The relationship between properties of fluorinated graphite intercalates and matrix composition 7: Intercalates with ethyl acetate

Article abstract of DOI:10.1007/s10973-014-3635-4

Inclusion compounds (intercalates) of fluorinated graphite matrix with ethyl acetate (C₂F_xBr_z·yCH ₃COOC₂H₅, x = 0.49, 0.69, 0.87, 0.92, z = 0.01) were prepared by guest substitution from ac

Full text of DOI:10.1007/s10973-014-3635-4

J Therm Anal Calorim (2014) 117:235–241
DOI 10.1007/s10973-014-3635-4
The relationship between properties of fluorinated graphite
intercalates and matrix composition 7
Intercalates with ethyl acetate
D. V. Pinakov
•
V. A. Logvinenko G. N. Chekhova
•
Received: 5 July 2013 / Accepted: 2 January 2014 / Published online: 27 April 2014
Akad e´ miai Kiad o´ , Budapest, Hungary 2014
ꢀ
Abstract Inclusion compounds (intercalates) of fluorinated
graphite matrix with ethyl acetate (C F Br ꢀyCH COOC H ,
[1, 2], tends to increase with decrease of x in the compounds
with 1,2-C H Cl , CH Cl , and CH COCH [3–5], and
3
2
x
z
3
2
5
2
4
2
2
2
3
x = 0.49, 0.69, 0.87, 0.92, z = 0.01) were prepared by guest
substitution from acetonitrile to ethyl acetate. The kinetics of
the thermal decomposition (the first stage of filling ? the
second stage of filling) was studied under isothermal condi-
tions at 291–307 K. The relationship of the host matrices’
structure with inclusion compounds’ thermal properties and
kinetic parameters is discussed.
increases, more explicitly between x = 0.69 and 0.49, in the
compounds with butanone [6]. According to DTA investiga-
tion, FGIC-1 thermal stability obviously increased with
decrease of x from 0.92 to 0.49 [1–6]. Topochemical mecha-
nism of FGIC-1 deintercalation changes from phase boundary
reaction to diffusion for FGICs with CH CN and CH Cl [1, 4],
3
2
2
and the diffusive mechanism increases its contribution with
decrease of x. For inclusion compounds with chloroform [2],
dichloroethane [3], and butanone [6], deintercalation mecha-
nism was mostly diffusive; this reaction for FGICs with acetone
passed under phase boundary mechanism [5]. The increase of
diffusive interactions (and of FGIC-1 deintercalation time)
with decrease of x correlates with reduction of interlayer space
in these clathrate systems [1–6]. FGIC-1 decomposition rate is
maximal in the case of compounds with x = 0.92 for all the
guest components. On the other hand, the 1st stage FGICs with
x = 0.49 have the maximum formation rate. It can correspond
to the increase of both interlayer host–host interaction and host–
guest interaction as the fluorine content in matrix decreases.
To continue our investigations of FGICs’ physicochemical
properties in this work, we studied FGICs with ethyl acetate
(CH COOC H ). This solvent, due to its relatively low boil-
Keywords Inclusion compounds ꢀ Intercalates ꢀ
Fluorinated graphite ꢀ Isothermal kinetics ꢀ Thermal
stability
Introduction
In [1–6] fluorinated graphite intercalation compounds (FGICs)
of common formula C F Br ꢀy G (where x = 0.49–0.92,
2
x
z i
z = 0.008–0.010, and y and y are numbers of the intercalated
2
1
guest molecule per 2 carbon atoms for the 2nd and the 1st stage
of filling, respectively) with acetonitrile, chlorinated hydro-
carbons and ketones were studied by physicochemical meth-
ods. The number of guest molecules intercalated into FGIC (the
y and y value) reduced with decrease of the matrix fluorina-
3
2 5
ing point, allows us to work with the 1st stage inclusion
compounds of fluorinated graphite. FGICs with CH3-
COOC H were investigated to continue research work for
1
2
tion degree (x). It was shown by determination of effective
energies for the 1st stage inclusion compounds (FGIC-1) that
their kinetic stability is similar within error for each x with the
same guest for inclusion compounds with CH CN and CHCl
2
5
compounds with oxygen-containing organic guest compo-
nents. The ethyl acetate molecule has its own symmetry C ; its
1
3
3
˚
dimensions are 4.08 and 8.89 A in minimal and maximal
projection, respectively. Dipole moment of CH COOC H is
3 2 5
D. V. Pinakov (&) ꢀ V. A. Logvinenko ꢀ G. N. Chekhova
Nikolaev Institute of Inorganic Chemistry, Siberian Branch of
Russian Academy of Sciences, Ac. Lavrentyev Ave. 3,
Novosibirsk-90 630090, Russia
1
.8–1.9 D at 295–323 K [7] which allowed synthesis of its
inclusion compounds by substitution of intercalated CH CN
3
to new guest component [1–6, 8]. Ethyl acetate has vapor
pressure about 12.0 kPa at 298.15 K [9], and boiling point is
e-mail: pinakov@niic.nsc.ru
123

2
36
D. V. Pinakov et al.
Fig. 1 IR absorption spectra for
pure guest components:
acetonitrile (a), ethyl acetate
a
b
CH CN
3
CH COOC H
2 5
3
(
b), and their inclusion
compounds based on x = 0.92,
.87, 0.69, and 0.49 fluorinated
graphite matrices
0
x = 0.92
x = 0.92
x = 0.87
x = 0.87
x = 0.69
x = 0.69
x = 0.49
x = 0.49
2400
2000
1600
1200
800
3200
2400
1600
800
–
1
Wavenumber/cm
–1
Wavenumber/cm
3
50.3 K. These properties of CH COOC H allow us to
3 2 5
Experimental
perform thermoanalytical investigations of the 1st stage
FGICs near room temperature, because their deintercalation
temperatures must be much lower than the temperatures of
matrix destruction (500–600 K [10, 11]).
Synthesis of layered inclusion compounds with acetonitrile
was described thoroughly in [1, 12]. Stable intercalates
with acetonitrile [11, 12] were used as initial components
Table 1 Elemental composition and stoichiometry of C
gravimetric analysis
2 x
F Br
z
ꢀy
2
CH
3
COOC
2
H
5
(the 2nd stage inclusion compounds) by elemental and
Gravimetry
No.
Elemental analysis
Found elements/mass%
The 2nd stage inclusion compound formula: x (± 0.01),
z (± 0.003), y (± 0.011)
Values of
2
y (± 0.011)
2
C ± 0.50
F ± 0.30
Br ± 0.30
1
2
3
4
56.49
57.61
62.34
68.79
35.87
34.53
30.27
24.15
1.64
1.67
1.66
1.66
C
C
C
C
2
F
2
F
2
F
2
F
0.92Br0.010ꢀ0.073CH
0.87Br0.010ꢀ0.074CH
3
COOC
COOC
2
H
5
5
0.073
0.074
0.062
0.052
3
2
H
0.69Br0.009ꢀꢀ0.062CH
3
COOC
2 5
H
0.49Br0.008ꢀ0.052CH
3
COOC H
2 5
Table 2 FGIC-1 C
2 x
F Br
z
•y
1 3 2 5
CH COOC H properties
b
-1
No.
The 1st stage inclusion compound stoichiometry
Decomposition maximum
DTA)/ꢁC (± 0.4)
a
E /kJ mol (of the 1st
(
stage compound)
a
Dm /mass% (± 0.2)
1
FGIC-1 formula y (± 0.015)
1
2
3
4
a
16.1
15.8
15.3
13.0
C
C
C
C
2
2
2
2
F
F
F
F
0.92Br0.01ꢀ0.216CH
3
3
3
3
COOC
COOC
COOC
COOC
2
2
2
2
H
H
H
H
5
5
5
5
113.1
118.0
123.1
127.4
64.4
68.2
0.87Br0.01ꢀ0.206CH
0.69Br0.01ꢀ0.174CH
0.49Br0.01ꢀ0.139CH
83.8
137.1
Dm the samples’ mass increase during the 2nd to the 1st stage inclusion compound transformation (mFGIC-2 = 100 %)
b
a
E activation energy for FGIC-1 decomposition to FGIC-2 and gaseous ethyl acetate
1
23

Relationship between properties of FGICs
237
1
2
3
4
stoichiometry of the 2nd stage inclusion compounds with
ethyl acetate with a good reproducibility. It comes from
1
1
6
2
comparison of stoichiometric coefficients y , which were
2
obtained from the chemical analysis data and results of
gravimetric measurements (Table 1). The repeated satura-
tion of FGIC-2 by ethyl acetate was performed to define the
stoichiometry of the 1st stage FGICs (Table 2) and to plot
kinetic saturation curves in order to determine the time of
full saturation to FGIC-1.
8
4
Thermal decomposition of the first stage inclusion
compounds with CH COOC H was investigated by the
3
2 5
homemade differential thermal analysis equipment [1].
1
20
240
360
480
Accuracy of temperature measurement was about ± 0.4 ꢁC;
τ/min
-1
heating rate was 3.2 ꢁC min , and sample (FGIC-1 with
slight excess of CH COC H ) masses were about
3
2 5
Fig. 2 Saturation curves for FGIC-2 with ethyl acetate (P = 1 bar,
T = 298 ± 0.5 K) for x = 0.92 (1), 0.87 (2), 0.69 (3), and 0.49 (4)
30–40 mg.
IR absorption spectra of FGIC-2 were taken on Fourier
spectrometer SCIMITAR FTS 2000; samples were pre-
pared by pressing of 3 mg of FGIC-2 into tablets with KBr.
Investigations of kinetic parameters for thermal
decomposition of the 1st stage inclusion compounds were
carried out by periodical fixing of the FGIC-1 sample mass
loss. These original kinetic data were processed mathe-
matically to calculate required values. We used thermo-
statically controlled analytic balance (± 0.015 mg), and
measurements were taken at fixed temperatures (± 0.2 K)
from 291 to 307 K.
for the synthesis of FGICs with CH COOC H . Refined by
3 2 5
known technology, ethyl acetate [13] had melting point
1
89.5 K and boiling point 350.4 K.
The inclusion compounds with ethyl acetate were pre-
pared by isopiestic method as it was shown in [2–6] for
compounds with chlorinated hydrocarbons and ketones.
After 3–4 cycles of saturation (in the atmosphere of CH3-
COOC H ) and decomposition (in the air to form FGIC-2),
2
5
all acetonitrile (Fig. 1a) was substituted to ethyl acetate
Fig. 1b). These experiments allowed defining the
(
Fig. 3 Isothermal
decomposition curves for FGIC-
2
a
2
b
100
80
1
with ethyl acetate: a x = 0.92
80
60
40
20
at 291.0 K (1) and 303.5 K (2);
b x = 0.87 at 296.2 K (1) and
1
60
40
3
2
06.8 K (2); c x = 0.69 at
96.3 K (1) and 306.9 K (2);
1
α
α
d x = 0.49 at 296.3 K (1) and
01.8 K (2)
3
20
60
120 180 240
300 360
120
240
360
480
τ/min
τ/min
c
80
d 80
2
2
7
6
5
4
3
2
1
0
0
0
0
0
0
0
6
0
1
1
40
α
α
20
60
120 180 240 300 360 420
60
120 180 240 300 360 420
τ/min
τ/min
123

2
38
D. V. Pinakov et al.
Fig. 4 Dependences of
ln[-ln(1-a)] versus ln(s, s),
numbers of curves correspond
to those in Fig. 3
a
b
0.0
1.0
2.0
2
2
1
0.0
0.6
1.2
α
1
α
–
–
–
–
7
.0
8.0
9.0
8.0
9.0
10.0
In τ
In τ
c
d
2
2
0.0
0
.0
1
α
α
1
–9.0
–1.8
–
0.6
1.2
–
8
.0
9.0
10.0
6.0
8.0
10.0
In τ
In τ
Results and discussion
guest and host–host interactions are probably becoming
stronger due to more developed ‘‘surface’’ of less fluori-
nated graphite matrix and the layers’ approach with
decrease of x. This effect leads to the increase of FGIC-1
stability in the case of FGIC-1 based on less-fluorinated
matrices.
FGIC-2 to FGIC-1 with ethyl acetate saturation curves at
98.2 ± 0.5 K are shown in Fig. 2. Equilibration time of
2
satiety through gas phase depended from the matrix fluo-
rination degree x and varied from 150–180 min for
x = 0.49 to 480–540 min for x = 0.92.
Experimental data of FGIC-1 deintercalation rate
(decomposition degree a versus time s) on air for each
temperature and x were mapped by the equation
ln½ꢁ lnð1 ꢁ aÞꢂ ¼ n lnðK=nÞ þ n ln s (getting after taking
twofold logarithm from the Erofeev’s equation [14] subject
to the Sakovich’s correlation [15]), where n is non-
dimensional coefficient and K is generalized rate constant,
Deintercalation time in ambient atmosphere (Fig. 3a–d)
depended both on fluorination degree x and on temperature
for each x; it lasted from 500 (x = 0.92) to 2,500 min
(
x = 0.49) in the temperature range 291–307 K. The host–
-
1
–9.5
s . This equation was used by many authors for kinetic
investigations of both thermal decomposition of different
compounds [1–6, 16] and phase transitions, solvation, and
absorption [17]. Kinetic curves (Fig. 3) can be approxi-
mated by nearly parallel lines (Fig. 4); it points on the
kinetic parameter n constancy for the 1st stage inclusion
compounds for each x in considered range of temperatures.
–
–
10.0
10.5
b
a
–
–
11.0
11.5
c
The ‘‘effective’’ activation energy (E ) values found
a
4
from line slope of ln K-10 T (Fig. 5 a–d) are 64.4,
-1
-
8.2, 83.8, and 137.1 kJ mol for x = 0.92, 0.87, 0.69,
1
6
d
and 0.49, respectively. It has higher value than the evap-
–
12.0
oration enthalpy of pure ethyl acetate in explored range of
-1
32.5
33.0
33.5
4
34.0
34.5
temperatures (DH = 36.13 kJ mol at 298.15 K and
vap
-1
2.32 kJ mol at 349.15 K [18]). The values of E for
1
0 /T
3
a
4
-1
FGIC-1 with CH COOC H are considerably higher than
3 2 5
Fig. 5 Dependence of ln K versus 10 T : x = 0.92 (a), 0.87 (b),
.69 (c), and 0.49 (d)
0
those for FGICs with previously reported guest
1
23

Relationship between properties of FGICs
239
Fig. 6 Dependences of da/ds
a
b 0.025
versus reduced time s/s0.5
(
dashed line—calculated
0.012
0.008
0
.020
curves, solid line—fitted ones):
a x = 0.92, T = 291.0 K;
b x = 0.87, T = 296.2 K;
c x = 0.69, T = 296.3 K;
d x = 0.49, T = 296.3 K
τ
0.015
τ
α
α
0
0
.010
.005
0
.004
0
.2
0.4
0.6
0.8
0.4
0.8
1.2
1.6
τ/τ0.5
τ/τ0.5
c
d 0
.020
0
.03
0.015
τ
0.02
τ
α
α
0.010
0
.01
0.005
0
.2
0.4
0.6
0.8
1.0
0.5
1.0
1.5
2.0
τ/τ0.5
τ/τ0.5
0
0
0
0
0
0
0
0
0
0
.22
.20
.18
.16
.14
.12
.10
.08
.06
.04
1
2
3
150
140
1
2
3
1
1
30
20
110
0.5
0.6
0.7
0.8
0.9
Fluorination °/x
Fig. 7 Dependences of the 1st stage (y
stage (y , on the bottom) inclusion compounds’ stoichiometry with
CH COCH (1), CH COC (2), and CH COOC (3) versus
matrix fluorination degree (x)
1
, on the top) and of the 2nd
2
100
3
3
3
H
2 5
3
2
H
5
0.5
0.6
0.7
0.8
0.9
Fluorination °/x
Fig. 8 Dependences of the 1st stage inclusion compounds’ reversible
except for C 0.49Br0.008 with butanone [6]) deintercalation temper-
components [1–5] and are closer to the E values for
a
(
2
F
intercalates with butanone [6], surpassing them for
ature versus matrix fluorination degree (x): for CH
CH COC H (2), and CH COOC H (3)
3 3
COCH (1),
x = 0.69 and 0.49.
3
2
5
3
2 5
123

2
40
D. V. Pinakov et al.
For determination of the first stage inclusion compound
decomposition reaction mechanism in isothermal condi-
tions, we checked dependencies of da/ds from reduced
time s/s0.5 [19]. Analysis of these dependencies curves
1
1
1
1
1
40
30
20
10
00
(Fig. 6) indicates, in accordance with the reference work,
about evidently diffusive reaction mechanism for FGIC-1
with x = 0.49–0.92 in our temperature range.
Coefficient n of generalized Erofeev’s equation had val-
ues of 0.77–0.78, 0.82–0.83, 0.65–0.66, and 0.41–0.43 for
FGIC-1 with x = 0.92, 0.87, 0.69, and 0.49, respectively.
According to [16, 19], values n [ 1 could correspond to
reaction with kinetic control and n \ 1 corresponds to
reactions with diffusion control. Graphical representation of
these dependences also confirms diffusive reaction mecha-
nism. Due to n values, we can see the growth of diffusive
hindrance with decrease of x.
1
2
3
9
8
7
6
5
0
0
0
0
0
Effective thickness of the guest layer (about
˚
3.80–3.95 A for all matrices) calculated from identity
period values of FGIC-2 and FGIC-1 is considerably less
than CH COOC H molecule size in the minimal Van der
3
2 5
˚
Waals projection (4.08 A); so, CH COOC H molecules
3
2 5
0.5
0.6
0.7
0.8
0.9
are distributed in the interlayer space by the principle of
close packing of molecules into the cavities of relief
‘‘surface’’ of matrix layers. The fluorination decrease
increases diffusive hindrance, and activation energy values
grow with x decrease, especially for x = 0.69 and 0.49.
Fluorination °/x
Fig. 9 Dependences of the 1st stage inclusion compounds’ reversible
deintercalation activation energies versus matrix fluorination degree
(
x): for CH
3
COCH
3
(1), CH
3
2 5 3 2 5
COC H (2), and CH COOC H (3)
x = 0.69
x = 0.69
Conclusions
5
2
1
12
56
28
x = 0.92
From the experimental material listed here and before
[
5, 6] for FGICs with oxygen-containing guest molecules,
x = 0.92
we can see a number of tendencies of FGIC properties
connected with both host matrix fluorination degree x and
included guest molecule dimensions.
x = 0.69
x = 0.87
Analyzing stoichiometry dependencies of the second and
the first stage inclusion compounds from fluorination degree
x for all investigated guest molecules (CH COCH , CH
3-
x = 0.87
3
3
τ
x = 0.92
COC H , and CH COOC H ) (Fig. 7), we can see decrease
2
5
3
2 5
of included molecules’ number with decrease of x. For
x = 0.92–0.87, number of intercalated molecules was nearly
constant within error, but for x \ 0.87 it visibly tends to
decrease. Dependence of the reversible first to second stage
deintercalation temperatures from fluorination degree
6
3
4
2
x = 0.87
1
2
3
(Fig. 8) can be explained by the increase of both ‘‘host–
guest’’ and ‘‘host–host’’ intermolecular interactions. With
decrease of fluorination degree, the increase of FGIC-1
deintercalation temperature is observed; in all cases, the first
stage compound deintercalation temperatures are consider-
ably higher than boiling points of pure guest components.
Activation energies of deintercalation (Fig. 9) tend to grow
with decrease of x, and this tendency is evident for inclusion
compounds with butanone and ethyl acetate.
1
6
15
20
25
30
35
40
T/°C
Fig. 10 Dependences of the reversible deintercalation half-reaction
time s0.5 versus temperature for the 1st stage inclusion compounds
with CH COCH (1), CH COC H (2), and CH COOC H (3) based
3 3 3 2 5 3 2 5
on matrices with different fluorination degree
1
23

Relationship between properties of FGICs
241
Looking at temperature dependences of deintercalation
half-reaction time (s0.5–T) for all FGICs with oxygen-
containing solvents [5, 6, and this paper] (Fig. 10), we can
see the influence of guest component boiling point and its
molecular mass on the total stability of these compounds at
a room temperature. Kinetic hindrances are not the limiting
factor of the 1st stage fluorinated graphite inclusion com-
pounds’ total stability due to their layered structure—these
compounds with investigated oxygen-containing guest
components are kinetically labile, and their total stability is
mostly determined by thermodynamic properties of guest
components. Unlike the 1st stage inclusion compounds, the
5. Pinakov DV, Logvinenko VA, Chekhova GN, Shubin YV. The
relationship between properties of fluorinated graphite interca-
lates and matrix composition. Part 5. Intercalates with acetone.
J Therm Anal Calorim. 2011;104:1077–82.
6. Pinakov DV, Logvinenko VA, Chekhova GN, Shubin Y (2013) The
relationship between properties of fluorinated graphite intercalates
and matrix composition. Part 6. Intercalates with butanone.
J Therm Anal Calorim. doi:10.1007/s10973-013-3188-y.
7
. Osipov OA, Minkin VI, Kletenik Y. Dipole moments reference
book (in Russian). Rostov: Vysshaya Shkola; 1965.
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9
. Nikolsky BP, editor. Chemical reference book, vol. 1. Moscow:
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2
nd stage compounds probably have the structure which
10. Chekhova GN, Ukraintseva EA, Ivanov IM, Yudanov NF, Shubin
YV, Logvinenko VA, Pinakov DV, Fadeeva VP, Alferova NI.
Influence of the matrix composition on the properties of fluori-
nated graphite inclusion compounds with acetonitrile. J Inorg
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results in their kinetic inertness because of matrix layer
deformation. It causes closure of communication lines
between the interlayer space and ambient atmosphere; so,
open interlayer spaces transform into closed cellular
chambers of host matrix. These chambers are surrounded
by host matrix; so, the further guest component yield
becomes impossible till the fluorinated matrix destruction
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vinenko VA. Phase transitions of intercalation inclusion com-
pounds
2
C
2
F
0.92Br0.01ꢀyCH
3
CN in the temperature range
0–260 ꢁC. J Struct Chem. 2006;47:1141–54.
12. Pinakov DV (2007) Different fluorination degree fluorinated
graphite matrices intercalates synthesis and thermal stability.
Ph.D. Thesis. Novosibirsk, p 163.
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3
1
3. Gordon AJ, Ford RA. The chemist’s companion. New York:
Wiley; 1972.
4. Erofeev BV. Generalized equation of chemical kinetics and its
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Acknowledgements Special thanks to Yu. V. Shubin, N. I. Alfer-
ova, and V. P. Fadeeva for collaboration.
1
1
946;52(6):515–8.
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