Safer Solvents

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Course on Green Chemistry Todai Kashiwa April
May 2008

Safer Solvents
Thanks to Prof. C.-J. Li, McGill University,
Canada for use of slides
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Earth Day at MIT April 21 25 !
A highlight of the week will be the Earth Day
Fair on April 24. There will be free food, live
music, and free massages! Don't miss it!

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C.-J. Li, McGill University
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onsen (??)

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C.-J. Li, McGill University
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• Current practice relies on volatile organic
• compounds (VOCs)
• methylene chloride
• benzene, toluene
• tetrahydrofuran
• ethers
• perchloroethylene (PERC) for dry-cleaning
• acetone

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Life cycle flow chart for solvent usage. Primary
life cycle stages are represented by
rectangles. -- from Alternative Solvents
Shades of Green by J.H. Clark and S.J. Tavener,
Organic Process Research Development 11, 149
(2007).

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Where do these solvents end up?

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Cleaner Reaction Media (Green Solvents)

• Supercritical fluids
• Ionic liquids
• Water
• Perfluorinated hydrocarbons
• No solvent at all !

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What is a supercritical fluid?

• What is a fluid?

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Solid, liquid, and vapor phases of water

water
?1 atmosphere pressure (1 bar)?
steam
ice
Room T (20ºC)
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In the Supercritical region the substance is
neither a gas nor a liquid it is a fluid that
has properties of both. There are no sharp
boundaries between gas and liquid. Properties of
SCFs can be very different from the normal liquid
phase.

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This is not

Above the critical point, the phase boundary
(meniscus) between liquid and vapor phases
disappears, and the substance is a single
homogeneous fluid.
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• Possible advantages of supercritical fluids
• increased solubilities of reactants or products
• single homogeneous phase, no transport
  limitations
• reaction conditions can be fine-tuned by varying
  pressure and/or temperature
• separation step can be eliminated
• SCFs such as water, CO2 can be recovered, or
  disposed of with little or no environmental
  impact
• organic compounds are soluble in SCW, inorganic
  salts are insoluble ? SCWO

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SCCO2 is particularly useful for organic
syntheses SAKAKURA Toshiyasu and co-workers
(NIMCR Tsukuba) J. Org, Chem. 64, 4506
(1999) J. Am. Chem. Soc. 121, 3793
(1999) Synthesize dimethyl acetate from carbon
dioxide

Carry out reaction in supercritical CO2
Carbonyl co-product can be recycled to starting
acetal.
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Hydrogenation reaction in supercritical CO2
Martyn Poliakoff U. of Nottingham Chem.
Commun. 4632 (2007)

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• Ionic liquids are salts which are fluid at
  ambient temperatures.
• They have several advantages over conventional
  molecular
• solvents, which make them environmentally
  compatible
• Dissolves many different inorganic and organic
  materials
• Highly polar
• Consist of loosely co-ordinating bulky ions
• Very low vapor pressure
• Liquid window of up to 300 ºC enabling wide
  kinetic control
• Most liquids thermally stable gt200 ºC
• Immiscible with many organic solvents
• Non-aqueous polar alternatives for phase transfer
  processes
• Relatively inexpensive
• Easy to handle and store

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Ionic liquids

Provided by Prof. C.-J. Li
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Typical Ionic Liquids

Provided by Prof. C.-J. Li
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Example of reactions in ionic liquids
Friedel-Crafts acetylation of ferrocene in emimI

1-ethyl-3-methyl-imidazolium iodide emimI
(liquid at room T)
Solvent can be acidic or basic depending on
emimI to AlCl3 ratio
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The first industrial process using ionic liquids
did not appear until the middle of 2003
Biphasic Acid Scavenging using Ionic
Liquids (BASF Corp.) to make alkoxyphenylphosphine
s

pure product phase
1-methylimidazole (mim) with HCl by-product
K.R. Seddon, Nature Materials 2, 383 (June 2003)
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An intriguing possibility for biofuels?
"Dissolution of Cellulose with Ionic Liquids.
Swatloski, R. P. Spear, S. K. Holbrey, J. D.
Rogers, R. D. J. Am. Chem. Soc. 124, 4974
(2002).                                           
      

We report here initial results that demonstrate
that cellulose can be dissolved without
activation or pretreatment in, and regenerated
from, 1-butyl-3-methylimidazolium chloride and
other hydrophilic ionic liquids. This may enable
the application of ionic liquids as alternatives
to environmentally undesirable solvents currently
used for dissolution of this important
bioresource.
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Reactions in aqueous media (water)Adipic acid
HOOC(CH2)4COOH is an important intermediate in
the manufacture of nylon

NOYORI Ryoji et al. developed a green synthesis
of adipic acid using aqueous solution of hydrogen
peroxide Science 281, 1646 (1998)
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Synthesis of a complex natural product in aqueous
solution

I. Vilotijevic and T. Jameson, Science 317, 1189
(2007)
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Solvent Free Reactions
The demand for increasingly clean and efficient
chemical syntheses is continuously becoming more
urgent from both an economic and an environmental
standpoint. So-called green technologies are
looking for alternatives, yet they focus on large
quantities of hazardous even toxic solvents. One
could even say that the best solvent is no
solvent. It is against this background that
chemical synthesis without the use of solvents
has increasingly developed into a powerful
methodology. Once the chemical reactivity is
increased, the amount of initial substances
needed is reduced in particular it removes the
need for the complex recycling and disposal of
solvents. In this book, the third in our open
"Green Chemistry" series, Prof. Koichi Tanaka
(Kansai University) describes the latest
developments in this exciting field. Packed with
advice on applications, this will be equally
useful to practitioners in research as well as
process chemists in industry, such that it is
sure to become an invaluable reference source.

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Solvent-free reactions of fullerenes and
N-alkylglycines with and without aldehydes under
high-speed vibration milling Guan-Wu Wang,
Ting-Hu Zhang, Er-Hong Hao, Li-Juan Jiao,
Yasujiro Murata and Koichi Komatsu Department of
Chemistry, University of Science and Technology
of China, Hefei, Anhui 230026, People's Republic
of China Institute for Chemical Research, Kyoto
University, Uji, Kyoto 611-0011, Japan

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and if you can find a way to use no solvent at
all, that may even be better!