Home

About

Advanced Search

Browse by Discipline

Scientific Societies

E-print Alerts

Add E-prints

E-print Network
FAQHELPSITE MAPCONTACT US


  Advanced Search  

 
Electronic Basis of Improper Hydrogen Bonding: A Subtle Balance of Hyperconjugation and Rehybridization
 

Summary: Electronic Basis of Improper Hydrogen Bonding: A Subtle
Balance of Hyperconjugation and Rehybridization
Igor V. Alabugin,*, Mariappan Manoharan, Scott Peabody, and Frank Weinhold
Contribution from the Department of Chemistry and Biochemistry, Florida State UniVersity,
Tallahassee, Florida 32306-4390, and Theoretical Chemistry Institute and Department of
Chemistry, UniVersity of Wisconsin-Madison, Madison, Wisconsin 53706
Received February 13, 2003; E-mail: alabugin@chem.fsu.edu.
Abstract: The X-H bond length in X-H..Y hydrogen bonded complexes is controlled by a balance of two
main factors acting in opposite directions. "X-H bond lengthening" due to n(Y)f*(H-X) hyperconjugative
interaction is balanced by "X-H bond shortening" due to increase in the s-character and polarization of the
X-H bond. When hyperconjugation dominates, X-H bond elongation is reflected in a concomitant red
shift of the corresponding IR stretching frequency. When the hyperconjugative interaction is weak and the
X-hybrid orbital in the X-H bond is able to undergo a sufficient change in hybridization and polarization,
rehybridization dominates leading to a shortening of the X-H bond and a blue shift in the X-H stretching
frequency.
Introduction
Hydrogen bonding is essential to many chemical and bio-
chemical processes.1 A characteristic feature of H...Y hydrogen
bond formation in an X-H...Y system is X-H bond lengthening
with a concomitant red shift of the X-H stretching frequency.

  

Source: Alabugin, Igor - Department of Chemistry and Biochemistry, Florida State University

 

Collections: Chemistry; Biology and Medicine