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NEET Previous Year Questions (2014-2024): Haloalkanes & Haloarenes | Chemistry Class 12 PDF Download

2023

Q1: The given compound    (2023)
NEET Previous Year Questions (2014-2024): Haloalkanes & Haloarenes | Chemistry Class 12is an example of ______.
(a) Benzylic halide
(b) Aryl halide
(c) Allylic halide
(d) Vinylic halide
Ans: 
C
α-carbon is sp3 carbon which is right next to   NEET Previous Year Questions (2014-2024): Haloalkanes & Haloarenes | Chemistry Class 12 
This a-position is known as allylic position
Hence,  
NEET Previous Year Questions (2014-2024): Haloalkanes & Haloarenes | Chemistry Class 12

 is allylic halide 

2021

Q1: The major product of the following chemical reaction is :    (NEET 2021)

NEET Previous Year Questions (2014-2024): Haloalkanes & Haloarenes | Chemistry Class 12(a) NEET Previous Year Questions (2014-2024): Haloalkanes & Haloarenes | Chemistry Class 12

(b) NEET Previous Year Questions (2014-2024): Haloalkanes & Haloarenes | Chemistry Class 12

(c) NEET Previous Year Questions (2014-2024): Haloalkanes & Haloarenes | Chemistry Class 12

(d)  NEET Previous Year Questions (2014-2024): Haloalkanes & Haloarenes | Chemistry Class 12
Ans: (d)
Addition of HBr to an alkene in presence of a peroxide (benzoyl peroxide [(C6H5CO)2O2] gives an anti Markownikoff’s product. Anti-Markownikoff’s rule states that hydrogen is added to a more substituted carbon atom of an unsymmetrical alkene.

NEET Previous Year Questions (2014-2024): Haloalkanes & Haloarenes | Chemistry Class 12
Q2: The major product formed in dehydrohalogenation reaction of 2-Bromo pentane is Pent-2-ene.This product formation is based on-     (NEET 2021)
(a) Hofmann Rule
(b) Huckel's Rule
(c) Saytzeff's Rule
(d) Hund's Rule
Ans:
(c)
Major product formed in dehydrohalogenation reaction of 2-bromopentane is pent-2-ene because according to Saytzeff's Rule, in dehydrohalogenation reactions, the preferred product is that alkene which has greater number of alkyl group(s) attached to the doubly bonded carbon atoms.
NEET Previous Year Questions (2014-2024): Haloalkanes & Haloarenes | Chemistry Class 12

2020

Q1: Which of the following alkane cannot be made in good yield by Wurtz reaction?    (NEET 2020)
(a) n-Heptane
(b) n-Butane
(c) n-Hexane
(d) 2,3-Dimethylbutane
Ans: 
A
Wurtz reaction is used to prepare symmetrical alkanes like

NEET Previous Year Questions (2014-2024): Haloalkanes & Haloarenes | Chemistry Class 12

Using Wurtz reaction, n-Heptane can not be produced in good production because it is unsymmetrical alkane.

Q2: Elimination reaction of 2-Bromo-pentane to form pent-2-ene is:    (NEET 2020)
(a) β-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)

NEET Previous Year Questions (2014-2024): Haloalkanes & Haloarenes | Chemistry Class 12

Since β-hydrogen is abstracted it is β-elimination.
Since more substituted alkene is formed (stable and major product), it follows Zaitsev's rule or Saytzev's rule.
Since H and Br are removed, it is dehydrohalogenation.

2018

Q9. The compound C7H8 undergoes the following reactions :    (NEET 2018)

NEET Previous Year Questions (2014-2024): Haloalkanes & Haloarenes | Chemistry Class 12

The product ‘C’ is

(a) m–bromotoluene
(b) o–bromotoluene
(c) 3–bromo–2,4,6–trichlorotoluene
(d) p–bromotoluene
Ans: 
(d)

NEET Previous Year Questions (2014-2024): Haloalkanes & Haloarenes | Chemistry Class 12
2017

Q10. Identify A and predict the type of reaction    (NEET 2017)
NEET Previous Year Questions (2014-2024): Haloalkanes & Haloarenes | Chemistry Class 12
(a)NEET Previous Year Questions (2014-2024): Haloalkanes & Haloarenes | Chemistry Class 12
(b)NEET Previous Year Questions (2014-2024): Haloalkanes & Haloarenes | Chemistry Class 12
(c)NEET Previous Year Questions (2014-2024): Haloalkanes & Haloarenes | Chemistry Class 12
(d)NEET Previous Year Questions (2014-2024): Haloalkanes & Haloarenes | Chemistry Class 12
Ans: 
(d)

NEET Previous Year Questions (2014-2024): Haloalkanes & Haloarenes | Chemistry Class 12

m-Bromoanisole gives only the respective meta substituted aniline. This is a substitution reaction which goes by an elimination-addition pathway.

2016

Q1: Consider the reaction,                     (NEET 2016 Phase 2)
CH3CH2CH2Br + NaCN CH3CH2CH2CN + NaBr

This reaction will be the fastest in
(a) ethanol
(b) methanol
(c) N, N' -dimethylformamide (DMF)
(d) Water
Ans:
(c)
The reaction,
CH3CH2CH2Br + NaCN  CH3CH2CH2CN + NaBr
follows SN2 mechanism which is favoured by polar aprotic solvent i.e., N, N'–dimethylformamide (DMF). 

2015

Q1: In an SN1 reaction on chiral centers, there is                      (NEET / AIPMT 2015
(a) inversion more than retention leading to partial racemisation
(b) 100% retention
(c) 100% inversion
(d) 100% racemisation
Ans: 
(a)

  • In case of optically active alkyl halides, SN1 reaction is accompanied by racemisation. The carbocation formed in the slow step being sp2 hybridised is planar and attack of nucleophile may take place from either side resulting in a mixture of products, one having the same configuration and other having inverted configuration.
  • The isomer corresponding to inversion is present in slight excess because SN1 also depends upon the degree of shielding of the front side of the reacting carbon.

2014

Q1: Which of the following compounds will undergo racemisation when solution of KOH  hydrolyses?  (AIPMT 2014)
NEET Previous Year Questions (2014-2024): Haloalkanes & Haloarenes | Chemistry Class 12
(a) (iii) and (iv)
(b) (i) and (iv)
(c) (iv)
(d) (ii) and (iv)
Ans:
(c)
Out of the given four compounds only (iv) compound is chiral and hence only this compound will undergo racemisation.

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FAQs on NEET Previous Year Questions (2014-2024): Haloalkanes & Haloarenes - Chemistry Class 12

1. What is the difference between haloalkanes and haloarenes?
Ans. Haloalkanes are compounds in which one or more hydrogen atoms are replaced by halogen atoms, whereas haloarenes are aromatic compounds in which one or more hydrogen atoms in the benzene ring are replaced by halogen atoms.
2. How are haloalkanes and haloarenes classified?
Ans. Haloalkanes and haloarenes are classified based on the number of halogen atoms attached to the carbon atom. They can be classified as mono-halo, di-halo, tri-halo, or poly-halo compounds.
3. What are the common uses of haloalkanes and haloarenes?
Ans. Haloalkanes are used as solvents, refrigerants, and in the manufacturing of plastics, while haloarenes are used in the synthesis of pharmaceuticals, pesticides, and as intermediates in organic reactions.
4. How do haloalkanes and haloarenes participate in nucleophilic substitution reactions?
Ans. Haloalkanes and haloarenes undergo nucleophilic substitution reactions where the halogen atom is replaced by a nucleophile, resulting in the formation of a new compound.
5. What are some environmental concerns associated with haloalkanes and haloarenes?
Ans. Haloalkanes and haloarenes are considered to be persistent organic pollutants (POPs) that can bioaccumulate in the environment and have harmful effects on human health and wildlife. Efforts are being made to regulate their use and disposal to minimize environmental impact.
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