Question

1) What conclusion(s) can you make concerning the H-X-H bond angles and the number of unshared (lone) pairs of electrons around the central atom X for methane, ammonia and water?
2) Compare the Semi-Empirical values for Heat of Formation between ‘’cis’’ and ‘’trans’’ HONO and explain which one is more stable. Remember to convert the energy values from kcal mol-1 to kJ mol-1 on your pro-forma sheet.
3) Write down the PM3 and HF optimised structures of the cis/trans isomers and the transition state (use the table on the pro-forma sheet). Compare your results against the experimental values2,4.
4) Plot a graph for both sets of Rotation Barrier data (Semi-Empirical (PM3) and HartreeFock (HF)).  

Answer 1

Solution 1.