From fuchs@chemdc1.tau.ac.il  Sat Apr 17 11:38:26 1993
Date: Sat, 17 Apr 1993 13:38:26 -0200
From: fuchs@chemdc1.tau.ac.il (Benzion Fuchs)
Message-Id: <9304171538.AA11391@chemdc1.tau.ac.il>
To: chemistry@ccl.net, hogue@canada.den.mmc.com
Subject: Re:  Perfluorodimethyl ether


Received: from canada.den.mmc.com  for hogue@canada.den.mmc.com
	by oscsunb.ccl.net (5.65c+KVa/921206.2314) id AA00459; Wed, 14 Apr 1993 18:35:19 -0400
Date: Wed, 14 Apr 93 16:35:18 MDT
From: hogue@canada.den.mmc.com (Pat Hogue 1-2183)
Subject: Perfluorodimethyl ether

>>    I keep getting an excessivly long C-F bond length for one of the bonds on >>    either end of perfluorodimetyl ether usinf AM1.  Can anyone offer an explaination?
>>    Thanks in advance.

---
      It is, I bet, the gauche C-F bond on each side that is lengthened.
      This is a manifestation of the stereoelectronic "anomeric effect"
      which AM1 can sometime reproduce.
      A contribution from our group on this subject (O-C-F & N-C-F systems)
      is about to appear in Tetrahedron (in 2-3 weeks), including pertinent
      earlier references (Pople et al., Schleyer, Wolfe, Dunitz, etc.) If you
      need the information sooner, I would be glad to let you have a preprint.
      Sincerely,
      Benzion Fuchs

 
N.B. Address and Communication channels:
Prof. Benzion Fuchs                  Tel.: (+972-3) 640-8623 /-8436
School of Chemistry                        (+972-3) 641-6791 (home).
Tel-Aviv University                  FAX : (+972-3) 640-9293
Ramat-Aviv, 69978 Tel-Aviv  ISRAEL   E-mail: fuchs@chemdc1.tau.ac.il

From B_DUKE@DARWIN.NTU.EDU.AU  Sun Apr 18 11:30:08 1993
Date:    Sun, 18 Apr 1993 11:30:08 GMT
From: B_DUKE@DARWIN.NTU.EDU.AU (Brian Duke)
Message-Id: <930418113008.b90c@DARWIN.NTU.EDU.AU>
Subject: Semi-empirical methods
To: CHEMISTRY@ccl.net


Although very old, I still commend the article by Klopman and O'Leary in 
Topics in Current Chemistry, Springer-Verlag, 1970. I also agree with 
the post about Karl Jug's article. There still remains a real gap -
a proper scholarly study of semi-empirical methods, rather than a detailed
study biased towards the contributions of the authors.

                  Brian Salter-Duke (Brian Duke)
School of Chemistry and Earth Sciences, Northern Territory University
        GPO Box 40146, Casuarina, NT 0811, Australia.
Phone 089-466702   FAX 089-410460    E-mail B_DUKE@DARWIN.NTU.EDU.AU