Solution of Chapter 13. Hydrocarbons (Chemistry - Exemplar Book)

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

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

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) H₃C – CH₂^-

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?

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

Which are the correct IUPAC names of the following compound?

Which are the correct IUPAC names of the following compound?

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

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

Which of the following are correct?

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

The molecules having dipole moment are __________.

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

(i) p – nitrobromobenzene

(ii) 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 halo-arenes. 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.

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.

The relative reactivity of 1°, 2°, 3° hydrogen’s towards chlorination is 1: 3.8: 5. Calculate the percentages of all mono-chlorinated 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)−electrons in the ring where n is an integer (n = 0, 1, 2,...........) [Huckel rule].

Using this information classify the following compounds as aromatic/nonaromatic.

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

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

In the following questions a statement of assertion (A) followed by a statement of reason (R) is given. Choose the correct option out of the choices given below each question.

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.

(i) Both A and R are correct and R is the correct explanation of A.

(ii) Both A and R are correct but R is not the correct explanation of A.

(iii) Both A and R are not correct.

(iv) A is not correct but R is correct.

In the following questions a statement of assertion (A) followed by a statement of reason (R) is given. Choose the correct option out of the choices given below each question.

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.

(i) Both A and R are correct and R is the correct explanation of A.

(ii) Both A and R are correct but R is not the correct explanation of A.

(iii) Both A and R are not correct.

(iv) A is not correct but R is correct.

In the following questions a statement of assertion (A) followed by a statement of reason (R) is given. Choose the correct option out of the choices given below each question.

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, NO₂⁺ .

(i) Both A and R are correct and R is the correct explanation of A.

(ii) Both A and R are correct but R is not the correct explanation of A.

(iii) Both A and R are not correct.

(iv) A is not correct but R is correct.

In the following questions a statement of assertion (A) followed by a statement of reason (R) is given. Choose the correct option out of the choices given below each question.

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

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

(i) Both A and R are correct and R is the correct explanation of A.

(ii) Both A and R are correct but R is not the correct explanation of A.

(iii) Both A and R are not correct.

(iv) A is not correct but R is correct.

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 involved.

896 mL vapour of a hydrocarbon ‘A’ having carbon 87.80% and hydrogen 12.19% weighs 3.28g 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.