From owner-chemistry@ccl.net Thu Jan 24 12:33:00 2013 From: "Rinderspacher, Berend C CIV (US) berend.c.rinderspacher.civ{}mail.mil" To: CCL Subject: CCL: Why Chlorine atom is more hydrophobic than Hydrogen (UNCLASSIFIED) Message-Id: <-48127-130124113834-3263-nG3Pwo15+Uxzf8UEA5/YBA/./server.ccl.net> X-Original-From: "Rinderspacher, Berend C CIV (US)" Content-Language: en-US Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset="iso-8859-1" Date: Thu, 24 Jan 2013 16:38:19 +0000 MIME-Version: 1.0 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> > > -- Prof. Dr. Andreas Klamt CEO / Geschäftsführer COSMOlogic GmbH & Co. KG Burscheider Strasse 515 D-51381 Leverkusen, Germany phone +49-2171-731681 fax +49-2171-731689 e-mail klamt:-:cosmologic.de web www.cosmologic.de [University address: Inst. of Physical and Theoretical Chemistry, University of Regensburg] HRA 20653 Amtsgericht Koeln, GF: Prof. Dr. Andreas Klamt Komplementaer: COSMOlogic Verwaltungs GmbH HRB 49501 Amtsgericht Koeln, GF: Prof. Dr. Andreas Klamthttp://www.ccl.net/cgi-bin/ccl/send_ccl_messagehttp://www.ccl.net/chemistry/sub_unsub.shtmlhttp://www.ccl.net/spammers.txtThis communication is for use by the intended recipient and contains information that may be Privileged, confidential or copyrighted under applicable law. If you are not the intended recipient, you are hereby formally notified that any use, copying or distribution of this e-mail, in whole or in part, is strictly prohibited. Please notify the sender by return e-mail and delete this e-mail from your system. 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