(a) For formic acid, HCOOH, find the two stable conformers at the HF/6-31G* level; check that each conformer is a local minimum. Then find the structure of the HF/6-31G* transition state between these conformers. (Problem 16.45.) What is the HF/6-31G* barrier to internal rotation about the CO single bond (omit zero-point energies)?
(b) Repeat for vinyl alcohol.
In problem 16.45
Consider the reaction HCN → CNH.
(a) Find the HF/6-31G* equilibrium geometries of HCN and HNC. (Recall that 180o is not allowed as a Z-matrix bond angle.)
(b) Find the HF/6-31G* transition-state structure for this reaction. Hints: We expect the transition-state (TS) structure to be roughly halfway between the reactant and product structures. Thus we expect a triangular TS with the CN distance somewhere between its values in the reactant and product, the HC distance somewhat longer than its values in the reactant, and the HN distance somewhat longer than its value in the product. Start with an initial guess for the TS structure. In Gaussian, one way to find a TS is to replace Opt by Opt(CalcFC,TS).