Number of molecules from below which cannot give iodoform reaction is : Ethanol, Isopropyl alcohol, Bromoacetone, 2-Butanol, 2-Butanone, Butanal, 2-Pentanone, 3-Pentanone, Pentanal and 3-Pentanol

Positive iodoform test requires presence of: - Methyl ketone: CH3-C(=O)-R - Methyl carbinol: CH3-CH(OH)-R Evaluate each compound: 1. Ethanol (CH3CH2OH) arrow Gives test (Gives CHI3) 2. Isopropyl alcohol (CH3CH(OH)CH3) arrow Gives test 3. Bromoacetone (BrCH2COCH3) arrow Gives test 4. 2-Butanol (CH3CH(OH)CH2CH3) arrow Gives test 5. 2-Butanone (CH3COCH2CH3) arrow Gives test 6. Butanal (CH3CH2CH2CHO) arrow **Does NOT give test** 7. 2-Pentanone (CH3COCH2CH2CH3) arrow Gives test 8. 3-Pentanone (CH3CH2COCH2CH3) arrow **Does NOT give test** 9. Pentanal (CH3CH2CH2CH2CHO) arrow **Does NOT give test** 10. 3-Pentanol (CH3CH2CH(OH)CH2CH3) arrow **Does NOT give test** The 4 compounds that cannot give the iodoform reaction are: Butanal, 3-Pentanone, Pentanal, and 3-Pentanol. Requires CH3-CO- or CH3-CH(OH)- group. Aldehydes other than acetaldehyde do not give iodoform test. Symmetrical 3-ketones and 3-alcohols fail the test. Class 12 Chemistry: Aldehydes, Ketones and Carboxylic Acids

Number of molecules from below which cannot give iodoform reaction is : Ethanol, Isopropyl alcohol, Bromoacetone, 2-Butanol, 2-Butanone, Butanal, 2-Pentanone, 3-Pentanone, Pentanal and 3-Pentanol

Positive iodoform test requires presence of: - Methyl ketone: CH3-C(=O)-R - Methyl carbinol: CH3-CH(OH)-R Evaluate each compound: 1. Ethanol (CH3CH2OH) arrow Gives test (Gives CHI3) 2. Isopropyl alcohol (CH3CH(OH)CH3) arrow Gives test 3. Bromoacetone (BrCH2COCH3) arrow Gives test 4. 2-Butanol (CH3CH(OH)CH2CH3) arrow Gives test 5. 2-Butanone (CH3COCH2CH3) arrow Gives test 6. Butanal (CH3CH2CH2CHO) arrow **Does NOT give test** 7. 2-Pentanone (CH3COCH2CH2CH3) arrow Gives test 8. 3-Pentanone (CH3CH2

Number of molecules from below which cannot give iodoform reaction is : Ethanol, Isopropyl alcohol, Bromoacetone, 2-Butanol, 2-Butanone, Butanal, 2-Pentanone, 3-Pentanone, Pentanal and 3-Pentanol

Positive iodoform test requires presence of: - Methyl ketone: CH3-C(=O)-R - Methyl carbinol: CH3-CH(OH)-R Evaluate each compound: 1. Ethanol (CH3CH2OH) arrow Gives test (Gives CHI3) 2. Isopropyl alcohol (CH3CH(OH)CH3) arrow Gives test 3. Bromoacetone (BrCH2COCH3) arrow Gives test 4. 2-Butanol (CH3CH(OH)CH2CH3) arrow Gives test 5. 2-Butanone (CH3COCH2CH3) arrow Gives test 6. Butanal (CH3CH2CH2CHO) arrow **Does NOT give test** 7. 2-Pentanone (CH3COCH2CH2CH3) arrow Gives test 8. 3-Pentanone (CH3CH2COCH2CH3) arrow **Does NOT give test** 9. Pentanal (CH3CH2CH2CH2CHO) arrow **Does NOT give test** 10. 3-Pentanol (CH3CH2CH(OH)CH2CH3) arrow **Does NOT give test** The 4 compounds that cannot give the iodoform reaction are: Butanal, 3-Pentanone, Pentanal, and 3-Pentanol. Requires CH3-CO- or CH3-CH(OH)- group. Aldehydes other than acetaldehyde do not give iodoform test. Symmetrical 3-ketones and 3-alcohols fail the test. Class 12 Chemistry: Aldehydes, Ketones and Carboxylic Acids

Number of molecules from below which cannot give iodoform reaction is : Ethanol, Isopropyl alcohol, Bromoacetone, 2-Butanol, 2-Butanone, Butanal, 2-Pentanone, 3-Pentanone, Pentanal and 3-Pentanol

Positive iodoform test requires presence of: - Methyl ketone: CH3-C(=O)-R - Methyl carbinol: CH3-CH(OH)-R Evaluate each compound: 1. Ethanol (CH3CH2OH) arrow Gives test (Gives CHI3) 2. Isopropyl alcohol (CH3CH(OH)CH3) arrow Gives test 3. Bromoacetone (BrCH2COCH3) arrow Gives test 4. 2-Butanol (CH3CH(OH)CH2CH3) arrow Gives test 5. 2-Butanone (CH3COCH2CH3) arrow Gives test 6. Butanal (CH3CH2CH2CHO) arrow **Does NOT give test** 7. 2-Pentanone (CH3COCH2CH2CH3) arrow Gives test 8. 3-Pentanone (CH3CH2

Number of molecules from below which cannot give iodoform reaction is : Ethanol, Isopropyl alcohol, Bromoacetone…

Year	2026	2025	2024	Total
Questions	14	21	11	46

Year

2026

2025

2024

Total

Questions

Solution & Explanation

Related Formula

Positive iodoform test requires presence of:

Methyl ketone: $CH₃-C(=O)-R$ $\mathrm{CH_3-C(=O)-R}$
Methyl carbinol: $CH₃-CH(OH)-R$ $\mathrm{CH_3-CH(OH)-R}$

Core Logic

Evaluate each compound:

Ethanol ( $CH₃CH₂OH$ $\mathrm{CH_3CH_2OH}$) $arrow$ $\rightarrow$ Gives test (Gives $CHI₃$ $\mathrm{CHI_3}$)
Isopropyl alcohol ( $CH₃CH(OH)CH₃$ $\mathrm{CH_3CH(OH)CH_3}$) $arrow$ $\rightarrow$ Gives test
Bromoacetone ( $BrCH₂COCH₃$ $\mathrm{BrCH_2COCH_3}$) $arrow$ $\rightarrow$ Gives test
2-Butanol ( $CH₃CH(OH)CH₂CH₃$ $\mathrm{CH_3CH(OH)CH_2CH_3}$) $arrow$ $\rightarrow$ Gives test
2-Butanone ( $CH₃COCH₂CH₃$ $\mathrm{CH_3COCH_2CH_3}$) $arrow$ $\rightarrow$ Gives test
Butanal ( $CH₃CH₂CH₂CHO$ $\mathrm{CH_3CH_2CH_2CHO}$) $arrow$ $\rightarrow$ Does NOT give test
2-Pentanone ( $CH₃COCH₂CH₂CH₃$ $\mathrm{CH_3COCH_2CH_2CH_3}$) $arrow$ $\rightarrow$ Gives test
3-Pentanone ( $CH₃CH₂COCH₂CH₃$ $\mathrm{CH_3CH_2COCH_2CH_3}$) $arrow$ $\rightarrow$ Does NOT give test
Pentanal ( $CH₃CH₂CH₂CH₂CHO$ $\mathrm{CH_3CH_2CH_2CH_2CHO}$) $arrow$ $\rightarrow$ Does NOT give test
3-Pentanol ( $CH₃CH₂CH(OH)CH₂CH₃$ $\mathrm{CH_3CH_2CH(OH)CH_2CH_3}$) $arrow$ $\rightarrow$ Does NOT give test

Step 1: Final Count

The 4 compounds that cannot give the iodoform reaction are: Butanal, 3-Pentanone, Pentanal, and 3-Pentanol.

Pattern Recognition

Requires $CH₃-CO-$ $\mathrm{CH_3-CO-}$ or $CH₃-CH(OH)-$ $\mathrm{CH_3-CH(OH)-}$ group. Aldehydes other than acetaldehyde do not give iodoform test. Symmetrical 3-ketones and 3-alcohols fail the test.

Chapter Mix

Class 12 Chemistry: Aldehydes, Ketones and Carboxylic Acids

More Aldehydes, Ketones and Carboxylic Acids Previous-Year Questions — Page 10

Q jee_main_2024_31_jan_morning Reactions with Grignard Reagent

The product of the following reaction is P.

Reactions with Grignard Reagent diagram for Q84 - JEE Main 2024 Morning — The image shows p-hydroxybenzaldehyde reacting with one equivalent of PhMgBr followed by aqueous ammonium chloride.

The number of hydroxyl groups present in the product P is

Numerical Answer. Answer: 0 to 0

Solution

Core Logic

The given reactant is p-hydroxybenzaldehyde, which contains both a phenolic $-OH$ $-OH$ group (acidic) and an aldehyde group (electrophilic).

When one equivalent of Grignard reagent ( $PhMgBr$ $PhMgBr$) is added, it behaves primarily as a strong base due to the presence of an acidic proton. Acid-base reactions are extremely fast compared to nucleophilic additions.

The acidic phenolic $-OH$ $-OH$ reacts with $PhMgBr$ $PhMgBr$:

PhMgBr + HO-C₆H₄-CHO arrow Ph-H (Benzene) + BrMg-O-C₆H₄-CHO

Upon workup with $aq. NH₄Cl$ $aq. NH_4Cl$, the phenoxide ion simply regenerates the starting p-hydroxybenzaldehyde. However, the question asks for the number of hydroxyl groups present in the formed product (Benzene).

The distinct product formed in the reaction is Benzene. Benzene has 0 hydroxyl groups.

Pattern Recognition

Whenever a Grignard reagent encounters a molecule with an acidic hydrogen (alcohol, phenol, amine, alkyne), it will invariably act as a base first. If only 1 equivalent is used, nucleophilic addition to carbonyls will NOT happen.

Chapter Mix

Class 12 Chemistry: Aldehydes, Ketones and Carboxylic Acids Class 12 Chemistry: Alcohols, Phenols and Ethers

Number of molecules from below which cannot give iodoform reaction is : Ethanol, Isopropyl alcohol, Bromoacetone, 2-Butanol, 2-Butanone, Butanal, 2-Pentanone, 3-Pentanone, Pentanal and 3-Pentanol

Solution & Explanation

Related Formula

Core Logic

Step 1: Final Count

Pattern Recognition

Chapter Mix

Reference Study Guides

More Aldehydes, Ketones and Carboxylic Acids Previous-Year Questions — Page 10

Solution

Core Logic

Pattern Recognition

Chapter Mix

More Aldehydes, Ketones and Carboxylic Acids Questions — jee_main_2025_03_april_morning

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Number of molecules from below which cannot give iodoform reaction is : Ethanol, Isopropyl alcohol, Bromoacetone, 2-Butanol, 2-Butanone, Butanal, 2-Pentanone, 3-Pentanone, Pentanal and 3-Pentanol

Solution & Explanation

Related Formula

Core Logic

Step 1: Final Count

Pattern Recognition

Chapter Mix

Reference Study Guides

More Aldehydes, Ketones and Carboxylic Acids Previous-Year Questions — Page 10

Solution

Core Logic

Pattern Recognition

Chapter Mix

More Aldehydes, Ketones and Carboxylic Acids Questions — jee_main_2025_03_april_morning

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