NEET Practice Questions (MCQs) with Answers & Solutions

(d) (a) and (b) are test for alkene.

 ${\mathrm{CH}}_4\stackrel{\left[\mathrm{O}\right]}{\to }{\mathrm{H}}_2\mathrm{O} + \mathrm{CO}$

                        HBr/H₂O₂
CH₃CH₂CH=CH₂→CH₃CH₂CH₂CH₂Br
                   Anti-Markownikoff's rule
                         C₂H₅ONa
CH₃CH₂CH₂CH₂Br→CH₃CH₂CH₂CH₂OC₂H₅
                              SN² reaction

Ethyne (C₂H₂) contains two carbon atoms that are sp hybridized, just like in CO₂. The other options have different hybridization states for their carbon atoms.

 Nitro group being electron withdrawing deactivates the benzene nucleus to such as extent so that it becomes incapable to give Fridel-Crafts reaction.

Nitrobenzene because of its unreactivity towards Friedel-Craft's reaction is used as a solvent for this reaction.

Key Idea Lower hydrocarbons exist in gaseous state while higher ones are in liquid state or solid state. On cracking or pyrolysis, the hydrocarbon with higher molecular mass gives a mixture of hydrocarbons having lower molecular mass. Hence, we can say that by cracking a liquid hydrocarbon can be converted into a mixture of gaseous hydrocarbons.

Key Idea Proton donor are acids and proton acceptor are bases.
Conc. H₂SO₄ and conc HNO₃, react in the following manner:

$$\begin{gathered} {\mathrm{HNO}}_3 + {\mathrm{H}}_2{\mathrm{SO}}_4 \stackrel{ }{\to }{\mathrm{H}}_2{\mathrm{NO}}_3^{+} + {\mathrm{HSO}}_4^{-} \\ \mathrm{base} \mathrm{acid} \\ {\mathrm{H}}_2{\mathrm{NO}}_3^{+} \stackrel{ }{\to } {\mathrm{NO}}_2^{+} + {\mathrm{H}}_2\mathrm{O} \\ \mathrm{nitronium} \mathrm{ion} \end{gathered}$$

Hence, in this reaction HNO₃ acts as a base and H₂SO₄ as an acid.

In the Friedel-Crafts alkylation reaction, benzene reacts with an alkyl halide like methyl chloride (CH₃Cl) in the presence of a Lewis acid catalyst (anhydrous AlCl₃) to form an alkylated product, toluene.

Benzene having any activating group i.e., OH, R etc., undergoes electrophilic substitution very easily as compared to benzene itself. Thus toluene (C₆H₅CH₃ ), phenol (C₆H₅OH) undergo electrophilic substitution very readily than benzene. Chlorine with +E and +M effect deactivates the ring due to strong -I effect. So, it is difficult to carry out the substitution in chlorobenzene than in benzene,so correct order is:-

Phenol>Toluene>Benzene>Chlorobenzene
(iv) (ii) (i) (iii)