From: Heidi M. Muchall <muchall@alcor.concordia.ca>
Date: Tue, Nov 23, 2010 at 2:21 AM
Subject: Re: [SPECTROSCOPY-GROUP] Hydrogen bond
To: Arunan <arunan@ipc.iisc.ernet.in>
 
 
Dr Arunan,
I have read the report and have a few comments.
- On line 67, the term "theoretical" is used. I do not think that I'm
splitting hairs if I suggest the term "computational" instead, because that
is how these data would be generated. Theoretical chemistry only provides
the framework in which computational data can be obtained.
- I guess I agree with the phrasing in E4, which concerns the lengthening of
X-H with its corresponding red-shifting stretching vibration. I also approve
of the use of "usually" in this context, seeing that F6 clarifies that there
might not be any vibrational shift at all. Yet F6 seems to go further, as it
refers to the so-called "blue-shifting H-bonds" also as hydrogen bonds. I
think if F6 stays phrased as is, we (the community) will lose this
distinction. Is that the intent of the committee? If so, I think this needs
to be clarified much more strongly. If not, I also suggest to rephrase.
- I do not agree with F7. What constitutes "practical" must be left up to
the individual researcher. If a H-bonding interaction is only obvious at low
temperatures, but because of its presence at these lower temperatures leads
to unique or preferred conformers or even to unique reactivities, this
should not be disregarded! I think that nowadays we have to accommodate
strange environments in our considerations, be they in outer space
(astronomers will probably have a different definition of "practical" than
intended here) or in deep sea thermal vents.
- As someone who works with QTAIM, I think C6 does not go far enough and may
be quite misleading to someone unfamiliar with the analysis of electron
densities. After all, additional criteria were put in place to prevent the
over-use of the H-bond description. But I also agree that this would not be
the place to address the finer details. I will leave suggestions to the more
outspoken supporters of QTAIM.
That is all for now. Thanks for listening,
Heidi Muchall
 
 
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Dr. Heidi M. Muchall
Associate Professor
Department of Chemistry and Biochemistry
and
Centre for Research in Molecular Modeling
Concordia University
Montreal, Quebec H4B 1R6
Canada
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e-mail: muchall@alcor.concordia.ca
phone: (514) 848-2424 x3342
fax: (514) 848-2868
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