From owner-chemistry@ccl.net Thu Nov  3 09:12:00 2005
From: "yang zhen na yangzn553::nenu.edu.cn" <owner-chemistry*|*server.ccl.net>
To: CCL
Subject: CCL: intramolecular proton transfer
Message-Id: <-29871-051103090948-15742-1b0gFmq+9LKAduNV6os+8g*|*server.ccl.net>
X-Original-From: "yang zhen na" <yangzn553-$-nenu.edu.cn>


Sent to CCL by: "yang zhen na" [yangzn553[]nenu.edu.cn]
I calculate the proton transfer reaction of a molecule, the experiment revealed that in the ground state the enol form is more stable than the keto form, but in the excited state keto form is more stable than the enol form.
First, the energy of the excited state was obtained by summing the energy of the ground state and the corresponding excitation energy. And get the conclusion that keto form is more stable the enol form in the first excited state.
Sencod, I optimize the geometries of two forms in the excited state using cis method and find the energy by keywords scf done. But the conclusion is that enol form is more stable than the keto form.
I dont know why different methods get different conclusion and which one is right. The first method is agreement with the experiment value. So I think whether there is two mechanisms for proton transfer in the excited state. First, the proton transfers as the molecule get the excited state and the geometry have not been changed. Second, the molecule relaxes first and then the proton transfers, the molecule I studied is obey the first mechanism. I dont know whether I am right, please help me and give me an answer.
I am anxious of getting your help. Think you with the great wishes!