Chemistry

Hydrocarbons

Question:

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

Answer:

ncert-solutions-class-11th-chemistry-chapter-13-hydrocarbons-32

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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.

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 4.

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

Q 5.

What happens when ethanol is heated with cone. H2SO4?

Q 6.

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

Q 7.

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

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.

Which is more acidic: ethene or ethyne and why?

Q 11.

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 12.

What is polymerization? Give an example.

Q 13.

How will you distinguish between propene and propane?

Q 14.

What are Arenes ?

Q 15.

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

Q 16.

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

Q 17.

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 18.

What do you mean by pyrolysis?

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.

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 21.

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

Q 22.

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

Q 23.

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

Q 24.

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 25.

What is electrophile in sulphonation?

Q 26.

Discuss the shape of methane and ethane.

Q 27.

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

Q 28.

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 29.

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

Q 30.

What is decarboxylation ? Give an example.

Q 31.

How do you account for the formation of ethane during chlorination of methane?

Q 32.

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

Q 33.

ncert-solutions-class-11th-chemistry-chapter-13-hydrocarbons-34

Q 34.

What is Lindlar’s catalyst? Give its use.

Q 35.

Why are alkanes called paraffins?

Q 36.

How will you distinguish between acetylene and ethylene?

Q 37.

How will you convert ethanoic acid into ethene?

Q 38.

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

Q 39.

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 40.

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 41.

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

Q 42.

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

Q 43.

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

Q 44.

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

Q 45.

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

Q 46.

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 47.

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

Q 48.

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 mol–1 and 296.8 kJ mol-1 What will be the other of reactivity of these halogen acids?

Q 49.

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

Q 50.

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’.