Nomenclature, Structure and Reactivity of Alcohols

Nomenclature, Structure and Reactivity of Alcohols MDCAT MCQs with answers

29 past paper MCQs on Nomenclature, Structure and Reactivity of Alcohols, from the Alcohols and Phenols unit of MDCAT Chemistry. The year each question appeared is shown where known; tap “Show answer” for the correct option and a short solution.

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1.What is the common name of 1,2,3-propanetriol? (MDCAT 2022)

  1. butyl alcohol
  2. glycol
  3. glycerol
  4. propyl alcohol
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Correct answer: (c) glycerol

Three hydroxyl groups on a propane chain make glycerol.

2.Ethanol gives which of the following products in the presence of $\mathrm{H_2SO_4}$ at $140^\circ$C? (MDCAT 2023)

  1. ether
  2. alkene
  3. ethyl acetate
  4. aldehyde
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Correct answer: (a) ether

At $140^\circ$C two molecules of alcohol condense to diethyl ether; at $180^\circ$C the product is ethene instead.

3.The complete oxidation of a primary alcohol gives which of the following? (MDCAT 2023)

  1. aldehyde
  2. alkene
  3. carboxylic acid
  4. ketone
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Correct answer: (c) carboxylic acid

The aldehyde is only the halfway stage; oxidation carried to completion gives the acid.

4.Which of the following alcohols can give the iodoform reaction? (MDCAT 2024)

  1. methanol
  2. 1-butanol
  3. 1-propanol
  4. ethanol
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Correct answer: (d) ethanol

The test needs a $\mathrm{CH_3CH(OH)}-$ group, and of these only ethanol has one.

5.Which of the following alcohols will give oily layer upon heating? (NUMS MDCAT 2025)

  1. 3-Methyl-2-butanol
  2. 2-Methyl-2-butanol
  3. 2-Butanol
  4. Ethyl alcohol
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Correct answer: (b) 2-Methyl-2-butanol

A tertiary alcohol reacts at once in the Lucas test, and the halide separates as an oily layer.

6.The order of reactivity of alcohol with respect to cleavage of C–O bond: (NUMS MDCAT 2025)

  1. Tertiary > Secondary > Primary
  2. Primary > Tertiary > Secondary
  3. Secondary > Tertiary > Primary
  4. Tertiary < Secondary < Primary
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Correct answer: (a) Tertiary > Secondary > Primary

The tertiary carbocation is the most stable, so the carbon oxygen bond breaks most readily there.

7.Rate of dehydration of alcohol is: (SIBA MDCAT 2025)

  1. 3°>2°>1°
  2. 1°>3°>2°
  3. 2°>3°>1°
  4. 3°>1°>2°
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Correct answer: (a) 3°>2°>1°

Dehydration goes through a carbocation, and the tertiary one is the most stable.

8.Which of the following alcohol can give Iodoform reaction? (UHS MDCAT 2024)

  1. Methanol
  2. 1-Butanol
  3. 1-Propanol
  4. Ethanol
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Correct answer: (d) Ethanol

Only an alcohol with a $\mathrm{CH_3CH(OH)}$ group gives iodoform, and ethanol is the one here.

9.Which of the following has the highest boiling point? (KMU MDCAT 2024)

  1. ethyl alcohol
  2. isopropyl alcohol
  3. n-propyl alcohol
  4. tert-butyl alcohol
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Correct answer: (c) n-propyl alcohol

The straight chain has the largest surface for its dispersion forces, so n-propyl alcohol boils highest.

10.The reaction of an alcohol with sodium produces (KMU MDCAT 2024)

  1. Aldehyde
  2. Alkoxide
  3. Ethane
  4. Ethene
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Correct answer: (b) Alkoxide

Sodium displaces the hydrogen of the hydroxyl group and leaves the sodium alkoxide.

11.Oxidation of secondary alcohol gives (KMU MDCAT 2024)

  1. Carboxylic acid
  2. Ether
  3. Ketone
  4. Phenol
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Correct answer: (c) Ketone

A secondary alcohol has one hydrogen on the carbinol carbon, so oxidation stops at the ketone.

12.The increasing order of reactivity of alcohols towards nucleophile is: (NUMS MDCAT 2024)

  1. 2-methyl-2-pentanol < 3-methyl-2-pentanol < 2-methyl-1-pentanol
  2. 2-methyl-1-pentanol > 3-methyl-2-pentanol > 2-methyl-2-pentanol
  3. 2-methyl-2-pentanol > 3-methyl-2-pentanol > 2-methyl-1-pentanol
  4. 2-methyl-2-pentanol < 2-methyl-1-pentanol < 3-methyl-2-pentanol
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Correct answer: (a) 2-methyl-2-pentanol < 3-methyl-2-pentanol < 2-methyl-1-pentanol

Attack by a nucleophile is easiest where the carbon is least crowded, that is at the primary alcohol.

13.The most reactive alcohol towards Lucas reagent is: (NUMS MDCAT 2024)

  1. 2-butanol
  2. 2-methyl-1-butanol
  3. 2-methyl-2-butanol
  4. 2,2-dimethyl-1-butanol
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Correct answer: (c) 2-methyl-2-butanol

Lucas reagent works fastest on a tertiary alcohol, and only the third is tertiary.

14.The order of reactivity of alcohol when C-O bond breaks is: (NUMS MDCAT 2023)

  1. Tertiary alcohol > secondary alcohol > Primary alcohol
  2. Secondary alcohol > primary alcohol > tertiary alcohol
  3. Primary alcohol > secondary alcohol > tertiary alcohol
  4. Tertiary alcohol > primary alcohol > secondary alcohol
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Correct answer: (a) Tertiary alcohol > secondary alcohol > Primary alcohol

The carbocation left when the bond breaks is most stable for the tertiary alcohol.

15.Complete oxidation of alcohol gives which of the following? (UHS MDCAT 2023)

  1. Aldehyde
  2. Alkane
  3. Carboxylic acid
  4. Ketone
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Correct answer: (c) Carboxylic acid

A primary alcohol is oxidized first to the aldehyde and then on to the acid.

16.How are carboxylic acids formed from alcohol? (PMC Practice 2021)

  1. Hydrolysis
  2. Reduction
  3. Oxidation
  4. Protonation
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Correct answer: (c) Oxidation

A primary alcohol is oxidized first to the aldehyde and then on to the acid.

17.Which one of them is used as an automobile antifreeze? (PMC Practice 2021)

  1. Ethanol
  2. Ethene
  3. Ethylene glycol
  4. Propene
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Correct answer: (c) Ethylene glycol

Ethylene glycol lowers the freezing point of the water in a radiator.

18.In the Lucas test, tertiary alcohols form an oily layer of alkyl halide _________. (PMC Practice 2021)

  1. On heating
  2. Immediately
  3. After 5-10 minutes
  4. After 20 minutes
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Correct answer: (b) Immediately

A tertiary alcohol reacts at once, and the halide separates as an oily layer.

19.Which of the following reactions is used for the production of alcohols on industrial scale? (UHS MDCAT 2019)

  1. Hydrogenation of alkenes
  2. Hydration of alkenes
  3. Hydrohalogenation of alkenes
  4. Hydroxylation of alkenes
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Correct answer: (b) Hydration of alkenes

Ethene and steam over phosphoric acid give ethanol, which is how most industrial alcohol is made.

20.Treatment of ethene with cold sulphuric acid, followed by reaction with boiling water, yields: (UHS MDCAT 2019)

  1. Ethane
  2. Ethanal
  3. Ethanol
  4. Ethyne
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Correct answer: (c) Ethanol

The ethyl hydrogen sulphate formed in the cold hydrolyses on boiling to ethanol.

21.Why is it necessary to distill aldehyde formed from oxidation of primary alcohol through acidified potassium dichromate (VI) solution or acidified sodium dichromate (VI) solution? (UHS MDCAT 2018)

  1. Aldehyde formed may be oxidized further to carboxylic acid concerned
  2. Aldehyde formed is unstable and decompose back to original precursor i.e. primary alcohol
  3. Aldehyde may be oxidised further to a ketone
  4. Aldehyde formed may react with primary alcohol, the original reactant.
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Correct answer: (a) Aldehyde formed may be oxidized further to carboxylic acid concerned

The aldehyde boils below the alcohol, so distilling it off as it forms keeps it from being oxidized further.

22.Select one which is alcohol. (UHS MDCAT 2018)

  1. CH3- CH2- Br
  2. CH3- O – CH3
  3. CH3COOH
  4. CH3- CH2- OH
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Correct answer: (d) CH3- CH2- OH

Ethanol carries the hydroxyl group on a saturated carbon, so it is an alcohol.

23.Alcohol in which carbon atom bonded to OH group is further attached with three alkyl group is: (UHS MDCAT 2018)

  1. Tertiary alcohol
  2. Primary alcohol
  3. Aromatic alcohol
  4. Secondary alcohol
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Correct answer: (a) Tertiary alcohol

A carbinol carbon carrying three alkyl groups makes a tertiary alcohol.

24.Which one of the following compounds is known as tertiary alcohol? (UHS MDCAT 2018)

  1. 1 – Propanol
  2. 2- methyl – 2- propanol
  3. 2- methyl – 1- propanol
  4. 2 – propanol
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Correct answer: (b) 2- methyl – 2- propanol

2-methylpropan-2-ol carries three methyl groups on the carbinol carbon.

25.Reaction of alcohol with hydrogen chloride yields: (UHS MDCAT 2017)

  1. Alkyl Halide
  2. Carboxylic acid
  3. Aldehyde
  4. Ester
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Correct answer: (a) Alkyl Halide

Hydrogen chloride replaces the hydroxyl group and leaves the alkyl chloride.

26.Dehydration of methyl alcohol with concentrated sulphuric acid gives: (UHS MDCAT 2017)

  1. CH3CHO
  2. C2H4
  3. HCHO
  4. None of these
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Correct answer: (d) None of these

Methanol has only one carbon, so it cannot give an alkene or a symmetrical ether by simple dehydration.

27.Which one of the following is NOT able to denature the ethanol? (UHS MDCAT 2015)

  1. Methanol
  2. Lactic acid
  3. Pyridine
  4. Acetone www.PakLearningSpot.com
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Correct answer: (b) Lactic acid

Denaturing means adding something poisonous or foul; lactic acid is neither.

28.How will you distinguish between methanol and ethanol? (UHS MDCAT 2015)

  1. By Lucas test
  2. By silver mirror test
  3. By oxidation
  4. By Iodoform test
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Correct answer: (d) By Iodoform test

Ethanol has the $\mathrm{CH_3CH(OH)}$ grouping and gives iodoform; methanol does not.

29.To produce absolute alcohol (100%) from rectified spirit (95.6% alcohol), the remaining 4.4% water must be removed by a drying agent such as (UHS MDCAT 2015)

  1. Calcium oxide
  2. Calcium chloride
  3. Calcium carbonate
  4. Carbon monoxide
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Correct answer: (a) Calcium oxide

Quicklime takes up the last of the water and leaves absolute alcohol.

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