Chemistry

Hydrocarbons

Question:

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

Answer:

ncert-exemplar-problems-class-11-chemistry-chapter-13-hydrocarbons-30

Thus, but-2-ene is capable of showing geometrical isomerism

 

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Hydrocarbons

Q 1.

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 2.

How will you distinguish between propene and propane?

Q 3.

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

Q 4.

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 5.

Define resonance energy. What is resonance energy of benzene?

Q 6.

Discuss the shape of methane and ethane.

Q 7.

Convert ethylene to ethane.

Q 8.

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

Q 9.

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

Q 10.

Why are Alkenes called olefins?

Q 11.

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

Q 12.

An alkene ‘A’ contains three C-C, eight C-H σ bonds and one C-C Ï€ bond. ‘A' on ozonolysis gives two moles of an aldehyde of molar mass 44 u. Deduce IUPAC name of’A’.

Q 13.

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

Q 14.

How will you separate propene from propyne?

Q 15.

What happens when ethanol is heated with cone. H2SO4?

Q 16.

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

Q 17.

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 18.

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

Q 19.

What is Lindlar’s catalyst? Give its use.

Q 20.

How will you distinguish between acetylene and ethylene?

Q 21.

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

Q 22.

In an electrophilic substitution reaction of nitrobenzene, the presence of nitro group ________ ‘
(a) deactivates the ring by inductive effect
(b) activates the ring by inductive effect
(c) decreases the charge density at ortho- and para-positions of the ring relative to meta-position by resonance
(d) increases the charge density at meta-position relative to the ortho and para-positions of the ring by resonance

Q 23.

Why are alkanes called paraffins?

Q 24.

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

Q 25.

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 26.

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

Q 27.

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

Q 28.

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

Q 29.

(a) What effect the branching of an alkane has on its melting point?
(b) Which of the following has highest boiling point?
(i) 2-methyl pentane
(ii) 2, 3-diethyl butane
(iii) 2, 2-dimethyl butane

Q 30.

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

Q 31.

An alkene ‘A’ on ozonolysis gives a mixture of ethanal and pentan-3-one. Write the structure and IUPAC name of ‘A’.

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.

Write structures of all the alkenes which on hydrogeneration give 2-methylbutane.

Q 34.

What is electrophile in sulphonation?

Q 35.

How will you convert ethanoic acid into ethene?

Q 36.

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

Q 37.

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

Q 38.

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

Q 39.

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 40.

What do you mean by pyrolysis?

Q 41.

What are Arenes ?

Q 42.

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

Q 43.

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

Q 44.

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 45.

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

Q 46.

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

Q 47.

What are conformations?

Q 48.

Which is more acidic: ethene or ethyne and why?

Q 49.

What is polymerization? Give an example.

Q 50.

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