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Hydrocarbons

NEET (UG) 2022 (Phase 2)MCQEasy📈 Topic in 12% papers+4−1
Ques. 1NEET (UG) 2022 (Phase 2)

The incorrect method for the synthesis of alkenes is

  1. Treating vicinal dihalides with Zn metal
  2. Treating of alkynes with Na in liquid NH3
  3. Heating alkyl halides with alcoholic KOH
  4. Treating alkyl halides in aqueous KOH solution

Answer

(4) Treating alkyl halides in aqueous KOH solution

Solution

(1) Vicinal dihalide + Zn alkene + ZnX2 (dehalogenation) — gives alkene.

(2) Alkyne + Na in liquid NH3 trans-alkene (partial reduction) — gives alkene.

(3) Alkyl halide + alcoholic KOH, heat alkene (dehydrohalogenation, β-elimination) — gives alkene.

(4) As per NCERT, aqueous KOH supplies OH- as a nucleophile and replaces the halogen: R-X + KOH(aq) R-OH + KX — gives an alcohol, not an alkene.

∴ Method (4) is incorrect.

Answer: (4)

Keep practising — Hydrocarbons

Ques. 2NEET (UG) 2021

The major product of the following chemical reaction is : [figure]

  1. [figure]
  2. [figure]
  3. [figure]
  4. [figure]
Ques. 3NEET (UG) 2021

CH3CH2COO-Na+ [Heat]NaOH, +? CH3CH3 + Na2CO3 Consider the above reaction and identify the missing reagent/chemical.

  1. DIBAL-H
  2. B2H6
  3. Red Phosphorus
  4. CaO
Ques. 4NEET (UG) 2020

Which of the following alkane cannot be made in good yield by Wurtz reaction?

  1. 2, 3-Dimethylbutane
  2. n-Heptane
  3. n-Butane
  4. n-Hexane
Ques. 5NEET (UG) 2020

An alkene on ozonolysis gives methanal as one of the products, Its structure is :

  1. [figure]
  2. [figure]
  3. [figure]
  4. [figure]
Ques. 6NEET (UG) 2019

Among the following, the reaction that proceeds through an electrophilic substitution, is :

  1. [figure]
  2. [figure]
  3. [figure]
  4. [figure]
Ques. 7NEET (UG) 2019

The most suitable reagent for the following conversion, is : [figure]

  1. Zn / HCl
  2. Hg2+/H+, H2O
  3. Na / liquid NH3
  4. H2, Pd/C, quinoline
Ques. 8NEET (UG) 2019

An alkene “A” on reaction with O3 and Zn + H2O gives propanone and ethanal in equimolar ratio. Addition of HCl to alkene “A” gives “B” as the major product. The structure of product “B” is :

  1. H3C-CH2- Cl | CH3 |C-CH3
  2. H3C- Cl |CH- CH3 | CH3 |CH
  3. Cl-CH2-CH2- CH3 | CH3 |CH
  4. H3C-CH2- CH2Cl |CH-CH3
Ques. 9NEET 2018

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

  1. CH CH
  2. CH2 = CH2
  3. CH3 - CH3
  4. CH4
Ques. 10NEET 2017

Predict the correct intermediate and product in the following reaction : H3C-C CH [HgSO4]H2O, H2SO4 (A)Intermediate (B)Product

  1. A : H3C- OH |C=CH2 B : H3C- SO4 |C=CH2
  2. A : H3C- O \|C-CH3 B : H3C-C CH
  3. A : H3C- OH |C=CH2 B : H3C- O \|C-CH3
  4. A : H3C- SO4 |C=CH2 B : H3C- O \|C-CH3
Ques. 11NEET 2016 (Phase 1)

Consider the nitration of benzene using mixed conc. H2SO4 and HNO3. If a large amount of KHSO4 is added to the mixture, the rate of nitration will be

  1. unchanged
  2. doubled
  3. faster
  4. slower

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