From chemistry-request@server.ccl.net Wed Dec 23 03:17:41 1998 Received: from www.ccl.net (www.ccl.net [192.148.249.5]) by server.ccl.net (8.8.7/8.8.7) with ESMTP id DAA10229 for ; Wed, 23 Dec 1998 03:17:41 -0500 Received: from zzmkgtw.zzmk.unizh.ch (zzmkgtw.unizh.ch [130.60.67.3]) by www.ccl.net (8.8.3/8.8.6/OSC/CCL 1.0) with SMTP id DAA29172 Wed, 23 Dec 1998 03:13:28 -0500 (EST) Received: by zzmkgtw.zzmk.unizh.ch; (5.65v3.2/1.3/10May95) id AA05022; Wed, 23 Dec 1998 09:13:26 +0100 Message-Id: <3.0.3.32.19981223091823.006899c4@highdent> X-Sender: toukie@highdent (Unverified) X-Mailer: QUALCOMM Windows Eudora Light Version 3.0.3 (32) Date: Wed, 23 Dec 1998 09:18:23 +0100 To: chemistry@www.ccl.net From: "Hr. Dr. S. Shapiro" Subject: Winter recess question Cc: toukie@zui.unizh.ch Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Dear Colleagues; Here is a question that someone might care to ponder during the "slowdown" between Christmas and New Year's Day. Consider an amphipathic molecule containing a linear alkyl moiety, e.g. an n-hexyl or n-octyl or n-decyl group. When the molecule passes between hydrophobic and hydrophilic milieux, it can be expected that the linear alkyl moiety will experience changes in conformation: in a hydrophobic environment the linear alkyl moiety may be stretched out, where as in a hydrophilic environment it will probaby curl up on itself. I should like to know if there have been any studies on the _rate_ at which such conformational transitions occur when paraffinic moieties such as those considered above move between organic <---> aqueous phases. Of course, relevent references are most welcome. Thanking in advance all responders, and wishing all readers a joyous holiday season and a happy, healthy, and successful New Year, I remain Yours sincerely, S. Shapiro toukie@zui.unizh.ch From chemistry-request@server.ccl.net Wed Dec 23 23:06:34 1998 Received: from www.ccl.net (www.ccl.net [192.148.249.5]) by server.ccl.net (8.8.7/8.8.7) with ESMTP id XAA10649 for ; Wed, 23 Dec 1998 23:06:33 -0500 Received: from pigeon.vu.edu.au (pigeon.vut.edu.AU [140.159.30.12]) by www.ccl.net (8.8.3/8.8.6/OSC/CCL 1.0) with ESMTP id XAA06443 Wed, 23 Dec 1998 23:02:06 -0500 (EST) Received: from students.vut.edu.au ([140.159.60.8]) by pigeon.vu.edu.au (8.9.1a/8.9.1) with ESMTP id PAA22353 for ; Thu, 24 Dec 1998 15:07:19 +1100 (EST) Received: from Adnan.vut.edu.au ([140.159.75.221]) by students.vut.edu.au (Netscape Messaging Server 3.5) with SMTP id AAA46DC for ; Thu, 24 Dec 1998 15:00:27 +1100 X-Sender: s9610264@students.vut.edu.au (Unverified) X-Mailer: QUALCOMM Windows Eudora Pro Version 4.0.1 Date: Thu, 24 Dec 1998 15:04:38 +1100 To: chemistry@www.ccl.net From: "Adnan Hazar" Subject: summary: pKa - organic amines Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Message-ID: <7718EDA41B.AAA46DC@students.vut.edu.au> Sometime ago I posted a question about the availability of pKa valuses for organic amines. Please see the original message and the responses below: --------------- Dear all, I've been looking for either experimental or theoretical/calculated pKa values for mono and bidentate amines at different temperatures. So far I've been unable to gather any substantial information. I'd be greatful for any pointers I'd also be interested in a free reliable s/w either for windows or unix-linux platform for determining pKa values. ===================== One source I've used for small-molecule pKas is the Smith and Martell database, which is available from NIST (NIST Standard Reference Database 46). If you can get access to Bielstein Crossfire, that is also excellent. It allows one to draw a molecule or fragment and search the chemical literature for articles about it. The listing of articles it gives includes information on which molecular properties are given in each article. I have found some very useful pKa data this way. Hope this helps, Mike ------------------------------------------------------------------------------ Michael K. Gilson, Ph.D., M.D. Phone: (301) 738-6217 Center for Advanced Research in Biotechnology Fax: (301) 738-6255 National Institute of Standards and Technology 9600 Gudelsky Drive http://www.carb.nist.gov/carb/gilson.html Rockville, MD 20850-3479 e-mail: gilson@carb.nist.gov ------------------------------------------------------------------------------ ===================== My favorite book is: 1)Perrin, D. D.; Dempsey, B.; Serjeant, E. P. pKa Predictions for Organic Acids and Bases; Chapman and Hall: London, 1981. It has more about Hammett constants, but certainly is a good book. This one discusses the experimental determination: 1)Albert, A.; Serjeant, E. P. The Determination of Ionization Constants. A Laboratory Manual; Chapman and Hall: London, 1971. There are also a couple of special publications of the Royal Society of London with big tabulations of pKa's dating from probably 20 years ago. Yvonne Martin Abbott Laboratories ===================== Although I'm only a licenciate student i may be able to be of some assistance: at the VUB, the university of brussels, there's a professor(P.Geerlings) who studies organic compounds via quantum mechanical procedures; i know he is currently collaborating with the agricultural engineering departement of my own university(catholic university of leuven) to calculate the acid-base properties of zeolites with dft, but a few months ago i read in a belgian chemical magazine(a very insignificant one that certainly does not leave belgium) that one of his (quantum-chemistry) students had recently finished her Ph.D dissertion, and guess what: it was about the acid-base properties of organic amines! Perhaps they might be able to help you further. The homepage of the vub is at: http://www.vub.ac.be and my own university is at: http://www.kuleuven.ac.be P.Geerlings' email-adress is: pgeerlin@algc1.vub.ac.be (try pgeerlin@vub.ac.be) but i do not know if check's his mail of course. Hope this helps. ~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~* ~*~*~*~**~*~*~**~*~*~**~*~*~*~**~*~*~*~ ~*~* Adnan Hazar ~*~* School of Life Sciences ~*~* VUT - Australia ~*~* ~*~* adnan.hazar@students.vut.edu.au ~*~* Adnan.Hazar@staff.vut.edu.au ~*~* ~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~* ~*~*~*~**~*~*~**~*~*~**~*~*~*~**~*~*~*~