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NEET CHEMISTRYAlcohols, Phenols and EthersEasy

Question

The compound that will not form a yellow precipitate on heating with an alkaline solution of iodine is:

A

CH₃CH₂CH(OH)CH₃

B

CH₃OH

C

CH₃CH₂OH

D

CH₃CH(OH)CH₃

Step-by-Step Solution

The reaction described is the Iodoform test. A positive test (formation of a yellow precipitate of CHI3CHI_3) is given by compounds containing either a methyl ketone group (CH3C=OCH_3-C=O) or a methyl carbinol group (CH3CH(OH)CH_3-CH(OH)-) attached to at least one hydrogen atom or alkyl/aryl group.

  1. Ethanol (CH3CH2OHCH_3CH_2OH): Contains the CH3CH(OH)CH_3-CH(OH)- group. (Positive test).
  2. Propan-2-ol (CH3CH(OH)CH3CH_3CH(OH)CH_3): Contains the CH3CH(OH)CH_3-CH(OH)- group. (Positive test).
  3. Butan-2-ol (CH3CH2CH(OH)CH3CH_3CH_2CH(OH)CH_3): Contains the CH3CH(OH)CH_3-CH(OH)- group. (Positive test).
  4. Methanol (CH3OHCH_3OH): Does not contain the requisite CH3CH(OH)CH_3-CH(OH)- group. Therefore, it does not give a yellow precipitate with alkaline iodine.

Exam Context & Concepts Covered

This question aligns with the NEET CHEMISTRY syllabus, specifically targeting concepts from Alcohols, Phenols and Ethers. Mastering this topic is crucial for scoring well in the upcoming medical entrance examinations. Solving conceptually related problems will help you understand the nuances of these concepts and improve your problem-solving speed.

CHEMISTRYAlcohols, Phenols and Etherscompoundyellowprecipitateheatingalkaline

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