Chemistry

Hydrocarbons

Question:

An alkene ‘A’ contains three C—C, eight C—H, a-bonds, and one C—C n-bond. ‘A’ on ozonolysis gives two moles of an aldehyde of molar mass 44 u. Write the IUPAC name of’A’.

Answer:

 (i) An aldehyde with molar mass of 44 u is ethanal, CH3CH=0
(ii) Write two moles of ethanal side by side with their oxygen atoms pointing towards each other.
ncert-solutions-class-11th-chemistry-chapter-13-hydrocarbons-10
(iii) Remove the oxygen atoms and join them by a double bond, the structure of alkene ‘A’ is
ncert-solutions-class-11th-chemistry-chapter-13-hydrocarbons-11
As required, but-2-ene has three C—C, eight C—H a-bonds and one C—C π-bond.

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Hydrocarbons

Q 1.

In the alkane, CH3CH2—C(CH3)2—CH2—CH(CH3)2, identify 1 °, 2 °, 3 ° carbon atoms and give the number of H-atoms bonded to each one of these.

Q 2.

Convert ethylene to ethane.

Q 3.

What is the hybridisation of central carbon in 1,2-propadiene (CH2=C=CH2)?

Q 4.

How will you distinguish between propene and propane?

Q 5.

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.
ncert-exemplar-problems-class-11-chemistry-chapter-13-hydrocarbons-46

Q 6.

Out of benzene, m-dinitrobenzene and toluene which will undergo nitration most easily and why?

Q 7.

What happens when ethanol is heated with cone. H2SO4?

Q 8.

Which of the following are correct?
(a) CH3 – O – CH+2 is more stable than CH3 – CH+2
(b) (CH3)2CH+ is less stable than CH3 – CH2 – CH+2
(c) CH2 = CH – CH+2 is more stable than CH3 – CH2 – CH+2
(d) CH2 = CH+ is more stable than CH3 – CH+2
 

Q 9.

What are conformations?

Q 10.

Arrange the following: HCl, HBr, HI, HF in order of decreasing reactivity towards alkenes.

Q 11.

What happens when benzene is treated with acetyl chloride in presence of AlCl3?

Q 12.

Write the IUPAC names of the following compounds.
(i) (CH3)CCH2C(CH3)3    (ii) (CH3)2C(C2H5)2

Q 13.

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

Q 14.

For the following compounds, write structural formulas and IUPAC names for all possible isomers having the number of double or triple bond as indicated:
(a) C4H8 (one double bond) (b) C5H8 (one triple bond)

Q 15.

The molecules having dipole moment are________ .
(a) 2,2-Dimethylpropane                                            
(b) trans-Pent-2-ene
(c) cw-Hex-3-ene            
(d) 2,2,3,3-Tetramethylbutane

Q 16.

Explain why the following systems are not aromatic?
ncert-solutions-class-11th-chemistry-chapter-13-hydrocarbons-17

Q 17.

Which is more acidic: ethene or ethyne and why?

Q 18.

What effect does branching of an alkane chain has on its boiling point?

Q 19.

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

Q 20.

Why is benzene extra-ordinarily stable though it contains three double bonds?

Q 21.

What do you mean by pyrolysis?

Q 22.

What is electrophile in sulphonation?

Q 23.

Explain the following with examples:
(i) Wurtz reaction
(ii) Hydrogenation.

Q 24.

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

ncert-exemplar-problems-class-11-chemistry-chapter-13-hydrocarbons-10

Q 25.

Which of the following alkenes on ozonolysis gives a mixture of ketones only?
ncert-exemplar-problems-class-11-chemistry-chapter-13-hydrocarbons-16

Q 26.

Write chemical equations for the combustion reaction of the following hydrocarbons,  (i) Butane (ii) Pentene (iii) Hexyne (iv) Toluene

Q 27.

What are the necessary conditions for any system to be aromatic?

Q 28.

What effect does branching of an alkane chain has on its boiling point?

Q 29.

Why are alkanes called paraffins?

Q 30.

How will you distinguish between acetylene and ethylene?

Q 31.

What are Arenes ?

Q 32.

Classify the following compounds into (i) alkanes (ii) alkenes (iii) alkynes (iv) arenes.  (a) C6H6 (b) C4H8 (C) C8H8 (d) C5H8 (e) C6H14

Q 33.

What is polymerization? Give an example.

Q 34.

(a) Why are alkenes called unsaturated hydrocarbons?
(b) How will you test the presence of double bond in an alkene?
(c) Name the products formed when propene is subjected to ozonolysis.

Q 35.

How will you separate propene from propyne?

Q 36.

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

ncert-exemplar-problems-class-11-chemistry-chapter-13-hydrocarbons-36

 

Q 37.

An alkene ‘A’ contains three C—C, eight C—H, a-bonds, and one C—C n-bond. ‘A’ on ozonolysis gives two moles of an aldehyde of molar mass 44 u. Write the IUPAC name of’A’.

Q 38.

Arrange the following set of compounds in order of their decreasing relative reactivity with an electrophile, E+.
(a) Chlorobenzene, 2, 4-dinitrochlorobenzene, p-nitrochlorobenzene
(b) Toluene,p—H3C—C6H4—NO2, p—O2N—C6H4—NO2.

Q 39.

What is decarboxylation ? Give an example.

Q 40.

What happens when benzene is treated with acetyl chloride in presence of AlCl3?

Q 41.

Which type of isomerism is exhibited by but-l-yne and but-2-yne?

Q 42.

Define resonance energy. What is resonance energy of benzene?

Q 43.

Discuss the preparation of alkanes by Wurtz reaction. What is the limitaHon of the reaction?

Q 44.

How will you demonstrate that double bonds of benzene are somewhat different from that of olefins?

Q 45.

Write the structure of the alkene which on reductive ozonolysis gives butanone and ethanol.

Q 46.

Which are the correct IUPAC names of the following compound
ncert-exemplar-problems-class-11-chemistry-chapter-13-hydrocarbons-20

(a) 5-(2′,2′-Dimethylpropyl)decane
(b) 4-Butyl-2,2-dimethylnonane
(c) 2,2-Dimethyl-4-pentyloctane
(d) 5-neo-Pentyldecane

Q 47.

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

Q 48.

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

Q 49.

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

ncert-exemplar-problems-class-11-chemistry-chapter-13-hydrocarbons-32

Q 50.

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