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Arrange the following ia decreasing order of their boiling points.
(A) n-Butane
(B) 2-Methylbutane
(C) n-Pentane
(D) 2,2-Dimethylpropane
(a) A > B > C > D
(b) B > C > D > A
(c) D>C>B>A
(d) C >B>D > A read less

Order of priority of electronic effects in organic molecules:

resonance>hyperconjugation>inductive effect

So answer is both A and C

in A 

CH₃ – O – CH⁺_{2 has resonance with lone pair of oxygen while CH3 – CH⁺2 has hyperconjugation.}

_{in C}

_{CH2 = CH – CH⁺2 is more stable than CH3 – CH2 – CH⁺2, because CH2 = CH – CH⁺2 is resonance stabilised while CH3 – CH2 – CH⁺2 is  stabilised by hyperconjugation.}

 Alkenes are rich source of loosely held pi electrons, due to which they show electrophilic addition reaction. Electrophilic addition reactions of alkenes are accompanied by large energy changes so these are energetically favourable than that of electrophilic substitution reactions.
In special conditions alkenes also undergo free radical substitution reactions.
In arenes during electrophilic addition reactions aromatic character of benzene ring is destroyed while during electrophilic substitution reactions it remains intact. Electrophilic substitution reactions of arenes are energetically more favourable than that of electrophilic addition reaction.
That’s why alkenes prefer to undergo electrophilic addition reaction while arenes prefer electrophilic substitution reactions.

read less

-OCH3 group is an activating group with +I effect whereas -Cl and -NO2 are groups due to their -I and -M effect. CH3 is electron donating group while Cl and NO2 are electron withdrawing group. The presence of electron withdrawing group decreases the electron density in the benzene ring making it more favourable for nucleophile attack whereas the presence of electron donating group favours electrophile attack.

Hence the correct order is methoxy benzene>chlorobenzene>nitrobenzene.