Polar effect of successive fluorination of dimethyl carbonate on physical properties

Article abstract of DOI:10.1246/bcsj.80.1302

Successive fluorination of dimethyl carbonate (DMC) exerts a polar effect on various fundamental properties. We describe the temperature dependence of the mass density (ρ), refractive index (n_D), relative permittivity (ε_r), dynamic viscosity (η), and kinematic viscosity (ν) of trifluorinated, difluorinated, and monofluorinated DMCs (TFDMC, DFDMC, and MFDMC, respectively). η decreased in essentially the same order as ε_r: DFDMC > TFDMC > MFDMC > DMC. However, ν and the boiling point of the TFDMC were lower than those of the MFDMC.

Full text of DOI:10.1246/bcsj.80.1302

1302 Bull. Chem. Soc. Jpn. Vol. 80, No. 7, 1302–1306 (2007)
Ó 2007 The Chemical Society of Japan
Polar Effect of Successive Fluorination of Dimethyl
Carbonate on Physical Properties
ꢀ1
Noritoshi Nanbu, Masahiro Takehara,1;2 Susumu Watanabe,1 Makoto Ue,2 and Yukio Sasaki1
1Department of Nanochemistry, Faculty of Engineering, Tokyo Polytechnic University, 1583 Iiyama, Atsugi 243-0297
2Mitsubishi Chemical Group Science and Technology Research Center, Inc., 8-3-1 Chuo, Ami, Inashiki 300-0332
Received August 16, 2006; E-mail: nanbu@nano.t-kougei.ac.jp
Successive fluorination of dimethyl carbonate (DMC) exerts a polar effect on various fundamental properties. We
describe the temperature dependence of the mass density (ꢀ), refractive index (nD), relative permittivity ("r), dynamic
viscosity (ꢁ), and kinematic viscosity (ꢂ) of trifluorinated, difluorinated, and monofluorinated DMCs (TFDMC,
DFDMC, and MFDMC, respectively). ꢁ decreased in essentially the same order as "r: DFDMC > TFDMC >
MFDMC > DMC. However, ꢂ and the boiling point of the TFDMC were lower than those of the MFDMC.
Fluorine is the most electronegative of all the elements, and
the size is small next to hydrogen. Fluorine atoms show very
Experimental
Materials. Trifluorinated carbonate (TFDMC, difluoromethyl
fluoromethyl carbonate), difluorinated carbonate (DFDMC,
bis(fluoromethyl) carbonate), and monofluorinated carbonate
(MFDMC, fluoromethyl methyl carbonate) were synthesized by
direct fluorination of DMC13 (Chart 1) and were purified by
simple distillation followed by fractional distillation at atmo-
spheric pressure. TFDMC was isolated from the reaction mixture
in this work. However, the fraction of the TFDMC estimated from
the gas chromatogram was less than 10%. The boiling point of the
TFDMC (100 ꢁC) was close to that of the MFDMC (108 ꢁC).
Therefore, separation by two types of distillation greatly decreas-
ed the total yield of the TFDMC. The purity of TFDMC, DFDMC,
and MFDMC was determined to be 99.0, 99.5, and 99.7%, respec-
tively, by means of gas chromatography (Shimadzu, GC-1700).
DMC (Kishida, battery grade) was used as received. TFDMC,
DFDMC, and MFDMC were dehydrated with purified molecular
sieves 4A before use.
low polarizability and high enthalpy of ionization. Therefore,
partially fluorinated solvents can exert a strong polar effect
on various properties, unlike polyfluorinated and perfluori-
nated solvents. The polarity of the polyfluorinated and per-
fluorinated solvents is very low. They are the so-called fluo-
rous media and are often immiscible with organic solvents
as well as water.1–3
Dimethyl carbonate (DMC) is a chain carbonate and is com-
monly used as a low-viscosity solvent for electrochemical en-
ergy-storage devices, such as lithium-ion batteries.4–7 Recent-
ly, Smart et al. have reported several trifluorinated chain car-
bonates, such as methyl 2,2,2-trifluoroethyl carbonate, and
showed that the use of them as co-solvents improves the per-
formance of lithium-ion cells.8 However, there are scarcely
any systematic and detailed studies reported on the fundamen-
tal properties of partially fluorinated chain carbonates, except
for ours.9–12
The TFDMC, the DFDMC, and the MFDMC were identified by
using gas chromatography coupled with mass spectrometry (GC-
MS analysis) (JEOL, JMS-SX102A) and 1H, 13C, and 19F NMR
spectroscopy (JEOL, JNM-LA500). The results are as follows:
GC-MS (CI) (m=z): MFDMC, 109 ½M þ Hꢂþ; DFDMC, 127 ½M þ
Hꢂþ; TFDMC, 145 ½M þ Hꢂþ. GC-MS (EI) (m=z): MFDMC, 77
In this paper, we report the polar effect of successive fluori-
nation of DMC on the physical properties, such as mass den-
sity (ꢀ), refractive index (nD), relative permittivity (relative di-
electric constant, "r), dynamic viscosity (viscosity coefficient,
ꢁ), kinematic viscosity (ꢂ), and boiling point.
O
O
CH3
C
CH3
CH2F
C
CH3
O
O
O
O
Dimethyl carbonate (DMC)
Monofluorinated dimethyl carbonate
(MFDMC, Fluoromethyl methyl carbonate)
O
O
CH2F
C
CH2F
CHF2
C
CH2F
O
O
O
O
Difluorinated dimethyl carbonate
Trifluorinated dimethyl carbonate
(DFDMC, Bis(fluoromethyl) carbonate) (TFDMC, Difluoromethyl fluoromethyl carbonate)
Chart 1.
Published on the web July 11, 2007; doi:10.1246/bcsj.80.1302

N. Nanbu et al.
Bull. Chem. Soc. Jpn. Vol. 80, No. 7 (2007) 1303
TFDMC
DFDMC
7.2
6.8
6.4
6
TFDMC
DFDMC
1.4
1.2
1
MFDMC
DMC
MFDMC
DMC
ρ
(a)
(b)
5.6
0
20
40
60
80
0
20
40
60
80
θ
/ °C
θ
/ °C
Fig. 1. (a) ꢀ and (b) N of TFDMC, DFDMC, MFDMC, and DMC as a function of ꢄ from 10 to 70 ꢁC. N was calculated from ꢀ,
molar mass, and NA according to Eq. 1.
þ
COOCH2Fþ (4.33), 59 COOCH3 (84.25), 33 CH2Fþ (100);
ꢀNA
M
DFDMC, 77 COOCH2Fþ (15þ.74), 33 CH2Fþ (100); TFDMC,
N ¼
:
ð1Þ
33 CH2Fþ (46.27), 51 CHF2 (100), 77 COOCH2Fþ (7.05),
þ
95 COOCHF2 (3.52). 1H NMR (TMS/CDCl3, 500.00 MHz):
The ꢄ dependence of N has a pronounced contribution to
the change in physical constants, as described later. ꢀ decreas-
ed in the same order as the molecular weight: TFDMC
(144.05) > DFDMC (126.06) > MFDMC (108.07) > DMC
(90.08). However, N decreased in the inverse order. In general,
as the molecular weight increases, so too does the molecular
size. The increase in the molecular size results in the decrease
in N.
Optical and Electric Properties. The ꢄ dependence of
nD of the four chain carbonates is depicted in Fig. 2a. nD is
related to the propagation speed of light in a medium and is
a measure of the ability to bend (refract) light rays. The feature
of nD was similar to that of N. Successive fluorination of DMC
resulted in a lower N and, consequently, in lower nD. nD de-
pends on both electronic polarizability or dynamic polarizabil-
ity (ꢅe) of the molecules and N. This is because the propaga-
tion of light through a medium can be imagined to occur by the
incident light inducing an oscillating dipole moment, which
then radiates light of the same frequency.
2
MFDMC, ꢃ 4.23 (s, 3H), 6.08 (d, JHF ¼ 51:5 Hz, 2H); DFDMC,
2
2
ꢃ 6.04 (d, JHF ¼ 50 Hz, 2H); TFDMC, ꢃ 6.05 (d, JHF ¼ 49 Hz,
2H), 7.34 (t, JHF ¼ 71 Hz, 1H). 13C NMR (TMS/CDCl3, 125.65
2
1
MHz): MFDMC, ꢃ 55.10, 96.97 (d, JCF ¼ 219 Hz), 154.68;
1
DFDMC, ꢃ 97.28 (d, JCF ¼ 223 Hz), 152.97; TFDMC, ꢃ 97.17
1
1
3
(d, JCF ¼ 225 Hz), 114.13 (t, JCF ¼ 260 Hz), 149.90 (t, JCF
¼
5 Hz). 19F NMR (CF3COOD/D2O, 470.40 MHz): MFDMC, ꢃ
2
2
ꢃ158:05 (t, JFH ¼ 51:5 Hz, 1F); DFDMC, ꢃ ꢃ159:70 (t, JFH
¼
50 Hz, 1F); TFDMC, ꢃ ꢃ92:75 (d, 2JFH ¼ 71 Hz, 2F), ꢃ160:44 (t,
2JFH ¼ 49 Hz, 1F).
Apparatus and Measurements.
The temperature in a
TC-WAX capillary column for gas chromatography was increased
at a rate of 10 ꢁC minꢃ1 from 50 to 100 ꢁC.13 ꢀ was measured by
use of density/gravity meters (Kyoto Electronics, DA300 and
DA-310). nD was determined on an Abbe refractometer (model
2T) equipped with a jacket. Water supplied from a constant-tem-
perature bath was circulated through the jacket. "r was measured
by using a LF impedance analyzer (Hewlett Packard, 4192A) con-
nected to a thermostat (Ando Denki, TO-9). The electrostatic ca-
pacitance of air (C0) and sample (Csample) was measured at a
frequency of 1 MHz, and "r was approximated by the ratio
Csample=C0. The samples were deaerated by bubbling Ar gas
(99.9%) before the measurements. ꢂ was measured by using a
capillary-tube viscometer, Ostwald viscometer (Shibayama), im-
ꢅe is obtained by the following Lorentz–Lorenz equa-
tion:14–16
2
nD ꢃ 1
nD þ 2
M
NAꢅe
3"0
¼
;
ð2Þ
ꢄ ꢀ
2
mersed in a thermostat. ꢁ was determined as ꢂ ꢀ; ꢂ is defined
ꢄ
where "0 is permittivity of vacuum. The average of ꢅe at 10–
70 ꢁC decreased in the following order: TFDMC (8:593 ꢅ
as ꢁ=ꢀ and is directly proportional to the time required for the
liquid to flow through a capillary-tube viscometer under its
own hydrostatic head. The physical properties of TFDMC,
DFDMC, MFDMC, and DMC were investigated over the tempera-
ture range of 10 to 70 ꢁC.
10ꢃ40 C2 m2 Jꢃ1) > DFDMC
(8:426 ꢅ 10ꢃ40 C2 m2 Jꢃ1) >
DMC (8:346 ꢅ 10ꢃ40 C2 m2 Jꢃ1) > MFDMC (8:309 ꢅ 10ꢃ40
C2 m2 Jꢃ1). ꢅe can depend on the molecular mass and the fre-
quency of an applied electric field unlike the static polariza-
bility.15 Difluorination and trifluorination of DMC increased
ꢅe as compared to the DMC. Interestingly, despite the increase
of the molecular mass, monofluorination of the DMC caused a
slight decrease in ꢅe. It is well-known that nD of polyfluorinat-
ed and perfluorinated compounds, which may have a consider-
ably lower N, is lower than those of the corresponding fluo-
rine-free compounds.
Results and Discussion
Mechanical Properties.
Figure 1 shows the Celsius-
temperature (ꢄ) dependence of (a) ꢀ and (b) number density
of molecules (N) of TFDMC, DFDMC, MFDMC, and DMC.
N refers to the number of molecules per unit volume and is
calculated from ꢀ, molar mass (M), and Avogadro constant
(NA) according to the following equation:
Figure 2b shows the ꢄ dependence of "r of the four chain

1304 Bull. Chem. Soc. Jpn. Vol. 80, No. 7 (2007)
Physical Constants
15
10
5
TFDMC
DFDMC
MFDMC
DMC
1.36
1.34
1.32
ε
TFDMC
DFDMC
MFDMC
DMC
(a)
(b)
1.3
0
0
20
40
60
80
0
20
40
60
80
θ
/ °C
θ
/ °C
Fig. 2. (a) nD and (b) "r of TFDMC, DFDMC, MFDMC, and DMC as a function of ꢄ from 10 to 70 ꢁC.
carbonates. "r is characterized by the ease of dielectric polari-
zation and has a very significant effect on the strength of
the interactions between ions in an electrolytic solution. "r
decreased in the following order: DFDMC > TFDMC >
MFDMC > DMC. "r of the DFDMC, the TFDMC, and the
MFDMC decreased linearly with an increase in ꢄ. In contrast,
"r of the DMC increased only slightly with ꢄ, suggesting that
molecular association, which cancels out dipole moments,
takes place at low ꢄ like acetic acid. Vectorial addition of the
dipole moments associated with the presence of electronega-
tive fluorine and oxygen atoms indicates that the resultant elec-
tric dipole moments of the DFDMC and the TFDMC molecule
are higher than that of the MFDMC molecule. "r of the
DFDMC was higher than that of the TFDMC. Peaks appearing
15
10
5
70 °C
10 °C
ε
TFDMC
DFDMC
MFDMC
DMC
70 °C
0
1.7
1.8
1
on H and 19F NMR spectra were shifted to higher and lower
2
nD
frequencies, respectively, when fluorine atoms were intro-
duced into DMC. The 1H and 19F NMR data indicate that suc-
cessive fluorination of the DMC decreases the electron density
of the hydrogen atom and increases that of the fluorine atom.
These findings suggest that the participation of the intermolecu-
2
Fig. 3. Comparison between "r and nD of TFDMC,
DFDMC, MFDMC, and DMC.
with an increase in ꢄ. Even "r of a nonpolar liquid is higher
than the square of nD, because "r can result from atomic
polarization as well as electronic polarization.
lar hydrogen bonding (C–H F–C) is a key factor determining
ꢄꢄꢄ
the order of "r. The number of hydrogen atoms that are attach-
ed to the same carbon atom as fluorine atoms decreases in
the following order: DFDMC (4) > TFDMC (3) > MFDMC
(2) > DMC (0). Partial fluorination of the DMC can increase
the polarity, though the extent depends on both the number of
fluorine atoms and the position where the substitution takes
place (symmetry). Dipole–dipole interactions involving the
intermolecular hydrogen bonding are responsible for the coop-
erative orientation of the partially fluorinated DMC molecules,
which results in the increase in "r at lower ꢄ. Successive fluo-
rination of the DMC can decrease the electron-pair donicity of
oxygen atoms in the OCOO moiety, and the low electron-pair
donicity can weaken solvation of cations such as lithium ion.
Figure 3 compares "r with the square of nD. The values of
"r of the four chain carbonates were higher than predicted by
the Maxwell-derived equation "r ¼ nD2. Orientation, atomic,
and electronic polarization can contribute to "r at a frequency
of 1 ꢅ 106 Hz, while nD measured at a frequency of 5:0876 ꢅ
1014 Hz (light of the D-line of the sodium spectrum, wave-
length ðꢆÞ ¼ 589:26 nm) may involve only electronic polariza-
tion.16,17 The amount of the orientation polarization decreases
Transport Properties. Figure 4 shows (a), (c) ꢁ and (b),
(d) ꢂ of the four chain carbonates as a function of ꢄ or thermo-
dynamic temperature (T). ꢁ and ꢂ decreased with an increase
in the temperature, and plots of log(ꢁ/mPa s) or log(ꢂ=10ꢃ6
m2 sꢃ1) vs. Tꢃ1 gave straight lines. ꢁ decreased in essentially
the same order as "r: DFDMC > TFDMC > MFDMC >
DMC. ꢁ can be regarded as an internal friction based on inter-
molecular forces and can be governed by the mass, rigidity,
size, and shape of the molecule as well as the dipole moment
and the static polarizability.
ꢂ is defined as the ratio of ꢁ to ꢀ of a fluid. Liquids of high
viscosity have high boiling points. The order of ꢂ near room
temperature agreed with that of the boiling points: DFDMC
(120 ꢁC) > MFDMC (108 ꢁC) > TFDMC (100 ꢁC) > DMC
(90 ꢁC). The order observed for MFDMC and TFDMC was
the reverse of that of ꢁ. The value of ꢂ of TFDMC was lowest
at high ꢄ. Since both ꢁ and ꢀ are correlated with the molecular
mass, the resulting ꢂ may not be appreciably affected by it.
Therefore, the difference in ꢂ becomes smaller than that in
ꢁ, and the order of ꢂ can change. ꢂ can more explicitly reflect

N. Nanbu et al.
Bull. Chem. Soc. Jpn. Vol. 80, No. 7 (2007) 1305
2
1
TFDMC
DFDMC
MFDMC
DMC
TFDMC
DFDMC
MFDMC
DMC
1
η
ν
0.5
(a)
(b)
0
20
40
60
80
0
20
40
60
80
θ
/ °C
θ
/ °C
T / K
T / K
350
300
350
300
0.2
η
2
TFDMC
DFDMC
MFDMC
DMC
TFDMC
DFDMC
MFDMC
DMC
0.2
ν
0
1
0.9
0.8
0.7
0
−0.2
−0.4
1
0.9
0.8
η
−0.2
−0.4
0.7
0.6
0.6
0.5
0.4
0.5
ν
(c)
(d)
0.4
3
3.2
3.4
3.6
3
3.2
3.4
3.6
T −1 / K−1
T −1 / K−1
Fig. 4. (a), (c) ꢁ and (b), (d) ꢂ of TFDMC, DFDMC, MFDMC, and DMC as a function of ꢄ or T from 10 ꢁC (283.15 K) to 70 ꢁC
(343.15 K).
the intermolecular forces. Partial fluorination of the DMC in-
creases the dipole–dipole interactions, because the net dipole
moment of the molecule increases. On the other hand, poly-
fluorination or perfluorination may decrease the dispersion or
London interactions because of low polarizability of the fluo-
rine atoms. A suitable balance of the intermolecular forces, in-
cluding the dipole–dipole, the dipole–induced-dipole, and the
induced-dipole–induced-dipole interactions (so-called van der
Waals forces), can determine the order of ꢂ.
A higher translational kinetic energy can allow inter-
molecular attractions to be overcome more easily, and the in-
ternal friction is reduced at high temperatures. The apparent
activation energy for viscosity (Ea;ꢁ), which was obtained from
the relation proposed by Andrade,18 was 16.10, 13.10, 12.87,
and 10.35 kJ molꢃ1 for DFDMC, TFDMC, MFDMC, and
DMC, respectively.
direct fluorination of DMC,13 we could not isolate it from the
reaction mixture. We found that the boiling point of the gem-
DFDMC was as low as 85 ꢁC.13 ꢂ of the TFDMC was lower
than that of the MFDMC over the ꢄ range investigated, as de-
scribed above. These findings support the idea that the bonding
of two fluorine atoms and an oxygen atom to the same carbon
atom can weaken the intermolecular forces and that ꢂ of the
gem-DFDMC may be very low.
Influence of Number Density of Molecules on Physical
Constants. The values of ꢀ, nD, "r, ꢁ, and ꢂ of the four chain
carbonates gradually decreased with increasing ꢄ except for
"r of DMC, which had the lowest polarity. As ꢄ increases,
the thermal motion of the molecules becomes vigorous. The
greater thermal motion results in a lower N. ꢀ is correlated
with both the molecular mass and N. The value of nD depends
on both ꢅe of the molecules and N. The molecular mass and ꢅe
are independent of ꢄ. Therefore, the ꢄ dependence of ꢀ and nD
is simply determined by that of N.
ꢀ
ꢁ
Ea;ꢁ
RT
ꢁ ¼ A exp
:
ð3Þ
ꢁ
Dipole moments and static polarizability are essential for
the interpretation of the intermolecular forces. These molecu-
lar properties rather than N may have a strong influence on "r,
ꢁ, and ꢂ of polar liquids. The greater thermal motion over-
comes the mutual orientating effects of the dipoles at high ꢄ.
The order of the Ea;ꢁ was also in accord with that of ꢁ. The
higher Ea;ꢁ of the partially fluorinated DMCs indicates that ꢁ
and ꢂ decrease rapidly at high temperatures.
A gem-difluoride of DMC, difluoromethyl methyl carbonate
(gem-DFDMC), in which two fluorine atoms and an oxygen
atom are attached to the same carbon atom, is isomeric with
the DFDMC. Although gem-DFDMC is also generated by
Conclusion
The use of the simple chain carbonates allows us to inves-

1306 Bull. Chem. Soc. Jpn. Vol. 80, No. 7 (2007)
Physical Constants
8
M. C. Smart, B. V. Ratnakumar, V. S. Ryan-Mowrey, S.
tigate the polar effect of successive fluorination on various
properties in detail. The trade-off between high electronega-
tivity (excellent electron withdrawal) and low polarizability
of fluorine atoms plays a significant role in determination of
the magnitude of the polar effect.
Surampudi, G. K. S. Prakash, J. Hu, I. Cheung, J. Power Sources
2003, 119–121, 359.
9
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