca
c1
c2
Т = 60°С
4.836
4.802
4.722
4.817
Т = 75°С
4.754
4.690
4.717
4.776
n = 1
n = 49.5
1.80
1.71
1.75
1.78
n = 21.1
3.12
3.09
2.85
3.32
n = 12
3.38
3.40
3.33
3.44
n = 11.2
6.24
6.32
6.84
7.06
7.0
0.913
0.948
0.956
0.933
0.839
0.890
0.907
0.892
4.764
4.747
4.674
4.777
0.070
0.054
0.047
0.039
0.0023
0.0014
0.0011
0.0008
0.52
0.77
0.90
1.08
n = 1
1.49
1.88
2.16
2.83
n = 1
2.14
2.55
2.86
3.14
n = 1
3.39
4.24
5.21
6.02
n = 1
14.5
16.4
19.6
24.7
3.50
2.53
1.75
4.96
2.48
1.24
0.62
0.932
0.995
0.968
0.909
0.794
0.897
0.910
0.872
4.619
4.595
4.659
4.740
0.124
0.090
0.056
0.035
0.007
0.0035
0.0015
0.0005
Т = 87.5°С
4.676
4.57
2.28
1.14
0.57
0.955
0.955
0.886
0.929
0.779
0.841
0.822
0.891
4.512
4.566
4.683
4.665
0.151
0.104
0.060
0.0366
0.011
4.676
4.745
4.702
0.005
0.0017
0.0006
Т = 100°С
4.712
4.96
2.48
1.24
0.62
0.864
0.870
0.893
0.891
0.623
0.699
0.776
0.819
4.484
4.544
4.571
4.615
0.202
0.147
0.107
0.067
0.017
0.011
0.004
0.002
4.706
4.683
4.685
Т = 150°С
4.501
n = 12.2
30.0
25.6
29.1
29.4
1.24
0.62
0.31
0.15
0.857
0.857
0.873
0.885
0.615
0.699
0.760
0.817
4.274
4.349
4.376
4.409
0.199
0.140
0.103
0.063
0.020
0.009
0.004
0.002
4.501
4.486
4.474
The time the reaction mixture was in the reactor was 8.5 min for all experiments.
The water content was determined via the Fischer due entirely to the first stage of this reaction, which is
method using an MKC-500 titrator (Kyoto Electron- characterized by reaction rate constant ko, obs. For the
ics). Thermogravimetric experiments were conducted
with a SDT Q600 V7.0 Build 84 thermo analyzer
(Netzsch). Scanning speed was 8 K/min.
most part, the catalyst concentration varied in the
series of reactions presented in Table 1, with each
series consisting of four experiments. When n = 1, each
experiment was processed directly using Eq. (1); when
n ≠ 1, the reaction series was processed as a whole.
Statistical processing of the experimental data when
n ≠ 1 involved fitting parameter n, using the linear
least squares method so that the least square devia-
tions of the reaction rate constant from the average
value would be minimal. The minimum of function F
was thus determined:
RESULTS AND DISCUSSION
The primary experimental data on the oxyethyla-
tion of n-decanol at different temperatures, along with
the results from data processing using Eq. (1) with n =
1 (first order with respect to the total alcohol concen-
tration) and at n ≠ 1 (first order with respect to the
concentration of alcohol associates) are presented for
comparison in Table 1 as an example. It should be
noted that as in the case of С4–С7 alcohols [2], the
yield of the second product in most cases did not
exceed 5–6% of that of the first product of the reac-
tion, which allowing us to assume that the total reac-
N
2
,
(3)
F =
(ko,obs,i − ko,obs,av
)
∑
i=1
where
is the observed rate constant obtained in
ko,obs,i
tion rate determined from EO consumption could be the ith experiment of a given reaction series at a pre-
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KINETICS OF THE n-DECANOL OXYETHYLATION REACTION
757
Table 2. Values of constant kо, obs. and association parameter n in the reaction of decanol-1 oxyethylation at different tem-
peratures
t, °C
60
67.5
75
87.5
100
125
15
12.6
150
28.5
12.2
ko, obs. × 103, L2 mol−2 s−1 1.76 0.04 2.3 0.15
3.1 0.2
21.1
3.4 0.05
12
6.6 0.4
11.2
1
2
n
49.5
28.5
coordinates lnn–1/Т, where Т is the absolute tem-
perature, were used for quantitative assessment of the
temperature dependences of parameter n and their
comparison in [2]. These dependences for С4–С7
alcohols in coordinates lnn–1/T are straight lines over
the investigated range of temperatures with a gradual
decline in −ΔН* values from 11 kJ/mol for С4 alcohol
to 4 kJ/mol for С7 alcohol, due likely to the increasing
length of the hydrocarbon radical in this series. Based
on this, a further drop in –ΔН* could be expected for
С10 alcohol. Parameter n of С10 alcohol behaves as
expected in the temperature range of 87.5–150°C, and
is practically independent of the temperature; i.e.,
ΔН* ≈ 0 within the experimental error, testifying to the
high thermal stability of the associate when n = 12 with
regard to dissociation. A sharp increase in parameter n
is observed when the temperature falls below 87.5°C:
ΔН* = 45.5 6.4 kJ/mol in the temperature interval
60–87.5°C. In contrast to the С4–С7 alcohols, this
dependence for С10 alcohol consists of two parts that
form straight lines which intersect at approximately
87.5°C.
scribed n value;
is the arithmetic mean of the
ko,obs,av
rate constants in this reaction series at the same n
value; i is an index that assumes sequential integer val-
ues from 1 to N; and N is the number of experiments
in the reaction series (N = 4). The values of n at which
function F has a minimum and the least square devia-
tion of constants is minimal are presented in Table 1.
As can be seen from the above data, the same pat-
tern is observed when n = 1 as in the case of С4–С7
alcohols; i.e., with all other conditions being equal,
the higher the yield of the first reaction product in
each series of experiments, the lower the rate constant
calculated according to Eq. (1). Formal inhibition by
the reaction product is thus observed that is not
reflected by Eq. (1) when n = 1. The minimum and the
maximum rate constants within each series in this case
differ by a factor of ∼1.5–2. This is appreciably higher
than the experimental error and indicates that Eq. (1)
when n = 1 cannot be used to describe the kinetics of
this reaction for the investigated ranges of concentra-
tion and conversion. At the same time, processing the
data according to Eq. (1) when n ≠ 1 results in consis-
tent rate constants, as in the case of С4–С7 alcohols.
All of the points on the activation energy plot lie on
virtually the same straight line, except for the one at
87.5°C. The point at 87.5°C, which corresponds to the
inflection point on the lnn–1/Т dependence, drops
out of the graph. The rate constant value at that tem-
Our results from experiments on decanol-1 oxyeth-
ylation are presented in Tables 1 and 2. The depen-
dences of lnn and ln kо,obs on reciprocal temperature
are presented in Fig. 1.
It follows from the presented data that the funda- perature was found to be approximately 50% lower
mental difference between this alcohol and the С4–С7
alcohols lies in the temperature dependence of param-
eter n. The arbitrary values of enthalpy of association
than expected, which would put it on the dashed line
(Fig. 1). The activation energy determined over the
investigated range of temperatures without consider-
ΔН* calculated by processing the obtained n values in ing the missing point was 36.5 3.2 kJ/mol.
3.5
3.0
2.5
2.0
1.5
1.0
0.5
4.0
3.5
3.0
2.5
1
2
2.4
2.5
2.6
2.7
2.8
2.9
3.0
103/T, K−1
Fig. 1. (1) Dependences of k and (2) association parameter n on reciprocal temperature.
о
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758
STUL’
1.2
1.0
0.8
0.6
0.4
0.035
0.030
0.025
0.020
0.015
2
1
0.010
0.005
0.2
0
65
75
85
95
105
115
t, °C
Fig. 2. (1) Dependence of the mass loss of a sample (Δm) on temperature and (2) the derivative of this dependence; Δm =
100(m − m)/m , where Δm is the mass loss (%), m is the initial mass of the sample, and m is the current mass of the sample.
о
о
о
The rate of temperature scanning was 8 K/min.
It follows from the above data that the trend of the ments. The initial n-decanol with a water content of
temperature dependence of parameter n changes at a
temperature of around 87.5°C. Since parameter n,
obtained on the basis of kinetic studies, is related in
this model to the microscopic inner structure of liquid
decanol, and we would expect this relationship to be
preserved on the macrolevel, we may assume that a
structural transition occurs in liquid decanol at a tem-
perature of about 87.5°C, and is accompanied by a
corresponding change in the trend or pattern of
changes in some physical, physicochemical, or spec-
tral properties of n-decanol, depending on tempera-
ture. It should be noted that our assumption of a struc-
tural change was made exclusively on the basis of the
change in the trend of n dependence on temperature,
rather than that of the observed 50% drop in the rate
constant, relative to the expected value.
Our analysis of the temperature dependences of the
number of physical, physicochemical, and spectral
properties of n-decanol known from the literature did
not reveal any striking anomalies in their behavior
around the transition temperature; nevertheless, there
were certain indications of these. For example, the
dependence of vapor pressure on temperature in coor-
dinates lnP–1/Т for С6 alcohol in the considered
range of temperatures is a straight line, while for С10
alcohol this dependence shows a slight bend at 85–
90°C [7], which is in agreement with our results. Due
to the low impact of the expected effects, their discov-
ery likely requires especially precise experiments in
narrow temperature intervals around the transition
temperature, while the dependences available in the
literature were recorded in wide temperature intervals
with large steps.
0.016 wt % used in experiments on oxyethylation was
used in these experiments. The dependence of the
mass loss of the alcohol sample on temperature at a
scanning speed of 8 K/min is presented in Fig. 2, along
with the same dependence in differential form. As can
be seen from the figure, the differential dependence
displays a maximum around 87.5°C, which coincides
with the temperature determined using the kinetic
method. As the temperature rises, the derivative of the
mass loss decreases and increases again at 100°C. This
pattern is likely due to the presence of 0.016 wt % of
water in the sample. It is known [8] that large fluctua-
tions in the thermodynamic parameters are observed
near the temperatures of structural transitions. Since
the energy of hydrogen bonds is close to that of ther-
mal motion at a given temperature, a great many
hydrogen bonds rupture when the temperature
reaches 87.5°C, including those that held water mole-
cules in a liquid phase. The factors described above are
likely responsible for the sharp influx of water mole-
cules into the vapor phase. The next increase in the
rate of desorption into the vapor phase is observed at
100°C, the temperature at which water boils. The deca-
nol sample with a higher water content of 0.32 wt %
exhibits a peak at 92.5°C, so the maximum is shifted
toward higher temperatures and becomes wider as the
water content rises. The participation of water mole-
cules in this process was confirmed by the repeated
scanning of a sample that had undergone this proce-
dure earlier failing to produce a peak in the indicated
range of temperatures. In this case, water acted as a
probe that helped reveal the rearrangement of the liq-
uid phase structure. Using the terminology suggested
in [9] for the classification of coil–globule structural
transitions in polymer solutions, this transition can be
After a long search, it was established that the exis-
tence of the expected structural transition could be
confirmed by means of thermogravimetric experi- classified as a transition accompanied by a sharp loss
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KINETICS OF THE n-DECANOL OXYETHYLATION REACTION
759
of the adsorbed ligand, recorded by means of thermo-
gravimetry.
We may also assume that association occurs mainly
via the hydrogen bonds of the hydroxyl groups in С4–
С7 alcohols over the range of investigated tempera-
It should also be noted that the expression in [10]
for phase and structural transitions is valid for the tures, and only at temperatures above 87.5°C in С10
described transition:
Tt ≈ ΔTn
alcohol. Hydrocarbon radicals do not participate
directly in the association of alcohol molecules, but
they probably shield (protect) the chains of the hydro-
gen bonds of hydroxyl groups from thermal disruption
by wrapping around them and creating a peculiar type
of frame. The possibility of such framing, and the term
itself, were suggested in [11]. This lowers the –ΔН*
values in the series of С4–С7 alcohols, due to the
growing size of the hydrocarbon radical, which was
mentioned above. We suggest that complete shielding
is observed for С10 alcohol at temperatures above
87.5°C, and that the disrupted hydrogen bond is
restored, since the alcohol molecules that form this
bond do not have time to separate, being inside cells
made of hydrocarbon radicals.
It is of interest to discuss the purely kinetic conse-
quences of such a structural transition. As can be seen
in Fig. 1, the graph for activation energy before the
temperature interval where the transition occurs is a
continuation of this graph after this interval; i.e., the
activation energy and pre-exponential factor in the
expression for the reaction rate constant do not
change. The observed ∼50% reduction in the observed
rate constant at the temperature of transition (Fig. 1)
is likely related to the structural disordering (structural
chaos) of the liquid phase, which takes place at the
transition temperature, and which probably causes the
drop in the pre-exponential factor. Based on the
obtained data, we may also conclude that the contact
interaction of hydrocarbon chains, which occurs at
temperatures below the transition temperature for С10
alcohol, does not have any great impact on the reactiv-
ity of the terminal hydroxyl group of the alcohol asso-
ciate that participates directly in the reaction. The
abovementioned framing made of hydrocarbon radi-
cals protects the associate from decay at temperatures
above 87.5°C, but it also does not affect reactivity of
the terminal hydroxyl group.
,
(4)
where is the temperature of transition, K; ΔТ is the
Tt
width of the transition, K; n is the number of particles
in the region of transition (in this case, the association
number). According to curve 2 in Fig. 2, ΔТ ≈ 32 K.
Consequently, n ≈ 360.75/32 = 11.3. This is in good
agreement with the results from kinetic studies where
n = 12 1.2.
To a great extent, the results from thermogravimet-
ric experiments thus support the conclusion, drawn on
the basis of based kinetic studies, that a structural
transition occurs in n-decanol at 87.5°C. It is of inter-
est to discuss the nature of this transition and offer
some suggestions as to the structure of associates in the
series of considered alcohols in the investigated range
of temperatures.
Since the dependence of parameter n on tempera-
ture is not observed for the series of С4–С7 alcohols in
the investigated range of temperatures, we may
assumed that the contact (or, according to the termi-
nology in [9], bulk) interactions of hydrocarbon radi-
cals make a significant contribution (along with
hydrogen bonds) to the total energy of interaction for
С10 alcohol at temperatures below 87.5°C. In this case,
these interactions are likely related to Van der Waals
forces, with dispersion interactions providing the
major impact. Thermal motion below the transition
temperature does not interfere with such arrange-
ments of hydrocarbon radicals relative to one another
when these forces are maximal and the system reaches
its minimum free energy. We would also expect that at
temperatures below the transition temperature, the
hydrocarbon radicals of chain associates interact with
one another in a stretched trans-conformation and are
arranged parallel to one another, since such an
arrangement favors this interaction. Thermal motion
disrupts this arrangement and the respective interac-
tion of hydrocarbon radicals at temperatures of 87.5°C
and above.
CONCLUSIONS
The kinetics of the above reaction allows us to
investigate the supramolecular micro-irregular struc-
ture of liquid n-decanol and predicts the occurrence of
a structural transition in the liquid alcohol that is not
described in the literature, and has been verified to a
great extent by thermogravimetric experiments. Inves-
tigations of the structure of liquid decanol at tempera-
tures below and above the transition temperature are
required to prove this suggestion conclusively.
It is of interest to estimate the energy of the thermal
motion disrupting contact interaction, and thus the
energy of contact interaction. For this, we can use the
equation
,
(5)
ε = kBN ATt
where is the energy of thermal motion, kB is the
ε
Boltzmann constant, and NА is the Avogadro number.
Using the reference values kB = 1.38 × 1023 J/K and
NA = 6.02 × 1023 mol−1, we find that ε = 3 kJ/mol,
which is in good agreement with the estimates of the
energy of contact interactions (1–4 kJ/mol) presented
in the literature [4].
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No. 4
2016