What is the correct order of reactivity of alkyl bromides in SN2 reactions?
Correct answer A. Methyl > primary > secondary > tertiary
Topic / 37 questions
Alkyl Halides MCQs
Alkyl Halides MCQs are multiple-choice questions on the naming, structure and reactivity of haloalkanes, with a focus on nucleophilic substitution and elimination mechanisms. They follow the MDCAT chemistry curriculum, and every question on MCQs360 shows its correct answer instantly so you can test your grasp of mechanisms and products.
- Gases 40
- Liquids 40
- Solids 40
- Chemical Equilibrium 40
- Reaction Kinetics 40
- Thermochemistry and Energetics 40
- Electrochemistry 40
- Fundamental Concepts of Chemistry 40
- Atomic Structure 39
- Chemical Bonding 39
- Alcohols and Phenols 38
- Industrial Chemistry 37
- Aldehydes and Ketones 37
- Alkyl Halides 37
- s- and p-Block Elements 37
- Chemistry of Hydrocarbons 36
- Fundamental Principles of Organic Chemistry 36
- Carboxylic Acids 36
- Transition Elements 35
- Macromolecules 35
(CH₃)₂CHCl is classified as which type of alkyl halide?
Correct answer B. Secondary
In the carbon-halogen bond of an alkyl halide, the carbon atom carries ____.
Correct answer C. a partial positive charge
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For the same alkyl group, which alkyl halide reacts fastest in nucleophilic substitution?
Correct answer B. Alkyl iodide
An SN2 reaction at a chiral carbon results in ____.
Correct answer C. inversion of configuration
Which alkyl halide undergoes SN1 reactions most readily?
Correct answer D. (CH₃)₃CBr
In an SN2 reaction, rate = k. If both concentrations are doubled, the rate becomes ____.
Correct answer B. four times
In the SN1 hydrolysis of 2-bromo-2-methylpropane, is tripled and is doubled. By what factor does the rate change?
Correct answer A. 3
Heating bromoethane with aqueous KOH mainly produces ____.
Correct answer A. ethanol
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What is the rate law for an E1 elimination of an alkyl halide RX by a base?
Correct answer B. Rate = k[RX]
What is the approximate percentage by mass of bromine in bromoethane, C₂H₅Br (C = 12, H = 1, Br = 80)?
Correct answer C. 73.4%
Bromoethane reacts with potassium cyanide to give ____.
Correct answer D. propanenitrile
The SN2 reaction of hydroxide with bromomethane is described as bimolecular because ____.
Correct answer C. two species, the alkyl halide and the nucleophile, take part in the rate-determining step
How many structural isomers have the molecular formula C₄H₉Br?
Correct answer B. 4
What is the percentage by mass of bromine in bromomethane, CH₃Br (C = 12, H = 1, Br = 80)?
Correct answer B. 84.2%
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What mass of ethanol is formed when 10.9 g of bromoethane is completely hydrolysed (C = 12, H = 1, O = 16, Br = 80)?
Correct answer A. 4.6 g
What is the organic product when bromoethane is heated with ethanolic potassium cyanide?
Correct answer B. Propanenitrile
How many β-hydrogen atoms are present in 2-bromopropane, (CH₃)₂CHBr?
Correct answer B. 6
Which species cannot act as a nucleophile?
Correct answer B. BF₃
What is the major product when 2-bromobutane is heated with alcoholic KOH?
Correct answer B. But-2-ene
About Alkyl Halides MCQs
The first set of questions covers IUPAC names of alkyl halides, their classification as primary, secondary or tertiary, the polarity of the C–X bond and nucleophiles. You will also predict the organic product when bromoethane or similar compounds react with aqueous NaOH, ethanolic KCN or alcoholic KOH. Mechanism questions compare SN1 and SN2 substitution, including the number of steps, rate equations, the effect of changing concentrations on rate, stereochemistry and the type of alkyl halide that favours each. Elimination questions test the E1 and E2 mechanisms and the conditions that favour elimination over substitution.
Key facts to remember
- Alkyl halides are classified as primary, secondary or tertiary by the number of carbon atoms attached to the carbon bearing the halogen.
- SN2 is a one-step bimolecular reaction with rate = k[RX][Nu⁻] and inversion of configuration; it is favoured by primary alkyl halides.
- SN1 is a two-step reaction through a carbocation with rate = k[RX]; it is favoured by tertiary alkyl halides and gives racemisation at a chiral centre.
- Aqueous NaOH or KOH converts an alkyl halide to an alcohol, while alcoholic KOH mainly causes elimination to give an alkene.
- Heating an alkyl halide with ethanolic KCN gives a nitrile with one more carbon atom.
- E2 elimination is a one-step bimolecular reaction, and E1 is a two-step unimolecular reaction through a carbocation.
Exams that include Alkyl Halides MCQs
Pakistan
- MDCAT
- ECAT
- NUMS
- AKU
- FSc boards
India
- NEET
- JEE Main
Bangladesh
- HSC
- Medical Admission Test
How to prepare for Alkyl Halides MCQs
- Make a side-by-side table of SN1, SN2, E1 and E2: steps, rate law, intermediate and preferred substrate.
- For rate questions, multiply only by the concentrations that appear in the rate law.
- Remember the solvent rule: aqueous hydroxide gives substitution, alcoholic hydroxide gives elimination.
- Practise naming branched alkyl halides by finding the longest chain that contains the halogen-bearing carbon.
Frequently asked questions
What does the MDCAT syllabus include in Alkyl Halides?
The PMDC MDCAT curriculum for Alkyl Halides covers their IUPAC naming, structure and reactivity, the nucleophilic substitution mechanisms SN1 and SN2, and the elimination mechanisms E1 and E2. Questions often ask you to predict the mechanism or the product from the type of alkyl halide and the conditions.
Which exams ask Alkyl Halides MCQs?
Alkyl halide questions appear in MDCAT, ECAT, NUMS and AKU entry tests and FSc board papers in Pakistan. Haloalkanes are also a regular chapter in NEET and JEE Main in India and in HSC and medical admission tests in Bangladesh.
Why do tertiary alkyl halides prefer the SN1 mechanism?
Tertiary alkyl halides form relatively stable tertiary carbocations, because the three alkyl groups release electrons towards the positive carbon. Their bulky groups also block the backside attack needed for SN2, so substitution goes mainly through the two-step SN1 route.
Last reviewed October 2026