Hi Stefano - could you elaborate?
Certainly the medicinal chemists go on a great deal about how deltaH
balances deltaS and how it's bloody hard to know what is what even when
you try to measure it. Which is what that abstract also goes on about.
On 19/09/2018 10:54, Stefano Trapani wrote:
Le 2018-09-19 11:59, Frank von Delft a écrit :
I believe medicinal chemists do indeed talk about "enthalpic
interactions". Frank
Not a good choice either (à mon avis ...)
The Real Reason Why Oil and Water Don't Mix
Todd P. Silverstein
Journal of Chemical Education *1998* /75/ (1), 116
DOI: 10.1021/ed075p116
https://pubs.acs.org/doi/abs/10.1021/ed075p116
Stefano
On 19/09/2018 10:40, Stefano Trapani wrote:
Le 2018-09-18 19:31, Daniel M. Himmel, Ph. D. a écrit :
(where hydrophobic interactions result from van der Waals forces
in an aqueous environment).
Hi
I am not sure that, if one is to give a concise definition of
hydrophobic "interactions", this would be a convenient one, because
it may lead someone to identify vdW forces as the main factor that
maintains apolar aggregated molecules together in aqueous
environment. I have seen many students (and PhD's) believing to the
equality: hydrophobic 'forces'=vdW forces (and not understanding,
for example, that the side chains of a Ser and an Ile can also
establish vdW interactions).
It is true that apolar groups that aggregate establish van der Waals
interactions (like any molecule in contact with another one) but
these microscopic (real) forces are not (as far as I know) the main
reason of aggregation in aqueous environment.
The hydrophobic effect seem to be of a mainly entropic nature (and
it has much more to do with hydrogen bonds than van der Waals forces):
https://en.wikipedia.org/wiki/Hydrophobic_effect#Cause
https://en.wikipedia.org/wiki/Entropic_force#Hydrophobic_force
Being mainly of an entropic nature, hydrophobic "contacts" are not
the direct result of real microscopic "forces" that act between
apolar groups. The terms "forces" and "interactions" in widely used
expressions like "hydrophobic forces" and "hydrophobic interactions"
are somehow misleading.
Best
---
Stefano Trapani
Maître de Conférences
http://www.cbs.cnrs.fr/index.php/fr/personnel?PERS=Stefano%20Trapani
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