Okay. The original poster asked about hydrogen bonds and electrostatic
interactions. That's what I was referring to when I mentioned
"enthalpic interactions".
And I think you're saying the same thing - which is cool.
On 19/09/2018 15:06, Stefano Trapani wrote:
Hi Frank > > I mean that, in my opinion, the term "enthalpic interaction" is
not > appropriate to describe the hydrophobic effect, since the latter
is > mainly driven by changes in the (system) entropy, not enthalpy. > >
Table1 of the cited paper reports the thermodynamic functions for >
transferring some nonpolar solutes from a few organic solvents to >
water. The author says that: "The data collected in Table 1 clearly >
show that the thermodynamic barrier to the solution process is >
entropic rather than enthalpic". > > Also, after a brief description of
two theoretical models (the > cavity-based model and the clathrate cage
model) the author states: > "It is important to point out that both the
cavity-based model and > the clathrate cage model rest upon the fact
that the hydrophobic > effect is entropy, not enthalpy driven. The
models differ only in how > they explain the source of the entropy
loss." > > Best > > Stefano > > > > Le 2018-09-19 14:41, Frank von Delft
a écrit : >> >> 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 >>>
>>> -------------------------------------
Centre de Biochimie Structurale (CBS) 29 rue de Navacelles 34090 >>> MONTPELLIER Cedex, France >>> >>> Tel : +33 (0)4 67 41 77 29 Fax :
+33 (0)4 67 41 79 13 >>> -------------------------------------
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