NEET Previous Year Questions (2014-21): Haloalkanes & Haloarenes Notes | Study Chemistry Class 12 - NEET

Q.1. The correct sequence of bond enthalpy of 'C-X' bond for the following compounds is -    (2021)
(a) CH₃-F< CH₃-Cl> CH₃-Br >CH₃-I
(b) CH₃-Cl> CH₃-F> CH₃-Br > CH₃-I
(c) CH₃-F< CH₃-Cl < CH₃-Br < CH₃-I
(d)  CH₃-F> CH₃-Cl> CH₃-Br > CH₃-I
Ans: D
Correct sequence of bond enthalpy of C–X bond is
CH₃-F> CH₃-Cl> CH₃-Br > CH₃-I

Q.2. The major product formed in dehydrohalogenation reaction of 2-Bromo pentane is Pent-2-ene.This product formation is based on-     (2021)
(a) Hofmann Rule
(b) Huckel's Rule
(c) Saytzeff's Rule
(d) Hund's Rule
Ans: C

(Major product by Saytzeff's rule).

Q.3. Which of the following alkane cannot be made in good yield by Wurtz reaction?    (2020)
A: n-Heptane
B: n-Butane
C: n-Hexane
D: 2,3-Dimethylbutane
Ans: A
Wurtz reaction is used to prepare symmetrical alkane.

Q.4. Elimination reaction of 2-Bromo-pentane to form pent-2-ene is:    (2020)
(a) b-Elimination reaction
(b) Follows Zaitsev rule
(c) Dehydrohalogenation reaction
(d) Dehydration reaction
A: (b), (c), (d)
B: (a), (b), (d) 
C: (a), (b), (c)
D: (a), (c), (d)
Ans: C

In the reaction
(i) Dehydrohalogenation  
(ii) β - elimination reaction
(iii) follows zaitsev rule (highly substituted alkene is formed as major product)

Q.5. Hydrocarbon (A) reacts with bromine by substitution to form an alkyl bromide which by Wurtz reaction is converted to gaseous hydrocarbon containing less than four carbon atoms. (A) is    (2018)
A: CH≡CH
B: CH₂=CH₂
C: CH₃–CH₃
D: CH₄
Ans: D


Q.6. Identify A and predict the type of reaction    (2017)

A:
B:
C:
D:
Ans: D


Q.7. For the following reaction :    (2016)

Which of the following statements is correct ?
A: (a) is substitution, (b) and (c) are addition reactions.
B: (a) is elimination, (b) and (c) are substitution reactions.
C: (a) is elimination, (b) is substitution and (c) addition reaction.
D: (a) and (b) are elimination reactions and (c) is addition reaction.
Ans: C


Q.8. Which of the following compounds will undergo racemisation when solution of KOH    (2014)
hydrolyses ?

A: (iii) and (iv)
B: (i) and (iv)
C: (i) and (ii)
D: (ii) and (iv)
Ans: B
Correct option (None)
Due to chirality

Only compound (iv) will undergo racemisation. Hence, all the given options are incorrect.