Associates / Fellows
G. K. Surya Prakash
Professor and George A. and Judith A. Olah Nobel Laureate Chair in Hydrocarbon Chemistry
Synthetic Organic, Mechanistic and Hydrocarbon Chemistry
Professor Prakash and his group's research interests are in the area of Synthetic
Organic, Mechanistic and Hydrocarbon chemistry.
Our projects cover a wide range of subjects in the area of selective fluorinations,
oxidations, energetic materials, reductions, stereoselective reactions, electrochemical
synthesis, hydrocarbon activation and isomerization, direct oxidation fuel cells,
lithium ion battery electrolytes, electrochemistry, polymer chemistry, superacid
catalyzed reactions, stable carbocation chemistry, application of ab initio
and DFT theory and NMR chemical shift calculations. Our group also utilizes
extensively all the modern spectroscopic and analytical tools in organic structure
characterization as well as in mechanistic studies.
Synthetic Organic Chemistry
Our efforts in this area mainly emphasize the development new reactions and
reagents which greatly benefit practicing synthetic organic chemists. Although
our goal is not target molecule synthesis oriented, development of single step
selective and stereoselective transformations is of immense value in general
organic synthesis. Preparation of selectively fluorinated organic compounds
is of importance in medicinal chemistry. We have developed many fluorination
protocols based on pyridinium polyhydrogen fluorides (ionic liquids) as a room
temperature nucleophilic fluorinating agent. Many of the methods replace the
use of highly toxic HF and elemental fluorine. Selective trifluoromethyl- as
well as perfluoroalkylations were also achieved by the use trifluoromethyl-
and perfluoroalkyltrialkylsilanes. Related perfluoroalkylations using sulfur
based reagents have shown great promise. A number of silicon reagents such as
trialkylsilanes, trimethylsilyl nitrile and azide have been developed as useful
synthons. A new ionic hydrogenation method using trialkylsilanes as reducing
agent has resulted in general-purpose ether and sulfide synthesis method. We
have adopted the method for the preparation of polymers and crown ethers. Increasingly
superacids serve as excellent high acidity medium for electrophilic reactions
(so called superelectrophilic activation). Using CF3SO3H
or BF3-H2O as a high acidity and non-oxidizing medium
a host of new reactions for deactivated aromatics such as iodination, acylation,
nitration etc., are being developed. Use of solid strong acid catalysts such
as Nafion-HR (an ionomeric perfluoroalkane type sulfonic acid) are
also being investigated. New precursors for carbene based photoaffinity probes
are also being developed. New polymer bead chemistry at nanoscale (nanochemistry)
has been ongoing. The nanometer scale polymer spheres with pendant surface functionalities
serve as hosts for metal nanoparticles, which can be used as catalysts.
These studies involve generation of reactive electrophilic intermediates such
as carbocations, carbodications, halonium ions, diazonium ions, oxonium ions,
acylium ions, thioacylium ions, nitrenium ions, silicenium ions and selenonium
ions in low nucleophilicity highly acidic solvent systems and their characterization
using low temperature broad-band nuclear magnetic resonance spectroscopy (1H, 2H, 13C, 19F, 17O, 29Si, 77Se, 15N, 35Cl, etc.,). Other techniques such
as infrared and X-ray photoelectron spectroscopy are also employed to characterize
their structures. Using the above methods, a wide variety of trivalent (classical)
and bridged (non-classical) carbocations have been characterized along with
some new aromatic cationic systems. Several empirical correlations to relate
positive charge density and chemical shifts were developed. Other reactive intermediates
studied include carbanions and oxonium ylides. In conjunction with these studies
a wide array of two-dimensional NMR techniques and special pulse sequences are
routinely employed. Solid state 13C NMR spectra of carbocation salts
are also routinely obtained using cross polarization magic angle spinning techniques
(CPMAS). In this area ab initio and DFT calculations are routinely employed
to delineate structure and energetics of complex carbocation structures. The
minimized structures are also used in NMR chemical shift calculations.
Hydrocarbon and Related Chemistry
Utilization of saturated hydrocarbons including methane as raw materials to
synthesize value added compounds. Use of hydrocarbons and oxygenated hydrocarbons
(particularly methanol) as fuels in direct oxidation fuel cells. Hydrocarbon
isomerization, functionalization (nitration, carbonylation, hydroxylation, sulfuration,
etc.,) and synthesis of polycyclic cage hydrocarbons. Polymerization of ethylene
and a-olefins to polyolefins by aluminum subhalide chemistry. Polymerization
of unusual monomers. Proton conducting polymer electrolytes for fuel cells and
lithium ion batteries. Superacid facilitated upgrading of fossil fuels (such
as coal, methane, etc.) to industrially useful feedstocks. Electrochemical reduction
of anthropogenic carbon dioxide to methanol and related derivatives. Development
of the methanol economy concept.
||Ipso-Nitration of Aryl Boronic
Acids with Chlorotrimethylsilane-Nitrate Salts, G. K. S. Prakash, C. Panja,
T. Mathew, V. Surampudi, N. A. Petasis and G. A. Olah, Org. Lett. 6, 2205-2207 (2004).
||Difluoromethyl Phenyl Sulfone,
a Difluoromethylidene Equivalent: Use in the Synthesis of 1,1-Difluoro-1-Alkenes
from Primary Alkyl Halides, G. K. S. Prakash, J. Hu, Y. Wang and G. A. Olah,
Angew. Chem. Int. Ed., 116, 5315-5318 (2004).
of Primary Alkyl Halides Using Difluoromethyl Phenyl Sulfone as a Difluoromethyl
Anion Equivalent G. K. S. Prakash, J. Hu, Y. Wang and G. A. Olah Org.
Lett. 6, 4315-4317 (2004).
Efiicient Electrophilic Halogenating Systems for Aromatics, G. K. S. Prakash,
T. Mathew, D. Hoole, P. M. Esteves, Q. Wang, G. Rasul and G. A. Olah, J.
Am. Chem. Soc. 126, 15770-15776 (2004).
Methanol Fuel Cells, K. McGrath, G. K. S. Prakash and G. A. Olah, J.
Ind. & Eng. Chem. 10, 1063- 1080 (2004).
modification of polystyrene nanospheres, R. Desousa, G. K. S. Prakash and
G. A. Olah, J. Nanoscience and Nanotechnology, 5, 397-403, (2005).
Synthesis of Difluoromethyl Alcohols from Both Enolizable and Non-Enolizable
Carbonyl Compounds with Difluoromethyl Phenyl Sulfone, G. K. S. Prakash,
J. Hu, Y. Wang and G. A. Olah, Eur. J. Org. Chem. 2218-2223 (2005).
Liquid and Solid HF Equivalent Amine-Poly (Hydrogen Fluoride) Complexes
Effecting Environmentally Friendly Isobutane-Isobutylene Alkylation, G.
A. Olah, T. Mathew, A. Goeppert, B. Török, I. Bucsi, X-Y. Li,
Q. Wang, E. R. Marinez, P. Batamack, R. Aniszfeld and G. K. S. Prakash, J. Am. Chem. Soc. 127, 5964- 5969 (2005).
Enantioselective Organocatalytic Hydroxyalkylation of Indoles with Ethyl
Trifluoropyruvate (Hot Paper), B. Török, M. Abid, G. London, J.
Esquibel, M. Török, S. C. Mhadgut, P. Yan and G. K. S. Prakash, Angew. Chem. Int. Ed. 44, 2-4 (2005).
Triethylsilylation of Diphenylketene: The Question of C- vs O-Silylation,
G. K. S. Prakash, C. Bae, G. Rasul and G. A. Olah, Proc. Natl. Acad.
Sci. USA. 102, 6251-6254 (2005).