PYQSide ExamsMy practice

Haloalkanes and Haloarenes · Question 23

AIPMT 2011 (Mains)MCQMedium📈 Topic in 50% papers+4−1
1

Consider the reactions. (i) (CH3)2CH-CH2Br C2H5OH (CH3)2CH-CH2OC2H5 + HBr (ii) (CH3)2CH-CH2Br C2H5O- (CH3)2CH-CH2OC2H5 + Br- The mechanisms of reactions (i) and (ii) are respectively

  1. SN1 and SN2
  2. SN1 and SN1
  3. SN2 and SN2
  4. SN2 and SN1

Answer

(1) SN1 and SN2

Solution

(i) C2H5OH is a weak, neutral nucleophile and a polar protic solvent. The reaction is a solvolysis: the C–Br bond ionises first (slow step, assisted by the protic solvent) and the carbocation is then attacked by ethanol.

⇒ Reaction (i) follows the SN1 path.

(ii) C2H5O- is a strong, negatively charged nucleophile; it attacks the -CH2Br carbon from the back side in one step while Br- leaves (Williamson synthesis).

⇒ Reaction (ii) follows the SN2 path.

∴ The mechanisms are SN1 and SN2 respectively.

Answer: (1)

AIPMT 2011 (Mains)

Keep practising — Haloalkanes and Haloarenes

2

Which one is a nucleophilic substitution reaction among the following ?

  1. CH3-CH=CH2 + H2O H+ CH3- OH |CH-CH3
  2. RCHO + R'MgX R- OH |CH-R'
  3. CH3-CH2- CH3 |CH-CH2Br + NH3 CH3-CH2- CH3 |CH-CH2NH2
  4. CH3CHO + HCN CH3CH(OH)CN
AIPMT 2011 (Prelims)
3

In the following reaction C6H5CH2Br [2. H3O+]1. Mg, ether X, the product 'X' is

  1. C6H5CH2OCH2C6H5
  2. C6H5CH2OH
  3. C6H5CH3
  4. C6H5CH2CH2C6H5
AIPMT 2010 (Mains)
4

The reaction of toluene with Cl2 in presence of FeCl3 gives X and reaction in presence of light gives Y. Thus, X and Y are

  1. X = Benzal chloride, Y = o-chlorotoluene
  2. X = m-chlorotoluene, Y = p-chlorotoluene
  3. X = o- and p-chlorotoluene, Y = Trichloromethyl benzene
  4. X = Benzyl chloride, Y = m-chlorotoluene
AIPMT 2010 (Prelims)
5

Which one is most reactive towards SN1 reaction?

  1. C6H5CH(C6H5)Br
  2. C6H5CH(CH3)Br
  3. C6H5C(CH3)(C6H5)Br
  4. C6H5CH2Br
AIPMT 2010 (Prelims)
6

The correct order of increasing reactivity of [figure] C–X bond towards nucleophile in the following compounds is

  1. I < II < IV < III
  2. II < III < I < IV
  3. IV < III < I < II
  4. III < II < I < IV
AIPMT 2010 (Prelims)
7

Which of the following reactions is an example of nucleophilic substitution reaction?

  1. 2RX + 2Na R-R + 2NaX
  2. RX + H2 RH + HX
  3. RX + Mg RMgX
  4. RX + KOH ROH + KX
AIPMT 2009
8

Trichloroacetaldehyde, CCl3CHO reacts with chlorobenzene in presence of sulphuric acid and produces

  1. [figure]
  2. [figure]
  3. [figure]
  4. [figure]
AIPMT 2009
9

In an SN2 substitution reaction of the type R-Br + Cl- DMF R-Cl + Br- which one of the following has the highest relative rate?

  1. CH3- CH3 | CH3 |C-CH2Br
  2. CH3CH2Br
  3. CH3CH2CH2Br
  4. CH3- CH3 |CH-CH2Br
AIPMT 2008
10

Which of the following undergoes nucleophilic substitution exclusively by SN1 mechanism?

  1. Ethyl chloride
  2. Isopropyl chloride
  3. Chlorobenzene
  4. Benzyl chloride
AIPMT 2005
11

Which of the following is least reactive in a nucleophilic substitution reaction?

  1. (CH3)3C-Cl
  2. CH2=CHCl
  3. CH3CH2Cl
  4. CH2=CHCH2Cl
AIPMT 2004

All Haloalkanes and Haloarenes PYQs →

PDFDownload Haloalkanes and Haloarenes PYQs as PDF Free, with answer key and a QR code to every solution — print it or study offline⬇
All NEET Chemistry chapters
Physical ChemistrySome Basic Concepts of ChemistryStructure of AtomStates of MatterThermodynamicsEquilibriumRedox ReactionsSolid StateSolutionsElectrochemistryChemical KineticsSurface Chemistry
Inorganic ChemistryClassification of Elements and Periodicity in PropertiesChemical Bonding and Molecular StructureHydrogens-Block Elementsp-Block Elements (Group 13 & 14)Environmental ChemistryGeneral Principles of Isolation of Elementsp-Block Elements (Group 15–18)d- and f-Block ElementsCoordination Compounds
Organic ChemistryOrganic Chemistry – Some Basic Principles and TechniquesIsomerismHydrocarbonsHaloalkanes and HaloarenesAlcohols, Phenols and EthersAldehydes, Ketones and Carboxylic AcidsAminesBiomoleculesPolymersChemistry in Everyday LifePrinciples Related to Practical Chemistry