Subject: Allowed Spin Multiplicity of Transition States

From: "Joseph Capitani" <[email-masked]>
Date: Tue, 15 Sep 1998 10:15:41 EST5EDT

Hello, 

We have been trying to calculate transition state energies and 
geometries for reactions that can be be summarized as

AB   +   CD -----> { A---B---C---D}  ---->  AC  +  BD.

AB is a known singlet,  CD is a known triplet,   AC is a known 
singlet and BD  is a triplet.    {A--B--C---D} is the T.S.  and the 
reaction is not photochemical.

My questions are:

1.  What is/are the allowed spin(s) of the transition state?  Are 
there general rules that govern the choice(s)?

2.  Given the spin multiplicities of the reactants, are there general 
rules which fix the spins of the individual products?

Any information would be greatly appreciated!

Thanks,

Joe Capitani