Chemistry

Hydrocarbons

Question:

Write the structure and IUPAC names of different structural isomers of alkenes corresponding to C5H10.

Answer:

ncert-solutions-class-11th-chemistry-chapter-13-hydrocarbons-46

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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.

How will you distinguish between propene and propane?

Q 4.

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

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.

What happens when ethanol is heated with cone. H2SO4?

Q 7.

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 8.

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 9.

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

Q 10.

What are conformations?

Q 11.

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

Q 12.

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 13.

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 14.

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

Q 15.

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

Q 16.

Define resonance energy. What is resonance energy of benzene?

Q 17.

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

Q 18.

How will you convert benzene into
(i) p-nitrobromobenzene (ii) m-nitrobromobenzene
 

Q 19.

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 20.

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

Q 21.

Which is more acidic: ethene or ethyne and why?

Q 22.

What is electrophile in sulphonation?

Q 23.

What is polymerization? Give an example.

Q 24.

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

Q 25.

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

Q 26.

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

Q 27.

How will you distinguish between acetylene and ethylene?

Q 28.

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 29.

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 30.

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

Q 31.

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

Q 32.

(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 33.

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

Q 34.

Why does benzene undergo electrophilic substitution reactions easily and nucleophilic substitutions with difficulty?

Q 35.

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 36.

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 37.

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

Q 38.

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

Q 39.

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

Q 40.

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 41.

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

Q 42.

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

Q 43.

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

Q 44.

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

Q 45.

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 46.

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 47.

What is decarboxylation ? Give an example.

Q 48.

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

Q 49.

Why are Alkenes called olefins?

Q 50.

Write the structure and IUPAC names of different structural isomers of alkenes corresponding to C5H10.