Page 180 - Mechanism and Theory in Organic Chemistry

References for Problems 169

4. Draw orbital structures for +CH,- and for +-, and explain on the basis of the
structures why +H would be expected to be a weaker acid than +CH, and why a might
be different for the two compounds.
5. In cyclopropane, the GC-C bond angle is 60°, but it is thought that the
angle between the orbitals is greater, that is, that the bonds are bent outwards so that the
electron density is not a maximum along the GC line but rather is maximum along
some curve passing outside the GC line. If the H-GH bond angles are 119", find
the angle between the two hybrids the carbon uses to form GC bonds to its neighbors.
Find the percent s character of the C-C and of the C-H bonds, and compare the
percent s character of the C-H bonds with that of C-H bonds in acetylene, ethylene,
and cyclohexane. Compare these results to the acidities in Table 3.9. (Information
needed to solve this problem is in Appendix 1 to Chapter 1 .)

REFERENCES FOR PROBLEMS
5. See Appendix 1, Chapter 1. The H-C-H bond angle quoted is the average of
values obtained by 0. Hassel and H. Viervoll, Acta Chem. Scand., 1, 149 (1947)
(118.Z0, electron diffraction) and by Hs. H. Giinthard, R. C. Lord, and T. K.
McCubbin, Jr., J. Chem. Phys., 25, ,768 (1956) (120°, vibration-rotation spectrum).