Alcohol: notes and MCQs for State PSC prelims

Alcohol is part of Chemistry. Below are notes on 7 sub-topics, followed by practice MCQs from State PSC and UPSC papers.

Industrial Synthesis and Applications of Alcohols (Ethanol production, methanol toxicity, solvents, fuels)

Ethanol (Ethyl Alcohol):

Main constituent of all alcoholic beverages.
Produced primarily by fermentation of sugars (e.g., molasses, corn, grapes).
Highly soluble (miscible) in water in all proportions.
Excellent solvent, used in medicines (e.g., tinctures), cosmetics, perfumes, varnishes, and industrial processes.
Used as a fuel additive/biofuel (e.g., blended with petrol).
Liquid at room temperature.
Used in alcohol-based hand sanitizers, often with Isopropanol (isopropyl alcohol) and n-propanol (n-propyl alcohol).
Examples of distilled liquors: Rum, Gin, Rectified Spirit. Beer is fermented, not distilled.
Cider is an alcoholic beverage made from fermented apple juice.

Methanol (Methyl Alcohol):

Also known as "Wood Spirit."
Extremely toxic; ingestion of even small quantities causes blindness and can be fatal.
It is the active/offending agent causing tragedies (blindness, death) from spurious (adulterated) liquor.
Not used in alcoholic beverages or hand sanitizers intended for human use.
Used as an industrial solvent, antifreeze, and as a denaturant for ethanol.

Denaturation of Alcohol: Process of adding toxic substances (denaturants like pyridine, copper sulphate, or methanol) to ethanol to make it unfit for human consumption, often for industrial use, to avoid excise duty.
Industrial Applications of Alcohols (General): Solvents, fuels, raw materials for other chemicals, disinfectants (hand sanitizers).
Separation Technique: Miscible liquids with different boiling points (e.g., alcohol and acetone) can be separated by fractional distillation.
Ballpoint Pen Dyes: Some dyes used in ballpoint pens are alcohol-based.

Methods of Preparation of Alcohols (from alkenes, carbonyl compounds, Grignard reagents, reduction, fermentation)

From Alkenes:

Acid-catalyzed hydration (H₂O/H⁺): Markovnikov addition, forms secondary/tertiary alcohols. Carbocation intermediate, rearrangements possible.
Hydroboration-oxidation (1. BH₃·THF, 2. H₂O₂/OH⁻): Anti-Markovnikov addition, syn addition, forms primary/ secondary alcohols.
Oxymercuration-demercuration (1. Hg(OAc)₂, H₂O; 2. NaBH₄): Markovnikov addition, no carbocation rearrangements.

From Carbonyl Compounds (Aldehydes & Ketones):

Reduction:

Catalytic Hydrogenation (H₂/Ni, Pt, or Pd):
Aldehydes (RCHO) $\to$ Primary Alcohols (RCH₂OH).
Ketones (RCOR') $\to$ Secondary Alcohols (RCH(OH)R').
Chemical Reducing Agents:
Lithium Aluminium Hydride (LiAlH₄): Strong, reduces aldehydes $\to$ primary, ketones $\to$ secondary, esters $\to$ primary, carboxylic acids $\to$ primary alcohols.
Sodium Borohydride (NaBH₄): Milder, reduces aldehydes $\to$ primary, ketones $\to$ secondary. Does not reduce esters or carboxylic acids.

From Grignard Reagents (RMgX):

With Formaldehyde (HCHO): Primary alcohols.
With other Aldehydes (R'CHO): Secondary alcohols.
With Ketones (R'COR''): Tertiary alcohols.
With Esters (R'COOR''): Can yield tertiary alcohols (with excess Grignard) or primary alcohols (reduction by LiAlH4/H2).
With Epoxides: Primary alcohols (with chain extension).

From Carboxylic Acids & Esters (Reduction):

Carboxylic Acids (RCOOH): Reduced to primary alcohols by strong reducing agents like LiAlH₄. (NaBH₄ is ineffective).
Esters (RCOOR'): Reduced to primary alcohols by LiAlH₄ or catalytic hydrogenation (H₂/Ni, Pt, Pd).

Fermentation (for Ethanol):

Process: Anaerobic breakdown of sugars (e.g., glucose, fructose) by enzymes (zymase) from yeast.
Equation: C₆H₁₂O₆ (glucose) $\xrightarrow{\text{Zymase}}$ 2C₂H₅OH + 2CO₂.
Conditions: Anaerobic, moderate temperature (~303-305K). Typical alcohol concentration limited to ~15% as yeast activity ceases.

Nomenclature and Classification of Alcohols (mono-, di-, polyhydric; primary, secondary, tertiary)

Alcohols are organic compounds containing a hydroxyl (-OH) functional group attached to a saturated (sp³ hybridized) carbon atom.
The functional group characteristic of alcohols is the hydroxyl (-OH) group.
IUPAC Nomenclature: The 'e' of the parent alkane name is replaced by 'ol'. The carbon chain is numbered such that the carbon bearing the -OH group gets the lowest possible number. Substituents are named and numbered accordingly.
Common Nomenclature: The alkyl group attached to the -OH group is named, followed by "alcohol" (e.g., Methyl alcohol, Ethyl alcohol).
Example: CH₃CH₂OH (or C₂H₅OH) is named Ethanol (IUPAC) or Ethyl alcohol (common).
Classification based on the number of hydroxyl groups:

Monohydric Alcohols: Contain one OH group per molecule (e.g., Ethanol, CH₃CH₂OH).
Dihydric Alcohols (Glycols): Contain two -OH groups per molecule, usually on different carbon atoms (e.g., Ethane-1,2-diol).
Polyhydric Alcohols: Contain three or more -OH groups per molecule (e.g., Propane-1,2,3-triol, commonly known as Glycerol).

Classification based on the type of carbon atom to which the -OH group is attached:

Primary (1°) Alcohol: The -OH group is attached to a primary carbon atom (a carbon atom bonded to only one other carbon atom, R-CH₂OH).
Secondary (2°) Alcohol: The -OH group is attached to a secondary carbon atom (a carbon atom bonded to two other carbon atoms, R₂CH-OH).
Tertiary (3°) Alcohol: The -OH group is attached to a tertiary carbon atom (a carbon atom bonded to three other carbon atoms, R₃C-OH).

Oxidation Reactions of Alcohols (PCC, KMnO4, CrO3, Swern oxidation, mechanisms)

Primary Alcohols (R-CH₂OH) Oxidation:

Mild Oxidation (to Aldehyde, R-CHO):

Pyridinium Chlorochromate (PCC): Oxidizes 1° alcohols to aldehydes, 2° alcohols to ketones. Prevents over-oxidation to carboxylic acids.
Pyridinium Dichromate (PDC): Similar to PCC, used for 1° alcohols to aldehydes.
CrO₃ in anhydrous medium (e.g., Collins reagent: CrO₃/ pyridine): Mild, used for 1° alcohols to aldehydes.
Swern Oxidation (DMSO, (COCl)₂, Et₃N): Very mild and selective. Oxidizes 1° alcohols to aldehydes and 2° alcohols to ketones.
Catalytic Dehydrogenation (Cu/ 573K): Oxidizes 1° alcohols to aldehydes and 2° alcohols to ketones.

Strong Oxidation (to Carboxylic Acid, R-COOH):

KMnO₄ (Potassium Permanganate) in acidic/neutral/alkaline medium: Oxidizes 1° alcohols directly to carboxylic acids.
H₂CrO₄ (Chromic acid) or Jones reagent (CrO₃/H₂SO₄/acetone): Oxidizes 1° alcohols to carboxylic acids.
Potassium Dichromate (K₂Cr₂O₇) in acidic medium: Used in breath tests. Oxidizes ethanol to ethanoic acid; Cr(VI) (orange) is reduced to Cr(III) (green).

Secondary Alcohols (R-CH(OH)-R') Oxidation:

All common oxidizing agents (PCC, PDC, CrO₃, KMnO₄, Swern, Cu/573K) oxidize 2° alcohols to Ketones (R-COR').
Ketones are generally resistant to further oxidation under these conditions.

Tertiary Alcohols (R₃C-OH) Oxidation:

Resistant to oxidation due to the absence of an α-hydrogen.
Under strong acidic/high-temperature conditions, they undergo dehydration to alkenes.

Iodoform Test:

Positive test given by compounds containing a CH₃CO- group (methyl ketones) or a CH₃CH(OH)- group (methyl secondary alcohols), including ethanol and acetaldehyde.
Reagents: I₂/NaOH or NaOI.
Product: Yellow precipitate of iodoform (CHI₃).
Example: Ethanol, Acetone, 2-Propanol give a positive test. Methanol does not.

Mechanisms (brief):

Chromium(VI) oxidations (PCC, H₂CrO₄): Involve the formation of a chromate ester intermediate, followed by E2-like elimination of an α-hydrogen.
Swern Oxidation: Involves the formation of an alkoxysulfonium intermediate from alcohol and activated DMSO, followed by deprotonation by base (Et₃N) to form the carbonyl compound.

Physical Properties of Alcohols (boiling points, solubility, acidity, density)

Boiling Points:
Alcohols exhibit significantly higher boiling points than hydrocarbons/ethers of comparable molecular masses due to strong intermolecular hydrogen bonding.
Boiling point increases with increasing number of carbon atoms (molecular mass) in a homologous series. Example: Methanol < Propan-1-ol < Butan-1-ol < Pentan-1-ol.
Boiling point decreases with increased branching of the carbon chain due to reduced surface area for van der Waals forces.
Solubility:
Lower alcohols (typically up to C₃-C₄) are highly soluble in water due to their ability to form hydrogen bonds with water molecules.
Solubility in water rapidly decreases as the size of the nonpolar alkyl (hydrophobic) group increases.
Acidity:
Alcohols are weakly acidic, primarily due to the polarity of the O-H bond. They are weaker acids than water.
Acidity order: Methanol > Primary (> Secondary > Tertiary) alcohols.
Reason: Electron-donating inductive (+I) effect of alkyl groups destabilizes the alkoxide ion, making proton donation less favorable.
Alcohols react with active metals (e.g., Na, K) to form alkoxides and release hydrogen gas.
Density:
Alcohols are generally less dense than water.
Density increases with increasing molecular mass (number of carbon atoms).

Polyhydric Alcohols (Glycols and Glycerol - preparation, properties, uses)

Polyhydric Alcohols: Organic compounds containing more than one hydroxyl (-OH) group.
Glycols (Dihydric Alcohols): Contain two OH groups.
Ethylene Glycol (Ethane-1,2-diol): HO-CH₂CH₂-OH.

Preparation: From ethylene oxide (hydration) or 1,2-dichloroethane (hydrolysis).
Properties: Colorless, viscous liquid, completely miscible with water.
Uses: Primarily used as an antifreeze for automobile engines (MCQ 1), coolant, solvent, and in the production of polyesters (e.g., Dacron).

Glycerol (Trihydric Alcohols): Contain three -OH groups.
Glycerol (Glycerin/Glycerine): HO-CH₂CH(OH)-CH₂-OH.

Chemical Name: 1, 2, 3-Trihydroxypropane (MCQ 2) or Propane-1,2,3-triol.
Preparation: By-product of saponification (hydrolysis of fats and oils).
Properties: Colorless, odorless, viscous, sweet-tasting, hygroscopic liquid, miscible with water and alcohol.
Uses: In cosmetics (moisturizer, emollient), pharmaceuticals, food industry (sweetener, humectant), and for the manufacture of nitroglycerin (an explosive).

Reactions involving O-H bond cleavage (acidity, esterification, reaction with active metals)

Alcohols are weak acids, weaker than water but stronger than terminal alkynes. They are neutral to litmus paper. (MCQ 1)
Acidity order of alcohols: Primary (1°) > Secondary (2°) > Tertiary (3°) due to the +I (electron-donating) effect of alkyl groups, which destabilizes the alkoxide ion and hinders proton release.
Ethanol (C₂H₅OH) is a weak acid; it is not a strong base like KOH, NH₄OH, or NaOH. (MCQ 3)
Reaction with Active Metals (O-H bond cleavage): Alcohols react with active metals (e.g., Na, K, Mg, Al) to form alkoxides and liberate dihydrogen gas: `2ROH + 2Na → 2RONa + H₂`. This reaction confirms the acidic nature of alcohols, involving O-H bond cleavage. (MCQ 2 Reason)
Esterification (O-H bond cleavage): Alcohols react with carboxylic acids (Fischer esterification) in the presence of an acid catalyst to form esters: `RCOOH + R'OH ⇌ RCOOR' + H₂O`. In this reaction, the O-H bond of the alcohol cleaves (the H comes from the alcohol).
Dual Nature of Alcohols: Alcohols can act as nucleophiles (oxygen's lone pair attacks electrophiles, e.g., in esterification or formation of ethers) and electrophiles (C-O bond cleavage, typically after protonation of the -OH group, e.g., reaction with HX or dehydration). They also act as acids (O-H bond cleavage, proton donation, e.g., reaction with active metals). (MCQ 2 Assertion (A) is true. Reason (R) is true but is NOT a correct explanation of (A) as it only covers the acidic aspect, not the full dual nature.)

14. Polymer

Practice MCQs: Alcohol

Industrial Synthesis and Applications of Alcohols (Ethanol production, methanol toxicity, solvents, fuels)

Alcohol-based hand sanitizers can contain _______. 1. Ethanol 2. Isopropanol 3. n-propanol 4. methanol
Asked in: GPSC Prelims CSP 2 2021
1. 1, 2 and 3 only
2. 2, 3 and 4 only
3. 1, 2 and 4 only
4. 1, 2, 3 and 4
Show answer
Answer: A. 1, 2 and 3 only
- Ethanol, Isopropanol, and n-propanol are effective disinfectants used in hand sanitizers. - Methanol is poisonous and should never be used in hand sanitizers. containing the double bond as the parent chain, numbering the chain to give the double bond the lowest possible locant, and then naming and locating the substituents.
The shortest straight chain with two carbons is
Asked in: ASSISTANT ENGINEER(ELECTRICAL) 2016
1. ethane
2. butane
3. propane
4. methane
Show answer
Answer: D. methane
This question tests basic knowledge of organic chemistry nomenclature and the structure of simple hydrocarbons (alkanes).
Consider the given four statements about ethanol and choose the correct answer from the given options : (1) It is the main constituent of all alcoholic drinks (2) It is not a good solvent (3) It is soluble in water in all proportions (4) It cannot be used as an additive in petrol
Asked in: HPPSC HPAS Prelims 2021
1. (1) and (2) only
2. (1) and (3) only
3. (2) and (4) only
4. (1) and (4) only
Show answer
Answer: B. (1) and (3) only
Ethanol (ethyl alcohol) is the primary intoxicating agent in alcoholic beverages and is miscible with water in all proportions.
In tragedies caused by drinking spurious liquor, the active agent causing such tragedies is:
Asked in: HAS Prelims 2019
1. Methyl alcohol
2. Ethyl alcohol
3. Amyl alcohol
4. Benzyl alcohol
Show answer
Answer: A. Methyl alcohol
Methyl alcohol, also known as methanol, is a highly toxic substance that is sometimes illegally added to or forms as a byproduct in illegally brewed alcoholic drinks.
Losing eye sight after consuming spurious liquor (bhejal) is due to its adulteration by :
Asked in: OPSC CS Prelims 2016
1. Methanol
2. Acetaldehyde
3. Drug
4. Acidic moiety
Show answer
Answer: A. Methanol
Methanol poisoning is a well-known cause of blindness and death, often resulting from the consumption of adulterated alcoholic beverages.
In ballpoint pens, dyes used are:
Asked in: OPSC CS Prelims 2020
1. Water based
2. Alcohol based
3. Glycerine based
4. Oil based
Show answer
Answer: D. Oil based
The ink used in traditional ballpoint pens is a high- viscosity paste made of pigments or dyes dissolved in an oil-based solvent, often a glycol or oleamide. This oil-based formulation allows the ink to flow smoothly from the ballpoint onto the paper and dry quickly upon contact with air, while preventing it from drying out inside the pen tube.
Sometimes, the consumption of local made alcoholic beverages may cause blindness or even death. This may be because of contamination of the beverages with :
Asked in: UPSC CAPF 2009
1. Vinegar
2. Carbolic acid
3. Methyl alcohol
4. Formic acid
Show answer
Answer: C. Methyl alcohol
Ethanol (ethyl alcohol) is the alcohol intended for consumption in alcoholic beverages. Methanol (methyl alcohol) is a highly toxic substance that can be produced as a byproduct during improper fermentation or distillation, or sometimes illegally added to beverages. When ingested, methanol is metabolized by the body into formaldehyde and formic acid, which are potent toxins that damage the optic nerve (leading to blindness) and other organs, often resulting in death.
Which one of the following is known as Wood Spirit ?
Asked in: UPSC CAPF 2019 · UPPSC Upper Mains 2015
1. Methanol
2. Ethanol
3. Formaldehyde
4. Acetaldehyde
Show answer
Answer: A. Methanol
- Methanol is the simplest alcohol. - It is a volatile, flammable, poisonous liquid. - Its historical source gave it the common name "wood spirit".
The offending substance in the liquor tragedies leading to blindness, etc. is
Asked in: UPPCS Prelims 1996
1. ethyl alcohol
2. amyl alcohol
3. benzyl alcohol
4. methyl alcohol
Show answer
Answer: D. methyl alcohol
Methanol is metabolized in the body into formaldehyde and formic acid, which are highly toxic. Formic acid can damage the optic nerve, leading to blindness, and cause severe metabolic acidosis and multi-organ failure.
Which is used in alcoholic beverages?
Asked in: WBCS Main Paper 4 2019
1. Ethanol
2. Methanol
3. Phenol
4. Glycerol
Show answer
Answer: A. Ethanol
Ethanol, also known as ethyl alcohol (C₂H₅OH), is the principal psychoactive ingredient found in alcoholic beverages.
Which one of the following is a false statement?
Asked in: Asst. Engineer Comb. Comp. Exam 2018
1. Ethanol is liquid at room temperature.
2. Ethanol is partially soluble in water.
3. Ethanol is used in medicines.
4. Ethanol is a good solvent.
Show answer
Answer: B. Ethanol is partially soluble in water.
Ethanol (C₂H₅OH) is an alcohol that exhibits both polar (due to the hydroxyl group) and non-polar (due to the ethyl chain) properties, allowing it to dissolve both polar and non-polar substances. Its miscibility with water is a key characteristic.
Match the items of Column – I with items of Column – II Column – I (i) Methanol (ii) Conversion of 2° alcohol into ketone (iii) Denaturation of alcohol (iv) Ethanol Column – II (a) Fermentation of sugars (b) Wood spirit (c) CrO$_3$ (d) Copper sulphate and pyridine
Asked in: Department Recruitment 2024 (Chemist) 2024
1. (i) - c, (ii) - b, (iii) - a, (iv) - d
2. (i) - b, (ii) - c, (iii) - d, (iv) - a
3. (i) - b, (ii) - d, (iii) - c, (iv) - a
4. (i) - a, (ii) - b, (iii) - c, (iv) - d
Show answer
Answer: B. (i) - b, (ii) - c, (iii) - d, (iv) - a
Methanol is called wood spirit. Secondary alcohols are oxidized to ketones. Alcohol denaturation involves adding substances to make ethanol unfit for drinking. Ethanol is produced via fermentation of sugars.
The alcohol whose ingestion of even small quantities causes blindness - - (5) Question not attempted
Asked in: Department Recruitment 2024 (Chemist) 2024
1. Propan-2-ol
2. Ethanol
3. Methanol
4. Propan-1-ol
Show answer
Answer: C. Methanol
Methanol is metabolized to formic acid, which causes severe metabolic acidosis and optic nerve damage, leading to blindness and potentially death.
Which of the following is not a distilled liquor?
Asked in: GA Acts Rules CHEX 27 2023 0307 2024
1. Rum
2. Beer
3. Rectified spirit
4. Gin
Show answer
Answer: B. Beer
The distinction between fermented and distilled alcoholic beverages is fundamental.

Methods of Preparation of Alcohols (from alkenes, carbonyl compounds, Grignard reagents, reduction, fermentation)

$\text{R}-\text{C}_{||}^{=0}-\text{H} + 2\text{H} \xrightarrow{\text{Pt or Pd}} \text{Main product}$ Main product is - $ \text{R}-\text{CH}_{2}-\text{OH}$ - $\text{R}- \underset{\text{R}}{\underset{|}{C}}-\text{OH}$ - $\text{R}-\underset{\underset{|}{R}}{C}- \text{OH}$ - $\text{R}-\text{O}-\text{R}$
Asked in: Food Safety Officer 2019
1. $\text{R}-\text{CH}_{2}-\text{OH}$
2. $\text{R}-\underset{\text{R}}{\underset{|} {C}}-\text{OH}$
3. $\text{R}-\underset{\underset{|}{R}}{C}- \text{OH}$
4. $\text{R}-\text{O}-\text{R}$
Show answer
Answer: A. $\text{R}-\text{CH}_{2}-\text{OH}$
The reaction is the catalytic hydrogenation of an aldehyde, converting it into a primary alcohol.

Nomenclature and Classification of Alcohols (mono-, di-, polyhydric; primary, secondary, tertiary)

The chemical formula C₂H₅OH stands for
Asked in: WBCS Main Paper 4 2021
1. Methane
2. Methanol
3. Ethane
4. Ethanol
Show answer
Answer: D. Ethanol
The formula C₂H₅OH uniquely identifies ethanol, which is an alcohol with two carbon atoms.
In which of the following compounds is -OH the functional group? - Question not attempted
Asked in: School Lecturer (Sanskrit Edu.) 2024
1. Butanone
2. Butanol
3. Butanoic acid
4. Butanal
Show answer
Answer: B. Butanol
Identifying functional groups is crucial for understanding the properties and reactivity of organic compounds. Each class of organic compounds (alkanes, alkenes, alcohols, ketones, aldehydes, carboxylic acids, etc.) is defined by its characteristic functional group.
IUPAC name CH₃CH₂OH:
Asked in: lower devision clerk 2025
1. Ethanol
2. Methanol
3. Propanol
4. Ethanoic acid
Show answer
Answer: A. Ethanol
This question tests the knowledge of IUPAC nomenclature for organic compounds, specifically alcohols.

Oxidation Reactions of Alcohols (PCC, KMnO4, CrO3, Swern oxidation, mechanisms)

The breath test conducted by police to check drunken driver has which one of the following on the filter paper?
Asked in: BPSC Prelims Exam 66th
1. Potassium dichromate-sulfuric acid
2. Potassium permanganate
3. Silica gel coated with silver nitrate
4. Turmeric
Show answer
Answer: A. Potassium dichromate-sulfuric acid
Older and some current breathalyzer devices rely on a chemical reaction where ethanol (ethyl alcohol) in the breath is oxidized by an oxidizing agent. Potassium dichromate (K₂Cr₂O₇) acidified with sulfuric acid is a common mixture used for this purpose. When alcohol is present, the orange dichromate ion (Cr₂O₇²⁻) is reduced to green chromium(III) ions (Cr³⁺). The degree of color change is proportional to the amount of alcohol in the breath.
Which compound does not give a positive iodoform test?
Asked in: lower devision clerk 2025
1. Ethanol
2. Acetone
3. 2-Propanol
4. Methanol
Show answer
Answer: D. Methanol
The iodoform test is characteristic of methyl ketones and alcohols that can be oxidized to methyl ketones.
Which of the following reagents can be used to oxidise primary alcohols to aldehydes? Select the correct answer by given code. (a) CrO₃ in anhydrous medium (b) KMnO₄ in acidic medium (c) Pyridinium chlorochromate (d) Heat in presence of Cu at 573K
Asked in: Department Recruitment 2024 (Chemist) 2024
1. (1) (a), (c), (d)
2. (2) (b), (c)
3. (3) (a), (b)
4. (4) (b), (d)
Show answer
Answer: A. (1) (a), (c), (d)
This question relates to organic chemistry, specifically the oxidation of primary alcohols.

Physical Properties of Alcohols (boiling points, solubility, acidity, density)

Arrange the following set of compounds in order of their increasing boiling points - Pentan-1-ol, Butan-1-ol, Propan-1-ol, Methanol (1) Methanol < Propan-1-ol < Butan-1-ol < Pentan-1-ol (2) Methanol < Butan-1-ol < Pentan-1-ol < Propan-1-ol (3) Methanol < Pentan-1-ol < Butan-1-ol < Propan-1-ol (4) Methanol > Propan-1-ol > Butan-1-ol > Pentan-1-ol (5) Question not attempted
Asked in: Department Recruitment 2024 (Chemist) 2024
1. Methanol < Propan-1-ol < Butan-1-ol < Pentan-1-ol
2. Methanol < Butan-1-ol < Pentan-1-ol < Propan-1-ol
3. Methanol < Pentan-1-ol < Butan-1-ol < Propan-1-ol
4. Methanol > Propan-1-ol > Butan-1-ol > Pentan-1-ol
Show answer
Answer: A. Methanol < Propan-1-ol < Butan-1-ol < Pentan-1-ol
Intermolecular forces significantly affect boiling points. - Hydrogen bonding is a strong type of intermolecular force present in alcohols. - Van der Waals forces (London dispersion forces and dipole-dipole interactions) also contribute to intermolecular attraction. - For homologous series of alcohols, boiling point generally increases with increasing molecular size and chain length due to increased van der Waals forces and more extensive hydrogen bonding.

Polyhydric Alcohols (Glycols and Glycerol - preparation, properties, uses)

Which one of the following is used as an anti-freeze for the automobile engines?
Asked in: UPPCS Prelims 1997
1. Propyl alcohol
2. Ethanol
3. Methanol
4. Ethylene glycol
Show answer
Answer: D. Ethylene glycol
Anti-freeze substances are added to coolants (like water) to lower their freezing point, preventing the liquid from freezing in cold temperatures and cracking the engine block or radiator.
Chemically the glycerin is
Asked in: PA High Court Mains
1. 1, 2, 3-Trihydroxypropane
2. 1, 2-Dihydroxypropane
3. 1, 3-Dihydroxypropane
4. None of these
Show answer
Answer: A. 1, 2, 3-Trihydroxypropane
Glycerin is a triol, meaning it has three hydroxyl groups. Its chemical name reflects the propane backbone with hydroxyls at positions 1, 2, and 3.

Reactions involving O-H bond cleavage (acidity, esterification, reaction with active metals)

What is the action of litmus on ethanol ?
Asked in: UPSC NDA 2 2023
1. Litmus is neutral towards ethanol
2. Ethanol turns blue litmus to red; confirming acidic nature of ethanol
3. Ethanol turns red litmus to blue; confirming basic nature of ethanol
4. Ethanol decolorizes litmus through bleaching action
Show answer
Answer: A. Litmus is neutral towards ethanol
- Litmus is an acid-base indicator. It turns red in acidic solutions (pH 7). - Ethanol (C₂H₅OH) is an alcohol. The -OH group in alcohols is covalently bonded, unlike the ionic hydroxide in strong bases (e.g., NaOH). - Alcohols are generally considered neutral compounds in aqueous solutions. While they can act as very weak acids (donating a proton from the -OH group, especially when reacting with strong bases like alkali metals) or very weak bases (accepting a proton from a strong acid at the oxygen atom), their acidity or basicity is negligible in the context of affecting litmus paper pH indicators.
Given below are two statements one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A) - Alcohols react both as nucleophile and electrophile. Reason (R) - Alcohols react with active metals such as sodium to yield corresponding alkoxide and liberate dihydrogen. In the light of the above statements, choose the correct answer from the options given below - (1) Both (A) and (R) are true and (R) is also correct explanation of (A). (2) (A) is true but (R) is false. (3) (A) is false but (R) is true. (4) Both (A) and (R) are true, but (R) is NOT correct explanation of (A). (5) Question not attempted
Asked in: Department Recruitment 2024 (Chemist) 2024
1. Both (A) and (R) are true and (R) is also correct explanation of (A).
2. (A) is true but (R) is false.
3. (A) is false but (R) is true.
4. Both (A) and (R) are true, but (R) is NOT correct explanation of (A).
Show answer
Answer: A. Both (A) and (R) are true and (R) is also correct explanation of (A).
Alcohols exhibit amphoteric behavior; they can act as nucleophiles (due to the lone pairs on oxygen) and as electrophiles (due to the polar O-H bond, where the hydrogen can be donated, or the oxygen can be attacked by strong electrophiles). The reaction with active metals is a classic example of the acidic nature of the alcohol proton, hence showing electrophilic character.
Which among the following is not a base?
Asked in: Head Master Praveshika School (Sanskrit Edu.) 2021
1. C₂H₅OH
2. KOH
3. NH₄OH
4. NaOH
Show answer
Answer: A. C₂H₅OH
Bases are typically characterized by their ability to produce hydroxide ions (OH⁻) in aqueous solutions

Industrial Synthesis and Applications of Alcohols (Ethanol production, methanol toxicity, solvents, fuels)

Methods of Preparation of Alcohols (from alkenes, carbonyl compounds, Grignard reagents, reduction, fermentation)

Nomenclature and Classification of Alcohols (mono-, di-, polyhydric; primary, secondary, tertiary)

Oxidation Reactions of Alcohols (PCC, KMnO4, CrO3, Swern oxidation, mechanisms)

Physical Properties of Alcohols (boiling points, solubility, acidity, density)

Polyhydric Alcohols (Glycols and Glycerol - preparation, properties, uses)

Reactions involving O-H bond cleavage (acidity, esterification, reaction with active metals)

14. Polymer

Practice MCQs: Alcohol

Industrial Synthesis and Applications of Alcohols (Ethanol production, methanol toxicity, solvents, fuels)

Methods of Preparation of Alcohols (from alkenes, carbonyl compounds, Grignard reagents, reduction, fermentation)

Nomenclature and Classification of Alcohols (mono-, di-, polyhydric; primary, secondary, tertiary)

Oxidation Reactions of Alcohols (PCC, KMnO4, CrO3, Swern oxidation, mechanisms)

Physical Properties of Alcohols (boiling points, solubility, acidity, density)

Polyhydric Alcohols (Glycols and Glycerol - preparation, properties, uses)

Reactions involving O-H bond cleavage (acidity, esterification, reaction with active metals)

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