Focusing on the cis-trans isomerization activation barrier, you should have found that it is significantly larger than what you might expect for a barrier for rotation about a single bond. For example, the gauche to anti-barrier for rotation about the C-C singlet bond in n-butane is only about 11 kJ/mol. Discuss possible reasons why the rotation barrier for HCSH might be so large. You might want to think about Lewis dot structures and possible resonance forms of the molecule. Also, you might also consider that the C-S bond length of CH₃SH is about 1.85 for comparison.