For ab initio calculation, one need to give the spin state of the molecule. With a cationic molecule like CH3(COH)CH3 (protonated acetone), does the spin state is singlet or doublet? I would have thought that since all electrons are paired, the spin state would be singlet. But GaussView don't allow me to enter a singlet spin when the charge is +1.
In the specific case of the protonated acetone, charge +1 means adding one proton. It seems that all electron are paired in all resonance forms [CH3-C+(OH)-CH3], or [CH3-C(=O+H)-CH3]. Where am i wrong?
Dear Serge,
Your molecule is either a neutral doublet, or a cationic singlet.
If you add H+, then you have the second case, If you add H0, then you have the first case.
Thank you Sergi. I had a doubt. Happy to know that i understand correctly. In acidic condition, the acetone get protonated, so H+ is added. This mean that my molecule is a singlet +1. In the input file, I should thus write "1 1" for the charge and multiplicity.
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