6. The triple bond energies in acetylene, hydrogen cyanide, and nitrogen, are 194, 213, and 226 kcal mole, respectively. Diagram these three molecules, showing the positions of all bonds and lone electron pairs. Why would one expect the observed progression of bond energies? In singly bonded -N-N-N-N- chains, it was stated previously that these were unstable in comparison with -C-C-C-C- chains because of repulsions between nitrogen lone electron pairs. Why is this apparently not a dominant factor in the comparison of HCCH, HCN, and N? Where are the lone pairs positioned in the N molecule?

7. The conventional numbering system for a three-ring carbon skeleton such as that of alizarin is


Hence the undissociated alizarin molecule shown previously in this chapter can be described as having carboryl (C=0) groups at Positions 9 and 10, and -OH groups at Positions 1 and 2. The resonance model for the alizarin ion shown in this chapter has -0 groups at Positions 1 and 2. Draw another resonance structure with -0 groups at Positions 9 and 10 and carbonyl groups at 1 and 2. What would this imply about shifts of electrons to and from the various oxygen atoms?