Physical properties of monofluorodimethyl carbonate

Article abstract of DOI:10.1246/cl.2004.338

Partial fluorination of solvents can improve various physical properties because of the polar effect. We have investigated the temperature dependence of relative permittivity (ε_r), viscosity (η), refractive index (n_D), and density (ρ) of monofluorodimethyl carbonate (MFDMC) over a range of 10 to 70°C and compared the physical properties with those of dimethyl carbonate (DMC). The ε_r, η, and ρ of the MFDMC are higher than those of the DMC, whereas the n_D becomes lower.

Full text of DOI:10.1246/cl.2004.338

338
Chemistry Letters Vol.33, No.3 (2004)
Physical Properties of Monofluorodimethyl Carbonate
Masahiro Takehara, Susumu Watanabe, Noritoshi Nanbuꢀ, Makoto Ue,y and Yukio Sasakiꢀ
Department of Applied Chemistry, Faculty of Engineering, Tokyo Polytechnic University
(Former name: Tokyo Institute of Polytechnics), 1583 Iiyama, Atsugi 243-0297
yMitsubishi Chemical Group Science and Technology Research Center, Inc., 8-3-1 Chuo, Ami, Inashiki 300-0332
(Received November 4, 2003; CL-031045)
Partial fluorination of solvents can improve various physical
T / K
305
350
properties because of the polar effect. We have investigated the
temperature dependence of relative permittivity ("r), viscosity
(ꢀ), refractive index (nD), and density (ꢁ) of monofluorodimeth-
yl carbonate (MFDMC) over a range of 10 to 70 ꢁC and com-
pared the physical properties with those of dimethyl carbonate
(DMC). The "r, ꢀ, and ꢁ of the MFDMC are higher than those
of the DMC, whereas the nD becomes lower.
10
8
viscosity (η)
η
kinematic viscosity (
MFDMC
ν)
0
−0.2
−0.4
1
0.9
MFDMC
DMC
DMC
6
ν
0.8
0.7
ν
ε
4
0.6
0.5
2
η
(a)
(b)
0.4
0
0
20
40
60
80
3
3.2
T −1 / 10−3 K−1
3.4
A fluorine atom is highly electronegative and shows a very
low electronic polarizability and high enthalpy of ionization.
Therefore, partially fluorinated solvents can exert the strong po-
lar effect on physical properties such as relative permittivity and
viscosity, as distinct from those of polyfluorinated or perfluori-
nated solvents. However, to our knowledge, there is no report
of the physical properties of partially fluorinated chain esters.
Dimethyl carbonate (DMC) is one of the low-viscosity chain es-
ters commonly used in such electrochemical energy storage de-
vices as lithium batteries.1–3 In the present paper, we report the
temperature dependence of relative permittivity ("r), viscosity
(ꢀ), refractive index (nD), and density (ꢁ) of monofluorodimeth-
yl carbonate (MFDMC), which we have newly developed, from
10 to 70 ꢁC. These physical properties are compared with those
of the DMC.
θ
/ °C
Figure 1. (a) Relative permittivity, "r, (b) viscosity, ꢀ, and (b) kine-
matic viscosity, ꢃ, of MFDMC and DMC as a function of temperature,
ꢄ, from 10 to 70 ꢁC.
the dipole–dipole interactions including the intermolecular hy-
drogen bonding in the MFDMC system is stronger than that in
the DMC system.
The electric dipole moment of the DMC is considerably
lower than those of cyclic esters such as ethylene carbonate
(EC) and propylene carbonate (PC). The cyclic nature of the
EC and the PC constrains –OCH2– moieties to align in a planar
geometry (cis orientation). Since the methoxy groups of the
DMC can readily rotate about the CO bond and avoid the steri-
cally hindered planar configuration, the two identical groups in
the molecule orient in the energetically more stable trans config-
uration.1,3 The lack of the planarity for the DMC molecule pro-
duces a partial cancellation of local electric dipole moments. The
partial cancellation results in very low polarity, namely the small
overall electric dipole moment and low "r, of the DMC. Since a
fluorine atom is highly electronegative, a local dipole moment
ascribable to a fluoromethoxy group, CH2FO–, in the MFDMC
molecule, would more than compensate for the partial cancella-
tion. Accordingly, the polarity of the MFDMC molecule be-
comes higher than that of the DMC molecule, and the dipole–di-
pole interactions including the intermolecular hydrogen bonding
can be stronger.
O
O
15% F2 / N2
5OC
CH3
C
CH3
CH3
C
CH2F
O
O
O
O
DMC
MFDMC
MFDMC was synthesized similarly to fluorinated ꢂ-butyro-
lactones4 by direct fluorination and purified by fractional distil-
lation at atmospheric pressure. We have isolated the MFDMC
from the fluorinated DMC sample in a 45% yield. Since this
yield was essentially the same as that of the MFDMC formed
by the direct fluorination of the DMC, almost all of the MFDMC
formed was successfully separated. The MFDMC was identified
by techniques of gas chromatography coupled with mass spec-
1
trometry (GC–MS analysis),5 elemental analysis,6 and H, 13C,
The ꢀ of both chain esters decreased with an increase of ab-
solute temperature, T, and plots of ln(ꢀ/mPa s) vs 1/T gave
straight lines. The ꢀ of MFDMC was higher than that of
DMC. The finding is in accord with a simple expectation based
on the increase of the "r, as distinct from fluorination of EC.10
The ꢀ of monofluoriated and difluorinated ECs is higher than
that of EC, but the "r becomes lower.
and 19F NMR spectroscopy.7 The purity of the MFDMC was de-
termined to be 99.7% by means of gas chromatography (GC-
1700, SHIMADZU). The apparatus and techniques for measure-
ments of relative permittivity, viscosity, density, and refractive
index are described elsewhere.8,9 The physical properties of
MFDMC and DMC were measured from 10 to 70 ꢁC.
The ꢀ can be regarded as an internal friction and be gov-
erned by the size, surface area, and shape of the molecule as well
as its polarity. In general, as the size and surface area of a mole-
cule increase, so too does the dispersion or London interaction
between the molecules. Thus, the larger size and surface area
of the MFDMC molecule can lead to the increase of the ꢀ in co-
Figure 1 shows the temperature dependence of (a) relative
permittivity, "r, (b) viscosity, ꢀ, and (b) kinematic viscosity,
ꢃ, of MFDMC and DMC. The "r of the MFDMC was higher
than that of the DMC and decreased linearly with temperature,
ꢄ. On the other hand, the "r of the DMC was almost independent
of the ꢄ over a range of 10 to 70 ꢁC. These findings indicate that
Copyright Ó 2004 The Chemical Society of Japan

Chemistry Letters Vol.33, No.3 (2004)
339
10
8
7.4
7.2
7
MFDMC
DMC
MFDMC
DMC
1.2
10 °C
1.36
6
70 °C
ε
1.1
4
ρ
1.34
6.8
6.6
2
MFDMC
DMC
1
(a)
(b)
1.32
0
0
20
40
60
80
0
20
40
60
80
1.8
1.85
2
θ
/ °C
θ
/ °C
nD
2
Figure 2. (a) Refractive index, nD, (b) density, ꢁ, and (b) the number
density of molecules, N, of MFDMC and DMC as a function of tem-
perature, ꢄ, from 10 to 70 ꢁC. The N was calculated from the ꢁ, molar
mass, and Avogadro’s constant.
Figure 3. Comparison of "r and nD of MFDMC and DMC over a
temperature range of 10 to 70 ꢁC.
DMC. As the temperature rises, the thermal motion of the mole-
cules becomes vigorous. The greater thermal motion overcomes
the mutual orientating effects of the dipoles at higher tempera-
tures, and the internal friction is reduced. Therefore, the "r, ꢀ,
and ꢁ can decrease. Since the N also decreases, the nD can be-
come lower.
operation with the higher polarity. The apparent activation ener-
gies for viscosity, Ea,ꢀ, obtained from the relation proposed by
Andrade11 were 12.87 and 10.35 kJ molꢂ1 with regard to the
MFDMC and the DMC, respectively. The higher ꢀ of the
MFDMC can account for the increase of the Ea,ꢀ. Liquids of high
viscosity have high boiling points. The boiling points of the
MFDMC and the DMC are 108 and 90 ꢁC, respectively.
The density of MFDMC was higher than that of DMC, as
can be seen from Figure 2(b). The ꢃ of MFDMC was essentially
the same as that of DMC at high temperatures, whereas the ꢃ of
the MFDMC was higher at low temperatures. This finding indi-
cates that the larger size of the MFOMC molecule makes them
difficult to move at low temperatures.
Figure 3 shows a comparison of "r and the square of nD. The
values of the "r of both chain esters were higher than those of the
nD2. The deviation of the "r from the relation expressed by "r ¼
2
nD can result from atomic and orientation polarization,13 be-
cause the "r and the nD are measured at different frequencies
of 1 ꢃ 106 Hz and 5:087 ꢃ 1014 Hz (for light of the D-line of
the sodium spectrum, wavelength ꢇ ¼ 589:3 nm), respectively.
In conclusion, we have investigated the temperature depend-
ence of "r, ꢀ, nD, and ꢁ of MFDMC from 10 to 70 ꢁC and have
compared the physical properties with those of DMC. The
MFDMC exerted the polar effect on the physical properties.
The "r, ꢀ, and ꢁ of the MFDMC were higher than those of the
DMC, whereas the nD became lower. It is also very intriguing
to investigate the physical properties of other fluorinated chain
esters systematically.
Figure 2 shows the temperature dependence of (a) refractive
index, nD, and (b) density, ꢁ, of MFDMC and DMC. Moreover,
the number density of molecules, N, i.e., the number of mole-
cules per unit volume, which was calculated from the ꢁ, molar
mass, and Avogadro’s constant, is depicted in the figure (b).
The ꢁ of the MFDMC was higher than that of the DMC. A flu-
orine atom makes the larger contribution to the mass of the
MFDMC molecule than to the volume. The molecular weights
of the MFDMC and the DMC are 108.07 and 90.08, respective-
ly. The synergism of the higher molecular weight and higher po-
larity of the MFDMC can result in the increase of the ꢁ.
Interestingly, the nD of the MFDMC was lower than that of
the DMC, even though the MFDMC showed the higher ꢁ. The
nD is a measure of the ability to bend (refract) light rays and is
related to both electronic polarizability, ꢅe, of the molecule
and the N. This is because the propagation of light through a me-
dium can be imagined to occur by the incident light inducing an
oscillating dipole moment, which then radiates light of the same
frequency. In spite of the larger molecular size, the average ꢅe of
the MFDMC molecule, 8:309 ꢃ 10ꢂ40 C2m2Jꢂ1 (average polar-
References and Notes
1
L. A. Dominey, in ‘‘Lithium Batteries,’’ ed. by G. Pistoia, Elsevier,
Amsterdam (1994), Chap. 4.
M. Morita, M. Ishikawa, and Y. Matsuda, in ‘‘Lithium Ion Batteries,’’ ed.
by M. Wakihara and O. Yamamoto, KODANSYA and WILEY-VCH,
Tokyo (1998), Chap. 7.
2
3
M. Salomon, H.-P. Lin, E. J. Plichta, and M. Hendrickson, in ‘‘Advances
in Lithium-Ion Batteries,’’ ed. by W. A. van Schalkwijk and B. Scrosati,
Kluwer Academic/Plenum Publishers, New York (2002), Chap. 11.
Y. Sasaki, R. Ebara, N. Nanbu, M. Takehara, and M. Ue, J. Fluorine
Chem., 108, 117 (2001).
4
5
6
7
GC–MS (CI) (m/z):þ109 [M+H]þ. GC–MS (EI) (m/z): 77 COOCH2Fþ
(4.33), 59 COOCH3 (84.25), 33 CH2Fþ (100).
Anal. Calcd. for C3H5FO3: C, 33.3; H, 4.7; F, 17.6%. Found: C, 33.4; H,
3.9; F, 17.5%.
1H NMR (1% TMS/CDCl3, 500.00 MHz): ꢈ 4.23 (s, 3H), 6.08 (d,
2JHF ¼ 51:5 Hz, 2H). 13C NMR (1% TMS/CDCl3, 125.65 MHz): ꢈ
0
izability ꢅe ¼ ꢅe=4ꢆ"0 ¼ 7:468 ꢃ 10ꢂ30 m3), obtained by Lor-
entz-Lorenz equation12 was slightly low0er than that of the DMC
molecule, 8:346 ꢃ 10ꢂ40 C2m2Jꢂ1 (ꢅe ¼ 7:501 ꢃ 10ꢂ30 m3).
The lower ꢅe of the MFDMC molecule can be ascribed to the
low electronic polarizability of the fluorine atom. In addition,
the N of the MFDMC was smaller than that of the DMC because
of the larger size of the MFDMC molecule. The small number of
the MFDMC molecules with the lower ꢅe is responsible for the
decrease of the nD. We would expect a similar argument to apply
to nD of polyfluorinated or perfluorinated solvents.
55.10, 96.97 (d, JCF ¼ 219:0 Hz), 154.68. 9F NMR (2% CF3COOD/
1
D2O, 470.40 MHz): ꢈ ꢂ158:05 (t, 2JFH ¼ 51:5 Hz).
Y. Sasaki, T. Koshiba, H. Taniguchi, and Y. Takeya, Nippon Kagaku
Kaishi, 1992, 140.
8
9
M. Handa, M. Kataoka, M. Wakaumi, and Y. Sasaki, Bull. Chem. Soc.
Jpn., 70, 315 (1997).
10 M. Kobayashi, T. Inoguchi, T. Iida, T. Tanioka, H. Kumase, and Y. Fukai,
J. Fluorine Chem., 120, 105 (2003).
11 E. N. Andrade, Nature, 125, 309 (1930).
12 P. W. Atkins and R. S. Friedman, in ‘‘Molecular Quantum Mechanics,’’
3rd ed., Oxford, New York (1997), Chap. 12.
The "r, ꢀ, ꢁ, and nD of the MFDMC and the DMC gradually
decreased with increasing temperature except the "r of the
13 K. Izutsu, in ‘‘Electrochemistry in Nonaqueous Solutioins,’’ WILEY-
VCH, Weinheim (2002), Chap. 1.
Published on the web (Advance View) March 5, 2004; DOI 10.1246/cl.2004.338