Extraction of polysaccharides from Japanese cedar using phosphonate-derived polar ionic liquids having functional groups

Article abstract of DOI:10.1246/bcsj.20160073

Extraction of polysaccharides from Japanese cedar using ionic liquids has been demonstrated. To this aim, eleven types of phosphonate ionic liquids have been synthesized, their properties investigated, and applied to biomass processing. All ionic liquids prepared display strong hydrogen-bonding characteristics of Kamlet-Taft parameters (β > 1.1) which enabled the effective extraction of polysaccharides from Japanese cedar. In particular, 15wt% of polysaccharides was extracted from Japanese cedar powder using 1-(3-methoxypropyl)-3-methyl-imidazolium ethyl ethylphosphonate. Since the ionic liquid is easily prepared using conventional reagents and might be applicable to large-scale reactions, it is expected that practical polysaccharide extraction using the ionic liquid might be possible from a wide variety of biomass resources.

Full text of DOI:10.1246/bcsj.20160073

Extraction of Polysaccharides from Japanese Cedar Using
Phosphonate-Derived Polar Ionic Liquids Having Functional Groups
Yukinobu Fukaya,*1 Ryo-ichi Asai,2 Shiho Kadotani,2 Toshiki Nokami,1,2 and Toshiyuki Itoh*1,2
1Center for Research on Green Sustainable Chemistry, Tottori University, 4-101 Koyama-minami, Tottori 680-8552
2Department of Chemistry and Biotechnology, Graduate School of Engineering, Tottori University,
4-101 Koyama-minami, Tottori 680-8552
E-mail: yuki-fukaya@chem.tottori-u.ac.jp, titoh@chem.tottori-u.ac.jp
Received: March 3, 2016; Accepted: April 30, 2016; Web Released: May 12, 2016
Yukinobu Fukaya
Yukinobu Fukaya was born in Tokyo, Japan, in 1978. He graduated from Tokyo University of Agriculture and
Technology and received his Ph.D. in 2008 from the same university under the supervision of Prof. Hiroyuki
Ohno. He has been an Associate Professor at Research Center on Green Sustainable Chemistry, Tottori
University since 2014.
Toshiyuki Itoh
Toshiyuki Itoh was born in Mie, Japan, in 1954. He graduated from Tokyo University of Education (B.S. 1976)
and recieved his Ph.D. degree from The University of Tokyo (1986, Prof. T. Mukaiyama), and has held posi-
tions at Colorado State University (Postdoc, 1990–1991, Prof. A. G. M. Barrett), Okayama University (1987–
2002), and Tottori University (2002–current). He is Professor of Chemistry and Director of Research Center on
Green Sustainable Chemistry, Tottori University. He has been awarded The Society of Synthetic Organic
Chemistry Award, Japan (2010) and The 8th Green and Sustainable Chemistry Award, Japan (2009).
Abstract
abundant renewable resources on this planet. These compo-
nents are scarcely soluble in conventional molecular liquids.
Since polysaccharides and lignin form supramolecular struc-
tures,2 it is difficult to dissolve them by conventional molecular
liquids and this allows only limited use of them.
Extraction of polysaccharides from Japanese cedar using
ionic liquids has been demonstrated. To this aim, eleven types
of phosphonate ionic liquids have been synthesized, their
properties investigated, and applied to biomass processing. All
ionic liquids prepared display strong hydrogen-bonding char-
acteristics of Kamlet-Taft parameters (¢ > 1.1) which enabled
the effective extraction of polysaccharides from Japanese cedar.
In particular, 15 wt % of polysaccharides was extracted from
Japanese cedar powder using 1-(3-methoxypropyl)-3-methyl-
imidazolium ethyl ethylphosphonate. Since the ionic liquid is
easily prepared using conventional reagents and might be
applicable to large-scale reactions, it is expected that practical
polysaccharide extraction using the ionic liquid might be
possible from a wide variety of biomass resources.
There has been a great deal of interest in ionic liquids (ILs)3
as potential solvents for cellulosic biomass.4,5 ILs are designer
liquids which have the potential of designable properties, such
as polarity and affinity with other compounds;6 this makes it
possible for us to design “polar” ILs that enable dissolution of
cellulose and cellulosic biomass. Multiple inter-chain hydrogen
bonds are known to make cellulose insoluble in conventional
molecular liquids.7 ILs precisely designed to display strong
hydrogen-bonding basicity have been revealed to disrupt the
hydrogen bond network of the cellulose.8 In regard to the
preparation of such polar ILs, chloride,5,9 carboxylate,10 and
phosphonate11 are recognized as candidates.12 We also estab-
lished that amino acid salts ILs could dissolve cellulose
well13,14 and a mixture of dimethyl sulfoxide (DMSO) and
N,N-diethyl-N-(2-methoxy)ethyl-N-methylammonium alanate
([N221ME][Ala])13 dissolved cellulose at room temperature.15
These polar ILs have been used for wide ranging purposes such
as energy-saving biomass processing,16 analysis of biomass
components,17 and so forth. The studies indicate that develop-
1. Introduction
As one of the fundamental technologies to realize “sustain-
able society”, research studies on the conversion of renewable
resources to functional materials and even energy are explo-
sively increasing today.1 Cellulosic biomass, which is com-
posed mainly of cellulose, hemicellulose and lignin, is the most
Bull. Chem. Soc. Jpn. 2016, 89, 879–886 | doi:10.1246/bcsj.20160073
© 2016 The Chemical Society of Japan | 879

ment of more polar ILs for cellulosic biomass is required to
achieve new technologies and methodologies in biomass
sciences.
stirred for 24 h. During the reaction, clear liquid was sepa-
rated from reaction media and the precipitate formed was
washed repeatedly with diethyl ether. The precipitate was dried
in vacuo at 50 °C to give 1-ethyl-3-methylimidazolium bro-
mide ([C2mim]Br) as white solid. [C2mim]Br was dissolved in
Milli Q water, and the resulting solution was passed through a
column filled with anion-exchange resin (Amberliteμ IRN-78)
to give 1-ethyl-3-methylimidazolium hydroxide ([C2mim]OH)
aqueous solution.
We herein turn our attention to phosphonate-type polar ILs
as solvents for extraction of polysaccharides from woody
biomass, Japanese cedar, because phosphonate ILs have been
reported to dissolve cellulose under mild conditions11 and
these, in particular, have wide structural diversity. Extraction of
polysaccharides from plant biomass, bran, was in fact demon-
strated using such ILs,18 while no systematic study has been
conducted.
Our area, Tottori, is famous for having a forest of beautiful
Japanese cedar that has been a producing center of high-quality
lumber used for housing for hundreds of years. However, the
forest industry in Tottori is now faced with a crisis of extinc-
tion due to low-cost imported lumber and the fact that the
population of this area has decreased more and more over the
years. Recently, more people have gradually reconsidered
using high-quality lumber made in Japan. But in order to pro-
duce high-quality lumber, it is essential to continuously remove
unnecessary trees until the forest has grown for 60-100 years.
Therefore, the development of a means to utilize wooden
wastes has strongly been needed. So we decided to investigate
an extracting method of polysaccharides from Japanese cedar
using ILs. With the aim of realizing extraction of polysaccha-
ride from woody biomass, we prepared phosphonate-type ILs
systematically by changing the combination of cations and
anions and investigated the effect of ion structures on their
physicochemical properties, focusing on their ability to
dissolve cellulose and polysaccharides in Japanese cedar.
To the aqueous solution of [C2mim]OH, an equivalent molar
amount of diethyl ethyl ethylphosphonate was added, and the
resulting mixture was stirred. After the pH of the reaction mix-
ture became neutral, water and ethanol were removed by evapo-
ration. The product was washed repeatedly with diethyl ether
and dissolved into ethanol, and the resulting solution was stirred
with active carbon. After removal of the active carbon by filtra-
tion, ethanol was removed by evaporation and the residue was
then dissolved in dichloromethane, and the resulting solution
was passed through a short column filled with neutral activated
alumina. The solvent was removed by evaporation, and the
resulting liquid was dried under reduced pressure at 80 °C for
12 h, yielding 1-ethyl-3-methylimidazolium ethyl ethylphos-
1
phonate (8) as a colorless liquid: H NMR (500 MHz, CDCl3):
¤ 1.14 (3H, q, J = 12.8 Hz, PCH2CH3), 1.23 (3H, t, J = 7.3,
POCH2CH3), 1.56 (3H, m, NCHCH3), 3.66 (2H, dd, J = 7.0 Hz,
PCH2CH3), 3.91 (2H, q, J = 6.9 Hz, NCH2CH3), 4.08 (3H, s,
NCH3), 4.39 (2H, dd, J = 7.5 Hz, POCH2), 7.33 (2H, d, J = 11
Hz, NCH=CHN), 10.86 (1H, s, NCHN). 13C NMR (125 MHz,
CDCl3): ¤ 8.46 (JC-P = 5.9 Hz, PCH2CH3), 15.61 (NCH2CH3),
17.11 (JC-P = 6.0 Hz, POCH2CH3), 20.36 (JC-P = 134 Hz,
PCH2CH3), 36.42 (NCH3), 45.02 (NCH2CH3), 58.56 (JC-P
=
2. Experimental
6.1 Hz, POCH2CH3), 120.96, 123.02, 139.78. HRMS (ESI-
TOF) m/z: [M+] calcd for C6H11N2, 111.0923; found, 111.0911.
2.1 Materials and Instruments.
1-Ethylimidazole and
¹
1-methylimidazole were purchased from Tokyo Chemical
Industry Co., Ltd. (TCI). Ethyl bromide, n-butyl bromide, n-
hexyl bromide, bromoethyl methyl ether, 3-chloromethoxy
propane, ethyl ethylphosphonate, ethyl phosphonate, ethyl
phosphoramidate, and ethyl benzylphosphonate were also
purchased from TCI, and used as received. Amberliteμ IRN-
78 was purchased from SUPELCO. Neutral activated alumina
m/z: [X ] calcd for C4H10O3P, 137.0368; found, 137.0366.
2.2.1 1-Ethyl-3-methylimidazolium Ethylphosphonate
(1):11a-11c 1H NMR (500 MHz, CDCl3): ¤ 1.26 (3H, t, J =
7.3 Hz, CH2CH3), 1.58 (3H, t, J = 7.5 Hz, POCH2CH3), 3.92
(2H, q, J = 7.4 Hz, PCH2CH3), 4.07 (3H, s, NCH3), 4.38
(2H, dd, J = 7.3, NCH2), 6.95 (1H, d, JPH = 597 Hz, PH), 7.27
(2H, m, NCH=CHN), 10.75 (1H, s, NCHN). 13C NMR (125
MHz, CDCl3): ¤ 15.58 (NCH2CH3), 16.81 (JC-P = 6.0 Hz,
POCH2CH3), 18.51 (NCH2CH3), 36.38 (NCH3), 45.00 (NCH2-
CH3), 59.16 (JC-P = 4.8 Hz, POCH2CH3), 121.55, 123.54,
138.46. HRMS (ESI-TOF) m/z: [M+] calcd for C6H11N2,
1
was purchased from Aldrich. The measurements of H NMR
and 13C NMR spectra were carried out on a JEOL JNM-500.
Electrospray ionization mass spectra (ESI-MS) were recorded
on a Thermo Scientific Exactive spectrometer. The amount of
water was confirmed by Karl Fischer coulometric titration on a
Kyoto Electronics MLC-610 DT. The differential scanning
calorimetry (DSC) measurements were conducted at a scanning
¹
111.0923; found, 111.0910. m/z: [M ] calcd for C2H6O3P,
109.0054; found, 109.0047.
2.2.2 1-Butyl-3-methylimidazolium Ethylphosphonate
¹1
rate for both heating and cooling of 5 °C min in the tem-
(2):11a
1H NMR (500 MHz, CDCl3): ¤ 0.96 (3H, t, J =
perature range ¹120 to 100 °C. Thermogravimetric analyses
(TGA) were carried out using a RIGAKU Thermo Plus EVO II
with a heating rate of 10 °C min¹1 from 25 to 500 °C under dry
argon gas. Visible spectrum was measured using a JASCO UV
550. Viscosity of ILs was measured using a Brookfield DV2-T
Viscometer at valuable temperature.
5.8 Hz, CH2CH3), 1.25 (3H, q, J = 4.0 Hz, POCH2CH3), 1.36
(2H, m, CH2CH2CH3), 1.86 (2H, m, NCH2CH2), 3.90 (2H, t,
J = 5.5 Hz, POCH2), 4.08 (3H, s, NCH3), 4.29 (2H, t, J =
6.75 Hz, NCH2), 6.95 (1H, d, JPH = 591 Hz, PH), 7.24 (1H, s),
7.34 (1H, s), 10.83 (1H, s, NCHN). 13C NMR (125 MHz,
CDCl3): ¤ 13.48 (NCH2CH2CH2CH3), 16.85 (JC-P = 7.5 Hz,
POCH2CH3), 19.52, 32.21, 36.48 (NCH3), 49.75 (NCH2CH3),
59.07 (POCH2CH3), 121.38, 123.04, 139.89. HRMS (ESI-
TOF) m/z: [M+] calcd for C8H15N2, 139.1237; found,
2.2 Preparation of ILs.
As a typical procedure for
preparing ILs, preparation of 1-ethyl-3-methylimidazolium
ethyl ethylphosphonate (8) is described as follows: to 1-methyl-
imidazole in toluene, an excess amount of ethyl bromide was
added at room temperature, and the resulting mixture was
¹
139.1224. m/z: [M ] calcd for C2H6O3P, 109.0054; found,
109.0047.
880 | Bull. Chem. Soc. Jpn. 2016, 89, 879–886 | doi:10.1246/bcsj.20160073
© 2016 The Chemical Society of Japan

2.2.3 1-n-Hexyl-3-methylimidazolium Ethylphosphonate
(3): 1H NMR (500 MHz, CDCl3): ¤ 0.88 (3H, t, J = 6.8 Hz,
CH2CH3), 1.25 (3H, t, J = 7.0 Hz, POCH2CH3), 1.31 (6H, m,
CH2CH2CH2CH3), 1.89 (2H, q, J = 7.3 Hz, NCH2CH2), 3.91
(2H, q, J = 7.3 Hz, POCH2CH3), 4.08 (3H, s, NCH3), 4.28
(2H, t, J = 7.5 Hz, NCH2), 6.98 (1H, d, JPH = 588 Hz, PH).
13C NMR (125 MHz, CDCl3): ¤ 13.92 (NCH2(CH2)4CH3),
16.86 (JC-P = 7.3 Hz, POCH2CH3), 22.38, 25.89, 30.24,
31.11, 36.35 (NCH3), 49.88 (NCH2CH2), 58.96 (JC-P = 4.8
Hz, POCH2CH3), 121.57, 123.38, 139.51. HRMS (ESI-TOF)
m/z: [M+] calcd for C10H19N2, 167.1550; found, 167.1535.
(NCH2), 59.96 (JC-P = 4.8 Hz, POCH2), 121.05, 123.20,
138.91. HRMS (ESI-TOF) m/z: [M+] calcd for C6H11N2,
111.0923; found, 111.0903. m/z: [X ] calcd for C2H7NO3P,
¹
124.0164; found, 124.0156.
2.2.8 1-Ethyl-3-methylimidazolium Ethyl (Methoxy-
methyl)phosphonate (9): 1H NMR (500 MHz, DMSO-d6):
¤ 1.05 (3H, t, J = 7.0 Hz, PCH2CH3), 1.41 (3H, t, J = 7.3 Hz,
NCH2CH3), 3.17 (2H, d, J = 8 Hz, PCH2OCH3), 3.22 (3H, s,
OCH2CH3), 3.67 (2H, q, J = 7.1 Hz, POCH2), 3.86 (3H, s,
NCH3), 4.20 (2H, dd, J = 7.2 Hz, NCH2), 7.72 (1H, s), 7.80
(1H, s), 9.37 (1H, s, NCHN). 13C NMR (125 MHz, CDCl3): ¤
15.62 (NCH2CH3), 17.17 (JC-P = 7.2 Hz, POCH2CH3), 36.45
(NCH3), 45.04 (NCH2CH3), 60.91 (JC-P = 13.2 Hz, PCH2-
OCH3), 60.28 (JC-P = 5.9 Hz, PCH2OCH3), 69.64 (JC-P = 13.2
Hz, POCH2CH3), 120.94, 123.02, 139.77. HRMS (ESI-TOF)
m/z: [M+] calcd for C6H11N2, 111.0923; found, 111.0912. m/z:
¹
m/z: [M ] calcd for C2H6O3P, 109.0054; found, 109.0047.
2.2.4 1-(2-Methoxyethyl)-3-methylimidazolium Ethyl-
phosphonate (4): 1H NMR (500 MHz, CDCl3): ¤ 1.27 (3H,
t, J = 7.3 Hz, POCH2CH3), 3.37 (3H, s, CH2CH2OCH3), 3.77
(2H, t, J = 5.0 Hz, NCH2CH2), 3.92 (2H, q, J = 7.3 Hz,
POCH2), 4.06 (3H, s, NCH3), 4.57 (2H, t, J = 4.8 Hz, NCH2),
6.97 (1H, d, JPH = 592 Hz, PH), 7.29 (1H, s), 7.42 (1H, s), 10.76
¹
[X ] calcd for C4H10O4P, 153.0317; found, 153.0316.
2.2.9 1-Ethyl-3-methylimidazolium Ethyl Benzylphospho-
nate (10): 1H NMR (500 MHz, CDCl3): ¤ 1.24 (3H, t, J = 7.0
Hz, PCH2CH3), 1.55 (3H, t, J = 7.5 Hz, NCH2CH3), 3.40 (3H,
s, PCH2OCH3), 3.60 (2H, d, J = 2.8 Hz, PCH2Ph), 3.71 (3H, s,
NCH3), 3.84 (2H, q, J = 11.3 Hz, NCH2CH3), 4.38 (2H, q, J =
11.3 Hz, POCH2CH3), 7.29 (1H, s), 7.33 (1H, s), 10.73 (1H, s,
NCHN). 13C NMR (125 MHz, CDCl3): ¤ 15.51 (NCH2CH3),
17.14 (JC-P = 6.0 Hz, POCH2CH3), 35.81 (JC-P = 51.5 Hz,
PCH2PH), 36.60 (NCH3), 44.67 (NCH2), 59.97 (JC-P = 14.8
Hz, POCH2), 120.82, 124.80, 124.83, 138.1 (JC-P = 8.3 Hz),
139.75. HRMS (ESI-TOF) m/z: [M+] calcd for C6H11N2,
(1H, s, NCHN). 13C NMR (125 MHz, CDCl3): ¤ 16.85 (JC-P
=
7.3 Hz, POCH2CH3), 36.39 (NCH2CH3), 49.72 (NCH2CH2),
58.98 (OCH3), 59.05 (JC-P = 10.8 Hz, POCH2CH3), 70.74
(NCH2CH2CH2OCH3), 122.32, 123.03, 139.75. HRMS (ESI-
TOF) m/z: [M+] calcd for C7H13N2O, 141.1029; found,
¹
141.1021. m/z: [M ] calcd for C2H6O3P, 109.0054; found,
109.0047.
2.2.5 1-(3-Methoxypropyl)-3-methylimidazolium Ethyl-
phosphonate (5): 1H NMR (500 MHz, CDCl3): ¤ 1.26 (3H,
t, J = 6.8 Hz, POCH2CH3), 2.19 (2H, q, J = 6.2 Hz, NCH2-
CH2CH2), 3.32 (3H, s, CH2CH2OCH3), 3.42 (2H, t, J = 5.6 Hz,
NCH2CH2CH2), 3.92 (2H, dd, J = 7.5 Hz, POCH2), 4.08 (3H,
¹
111.0923; found, 111.0912. m/z: [X ] calcd for C9H12O3P,
199.0524; found, 199.0521.
s, NCH3), 4.42 (2H, t, J = 7.3 Hz, NCH2), 6.95 (1H, d, JPH
=
2.2.10 1-(3-Methoxypropyl)-3-methylimidazolium Ethyl
Ethylphosphonate (11): 1H NMR (500 MHz, CDCl3): ¤ 1.14
(3H, dt, J = 6.1 Hz, POCH2CH3), 1.23 (3H, t, J = 7.0 Hz,
PCH2CH3), 1.60 (2H, m, NCH2CH2), 2.20 (2H, m, PCH2), 3.32
(3H, s, CH2CH2OCH3), 3.41 (2H, t, J = 5.8 Hz, NCH2CH2-
CH2OCH3), 3.92 (3H, m, POCH2), 4.10 (3H, s, NCH3), 4.30
(2H, t, J = 7.0 Hz, NCH2CH2CH2), 7.30 (1H, s), 7.45 (1H, s),
11.19 (1H, s, NCHN), 13C NMR (125 MHz, CDCl3): ¤ 8.61
(JC-P = 5.9 Hz, PCH2CH3), 17.10 (JC-P = 5.9 Hz, POCH2CH3),
20.46 (JC-P = 133 Hz, PCH2CH3), 30.24 (NCH2CH2CH2-
OCH3), 36.32 (NCH3), 47.02 (NCH2CH2CH2OCH3), 58.45
(NCH2CH2CH2OCH3), 59.37 (JC-P = 4.8 Hz, POCH2CH3),
68.40 (NCH2CH2CH2OCH3), 121.97, 122.81, 140.42. HRMS
(ESI-TOF) m/z: [M+] calcd for C8H15N2O, 155.1186; found,
594 Hz, PH), 7.24 (1H, s), 7.28 (1H, s), 10.68 (1H, s, NCHN).
13C NMR (125 MHz, CDCl3): ¤ 16.86 (JC-P = 6.0 Hz, POCH2-
CH3), 30.28 (NCH2CH2CH2OCH3), 36.56 (NCH3), 47.30
(NCH2CH2CH2OCH3), 59.00 (JC-P = 44.4 Hz, POCH2CH3),
68.50 (NCH2CH2CH2OCH3), 122.07, 122.63, 139.85. HRMS
(ESI-TOF) m/z: [M+] calcd for C8H15N2O, 155.1186; found,
¹
155.1077. m/z: [M ] calcd for C2H6O3P, 109.0054; found,
109.0046.
2.2.6 1-(2-Phenoxyethyl)-3-methylimidazolium Ethyl-
phosphonate (6): 1H NMR (500 MHz, CDCl3): ¤ 1.24 (3H,
t, J = 7.3 Hz, POCH2CH3), 3.91 (2H, q, J = 7.3 Hz, POCH2),
4.01 (3H, s, NCH3), 4.36 (2H, t, J = 4.8 Hz, NCH2CH2),
4.82 (2H, t, J = 4.8 Hz, NCH2), 6.87 (2H, d, J = 8.5 Hz,
CHCHCH), 6.96 (1H, t, J = 7.5 Hz, CHCHCH), 6.99 (1H, d,
¹
155.1170. m/z: [X ] calcd for C4H10O3P, 137.0368; found,
J
PH = 588 Hz, PH), 7.50 (1H, s), 7.64 (1H, s), 10.8 (1H, s,
NCHN). 13C NMR (125 MHz, CDCl3): ¤ 16.85 (JC-P = 7.3 Hz,
POCH2CH3), 36.45 (NCH3), 49.32 (NCH2CH2), 59.13 (JC-P
137.0368.
2.3 Measurements of the Kamlet-Taft Parameters.19 The
Kamlet-Taft parameters of ILs were determined as follows.
Spectroscopic grade solvatochromic dyes, 2,6-dichloro-4-
(2,4,6-triphenyl-1-pyridinio)-phenolate (Reichardt’s dye #33)
(from Fluka), 4-nitroaniline (from Tokyo Chemical Ind. Co.,
Ltd), and N,N-diethyl-4-nitroaniline (from Kanto Chem.), were
used as received. A concentrated dry methanol solution of the
dye was added to the ILs, and the methanol was removed under
reduced pressure at 40 °C. To prevent dye aggregation, the dye
concentration in any series of ILs was chosen to be low but
sufficient to allow an absorbance greater than 0.15.
=
3.6 Hz, POCH2CH3), 66.6 (NCH2CH2OPh), 114.47, 121.85,
122.51, 123.13, 129.8, 139.78, 157.56. HRMS (ESI-TOF) m/z:
[M+] calcd for C12H15N2O, 203.1186; found, 203.1172. m/z:
¹
[M ] calcd for C2H6O3P, 109.0054; found, 109.0047.
2.2.7 1-Ethyl-3-methylimidazolium Ethyl Phosphor-
amidate (7): 1H NMR (500 MHz, CDCl3): ¤ 1.22 (3H, t,
J = 6.3, OCH2CH3), 1.54 (3H, t, J = 6.9 Hz, NCH2CH3), 3.92
(2H, m, PCH2CH3), 4.10 (3H, m, NCH3), 4.38 (2H, d, J =
7.5 Hz, OCH2CH2), 7.43 (1H, s), 7.49 (1H, s), 11.0 (1H, s,
NCHN). 13C NMR (125 MHz, CDCl3): ¤ 15.67 (NCH2CH3),
16.88 (JC-P = 8.4 Hz, POCH2CH3), 36.38 (NCH3), 44.93
These dye solutions were placed in quartz cells with an
optical path length of 1 mm. The temperature of the quartz
Bull. Chem. Soc. Jpn. 2016, 89, 879–886 | doi:10.1246/bcsj.20160073
© 2016 The Chemical Society of Japan | 881

cell was maintained at 25 °C. Once the maximum absorption
wavelength (-max) was determined, the Kamlet-Taft parameters
(¡: hydrogen-bonding acidity, ¢: hydrogen-bonding basic-
ity, and ³ꢀ: dipolarity) were calculated from the following
equations:
solution property versus micro crystalline cellulose. Then we
attempted to use them for the extraction of polysaccharide from
Japanese cedar. Their thermal properties are summarized in
Table 1. DSC analysis revealed that these ILs showed only
glass-transition points. No crystallization was observed even
after storing them at ¹20 °C for several weeks, indicating that
the ILs existed in a stable super cooled state. TGA showed
that these ILs were stable up to 220 °C; it was thus found that
these phosphonate type ILs are more thermally stable than ILs
derived from carboxylates.20
¯ðdyeÞ ¼ 1=ð-maxðdyeÞ ꢁ 10ꢂ4
Þ
ð1Þ
ETð30Þ ¼ 0:9986½28592=-maxðReichardt’s dye #33Þꢃ
ꢂ 8:6878
ð2Þ
ꢀ
³ ¼ 0:314½27:52 ꢂ ¯ðN,N-diethyl-4-nitroanilineÞꢃ ð3Þ
ꢀ
¡ ¼ 0:0649ETð30Þ ꢂ 2:03 ꢂ 0:72³
¢ ¼ ½1:035¯ðN,N-diethyl-4-nitroanilineÞ þ 2:64
ꢂ ¯ð4-nitroanilineÞꢃ=2:80
ð4Þ
We next evaluated their hydrogen-bonding ability using
the Kamlet-Taft parameters (¡; hydrogen-bonding acidity, ¢;
hydrogen-bonding basicity, and ³*; dipolarity) and the results
are shown in Table 1.14 These ILs showed moderate ¡ value
which was caused by the presence of an acidic hydrogen atom
at the 2 position of the imidazolium ring.21 As for ¢ value, the
series of ILs prepared here had greater hydrogen-bonding
basicity than conventional ILs. The ¢ value of ILs generally
depends mainly on the species of anions, however, this value
also depends on the cation structure. Among these ILs, IL 5
showed the highest ¢ value and the lowest observed for IL 1.
It has been reported that viscosity of ILs is one of the
important factors in dissolving cellulose and other biomass,
hence, we then measured that element of these ILs. Figure 2
shows the temperature dependence of their viscosity. The
viscosity increased with increasing alkyl chain length and the
lowest value was obtained for IL 1. Moreover, viscosity was
slightly lower for IL 4 than for IL 2, and IL 5 also had much
lower viscosity than IL 2. This should be explicable in terms of
size of the cation, van der Waals interaction, and Tg value.
Among these ILs, IL 6 showed the highest viscosity among the
ethylphosphonate salts studied here. This might be due to the
relatively strong interaction between phenyl groups. However,
viscosity of these ILs dropped with rising temperature and all
showed similar values above 90 °C (Figure 2).
ð5Þ
2.4 Dissolution of Cellulose. Suspensions of microcrystal-
line cellulose (Cellulose powder C, ADVANTEC; 2.0 wt %) in
dried ILs were prepared and the mixtures were stirred for 1 h
at each temperature until the solution became a homogeneous
clear solution by heating from 25 to 100 °C in 5 °C increments
under nitrogen in a temperature controlled oil bath. The lowest
temperature to give a clear solution was recorded as the dis-
solution temperature.
2.5 Extraction of Polysaccharides from Japanese Cedar.
A powder of Japanese cedar (0.11 g, particle diameter 53-112
¯m,) was added to dry ILs (2.0 g), and the resulting mix-
tures were stirred at 100 °C for 24 h under dry nitrogen. After
allowing it to cool to rt, the insoluble part was filtered off and
to the resulting filtrate (X g) was added hot ethanol to form a
precipitate; the precipitate was then washed repeatedly with
hot ethanol and dried under reduced pressure at 70 °C to give
the polysaccharide samples (Y g). The degree of extraction was
calculated from the following equation:
Degree of extraction ð%Þ ¼ ½Y=ðX ꢂ YÞ ꢁ 2:0ꢃ=0:11 ꢁ 100
ð6Þ
3. Results and Discussion
We then evaluated the solubility of these ILs versus micro
crystalline cellulose; Table 2 shows dissolution temperature of
the cellulose in them. We mixed cellulose powder with each IL
at concentrations of 2.0 wt %, and the resulting mixtures were
stirred at 25 °C. ILs 1, 2, 4, and 5 successfully dissolved
cellulose at 25 °C. On the other hand, complete dissolution
of cellulose in IL 3 and IL 6 required heating at 50 and
60 °C, respectively. The solubility of polysaccharides generally
depends on the ¢ value of the ILs. However, the dissolution
3.1 Effect of Cation Structures. First, we prepared six
types of ethylphosphonate salts coupled with alkylimidazolium
cations that have different side chains as shown in Figure 1; we
then investigated the effect of the side chain on the imidazo-
lium ring with their physicochemical properties and the dis-
Table 1. Physicochemical properties of ethylphosphonate
salts
Kamlet-Taft parameters
ILs
Tg/°Ca)
T
dec/°Cb)
at 25 °C
¡
¢
³*
1
2
3
4
5
6
¹74
¹68
¹66
¹63
¹70
¹31
266
239
221
234
250
228
0.55
0.52
0.54
0.52
0.46
0.43
1.02
1.05
1.07
1.05
1.12
1.03
1.02
1.04
0.95
1.04
1.02
1.06
Figure 1. List of ethylphosphonate salts prepared in this
study.
a) Temperature at signal peak. b) Temperature for 10%
weight loss.
882 | Bull. Chem. Soc. Jpn. 2016, 89, 879–886 | doi:10.1246/bcsj.20160073
© 2016 The Chemical Society of Japan

Figure 3. List of phosphonate salts prepared in this study.
well known that ILs with lower viscosity allow good poly-
saccharide extraction because of better dispersion in ILs. Since
IL 1 had the lowest viscosity, we anticipated that this IL might
show better extraction. However, the degree of extraction of
polysaccharides from Japanese cedar powder was independent
of their viscosity. No relationship was observed between the IL
viscosity and the degree of extraction because we examined the
extraction experiment from Japanese cedar conducted at 100 °C
with stirring for 24 h: their viscosity thus might not influence
the extraction under these conditions. On the other hand, the
degree of extraction of polysaccharides from Japanese cedar
strongly depended on the ¢ value of their ILs. IL 5 which
has the highest hydrogen-bonding activity (¢ value = 1.12)
showed the best extraction of polysaccharides from Japanese
cedar.
3.2 Effect of Anion Structure. The cation structure of ILs
has now been revealed to affect their physicochemical prop-
erties and the dissolution ability of polysaccharides and ILs
with greater hydrogen-bonding basicity (¢ value) successfully
extracted polysaccharides from Japanese cedar powder, though
this value strongly depends on the anion structure. In fact, we
found that the cation structure significantly affected the cellu-
lose dissolution property for amino acid ILs.13 Hence, we next
investigated the cellulose dissolution ability of four 1-ethyl-3-
methylimidazolium salts (7-10) coupled with the phosphonates
shown in Figure 3.
/°C
Figure 2. Temperature dependence of viscosity.
Table 2. Solubility of the model cellulose and the degree of
extraction of polysaccharides from Japanese cedar
Dissolution temp.
/°C
Degree of extraction
/%
ILs
1
2
3
4
5
6
25
25
50
25
25
60
5.4
7.3
7.1
8.8
13.3
6.2
temperature of cellulose in the ILs evaluated here did not
directly depend on the ¢ value. Previous studies have revealed
that ILs with sufficient ¢ value to dissolve cellulose, the
dissolution temperature over limited time depends on their
viscosity.11 IL 3 and IL 6 had higher viscosity than others
evaluated here; cellulose powder dispersed more easily in
lower viscosity ILs, so that higher dissolution temperature
might be observed in IL 3 and IL 6 over short mixing time.
From these results, it was anticipated that these ILs might
allow extraction of polysaccharides from Japanese cedar.
Hence, we next evaluated them as solvents for such extraction
by mixing the cedar powder with the ILs at concentrations of
5 wt % at 100 °C for 24 h with stirring. After being allowed to
cool to rt, the remaining insoluble portion was removed by
filtration, and excess ethanol was added to the filtrate with con-
tinuous stirring. The resulting precipitate was collected by a
second filtration and washed repeatedly with hot ethanol to
remove residual ILs. The extracted materials were analysed
using FT-IR and NMR, and the results indicated that the
extracted materials were a mixture of cellulose, hemicellulose,
and a slight amount of lignin (Figures S1 and S2 in ESI),
though it was not possible to determine the ratio of each
contents.
Among the series of 1-ethyl-3-methylimidazolium salts,
only IL 7 was obtained as a solid at room temperature and
showed a melting point at 85 °C. This high melting temperature
might be due to the strong interaction between phosphoamide
groups. Since IL 7 had a high melting point, further inves-
tigation on it was cancelled. On the other hand, ILs 8-10 are
liquids at room temperature and show only a glass-transition
temperature. They remained liquids even after being kept at
¹5 °C for several weeks, indicating they are in a super cooled
state at room temperature. Their TGA analysis showed that
they are stable up to 250 °C.
The polarity of the ILs prepared here was estimated via the
Kamlet-Taft parameters. Table 3 also lists the Kamlet-Taft
parameters of the series of ILs. All the ILs 8-10 studied herein
showed strong hydrogen-bonding characteristics. The ¢ value
of newly developed 1-ethyl-3-methylimidazolium salts was
over 1.12, greater than those of 1-ethyl-3-methylimidazolium
ethylphosphonate (1).11a As described above, ethylphosphonate
anion has greater hydrogen-bonding basicity. Because the
series of anions studied here have the same basic unit structure
([(EtO)(R)PO2]), the disparity among ¢ values of these ILs can
be explained by the difference in the electron-releasing capa-
bility of their side chains.
The extraction degree of polysaccharides from cedar
depends on the cation structure. For instance, this degree was
influenced by the cation structure of the ILs in the follow-
ing value order: IL 1 (5.4%) < IL 6 (6.2%) < IL 3 (7.1%) <
IL 2 (7.3%) < IL 4 (8.8%) < IL 5 (13.3%). As mentioned, it is
As seen in Figure 4, substitution of the ether group and alkyl
group on anionic parts resulted in the increase of their viscos-
ity. The highest viscosity was recorded for IL 10. These results
might be attributable to the increased interaction of polar
groups and the size of ions.
Bull. Chem. Soc. Jpn. 2016, 89, 879–886 | doi:10.1246/bcsj.20160073
© 2016 The Chemical Society of Japan | 883

Table 3. Physicochemical properties of ethylphosphonate
salts
Kamlet-Taft
parameters at 25 °C
Tg
/°Ca)
Tm
/°Ca)
Tdec
/°Cb)
ILs
¡
¢
³*
c)
7
8
9
®
85
250
272
267
258
Not measured
1.16
c)
¹60
¹62
¹33
®
®
0.52
0.46
0.42
1.02
1.02
1.02
c)
1.14
1.12
c)
10
®
a) Temperature at signal peak. b) Temperature for 10% weight
loss. c) Not detected.
Figure 5. Relationship of ¢ value between the degree of
extraction of the ILs.
Figure 6. Chemical structure of IL 11.
Table 5. Physicochemical properties of 1-(3-methoxyprop-
yl)-3-methylimidazolium ethyl ethylphosphonate (11)
Kamlet-Taft parameters
at 25 °C
IL
Tg/°Ca)
¹63
T
dec/°Cb)
/°C
¡
¢
³*
Figure 4. Temperature dependence of viscosity.
11
2.39
0.49
1.21
0.95
Table 4. Solubility of the model cellulose and the degree of
extraction of polysaccharides from Japanese cedar
a) Temperature at signal peak. b) Temperature for 10% weight
loss.
Dissolution temp
/°C
Degree of extraction
/%
ILs
of anion structures, the degree of extraction is influenced more
by the cation structure. This difference might be explained
by compatibility and the affinity of side chain of imidazolium
cation to the polysaccharide-lignin supramolecular complex in
Japanese cedar powder.
8
9
10
25
25
50
7.7
7.0
6.5
Considering the above mentioned tendency, we prepared 1-
(3-methoxypropyl)-3-methylimidazolium ethyl ethylphospho-
nate (11) shown in Figure 6. It was obtained as a liquid at room
temperature. From the results of DSC analysis, IL 11 was
revealed to show only a glass transition at ¹63 °C, indicating a
stable super cooling state. TGA analysis revealed that IL 11 is
thermally stable up to 239 °C. It exhibits strong hydrogen-
bonding characteristics, displaying the highest ¢ value of 1.21
among ILs evaluated in this study (Table 5).
As expected, we succeeded in extracting polysaccharides
from Japanese cedar using IL 11 (Figure 7). The degree of
extraction of IL 11 reached ca. 15% at 100 °C, this is three
times higher than that of IL 1. NMR spectra of this after extrac-
tion experiments were examined to confirm the stability of the
newly designed IL 11, and the results confirm that there was
no structural change in it during the polysaccharide extrac-
tion process (see ESI). This observation strongly indicates
that IL 11 can be recycled and reused efficiently in biomass
processing.
All these new ILs 8-10 dissolved cellulose well under mild
conditions and ILs 8 and 9 dissolved it even at room temper-
ature (Table 4). However, IL 10 required heating at 50 °C to
obtain a homogeneous solution of cellulose. This might be due
to the higher viscosity of IL 10 than that of other ILs evaluated
herein. In regard to the degree of extraction of polysaccharides
from Japanese cedar, there are slight differences according to
the anion structure: the degree of extraction is highest for IL 8
and lowest for IL 10. With increasing ¢ value, the degree of
extraction gradually increased from 5.3 to 7.7%.
As mentioned, the degree of extraction of polysaccharides
from Japanese cedar is related to the Kamlet-Taft ¢ value.
Figure 5 shows the relation between the degree of extraction
from Japanese cedar and the Kamlet-Taft ¢ value; ILs with
high ¢ value had good capacity to extract polysaccharides from
Japanese cedar. However, it should be noted that the Kamlet-
Taft ¢ value is not the only determinant of the degree of
extraction. As seen in this Figure, compared to the influence
884 | Bull. Chem. Soc. Jpn. 2016, 89, 879–886 | doi:10.1246/bcsj.20160073
© 2016 The Chemical Society of Japan

1002/9783527621194. b) R. D. Rogers, K. R. Seddon, Science
2003, 302, 792.
4
Reviews see. a) P. Mäki-Arvela, I. Anugwom, P. Virtanen,
R. Sjöholm, J. P. Mikkola, Ind. Crops Prod. 2010, 32, 175. b) T.
Itoh, Design of Ionic Liquids for Cellulosed Dissolution, in
Production of Biofuels and Chemicals with Ionic Liquids, Biofuels
and Biorefineries, ed. by Z. Fang, R. L. Smith, Jr., X. QI, Springer,
New York, Vol. 1, pp. 91-106, 2014. doi:10.1007/978-94-007-
7711-8_4. c) H. Miyafuji, J. Wood Sci. 2015, 61, 343. d) K. C.
Badgujar, B. M. Bhanage, Bioresour. Technol. 2015, 178, 2. e) S.
Peleteiro, S. Rivas, J. L. Alonso, V. Santos, J. C. Parajó, J. Agric.
Food Chem. 2015, 63, 8093.
5
The first example of cellulose dissolution in an IL: R. P.
Swatloski, S. K. Spear, J. D. Holbrey, R. D. Rogers, J. Am. Chem.
Soc. 2002, 124, 4974.
6
a) P. Bonhôte, A.-P. Dias, N. Papageorgiou, K.
Kalyanasundaram, M. Grätzel, Inorg. Chem. 1996, 35, 1168.
b) C. Reichardt, Green Chem. 2005, 7, 339. c) L. Crowhurst, P. R.
Mawdsley, J. M. Perez-Arlandis, P. A. Salter, T. Welton, Phys.
Chem. Chem. Phys. 2003, 5, 2790. d) P. G. Jessop, D. A. Jessop,
D. Fu, L. Phan, Green Chem. 2012, 14, 1245.
/°C
Figure 7. Temperature dependence of the degree of
extraction.
7
717.
8
T. Kondo, J. Polym. Sci., Part B: Polym. Phys. 1997, 35,
4. Conclusion
a) R. C. Remsing, R. P. Swatloski, R. D. Rogers, G. Moyna,
Chem. Commun. 2006, 1271. b) D. A. Fort, R. C. Remsing, R. P.
Swatloski, P. Moyna, G. Moyna, R. D. Rogers, Green Chem. 2007,
9, 63.
In this study we prepared a series of novel highly polar
phosphonate ILs and investigated their dissolution properties
of cellulosic biomass. We have established that 1-(3-meth-
oxypropyl)-3-methylimidazolium diethylphosphonate (11) dis-
played higher hydrogen-bonding basicity (¢ value 1.21) and
most effectively extracted polysaccharides from Japanese cedar
(15 wt %). Since IL 11 is easily prepared using conventional
reagents and might be applicable to large-scale reactions, it is
expected that practical polysaccharide extraction using this IL
might be possible from a wide variety of biomass resources.
9
a) M. B. Turner, S. K. Spear, J. D. Holbrey, R. D. Rogers,
Biomacromolecules 2004, 5, 1379. b) H. Zhang, J. Wu, J. Zhang, J.
He, Macromolecules 2005, 38, 8272. c) P. Mäki-Arvela, I.
Anugwom, P. Virtanen, R. Sjöholm, J. P. Mikkola, Ind. Crops
Prod. 2010, 32, 175. d) L. Wei, K. Li, Y. Ma, X. Hou, Ind. Crops
Prod. 2012, 37, 227. e) A. Abdulkhani, E. H. Marvast, A. Ashori,
A. N. Karimi, Carbohydr. Polym. 2013, 95, 57. f) S. S. Mohtar,
T. N. Z. Tengku Malim Busu, A. M. Md Noor, N. Shaari, N. A.
Yusoff, M. A. Bustam@Khalil, M. I. Abdul Mutalib, H. B. Mat,
Bioresour. Technol. 2015, 192, 212.
10 a) Y. Fukaya, A. Sugimoto, H. Ohno, Biomacromolecules
2006, 7, 3295. b) B. Kosan, C. Michels, F. Meister, Cellulose
2008, 15, 59. c) D. G. Raut, O. Sundman, W. Su, P. Virtanen, Y.
Sugano, K. Kordas, J.-P. Mikkola, Carbohydr. Polym. 2015, 130,
18. d) Q. Hou, W. Li, M. Ju, L. Liu, Y. Chen, Q. Yang, J. Wang,
Carbohydr. Polym. 2015, 133, 517. e) M. Sharma, J. P. Chaudhary,
D. Mondal, R. Meena, K. Prasad, Green Chem. 2015, 17, 2867.
11 a) Y. Fukaya, K. Hayashi, M. Wada, H. Ohno, Green Chem.
2008, 10, 44. b) N. Kamiya, Y. Matsushita, M. Hanaki, K.
Nakashima, M. Narita, M. Goto, H. Takahashi, Biotechnol. Lett.
2008, 30, 1037. c) D. Zhao, H. Li, J. Zhang, L. Fu, M. Liu, J. Fu, P.
Ren, Carbohydr. Polym. 2012, 87, 1490.
The present work was supported by JSPS KAKHNHI
KIBAN (A) Grant Number (No. 26241030) and WAKATE (B)
Grant Number (No. 26810096).
Supporting Information
13C NMR and IR spectra of extracts and microcrystalline cel-
1
lulose. H NMR spectra of IL 11 (recycled and the fresh one).
1H and 13C NMR spectra of IL 1-IL 11, and ESI-MS spectra
of IL 8-IL 11. This material is available on http://dx.doi.org/
10.1246/bcsj.20160073.
References
1
Reviews see. a) Cellulose Derivatives: Modification,
12 Selected examples for extraction of polysaccharides from
biomass using ILs see. a) I. Kilpeläinen, H. Xie, A. King, M.
Granstrom, S. Heikkinen, D. S. Argyropoulos, J. Agric. Food
Chem. 2007, 55, 9142. b) X.-D. Hou, T. J. Smith, N. Li, M.-H.
Zong, Biotechnol. Bioeng. 2012, 109, 2484. c) A. Brandt, J.
Gräsvik, J. P. Hallett, T. Welton, Green Chem. 2013, 15, 550. d) P.
Verdía, A. Brandt, J. P. Hallett, M. J. Ray, T. Welton, Green Chem.
2014, 16, 1617. e) L. Chen, M. Sharifzadeh, N. Mac Dowell, T.
Welton, N. Shah, J. P. Hallett, Green Chem. 2014, 16, 3098. f) P.
Yan, Z. Xu, C. Zhang, X. Liu, W. Xu, Z. C. Zhang, Green Chem.
2015, 17, 4913.
Characterization, and Nanostructures, ACS Symposium Series
688, ed. by T. H. Heinze, W. G. Glasser, American Chemical
Society, Washington, DC, 1997. doi:10.1021/bk-1998-0688.
b) M. E. Himmel, S.-Y. Ding, D. K. Johnson, W. S. Adney,
M. R. Nimlos, J. W. Brady, T. D. Foust, Science 2007, 315, 804.
c) A. J. Ragauskas, C. K. Williams, B. H. Davison, G. Britovsek, J.
Cairney, C. A. Eckert, W. J. Frederick, Jr., J. P. Hallett, D. J.
Leak, C. L. Liotta, J. R. Mielenz, R. Murphy, R. Templer, T.
Tschaplinski, Science 2006, 311, 484.
2
3
P. Zugenmaier, Prog. Polym. Sci. 2001, 26, 1341.
Reviews see. a) Ionic Liquids in Synthesis, ed. by P.
13 K. Ohira, Y. Abe, M. Kawatsura, K. Suzuki, M. Mizuno, Y.
Amano, T. Itoh, ChemSusChem 2012, 5, 388.
Wassersheid, T. Welton, Wiley-VCH, Weinheim, 2008. doi:10.
Bull. Chem. Soc. Jpn. 2016, 89, 879–886 | doi:10.1246/bcsj.20160073
© 2016 The Chemical Society of Japan | 885

14 Y. Hamada, K. Yoshida, R. Asai, S. Hayase, T. Nokami, S.
Izumi, T. Itoh, Green Chem. 2013, 15, 1863.
15 K. Ohira, K. Yoshida, S. Hayase, T. Itoh, Chem. Lett. 2012,
41, 987.
16 T. V. Doherty, M. Mora-Pale, S. E. Foley, R. J. Linhardt,
J. S. Dordick, Green Chem. 2010, 12, 1967.
17 a) Y. Fukaya, A. Sugimoto, H. Ohno, Biomacromolecules
2006, 7, 3295. b) B. Kosan, C. Michels, F. Meister, Cellulose
2008, 15, 59.
18 Recent examples see a) P. Yan, Z. Xu, C. Zhang, X. Liu, W.
Xu, Z. C. Zhang, Green Chem. 2015, 17, 4913. b) D. Glas, C.
Van Doorslaer, D. Depuydt, F. Liebner, T. Rosenau, K. Binnemans,
D. E. De Vos, J. Chem. Technol. Biotechnol. 2015, 90, 1821.
19 a) M. J. Kamlet, R. W. Taft, J. Am. Chem. Soc. 1976, 98,
377. b) T. Yokoyama, R. W. Taft, M. J. Kamlet, J. Am. Chem. Soc.
1976, 98, 3233. c) R. W. Taft, M. J. Kamlet, J. Am. Chem. Soc.
1976, 98, 2886. d) M. J. Kamlet, J. L. Abboud, R. W. Taft, J. Am.
Chem. Soc. 1977, 99, 6027.
20 R. E. Del Sesto, C. Corley, A. Robertson, J. S. Wilkes,
J. Organomet. Chem. 2005, 690, 2536.
21 a) T. L. Amyes, S. T. Diver, J. P. Richard, F. M. Rivas, K.
Toth, J. Am. Chem. Soc. 2004, 126, 4366. b) A. M. Magill, K. J.
Cavell, B. F. Yates, J. Am. Chem. Soc. 2004, 126, 8717. c) S.
Tsuzuki, H. Tokuda, K. Hayamizu, M. Watanabe, J. Phys. Chem. B
2005, 109, 16474.
886 | Bull. Chem. Soc. Jpn. 2016, 89, 879–886 | doi:10.1246/bcsj.20160073
© 2016 The Chemical Society of Japan