Question

Iodoform on heating with KOH gives (a) \(\mathrm{CH}_{3} \mathrm{COOK}\) (b) HCOOK (c) \(\mathrm{HCHO}\) (d) \(\mathrm{CH}_{3} \mathrm{CHO}\)

Short answer

(a) \( \text{CH}_3 \text{COOK} \)

Step-by-step solution

Understand the Reaction

Iodoform, also known as triiodomethane (\( \text{CHI}_3 \)), reacts with potassium hydroxide (KOH) in an alkaline hydrolysis reaction. This is also known as the haloform reaction.

Identify the Haloform Reaction Product

In the haloform reaction, iodoform (\( \text{CHI}_3 \)) reacts with an alkaline medium (such as KOH) to form potassium salt of carboxylic acid having one less carbon atom than the original ketone or alcohol that led to haloform formation.

Determine the Correct Carboxylic Acid

The starting alcohol or ketone is typically acetone (\( \text{CH}_3\text{COCH}_3 \)). In this reaction, the iodoform formed as an intermediate comes from acetone, leading to the formation of potassium acetate (\( \text{CH}_3\text{COOK} \)).

Choose the Correct Option

Given the products formed from the haloform reaction and the derived carboxylic acid, the correct answer is the salt of acetic acid, which is potassium acetate (\( \text{CH}_3\text{COOK} \)).

Key concepts

Iodoform

Iodoform, chemically known as triiodomethane, is a yellow crystalline solid with the formula \( \text{CHI}_3 \). It has a distinct antiseptic odor, often described as similar to hospitals or medical facilities. Historically, iodoform was used as a topical antiseptic, but nowadays, its primary importance in chemistry is as a reagent in organic synthesis.
Iodoform is especially recognized as a key player in the haloform reaction. This reaction involves the transformation of a methyl ketone or alcohol containing the \( \text{-CH}_3\text{CO} - \) group in the presence of a halogen source (like iodine) and a base (such as \( \text{KOH} \)). During the process, the system produces haloform (iodoform in this case) and a carboxylate ion derived from the initial carbonyl compound. This reaction highlights the ability of iodoform to indicate the presence of a particular methyl group configuration.

Potassium Hydroxide

Potassium hydroxide (KOH) is a pivotal reagent in many chemical reactions, including the haloform reaction. This strong base is invaluable in inducing deprotonation or saponification reactions. In its solid form, KOH is a white, caustic compound and is highly soluble in water.
In the context of the iodoform reaction, KOH acts as the base facilitating the halogenation and subsequent hydrolysis processes. It provides the hydroxide ions that deprotonate the methyl group adjacent to the carbonyl group, setting the stage for halogen substitution. As the reaction proceeds, KOH also facilitates the cleavage of the carbon-halogen bonds and helps in forming the carboxylate by interacting with the intermediate triiodomethane.

• Provides alkaline environment necessary for the reaction
• Helps in the halogenation of the methyl group
• Participates in the formation of the final carboxylate product

Potassium Acetate

Potassium acetate (\( \text{CH}_3\text{COOK} \)) emerges as a principal product in the haloform reaction involving iodoform. This compound is the potassium salt of acetic acid and is a key outcome when acetone undergoes haloform reaction.
The role of potassium acetate is significant as it illustrates the general outcome of a haloform reaction. When the original compound, such as a methyl ketone, undergoes sequential reactions with KOH and iodine, it eventually forms a carboxylate product with one carbon atom less than the starting carbonyl compound. In our specific case with acetone, the resulting carboxylate is, therefore, potassium acetate. Understanding this mechanism is essential, as it underscores the behavior and transformation of ketones in basic, halogenated environments.

Alkaline Hydrolysis

Alkaline hydrolysis is a crucial mechanism in many chemical transformations, including the haloform reaction. This process involves breaking chemical bonds by the action of a base, typically in aqueous conditions. In the context of the haloform reaction, alkaline hydrolysis is the step where the intermediate product, iodoform, reacts with hydroxide ions present in the solution.
During alkaline hydrolysis, the hydrolysis specifically breaks down iodoform to yield a simpler carboxylate form - potassium acetate in the case of acetone. This part of the reaction illustrates an essential aspect of organic chemistry: the modification and breakdown of complex molecules to simpler and often more stable entities.

• Key in converting intermediate haloforms into carboxylates
• Results from reaction of hydroxide ions with iodoform
• Illustrates transformation of methyl ketones/alcohols in alkaline settings