Alkyl Halides

7 free MDCAT Chemistry MCQs on Alkyl Halides (PM&DC syllabus), each with the answer, an explanation and the textbook line it comes from. Tap to check, no sign-up.

Tap an answer to check it · 7 questions

1. Question 1

   Tertiary alkyl halides in polar solvents usually undergo:
   • AUnimolecular substitution (SN1)
   • BBimolecular substitution (SN2)
   • CBimolecular elimination (E2)
   • DFree radical substitution
   Show answer and explanation

   Answer: A) Unimolecular substitution (SN1)

   Primary alkyl halides undergo SN2. Source: Chemistry 12 KPK (taleem360.com), p. 201.

2. Question 2

   The rate of an SN1 reaction depends on the concentration of the:
   • ASubstrate and nucleophile
   • BNucleophile only
   • CSubstrate only
   • DSolvent only
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   Answer: C) Substrate only

   Only the substrate ionizes in the slow step, so it is first order. Source: Chemistry 12 KPK (taleem360.com), p. 202.

3. Question 3

   Secondary alkyl halides follow the SN1 mechanism in polar solvents and the SN2 mechanism in:
   • AMolten salts
   • BPolar solvents
   • CAqueous acids
   • DNon-polar solvents
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   Answer: D) Non-polar solvents

   For secondary halides the solvent decides the mechanism. Source: Chemistry 12 KPK (taleem360.com), p. 204.

4. Question 4

   Reactions that remove atoms or groups from two adjacent carbon atoms to form a multiple bond are:
   • AElimination reactions
   • BSubstitution reactions
   • CAddition reactions
   • DCondensation reactions
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   Answer: A) Elimination reactions

   They are the reverse of addition: two sigma bonds break and a weaker pi bond forms. Source: Chemistry 12 KPK (taleem360.com), p. 204.

5. Question 5

   E2 elimination reactions are generally followed by:
   • ATertiary alkyl halides
   • BPrimary alkyl halides
   • CAryl halides
   • DGrignard reagents
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   Answer: B) Primary alkyl halides

   E2 is one-step and second order; E1 is followed by tertiary halides. Source: Chemistry 12 KPK (taleem360.com), p. 205.

6. Question 6

   2-Bromopropane treated with ethoxide ion, a strong base, gives mainly:
   • AAn alcohol by hydrolysis
   • BAn ether by substitution
   • CAn alkene by elimination
   • DAn alkane by reduction
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   Answer: C) An alkene by elimination

   A strong base favours elimination; the more nucleophilic, less basic C2H5S- gives substitution. Source: Chemistry 12 KPK (taleem360.com), p. 206.

7. Question 7

   Grignard reagents are prepared from alkyl halides and magnesium in:
   • AAqueous acid
   • BWater
   • CEthanol
   • DDry ether
   Show answer and explanation

   Answer: D) Dry ether

   Ether is the solvent and dissolves the reagent by solvation; it is used without isolation. Source: Chemistry 12 KPK (taleem360.com), p. 208.

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