Chemistry

Hydrocarbons

Question:

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)

Answer:

 (a) Isomers of C4H8 having one double bond are:
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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.

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.
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Q 5.

Explain the term aromaticity. What are the necessary conditions for any compound to show aromaticity?

Q 6.

How will you distinguish between propene and propane?

Q 7.

What happens when ethanol is heated with cone. H2SO4?

Q 8.

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 9.

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 10.

Which is more acidic: ethene or ethyne and why?

Q 11.

What are conformations?

Q 12.

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

Q 13.

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 14.

What are Arenes ?

Q 15.

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

Q 16.

Draw the cis- and trans-structures for hex-2-ene. Which iosmer will have higher b.p. and why?

Q 17.

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

Q 18.

What happens when benzene is treated with excess of Cl2 in presence of sunlight? Give chemical reaction.

Q 19.

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

Q 20.

How will you distinguish between acetylene and ethylene?

Q 21.

What is polymerization? Give an example.

Q 22.

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 23.

Suggest the name of another Lewis acid instead of anhydrous aluminium chloride which can be used during ethylation of benzene.

Q 24.

What do you mean by pyrolysis?

Q 25.

Discuss the shape of methane and ethane.

Q 26.

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

Q 27.

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

Q 28.

Write down the products ofozonolysis ofl, 2-dimethylbenzene (o-xylene). How does the result support Kekule structure of benzene?

Q 29.

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

Q 30.

Arrange the following carbanions in order of their decreasing stability.
(A) H3C-C ≡ C                                                                                
(B) H-C ≡ C
(C) H3C – CH2
(a) A>B>C
(b) B>A>C
(c) C>B>A
(d) C>A>B

Q 31.

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 32.

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 33.

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 34.

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Q 35.

Although benzene is highly unsaturated it does not undergo addition reactions. Why?

Q 36.

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

Q 37.

Define resonance energy. What is resonance energy of benzene?

Q 38.

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

Q 39.

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

Q 40.

The intermediate carbocation formed in the reactions of HI, HBr and HC1 with propene is the same and the bond energy of HCl, HBr and HI is 430.5 kJ mol-1,363.7 kJ mol1 and 296.8 kJ mol-1 What will be the other of reactivity of these halogen acids?

Q 41.

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

Q 42.

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

Q 43.

Arrange benzene, n-hexane and ethyne in decreasing order of acidic behaviour. Also give reason for this behaviour.

Q 44.

What is decarboxylation ? Give an example.

Q 45.

What is Huckel rule?

Q 46.

What is electrophile in sulphonation?

Q 47.

(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 48.

How will you separate propene from propyne?

Q 49.

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

Q 50.

What is Lindlar’s catalyst? Give its use.