Identify (B) and (D) in the following reaction:

Explanation

The reaction of quinones is that of `alpha`, `beta`-unsaturated ketone.
a.
b.
c.
d. It is an example of Diels-Alder reaction.

e.
f.
g.
The reaction is eneretically unfavourable because if Diels-Alder reaction occurs either in benzene ring I or in III (acts as a diene), the aromaticity of one of the benzene rings is lost. Hence, the reaction does not occur. However, anthracene undergoes Diels-Alder reaction (acts as a diene) because the aromaticity of two benzene rings is retained.
h.
Quinhydrone, a green-black, crystalline compounds, is formed. It is formed by `1:1` charge transfer complex, in which hydroquinone is the `bar e` donor and quinone is the `bar e` acceptor.
i.
Quinhydrone in basic solution is deeply colloured and paramagnetic because of the formation of radical antion. An `bar e` is transferred form the dianino of hydroquinone to quinone. But, two `bar e` 's are required for the reduction of benzoquinone to hydroquinone.

In the formation of semiquinone, one `bar e` is transferred.