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Chapter 13- Hydrocarbons Interview Questions Answers

Question 1 :
How do you account for the formation of ethane during chlorination of methane?

Answer 1 : Chlorination of methane is a free radical reaction which occurs by the following mechanism:

Fromthe above mechanism, it is evident that during propagation step, CH3 free radicals areproduced which may undergo three reactions, i.e., (i) — (iii). In the chaintermination step, the two CH3 freeradicals combine together to form ethane (CH3—CH3)molecule.

Question 2 : Write IUPAC names of the following compounds:

Answer 2 :

Question 3 : For the following compounds, write structuralformulas and IUPAC names for all possible isomers having the number of doubleor triple bond as indicated:
(a) C4H8 (onedouble bond) (b) C5H8 (one triple bond)

Answer 3 : (a) Isomers of C4H8 having one double bond are:

Question 4 : Write IUPAC names of the products obtained by theozonolysis of the following compounds:
(i) Pent-2-ene (ii) 3,4-Dimethylhept-3-ene (iii) 2-Ethylbut-l-ene (iv) 1-Phenylbut-l-ene.

Answer 4 :

Question 5 : An alkene ‘A’ on ozonolysis gives a mixture ofethanal and pentan-3-one. Write the structure and IUPAC name of ‘A’.

Answer 5 :

Step 1. Write the structure of the products side by side withtheir oxygen atoms pointing towards each other.

Step 2. Remove the oxygenatoms and join the two ends by a double bond, the structure of the alkene ‘A’is

Question 6 : 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 aldehydeof molar mass 44 u. Write the IUPAC name of’A’.

Answer 6 :

(i) An aldehyde with molar mass of44 u is ethanal, CH3CH=0
(ii) Write two moles of ethanal side by side with their oxygen atoms pointingtowards each other.

(iii) Remove the oxygen atoms and join them by a double bond, the structure ofalkene ‘A’ is

As required, but-2-ene has three C—C, eight C—H a-bonds and one C—C π-bond.

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

Answer 7 : (i)Write the structures of propanal and pentan-3-ene with their oxygen atomsfacing each other, we have,

(ii) Remove oxygen atoms and join the two fragments by a double bond, thestructure of the alkene is

Question 8 : Write chemical equations for the combustion reaction of the following hydrocarbons, (i) Butane (ii) Pentene (iii) Hexyne (iv) Toluene

Answer 8 :

Question 9 : Draw the cis- and trans-structures for hex-2-ene. Which iosmer will have higher b.p. and why?

Answer 9 :

The structures of cis- andtrans-isomer of hex-2-ene are:

The boiling point of a molecule depends upon dipole-dipole interactions. Sincecis-isomer has higher dipole moment, therefore, it has higher boiling point.

Question 10 : Why is benzene extra-ordinarily stable though it contains three double bonds?

Answer 10 :

The six electrons of the p-orbitalscover all the six carbon atoms, and are said to be delocalized. As a result ofdelocalization there formed a stronger n-bond and a more stable molecule.



Chapter 13- Hydrocarbons Contributors


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