1,2-Dicarbonyl compounds

1,2-Dicarbonyl compounds such as benzil, can be characterized by
reaction with o-phenylenediamine to form a substituted quinoxaline. See
reaction below:

a.) Write the structure for the quinoxaline derivative obtained when
benzil is the

reactant. Do you think this compound would be colored? If so, Why?

b.) Suggest a suitable mechanism for the formation of the quinoxaline
compounds based

on the above reaction scheme.

c.) What reagent would you react with o-phenylenediamine to prepare the
unsubstituted

compound quinoxaline? Show a reaction scheme giving the structure
of reactants and

products.

R

R

R

R

C = :O:

C = :O:

+

o-Phenylenediamine

(a quinoxaline)