Reactivity and Lone Pairs:  Proton Transfer and             Stereoelectronic Effects
{'Code': '03090003', 'Directorate': {'Abbreviation': 'MPS', 'LongName': 'Direct For Mathematical & Physical Scien'}, 'Division': {'Abbreviation': 'CHE', 'LongName': 'Division Of Chemistry'}}
{'SignBlockName': 'Thomas C. Farrar', 'PO_EMAI': None, 'PO_PHON': None}
This grant in the Organic and Macromolecular Chemistry Program                  is in the subfield of organic reaction dynamics, and supports                   research of Dr. Charles Perrin, University of California at San                 Diego, into the effects of non-bonding electron pairs and their                 spatial orientation on basic aspects of chemical reactivity                     such as proton transfer rates and stereoelectronic effects.  It                 is important to understand these effects and the rates of                       ultrafast mechanistic processes, since it is their cumulative                   effect that is perceived in the macroscopic world as slower                     chemical reactions.                                                                                                                                             The availability of nitrogen or oxygen lone pairs facilitates                   rapid proton transfer, occurring on a picosecond time scale,                    along with other important processes such as diffusion,                         rotation about single bonds, and solvent reorganization.                        According to current theories of stereoelectronic control,                      reactivity is increased when a lone pair is antiperiplanar to a                 leaving group or to an incoming nucleophile, but recent                         experimental results raise questions about this generalization.                 The first research area is a continuation of ongoing analyses                   of proton exchange processes in amides and of rotation in                       ammonium ion, in order to probe the role of hydrogen bonding in                 solvating ions.  Extensive use is made of modern NMR                            instrumentation, which permits measurement of proton exchange                   kinetics under equilibrium conditions.  A focal point here will                 be the phenomena of substrate selectivity and positional                        selectivity in encounter-controlled proton transfer from                        amidinium ions to hydroxide.  Evidence will be sought for a                     heretofore unreported concerted mechanism for amine-catalyzed                   proton exchange in water.  In a second research area, attempts                  will be made to determine the preferred stereochemical                          relationship between lone pairs and reacting bonds.                             Experimental systems will include kinetics for methoxy exchange                 in ortho esters and amide acetals, and of dehydration in                        epimeric gamma-amino allylic alcohols.  An alternative approach                 will involve product studies in the hydrolysis of amidinium                     ions and guanidines, and in the reactions of amidinium,                         imidatonium, and iminium ions with nucleophiles.  These                         experiments are designed to clarify the conditions under which                  stereoelectronic control might be operative and how much it                     contributes to increased reactivity.
{'FirstName': 'Charles', 'LastName': 'Perrin', 'PI_MID_INIT': 'L', 'PI_SUFX_NAME': None, 'PI_FULL_NAME': 'Charles L Perrin', 'EmailAddress': 'cperrin@ucsd.edu', 'NSF_ID': '000219398', 'StartDate': '01/01/1988', 'EndDate': None, 'RoleCode': 'Principal Investigator'}
{'Name': 'University of California-San Diego', 'CityName': 'LA JOLLA', 'ZipCode': '920930021', 'PhoneNumber': '8585344896', 'StreetAddress': '9500 GILMAN DR', 'StreetAddress2': None, 'CountryName': 'United States', 'StateName': 'California', 'StateCode': 'CA', 'CONGRESSDISTRICT': '50', 'CONGRESS_DISTRICT_ORG': 'CA50', 'ORG_UEI_NUM': 'UYTTZT6G9DT1', 'ORG_LGL_BUS_NAME': 'UNIVERSITY OF CALIFORNIA, SAN DIEGO', 'ORG_PRNT_UEI_NUM': None}
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{'Code': '1944', 'Text': 'BIMOLECULAR PROCESSES'}
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