Hydrocarbons (Alkane, Alkene and Alkyne) MCQ Questions & Answers in Organic Chemistry | Chemistry

This reaction is known as Friedel-Craft’s alkylation of benzene.

very stable carbocation.

$$nC{H}_2=C{H}_2\underset{\text{pressure,}\text{catalyst}}{\overset{\text{high temp}\text{.}}{\to }}{\sout{(}C{H}_2-C{H}_2\sout{)}}_n$$
A linear polyethene polymer is formed when ethene polymerises.

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is antiaromatic, hence less stable.

More is the stability, lower is the heat of combustion ( See Baeyer’s strain theory ). Cyclohexane is more stable.

$$Conc.$$  $${H_2}S{O_4}$$  and $$conc.$$  $$HN{O_3}$$  react in the following manner
\[\begin{align} & \underset{\text{Base}}{\mathop{HN{{O}_{3}}}}\,+\underset{\text{Acid}}{\mathop{{{H}_{2}}S{{O}_{4}}}}\,\to {{H}_{2}}NO_{3}^{+}+HSO_{4}^{-} \\ & {{H}_{2}}NO_{3}^{+}\to \underset{\begin{align} & \,\,\,\,\,\,\,\,\text{Nitronium}\text{.} \\ & \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\text{ion}\text{.} \\ & \text{Attacking species} \\ & \,\,\,\,\,\,\text{(electrophile)} \\ \end{align}}{\mathop{NO_{2}^{+}}}\,+{{H}_{2}}O \\ \end{align}\]
Hence, in this reaction $$HN{O_3}$$  acts as a base and $${H_2}S{O_4}$$  as an acid.

$$\eqalign{ & C - C\,bond\,energy = 348\,kj/mol = \frac{{348}}{{4.2}}kcal/mol \cr & = 82.85\,kcal/mol \approx 100\,kcal/mol. \cr} $$

Formation of carbocation is $$r.d.s.$$

3-Methylhexane can yield seven different monochlorinated products on chlorination.
\[{{H}_{3}}C-C{{H}_{2}}-C{{H}_{2}}\overset{\begin{smallmatrix} \,\,\,C{{H}_{3}} \\ |\,\,\,\, \end{smallmatrix}}{\mathop{-CH-}}\,C{{H}_{2}}-C{{H}_{3}}\]
Each carbon atom on chlorination givesa different product.