Question 1

In the following reaction, condition 'A' is -

Accepted Answer

The given reaction shows the conversion of phenol to p-benzoquinone. This transformation is an oxidation reaction. Phenol is oxidized to p-benzoquinone by strong oxidizing agents such as chromic acid ( Na _2 Cr _2 O _7 with H _2 SO _4 or CrO _3). In contrast, reduction with zinc dust converts phenol to benzene, and CS _2 at low temperature is used as a solvent for monohalogenation of phenol. Hence, condition 'A' is oxidation with CrO _3. Answer: Oxidation with CrO _3

Question 2

Which of the following alcohols contains the hydroxy group, at the side chain of the aromatic ring?

Accepted Answer

Aromatic alcohols are compounds in which the hydroxyl group (-OH) is attached to an sp^3 hybridized carbon atom of the side chain of an aromatic ring. For example, benzyl alcohol (C_6H_5CH_2OH) is an aromatic alcohol. If the hydroxyl group is directly attached to the aromatic ring, the compound is classified as a phenol rather than an alcohol. Thus, aromatic alcohols contain the hydroxy group at the side chain of the aromatic ring. Answer: aromatic alcohols

Question 3

Which among the following compounds has highest solubility in water?

Accepted Answer

Solubility of organic compounds in water depends on their ability to form hydrogen bonds with water molecules, the size of the hydrophobic part, and the lattice energy of the solid. 1. Phenol forms strong intermolecular hydrogen bonds with water, making it quite soluble (solubility 8.3 g/100 mL ). 2. p-Cresol contains an additional hydrophobic methyl (-CH_3) group, which increases the non-polar character and decreases its solubility compared to phenol (solubility 1.9 g/100 mL ). 3. o-Nitrophenol

Question 4

Identify product 'B' in following series of reactions 2-methylpropan-2-ol [ 363\ K ] 20\%\ H _2 SO _4 A [ Conc. H _2 SO _4 ] H _2 O \ \ B

Accepted Answer

The starting material, 2-methylpropan-2-ol, is a tertiary alcohol. On heating with 20\% H_2SO_4 at 363\ K , it undergoes acid-catalyzed dehydration to form an alkene, 2-methylpropene (product A). (CH_3)_3C-OH H^+, (CH_3)_2C=CH_2 + H_2O Product A is 2-methylpropene. When 2-methylpropene is treated with water in the presence of concentrated H_2SO_4 and heat, it undergoes acid-catalyzed hydration. The addition of water follows Markovnikov's rule, proceeding via the formation of a stable tertiary ca

Question 5

Which of the following on reaction with Grignard's reagent followed by hydrolysis forms tertiary alcohol ?

Accepted Answer

Grignard reagents react with carbonyl compounds to form addition products which on hydrolysis yield alcohols. Formaldehyde ( HCHO ) reacts with Grignard reagents to form primary alcohols. Other aldehydes (such as CH _3 CHO and CH _3 -CH _2 -CHO ) react with Grignard reagents to form secondary alcohols. Ketones (such as CH _3 - CO - CH _3) react with Grignard reagents to form tertiary alcohols. The reaction proceeds as follows: CH _3 - CO - CH _3 + RMgX CH _3 - C ( R )( OMgX ) - CH _3 CH _3 - C (

Question 6

Identify the compound obtained when ethyl methyl ketone is treated with CH _3 MgBr and hydrolyzed.

Accepted Answer

Ethyl methyl ketone is CH _3- CO - C _2 H _5. When it reacts with the Grignard reagent CH _3 MgBr , the nucleophilic methyl group attacks the electrophilic carbonyl carbon to form an intermediate alkoxide. CH _3- CO - C _2 H _5 + CH _3 MgBr CH _3- C ( OMgBr )( CH _3)- C _2 H _5 Upon hydrolysis, the alkoxide is protonated to yield a tertiary alcohol. CH _3- C ( OMgBr )( CH _3)- C _2 H _5 H _2 O C _2 H _5- C ( CH _3)_2- OH + Mg ( OH ) Br The final product is 2-methylbutan-2-ol, which matches the s

Question 7

Which from the following hydroxy compounds contain only one - OH group in a molecule?

Accepted Answer

Crotonyl alcohol (2-buten-1-ol) has the structure CH _3- CH = CH - CH _2 OH , which contains only one - OH group. Ethylene glycol (ethane-1,2-diol) has the structure HO - CH _2- CH _2- OH , which contains two - OH groups. Pyrogallol (benzene-1,2,3-triol) contains three - OH groups attached to a benzene ring. Hydroquinone (benzene-1,4-diol) contains two - OH groups attached to a benzene ring. Therefore, crotonyl alcohol is the only compound among the given options that contains a single - OH grou

Question 8

Which of the following pair of reagents is used for the conversion of carboxylic acid to alcohol ?

Accepted Answer

Carboxylic acids are reduced to primary alcohols by strong reducing agents such as lithium aluminium hydride ( LiAlH _4) followed by acid hydrolysis ( H _3 O ^+). RCOOH LiAlH _4 RCH _2 O ^- Li ^+ H _3 O ^+ RCH _2 OH Catalytic hydrogenation using H _2 / Ni or H _2 / Pd does not reduce carboxylic acids. B _2 H _6 / H _2 O _2, OH ^- is the reagent for the hydroboration-oxidation of alkenes to alcohols. Answer: LiAlH _4 / H _3 O ^+

Question 9

Which of the following isomers of C _4 H _9 OH has lowest boiling point ?

Accepted Answer

The boiling point of isomeric alcohols decreases with an increase in branching. As branching increases, the molecule becomes more spherical in shape, which decreases the effective surface area. A smaller surface area results in weaker van der Waals forces of attraction between the molecules, thereby lowering the boiling point. Among the given isomers of C _4 H _9 OH , tert-butyl alcohol is the most branched. Therefore, tert-butyl alcohol has the lowest boiling point. Answer: tert Butyl alcohol

Question 10

Select the correct decreasing order of acid strength for the following compounds. a) Ethanol   b) 2-Methyl propan-2-ol   c) Phenol   d) p - Nitrophenol

Accepted Answer

Acid strength is directly proportional to the stability of the conjugate base formed after the removal of an H^+ ion. The conjugate bases are: a) Ethoxide ion (CH_3CH_2O^-) b) tert-Butoxide ion ((CH_3)_3CO^-) c) Phenoxide ion (C_6H_5O^-) d) p-Nitrophenoxide ion (p-NO_2-C_6H_4O^-) Phenoxide ions are resonance stabilized, making phenols more acidic than aliphatic alcohols. Thus, (c) and (d) are more acidic than (a) and (b). In p-nitrophenol (d), the -NO_2 group exerts strong -I and -R effects, whi

Question 11

Which from following is obtained by hydroboration - oxidation of propene?

Accepted Answer

Hydroboration-oxidation of an alkene results in the anti-Markovnikov addition of water across the double bond. Propene (CH_3-CH=CH_2) reacts with diborane (B_2H_6) to form tripropylborane as an intermediate. Subsequent oxidation with hydrogen peroxide (H_2O_2) in an alkaline medium yields propan-1-ol. CH_3-CH=CH_2 [2. H_2O_2, OH^-] 1. B_2H_6 CH_3-CH_2-CH_2-OH Answer: Propan-1-ol

Question 12

Which among the following has lowest boiling point?

Accepted Answer

The boiling point of isomeric alcohols decreases with an increase in branching. As branching increases, the molecule becomes more spherical in shape, which decreases the surface area. A smaller surface area leads to weaker van der Waals forces of attraction between the molecules, thereby lowering the boiling point. Among the given isomers of butyl alcohol, tert-butyl alcohol is the most branched. Therefore, tert-butyl alcohol has the lowest boiling point. Answer: tert-Butyl alcohol

Question 13

Identify the product P obtained in following reaction

Accepted Answer

The given reaction is the condensation of phenol with formaldehyde in the presence of an acid catalyst, which is the first step in the synthesis of Bakelite (Lederer-Manasse reaction). In the presence of an acid, formaldehyde is protonated to generate the electrophile ^+CH_2OH: HCHO + H^+ ^+CH_2OH The -OH group of phenol is strongly activating and directs the incoming electrophile to the ortho and para positions. The electrophile ^+CH_2OH attacks the ortho and para positions of the phenol ring,

Question 14

Which among the following does NOT undergo Williamson's synthesis?

Accepted Answer

Williamson's synthesis is a method for preparing ethers by the reaction of an alkyl halide with a sodium alkoxide. This reaction follows an S_N2 mechanism. For an S_N2 reaction to occur favorably, the halide should be primary or secondary (primary being the most reactive). Let us evaluate the given options: 1. C _2 H _5 Br (Ethyl bromide) is a primary alkyl halide and readily undergoes Williamson's synthesis. 2. CH _3- CH ( CH _3)- CH _2- Br (Isobutyl bromide) is a primary alkyl halide and under

Question 15

Which of the following alcohols on addition of Lucas reagent reacts fast and turns the reagent turbid instantly.

Accepted Answer

Lucas reagent is a mixture of concentrated HCl and anhydrous ZnCl _2. The reaction of alcohols with Lucas reagent proceeds via an S_N1 mechanism, which involves the formation of a carbocation intermediate. The rate of reaction depends on the stability of the carbocation formed. The order of stability of carbocations is tertiary > secondary > primary. Therefore, the reactivity of alcohols towards Lucas reagent follows the order: tertiary > secondary > primary. Tertiary alcohols react instantly to

Question 16

Which among the following has highest melting point ?

Accepted Answer

p-Nitrophenol has the highest melting point among the given compounds. In p-nitrophenol, there is strong intermolecular hydrogen bonding between the -OH group of one molecule and the -NO_2 group of another molecule. This leads to the association of molecules, requiring more thermal energy to break the crystal lattice. In contrast, o-nitrophenol exhibits intramolecular hydrogen bonding (chelation), which restricts molecular association and lowers its melting point. Phenol and p-cresol also exhibi

Question 17

Which from the following is a correct decreasing order of boiling points for following organic compounds ?

Accepted Answer

Boiling point depends on the strength of intermolecular forces. Carboxylic acids form strong intermolecular hydrogen bonds and exist as dimers, leading to the highest boiling points among compounds of comparable molecular mass. Alcohols also form intermolecular hydrogen bonds, but they are weaker than those in carboxylic acids. Ketones and aldehydes lack intermolecular hydrogen bonding but possess dipole-dipole interactions. Ketones have slightly higher boiling points than isomeric aldehydes due

Question 18

Identify trihydric phenol from following.

Accepted Answer

Trihydric phenols are compounds that contain three hydroxyl (-OH) groups attached directly to the benzene ring. Hydroquinone is benzene-1,4-diol, which contains two -OH groups and is a dihydric phenol. Catechol is benzene-1,2-diol, which contains two -OH groups and is a dihydric phenol. o-Cresol is 2-methylphenol, which contains one -OH group and is a monohydric phenol. Pyrogallol is benzene-1,2,3-triol, which contains three -OH groups and is a trihydric phenol. Answer: Pyrogallol

Question 19

Identify ' Z' in the following reaction.

Accepted Answer

The given reaction is an esterification reaction where a phenol ( Ar-OH ) reacts with an acid chloride ( R-COCl ) in the presence of a base like pyridine. In this nucleophilic acyl substitution reaction, the oxygen atom of the phenol acts as a nucleophile and attacks the electrophilic carbonyl carbon of the acid chloride. Pyridine is used as a base to neutralize the HCl formed during the reaction, which prevents the backward reaction and drives the equilibrium in the forward direction. The react

Question 20

Identify the product X in the following reaction.

Accepted Answer

The given reaction is the acid-catalyzed dehydration of an alcohol. The reactant is 3,3-dimethyl-2-butanol. Step 1: Protonation of the hydroxyl group by H_2SO_4 to form a good leaving group (-OH_2^+). CH_3-C(CH_3)_2-CH(OH)-CH_3 + H^+ CH_3-C(CH_3)_2-CH(OH_2^+)-CH_3 Step 2: Loss of a water molecule to form a secondary (2^ ) carbocation. CH_3-C(CH_3)_2-CH(OH_2^+)-CH_3 CH_3-C(CH_3)_2-CH^+-CH_3 + H_2O Step 3: The 2^ carbocation undergoes a 1,2-methyl shift to form a more stable tertiary (3^ ) carboca

Alcohols Phenols and Ethers — Previous Year Questions & Solutions