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SUMMARY:New Tools for Understanding Structure and Mechanism
LOCATION:Chemistry A101
TZID:America/Denver
DTSTART:20192001T000000
UID:2026-04-25-05-49-48@natsci.colostate.edu
DTSTAMP:20260425T054948
Description:About the Seminar\n\nIn the first part\, I will discuss the inf
 luence of molecular motions on NMR chemical shifts. When quasiclassical dy
 namics are used to take motions into account\, very accurate chemical shif
 t predictions can be made without using empirical corrections. This method
  can also give insight into unusual structures such as [18]-annulene\, whi
 ch is [4n+2] aromatic.\n\nIn the second part\, I will describe the develop
 ment of ultrasensitive NMR methods for measuring 13C kinetic isotope effec
 ts as a broadly useful tool for probing reaction mechanisms. In glycosylat
 ion reactions\, these isotope effects reflect both the charge distribution
  and bond lengths of the transition structure\, allowing the SN1 and SN2 m
 echanisms to be distinguished. I will also use isotope effects to show tha
 t nucleophilic aromatic substitutions typically proceed through concerted 
 mechanisms\, and that textbook Meisenheimer complexes are actually transit
 ion states\, rather than intermediates.\n\n&nbsp\;\n\nAbout the Speaker\n\
 nEugene Kwan was recently a research fellow at Massachusetts General Hospi
 tal (cancer genomics)\, a lecturer at Harvard University\, and a postdocto
 ral fellow with Professor Eric Jacobsen.  He obtained his Ph.D. with Prof
 essor David Evans.  This spring\, he will take up a position at Merck Bos
 ton as a senior scientist specializing in nuclear magnetic resonance. 4:00
  pm
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