CCL: Why Chlorine atom is more hydrophobic than Hydrogen (UNCLASSIFIED)

 Sent to CCL by: "Rinderspacher, Berend C CIV (US)"
 [berend.c.rinderspacher.civ^_^mail.mil]
 Classification: UNCLASSIFIED
 Caveats: NONE
 My two cents:
 Fluorine is a very hard atom and not particularly polarizable compared to
 hydrogen or chlorine. Since vdW forces are lead by induced dipole interactions,
 fluorine screens these interactions. Given flat surfaces of hydrogenated,
 perfluorinated and perchlorinated hydrocarbons, the accessible surface area
 should be approximately the same in all cases, but I'd expect the fluorinated
 species to be the least wettable.
 -----Original Message-----
 > From: owner-chemistry+berend.rinderspacher==us.army.mil**ccl.net [mailto:owner-chemistry+berend.rinderspacher==us.army.mil**ccl.net] On
 Behalf Of Robert.L.Waterland,+,dupont.com
 Sent: Thursday, January 24, 2013 9:10 AM
 To: Rinderspacher, Berend C CIV (US)
 Subject: CCL: Why Chlorine atom is more hydrophobic than Hydrogen
 Sent to CCL by: [Robert.L.Waterland _ dupont.com] This is an interesting
 explanation but I wonder if there is something more to the story.  Fluorine is
 even more hydrophobic than chlorine - many of the best surfactants are heavily
 fluorinated and a terminal CF3 group often results in strong water repellency -
 but the vdW-radius of fluorine (~1.47 Angstrom) lies between that of chlorine
 (~1.75 Angstrom) and hydrogen (~1.20 Angstrom).
 Best wishes
 Rob
 Robert  Waterland
 DuPont Central R&D
 Experimental Station E320/314
 Rt 141 and Henry Clay
 Wilmington, DE 19880
 e-mail:  Robert.L.Waterland_._dupont.com
 phone: +1 302-695-1511
 fax:       +1 302 695-9873
 -----Original Message-----
 > From: owner-chemistry+robert.l.waterland==usa.dupont.com_._ccl.net
 > [mailto:owner-chemistry+robert.l.waterland==usa.dupont.com_._ccl.net]
 > On Behalf Of Andreas Klamt klamt]![cosmologic.de
 Sent: Wednesday, January 23, 2013 11:31 PM
 To: WATERLAND, ROBERT L
 Subject: CCL: Why Chlorine atom is more hydrophobic than Hydrogen
 Sent to CCL by: Andreas Klamt [klamt%%cosmologic.de] Hi Mannan,
 this can be quite nicely explained  within COSMO-RS theory. Basically the
 interactions in liquids are surface contacts. Hydrophobicity is sloppy
 expression for the fact that water does not like to make contayts to non- or
 slightly polar surface area. By the way, this is an entropic effect, because the
 really polar parts of water essentially will make no contacts to slightly polar
 surfaces, and the free high free energy of contact results from the entropy loss
 which goes along with placing the few "green" (in COMSO-RS the
 non-polar surface is colored in green) surface pieces of water on the non-polar
 solute surface area.
 Anyway, the larger the non-polar surface area, the more of the green water
 patches are required as contact partners and the higher the
 "hydrophobic" costs. And since the vdW-radius of hydrogen is ~ 1.1
 Angstrom, and that of Chlorine is ~ 1.7, the exposed non-polar surface area of
 chlorine is much larger than that of hydrogen.
 Best regards
 Andreas
 Am 23.01.2013 15:36, schrieb Mannan K malie_03(0)yahoo.co.in:
 > Sent to CCL by: "Mannan  K" [malie_03|*|yahoo.co.in] Hi CCLers,
 >
 > Chlorine/Fluorine atoms are commonly used to influence the hydrophobic
 contact in small molecule design.
 > But how the hydrophobicity is being measured for halogen atoms with
 reference to Hydrogen atom?
 > How Molar refractivity and steric paramemters are connected to
 hydrophobicity of an atom?
 >
 > Thanks in Advance,
 > Mannan>
 >
 >
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