NCERT Exemplar solutions for Chemistry [English] Class 11 chapter 13 - Hydrocarbons [Latest edition]

Arrange the following in decreasing order of their boiling points.

(A) n-butane

(B) 2-methylbutane

(C) n-pentane

(D) 2, 2-dimethylpropane

Arrange the halogens F₂, Cl₂, Br₂, I₂, in order of their increasing reactivity with alkanes.

The increasing order of reduction of alkyl halides with zinc and dilute HCl is ______.

The correct IUPAC name of the following alkane is:

\[\begin{array}{cc}
\ce{H3C - CH2 - CH - CH2 - CH2 - CH - CH2 - CH3}\\
\phantom{}|\phantom{...................}|\phantom{..}\\
\phantom{..}\ce{CH}\phantom{................}\ce{CH2}\phantom{.}\\
\phantom{.}/\phantom{.}\backslash\phantom{..................}|\phantom{....}\\
\phantom{}\ce{CH3}\phantom{.}\ce{CH3}\phantom{.............}\ce{CH3}\phantom{..}
\end{array}\]

The addition of HBr to 1-butene gives a mixture of products A, B and C

(A)
(B)
(C)	CH3 – CH2 – CH2 – CH2 – Br

The mixture consists of:

Which of the following will not show geometrical isomerism?

Arrange the following hydrogen halides in order of their decreasing reactivity with propene.

Arrange the following carbanions in order of their decreasing stability.

(A) H₃C – C ≡ C^–

(B) H – C ≡ C^–

(C) \[\ce{H3C - C\overset{-}{H2}}\]

Arrange the following alkyl halides in decreasing order of the rate of β– elimination reaction with alcoholic KOH.

Which of the following reactions of methane is incomplete combustion:

Some oxidation reactions of methane are given below. Which of them is/are controlled oxidation reactions?

(i) \[\ce{CH4 (g) + 2O2 (g) -> CO2 (g) + 2H2O (l)}\]

(ii) \[\ce{CH4 (g) + O2 (g) -> C (s) + 2H2O (l)}\]

(iii) \[\ce{CH4 (g) + O2 (g) ->[Mo2O3] HCHO + H2O}\]

(iv) \[\ce{2CH4 (g) + O2 (g) ->[Cu/523 /100 atm] 2CH3OH}\]

Which of the following alkenes on ozonolysis give a mixture of ketones only?

(i)	CH3 – CH = CH – CH3
(ii)	\[\begin{array}{cc} \ce{CH3 - C - CH = CH2}\\ |\phantom{.......}\\ \ce{CH3}\phantom{....} \end{array}\]
(iii)
(iv)	\[\begin{array}{cc} \phantom{...................}\ce{CH3}\\ \phantom{..............}/\\ \ce{(CH3)2 C = C}\\ \phantom{..............}\backslash\\ \phantom{...................}\ce{CH3} \end{array}\]

Which are the correct IUPAC names of the following compound?

\[\begin{array}{cc}
\ce{HC(CH3)2}\phantom{............}\\
|\phantom{.................}\\
\phantom{.....}\ce{H3C - CH2 - CH2 - CH - CH - CH2 - CH2 - CH2 - CH2 - CH3}\\
|\phantom{.....}\\
\phantom{}\ce{H3C - CH - CH2CH3}
\end{array}\]

(i) 5–Butyl – 4–isopropyldecane

(ii) 5–Ethyl – 4–propyldecane

(iii) 5–sec–Butyl – 4–iso-propyldecane

(iv) 4–(1-methylethyl)– 5 – (1–methylpropyl)–decane

Which are the correct IUPAC names of the following compound?

\[\begin{array}{cc}
\ce{H3C - CH2 - CH2 - CH2 - CH - CH2 - CH2 - CH2 - CH2 - CH3}\\
|\phantom{.........}\\
\ce{CH2}\phantom{......}\\
|\phantom{.........}\\
\ce{HC3 - C - CH3}\phantom{.........}\\
|\phantom{.........}\\
\ce{CH3}\phantom{......}
\end{array}\]

(i) 5 – (2′, 2′–Dimethylpropyl)-decane

(ii) 4 – Butyl – 2, 2– dimethylnonane

(iii) 2, 2– Dimethyl – 4– pentyloctane

(iv) 5 – neo-Pentyldecane

For an electrophilic substitution reaction, the presence of a halogen atom in the benzene ring:

(i) deactivates the ring by inductive effect

(ii) deactivates the ring by resonance

(iii) increases the charge density at ortho and para position relative to meta position by resonance

(iv) directs the incoming electrophile to meta position by increasing the charge density relative to ortho and para position.

In an electrophilic substitution reaction of nitrobenzene, the presence of nitro group:

(i) Deactivates the ring by inductive effect.

(ii) Activates the ring by inductive effect.

(iii) Decreases the charge density at ortho and para position of the ring relative to meta position by resonance.

(iv) Increases the charge density at meta position relative to the ortho and para positions of the ring by resonance.

Which of the following are correct?

(i) \[\ce{CH3 - O - CH^{⊕}2}\] is more stable than \[\ce{CH3 - CH^{⊕}2}\]

(ii) (CH₃)₂CH^⊕ is less stable than \[\ce{CH3 - CH2 - CH^{⊕}2}\]

(iii) \[\ce{CH3 = CH2 - CH^{⊕}2}\] is more stable than \[\ce{CH3 - CH2 - CH^{⊕}2}\]

(iv) \[\ce{CH2 - CH^{⊕}}\] is more stable than \[\ce{CH3 - CH^{⊕}2}\]

Four structures are given in options (i) to (iv). Examine them and select the aromatic structures.

(i)
(ii)
(iii)
(iv)

The molecules having dipole moment are:

(i) 2,2-Dimethylpropane

(ii) trans-Pent-2-ene

(iii) cis-Hex-3-ene

(iv) 2, 2, 3, 3 - Tetramethylbutane.

Why do alkenes prefer to undergo electrophilic addition reaction while arenes prefer electrophilic substitution reactions? Explain.

Alkynes on reduction with sodium in liquid ammonia form trans alkenes. Will the butene thus formed on reduction of 2-butyne show the geometrical isomerism?

Rotation around carbon-carbon single bond of ethane is not completely free. Justify the statement.

Draw Newman and Sawhorse projections for the eclipsed and staggered conformations of ethane. Which of these conformations is more stable and why?

The intermediate carbocation formed in the reactions of HI, HBr and HCl with propene is the same and the bond energy of HCl, HBr and HI is 430.5 kJ mol^–1, 363.7 kJ mol^–1 and 296.8 kJ mol^–1 respectively. What will be the order of reactivity of these halogen acids?

What will be the product obtained as a result of the following reaction and why?

How will you convert benzene into p – nitrobromobenzene

How will you convert benzene into m – nitrobromobenzene

Arrange the following set of compounds in the order of their decreasing relative reactivity with an electrophile. Give reason.

Despite their - I effect, halogens are o- and p-directing in haloarenes. Explain.

Why does presence of a nitro group make the benzene ring less reactive in comparison to the unsubstituted benzene ring. Explain.

Suggest a route for the preparation of nitrobenzene starting from acetylene?

Predict the major product (s) of the following reactions and explain their formation.

\[\ce{H3C - CH = CH2 ->[(Ph.CO.O)2][HBr]}\]

\[\ce{H3C - CH = CH2 ->[HBr]}\]

Nucleophiles and electrophiles are reaction intermediates having electron-rich and electron-deficient centres respectively. Hence, they tend to attack electron-deficient and electron-rich centres respectively. Classify the following species as electrophiles and nucleophiles.

(i) H₃CO^– 

(ii) \[\begin{array}{cc}
\phantom{.}\ce{O}\\
\phantom{.}||\\
\ce{H3C - C - O-}
\end{array}\]

(iii) \[\ce{\overset{\bullet}{C}l}\]

(iv) Cl₂C:

(v) (H₃C)₃C⁺ 

(vi) Br^– 

(vii) H₃COH

(viii) R – NH – R

The relative reactivity of 1°, 2°, 3° hydrogen’s towards chlorination is 1 : 3.8 : 5. Calculate the percentages of all monochlorinated products obtained from 2-methylbutane.

Write the structures and names of products obtained in the reactions of sodium with a mixture of 1-iodo-2-methylpropane and 2-iodopropane.

Write hydrocarbon radicals that can be formed as intermediates during monochlorination of 2-methylpropane? Which of them is more stable? Give reasons.

An alkane C₈H₁₈ is obtained as the only product on subjecting a primary alkyl halide to Wurtz reaction. On monobromination this alkane yields a single isomer of a tertiary bromide. Write the structure of alkane and the tertiary bromide.

The ring systems having following characteristics are aromatic.

(i) Planar ring containing conjugated π bonds.

(ii) Complete delocalisation of the π−electrons in ring system i.e. each atom in the ring has unhybridised p-orbital, and

(iii) Presence of (4n + 2) π−electrons in the ring where n is an integer (n = 0, 1, 2,...........) [Huckel rule].

Using this information classify the following compounds as aromatic/non-aromatic.

(A)	(B)	(C)	(D)
(E)	(F)	(G)

Which of the following compounds are aromatic according to Huckel’s rule?

(A)	(B)	(C)

(D)	(E)	(F)

Suggest a route to prepare ethyl hydrogensulphate (CH₃ – CH₂ – OSO₂ – OH) starting from ethanol (C₂H₅OH).

Match the reagent from Column I which on reaction with CH₃ – CH = CH₂ gives some product given in Column II as per the codes given below:

Match the hydrocarbons in Column I with the boiling points given in Column II.

Match the following reactants in Column I with the corresponding reaction products in Column II.

Match the reactions given in Column I with the reaction types in Column II.

Assertion (A): The compound cyclooctane has the following structural formula:

It is cyclic and has conjugated 8π-electron system but it is not an aromatic compound.

Reason (R): (4n + 2)π electrons rule does not hold good and ring is not planar.

Assertion (A): Toluene on Friedal Crafts methylation gives o– and p–xylene.

Reason (R): CH₃-group bonded to benzene ring increases electron density at o– and p– position.

Assertion (A): Nitration of benzene with nitric acid requires the use of concentrated sulphuric acid.

Reason (R): The mixture of concentrated sulphuric acid and concentrated nitric acid produces the electrophile, \[\ce{NO^{+}2}\].

Assertion (A): Among isomeric pentanes, 2, 2-dimethylpentane has highest boiling point.

Reason (R): Branching does not affect the boiling point.

An alkyl halide C₅H₁₁Br (A) reacts with ethanolic KOH to give an alkene ‘B’, which reacts with Br₂ to give a compound ‘C’, which on dehydrobromination gives an alkyne ‘D’. On treatment with sodium metal in liquid ammonia one mole of ‘D’ gives one mole of the sodium salt of ‘D’ and half a mole of hydrogen gas. Complete hydrogenation of ‘D’ yields a straight-chain alkane. Identify A, B, C and D. Give the reactions invovled.

896 mL vapour of a hydrocarbon ‘A’ having carbon 87.80% and hydrogen 12.19% weighs 3.28 g at STP. Hydrogenation of ‘A’ gives 2-methylpentane. Also ‘A’ on hydration in the presence of H₂SO₄ and HgSO₄ gives a ketone ‘B’ having molecular formula C₆H₁₂O. The ketone ‘B’ gives a positive iodoform test. Find the structure of ‘A’ and give the reactions involved.

An unsaturated hydrocarbon ‘A’ adds two molecules of H₂ and on reductive ozonolysis gives butane-1,4-dial, ethanal and propanone. Give the structure of ‘A’, write its IUPAC name and explain the reactions involved.

In the presence of peroxide addition of HBr to propene takes place according to anti Markovnikov’s rule but peroxide effect is not seen in the case of HCl and HI. Explain.