Chemistry Class 11 NCERT Solutions: Chapter 13 Hydrocarbons Part 6

Q: 7. Propanal and pentan-3-one are the ozonolysis products of an alkene? What is the structural formula of the alkene?

Answer:

As per the given information, propanal and pentan-3-one are the ozonolysis products of an alkene. Let the given alkene be ‘A’. Writing the reverse of the ozonolysis reaction, we get:

Q 7 Ans 1 Structure of propanal and Pentan-3-One are the Ozonolysis Products of an Alkene

Propanal and Pentan-3-One as Ozonolysis Products

Q 7 Ans 1 Structure of propanal and Pentan-3-One are the Ozonolysis Products of an Alkene

The products are obtained on the cleavage of ozonide ‘X’. Hence, ‘X’ contains both products in the cyclic form. The possible structure of ozonide can be represented as:

Q 7 Ans 2 Structure of Represented of Ozonide

Structure of Represented of Ozonide

Q 7 Ans 2 Structure of Represented of Ozonide

Now, ‘X’ is an addition product of alkene ‘A’ with ozone. Therefore, the possible structure of alkene ‘A’ is:

Q 7 Ans 3 Structure of Alkene

Q 7 Ans 3 Structure of Alkene

Q 7 Ans 3 Structure of Alkene

Q: 8. Write Chemical equations for combustion reaction of the following hydrocarbons

(I) Butane

(II) Pentene

(III) Hexyne

(IV) Toluene

Answer:

Combustion can be defined as a reaction of a compound with oxygen.

(I) Equation

(II) Equation

(III) Equation

(IV)

Q 8 Ans IV Structure of Toluene

Q 8 Ans IV Structure of Toluene

Q 8 Ans IV Structure of Toluene

Q: 9. Draw the Equation and Equation structures of hex-2-ene. Which isomer will have higher b.p. and why?

Answer:

Hex-2-ene is represented as:

Equation

Geometrical isomers of hex-2-ene are:

Q 9 Ans Structure of Geometrical Isomers of Hex-2-ene

Structure of Geometrical Isomers of Hex-2-Ene

Q 9 Ans Structure of Geometrical Isomers of Hex-2-ene

The dipole moment of cis-compound is a sum of the dipole moments of Equation and Equation bonds acting in the same direction. The dipole moment of trans-compound is the resultant of the dipole moments of Equation and Equation bonds acting in opposite directions. Hence, cis-isomer is more polar than trans-isomer. The higher the polarity, the greater is the intermolecular dipole-dipole interaction and the higher will be the boiling point. Hence, cis-isomer will have a higher boiling point than trans-isomer.

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