From chemistry-request@ccl.net Wed Mar 20 02:39:18 1991
Date: Mon, 18 Mar 91 17:06:31 PST
From: chiremv!andromeda!jeffb@uunet.UU.NET
Subject: molecular conformations
To: chemistry@ccl.net
Status: R

Dr. Nikolaos Sahinidis asked several questions re conformational analysis.

See J. Med. Chem., vol 31, p. 1669 (1988) for a review which should answer
these questions.  Another important recent paper is JACS, vol 112, p. 
1419 (1990), comparing several different methods for finding global and 
other low energy conformers of cycloheptadecane.  

Jeff Blaney
Protos
6455 Christie Ave.
Emeryville, CA 94608

chiremv!andromeda!jeffb@uunet.UU.NET


From chemistry-request@ccl.net Wed Mar 20 11:04:41 1991
Date: 20 Mar 91   10:47 LCL
From: PA13808%UTKVM1.BITNET@OHSTVMA.IRCC.OHIO-STATE.EDU
Subject: BITNET mail follows
To: CHEMISTRY@ccl.net
Status: R

   TOPIC BOND DISTANCES CALCULATED BY MOPAC
        I WOULD LIKE TO BRING TO THE ATTENTION OF THE PERSON WHO WAS
   CONCERNED ABOUT THE TYPE OF BOND DISTANCES  CALCULATED BY MOPAC A
  QUOTATION BY J. P. STEWART.
        "NO DIFERENTIATION IS MADE BETWEEN VARIOUS DEFINITIONS OF BOND
  LENGTHS.THUS THE BOND LENGTH CORRESPONDING TO THE BOTTOM OF THE
  HARMONIC WELL (R0)IS NOT DISTINGUISHED FROM THE EQUILIBRIUM BOND
  LENGTH."STEWART ALSO POINTS OUT THAT FOR SEMIEMPIRICAL METHODS THE
  AVERAGE ERROR IN BOND LENGTHS IS LARGE RELATIVE TO THE DIFFERENCES
  OBTAINED BY COMPARING THE DISTANCES CORRESPONDING TO THE VARIOUS
  DEFINITIONS.
     THE ARTICLE CONTAINING THE QUOTE IS MORE THAN ONE HUNDRED PAGES
 LONG AND CONTAINS A VERY AUTHORITATIVE DISCUSSION OF ALL ASPECTS OF
 MOPAC INCLUDING THE APPROX INVOLVED IN AM1 AND PM3.  A THOROUGH A
 DESCRIPTION OF THE MATHEMATICAL TECHNIQUES USED IN THE ALGORITHMS IN
 MOPAC IS GIVEN AND EVERYONE WHO IS A SERIOUS USER OF SEMIEMPIRICAL
 METHODS SHOULD HAVE THIS ARTICLE. IT APPEARED IN VOLUME FOUR OF
 THE JOURNAL OF COMPUTER-AIDED MOLECULAR DESIGN(1-105)1990.
      JOHN E. BLOOR
     DEPT OF CHEMISTRY
     UNIVERSITY OF TENNESSEE
     KNOXVILLE TENN 37996-1600