From: Guosheng Wu <wu_guosheng2002@yahoo.com>
Date: Thu, Dec 2, 2010 at 10:16 AM
Subject: On the defination of Hydrogen bond (IUPAC)
To: arunan@ipc.iisc.ernet.in
Cc: Guosheng Wu <wu_guosheng2002@yahoo.com>
 
 
Dear Dr. Arunan,
 
I noticed there is a version for the defination of Hydrogen bond (H-bond) at
the website of IUPAC
 
http://media.iupac.org/reports/provisional/abstract11/arunan_prs.pdf
 
"The hydrogen bond is an attractive interaction between a hydrogen atom from
a molecule or a molecular fragment X–H in which X is more electronegative
than H, and an atom or a group of atoms in the same or a different molecule,
in which there is evidence of bond formation"
 
In my opinion, it's not rigorous. (1) The word "bond" is confusing in this
context. A H-bond is usually not a chemical bond (usually interaction
between 2 atoms), but a weaker interaction for a multi-body system, although
there are a small percentage of strong H-bonds that behave more like a
chemical bond in some aspects. (2) The multi-body nature of H-bond
interaction suggests that defination has serious issue. It's well-known from
quantum physics, H-bond is at least the interaction between X, H and Y for a
H-bond (X-H...Y), where X or Y can be either a heavy atom or a group of
atoms. In the description of quantum physics, it is a state (or
wave-function) for the whole system, although it's mostly determined by the
nature of X, H and Y.
 
I suggest the IUPAC group modify the defination so that it reflects its
nature and avoid any confusion.
 
Sincerely,
Guosheng Wu, Ph.D.