From owner-chemistry@ccl.net Mon Jan 17 07:48:00 2011 From: "Dr. Paul Elsinghorst paul.elsinghorst .. gmail.com" To: CCL Subject: CCL: hemiketal formation, transition state optimization Message-Id: <-43659-110117013233-3656-B3NBcWbz8mxnSOEpBNuh6w**server.ccl.net> X-Original-From: "Dr. Paul Elsinghorst" Content-Type: text/plain; charset=ISO-8859-1 Date: Mon, 17 Jan 2011 07:32:20 +0100 MIME-Version: 1.0 Sent to CCL by: "Dr. Paul Elsinghorst" [paul.elsinghorst^-^gmail.com] I'm having trouble optimizing a transition state when going from an open ketone/phenol to a cyclic hemiketal. I chose the cyclic hemiketal with a proton still attached to the alcohol oxygen (positive formal charge) and a negatively charged ketone oxygen as the input structure for TS optimization. I preoptimized the structure applying a MMFF94 optimization and subjected that to ORCA giving: ! RKS B3LYP TZVP TightSCF SmallPrint Grid4 NoFinalgrid ! PAL8 NoSOSCF SlowConv OptTS NumFreq COSMO(Water) %geom Calc_Hess true end * xyzfile 0 1 TAXI_6_TS1.xyz Unfortunately ORCA optimizes the structure towards the open ketone/phenol which is obviously not the TS but finally a local minimum. Does someone know what's going wrong here? A further question is: does someone know, whether the proton in hemiketal formation is the one > from the alcohol migrating to the ketone? Is there a rule for this or does it differ depending on solvent? E.g. in protic solvents it might be relayed from solvent and in aprotic solvents it might migrate. I appreciate any ideas/help. Especially if I'm totally wrong in my approach. Thanks, Paul