Consider the following molecules:

1. Which of the above has a different molecular formula from the rest? Write the two formulas out.

    Compounds a-g have the formula C₅H₈, while h is C₅H₆.

2. Provide IUPAC names for a, b, c, and g.

    a: cyclopentene
    b: 1,4-pentadiene
    c:  1-pentyne
    g:  trans-1,3-pentadiene

3. Which of molecules a-g would you expect to be the most acidic? Why?

    Compound c (1-pentyne) is most acidic because the C orbital partner in the C-H bond is sp hybridized.  With relatively high sp character (50%) it is lower in energy than other C hybrids (such as sp², sp³; remember that s is lower in energy than p) so it can hold the pair of electrons left behind when H⁺ is pulled off to leave CH3CH2CH2C⁼C(-)

4. Which of a-h could be considered a conjugated diene?

    Compounds g and h are conjugated dienes.