In structure $$C{H_2} = C = C{H_2},$$ the middle carbon is attached with two $$\pi $$ -bonds, so it have $$sp$$ hybridisation.
$$\mathop {C{H_2}}\limits_{s{p^2}} = \mathop C\limits_{sp} = \mathop {C{H_2}}\limits_{s{p^2}} $$
Also, called allenes.
202.
Which one of the following is most reactive towards electrophilic reagent?
Due to $$ + M$$ - effect of $$ - OH$$ group and hyperconjugation of $$ - C{H_3}$$ group, the benzene of $$o$$ - cresol is highly reactive towards electrophilic substitution.
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208.
Electronegativity of carbon atoms depends upon their state of hybridisation. In which of the following compounds, the carbon marked with asterisk is most electronegative?
The greater the $$s$$ character of the hybrid orbitals, the greater is the electronegativity. Thus, a carbon atom having an $$sp$$ hybrid orbital with $$50\% \,s$$ character is more electronegative than those possessing $$s{p^2}$$ or $$s{p^3}$$ hybridised orbitals .
The asterisk marked carbon in $$C{H_3} - C{H_2} - C \equiv \mathop C\limits^ * H$$ is $$sp$$ hybridised hence, it is most electronegative.