環境物質化学
２００５年前期 ＃５−９(５)常温溶融塩（イオン液体）はグリーンか？
(５)常温溶融塩（イオン液体）はグリーンか？

垣内 隆（基礎エネルギー化学講座・機能性材料化学分野）
http://fm.ehcc.kyoto-u.ac.jp/japanese.html

Ionic liquids: Not so green?

C&EN, April 28,2002 page 4

C&EN has devoted a number of articles to ionic liquids and their applications. In the article by Michael Freemantle(C&EN, March 4, page 38) as well as other previous articles, ionic liquids have been called "green solvents" and"environmentally friendly." I strongly object to this classification.
The solvents in question--for example, 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6])--arenonvolatile. This seems to be their major advantage. On the other hand, they are most likely toxic and corrosive
because of the well-known decomposition of the PF6 anion. As these compounds are organic ammonium salts,
they will be flammable and then release large volumes of highly toxic fluorine and HF gas. If spilled, they will bealmost impossible to remove owing to their nonvolatility and their poor solubility. Because they cannot be distilled—which would be an easy and efficient method of recycling--they have to be extracted with organic solvents,for example dichloroethane, as quoted in the article. Is that "green chemistry"?
I think that a lot of unjustified hype is created about these compounds. They are an unusual class of solvents withunique properties that may find some industrial applications in very special areas, that's all. I have worked withthem myself and found them very useful in two-phase homogeneous catalysis. Conventional organic solvents thatcan be recycled by distillation or ultimately burned without toxic gases will, however, remain superior for mostapplications.
Albrecht Salzer
Aachen, Germany

Salzer has not fully realized the magnitude of the number of potential ionic liquid solvents. I am sure, for example,
that we can design a very toxic ionic liquid solvent. However, by letting the principles of green chemistry drive thisresearch field, we can ensure that the ionic liquids and ionic liquid processes developed are in fact green. Given
the large amount of new work appearing in this field, it is notable that the open literature has not yet been able tokeep pace with where the field actually stands now. It is not surprising, then, that many may get the impressionthat the field is being overhyped. I can only hope that the detailed literature (and not just the press coverage) isread and fully appreciated.
As stated in the overview chapter from the meeting that I coauthored with John Holbrey, ionic liquids are often
portrayed as green solvents; however, "greenness" can only be measured in the context of the overall process.
The basic, fundamental concepts behind both green chemistry and ionic liquids is not new; however, the growth ofinterest in ionic liquids and the influence of new minds, new approaches, and enthusiasm are generating new
solutions and driving changes in industrial and commercial practice.
While it is true that many ionic liquids have negligible vapor pressure and can be used as alternatives for volatileorganic chemicals as solvents for synthesis and separations processes, the simple replacement of one solventwith another does not necessarily make a process green.
The expectation that real benefits in technology will arise from ionic liquid research and the development of newprocesses is high, but there is a need for further work to demonstrate the credibility of ionic liquid-based processes
as viable green technology. In particular, comprehensive toxicity studies, physical and chemical property collationand dissemination, and realistic comparisons to traditional systems are needed. It is clear that while the newchemistry being developed in ionic liquids is exciting, many are losing sight of the green goals and falling back on
old habits in synthetic chemistry. Whereas it is true that incremental improvement is good, it is hoped that byfocusing on a green agenda, new technologies can be developed that truly are not only better technologically,
but are cleaner, cheaper, and safer as well. Ionic liquids are not new, not yet green in the full context of limited
data we have at present, but they do offer great opportunities to be used in green processes and to provide
radically new process solutions.
Robin D. Rogers
Tuscaloosa, Ala.

• AnionsF, Cl を含むものが多い
PF6- などは、HFを発生しやすい、etc• Cations
抗菌性Greener anions の探索

Green Chemistry, 4, 400-404 (2002).

問題はカチオンにもカチオン性界面活性剤の抗菌性「微生物の増殖を防ぐ」，三洋化成工業株式会社
研究本部編（１９９９），p.21,25．

生活の中のカチオン性界面活性剤

••
•
•

抗菌剤
柔軟剤
ヘアー・リンス
その他「柔らかくする」，三洋化成工業株式会社
研究本部編（１９９９），p.30．

界面活性剤の使用量など

M. J. Scott and M. N. Jones, Biochim. Biophys. Acta, 1508, 235-252 (2000).

界面活性剤の生産量の内訳

M. J. Scott and M. N. Jones, Biochim. Biophys. Acta, 1508, 235-252 (2000).

While there is little serious risk to the environment from
commonly used anionic surfactants, cationic surfactants areknown to be much more toxic and at present there is a lackof data on the degradation of cationics and their fate in theenvironment.

M. J. Scott and M. N. Jones, Biochim. Biophys. Acta, 1508, 235-252 (2000).

Ecotoxicol. And Environ. Safety, 54, 87-91 (2003).

Ecotoxicol. And Environ. Safety, 54, 87-91 (2003).
LD： Lethal Dose; LD50, a dose which is lethal to 50% of the animals tested.
LC: Lethal Concentration; LC50, a concentration which is lethal to 50% of the animal tested.
EC: Effective concentration; EC50: This test records the growth rate or total yield of biomass
that diminishes by 50% of normal in the presence of the test chemical or chemical mixture.

5. Conclusion
Quaternary ammonium compounds had high biological activity against
the bioindicators tested. They were toxic not only to bacteria, but also
to nontarget protozoa and crustacea. Their release into surface water
may be harmful to the aquatic environment.

Ecotoxicol. And Environ. Safety, 54, 87-91 (2003).

Green? No!

イオン液体の毒性に関する最近の報告

From Ref. (3).

From Ref. (6).

From Ref. (6).

From Ref. (6).

Green Ionic Liquids

Biodegradable IL
Green Chem., 6, 166-175 (2004), 7, 9-14 (2005)

溶解度を下げる
分極性の電位窓と溶解度の関係