and 
have a double bond, they
exhibit different type of addition reactions. Explain.
Answer:
The 
undergoes
electrophilic addition reactions while 
shows nucleophilic
addition reactions. This difference in behaviour is due to the different shapes
of their \[\pi \]-electron clouds. The \[\pi \]- electron cloud of bond due to similar
electro negatives of the two carbon atoms is almost symmetrical (Fig. 12.2b,
page 12/9) and surrounds both the carbon atoms equally. Consequently, if a reagent
is to attack one of the carbon atoms of the bond, it
has to pass through this electron cloud. Since the \[\pi \]-electron cloud
consists of loosely held electrons, therefore, it can readily allow electrophiles
to react. As a result, the typical reactions of are
electrophilic addition reactions. In contrast, the \[\pi \]-electron cloud of
the is unsymmetrical i.e.,
shifts towards oxygen (Fig. 12.2a, page 12/8) due to greater electro negativity
of O than C. As a result, the C-atom of the bond acquires
a partial +ve charge and hence is readily attacked by nucleophiles. Thus, the
typical reactions of are nucleophilic addition
reactions.
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