Problem 27 - A Complete Resource Book in Chemistry for JEE Main

Question

A yellow product is formed when an organic compound \(\mathrm{C}_{3} \mathrm{H}_{3} \mathrm{O}\) is warmed with aqueous sodium carbonate and iodine solution. The product formed is (a) iodoform (b) sodium iodate (c) sodium iodide (d) adduct of \(\mathrm{NaI}\) and \(\mathrm{C}_{3} \mathrm{H}_{8} \mathrm{O}\)

Step-by-Step Solution

Answer

The yellow product formed is iodoform, option (a).

Step 1: Identify the type of reaction

The reaction in question involves iodine and sodium carbonate with an organic compound, which suggests that it is a halogenation reaction. This particular setup strongly indicates the iodoform test, which is specific for methyl ketones or compounds that oxidize to methyl ketones.

Step 2: Analyze the organic compound

The given organic compound is \( \mathrm{C}_3 \mathrm{H}_3 \mathrm{O} \), which corresponds to a propenal or similar structure. It should ideally be able to form an oxidizable methyl group that fits the criteria for the iodoform reaction.

Step 3: Determine the iodoform reaction result

In the presence of excess iodine and a basic solution, such as sodium carbonate, certain compounds will undergo halogenation and release iodine. The characteristic iodoform (\( \mathrm{CHI}_3 \)) is a yellow solid compound.

Step 4: Verify the color of the product

The yellow product mentioned in the problem coincides with the appearance of iodoform. Therefore, the yellow product formed is iodoform, \( \mathrm{CHI}_3 \).

Step 5: Conclude the correct answer

Given that iodoform is the only yellow compound formed that matches the options provided, we conclude that option (a) is correct.

Key Concepts

Halogenation Reaction

A halogenation reaction is a type of chemical reaction where a halogen (fluorine, chlorine, bromine, iodine) is introduced into a compound. Halogens are highly reactive.
This makes them excellent candidates for such reactions. In organic chemistry, halogenation often involves the addition of a halogen to hydrocarbons.

• The reaction can be initiated by heat, light, or the presence of a catalyst.
• Halogens replace hydrogen atoms in the hydrocarbon.
• Commonly used for synthesizing various organic compounds, including alkyl halides.

In our exercise, iodine is the halogen that reacts under specific conditions with the organic compound. The resultant halogenated product in the iodoform reaction is yellow iodoform, indicating successful completion of the reaction.
This reaction is a perfect demonstration of halogenation in an aqueous environment with a basic medium.

Organic Chemistry

Organic chemistry is the branch of chemistry that deals with the structure, properties, reactions, and synthesis of organic compounds and materials.
These organic compounds are primarily made of carbon and hydrogen, but can also include other elements like oxygen, nitrogen, sulfur, and halogens.
This field is essential in the development of new materials, pharmaceuticals, and in biochemical processes that sustain life. Understanding organic chemistry is crucial when dealing with reactions like the iodoform reaction.

• The components such as methyl ketones involved in the reaction are a specific class of organic compounds.
• Reactions are often predictable, thanks to well-established rules of organic chemistry.
• The subject covers functional groups and their unique chemical properties.

The iodoform test highlights key principles of organic chemistry by showing functional group reactivity and the transformation of organic molecules.

Methyl Ketones

Methyl ketones are a specific group of organic compounds characterized by the presence of a carbonyl group (\( \mathrm{C} = \mathrm{O} \)) bonded to two carbon atoms, one of which must be a methyl group (\( \mathrm{CH}_3 \)).
This arrangement is crucial for the iodoform reaction, which targets these structures for oxidation.

• Methyl ketones are reactive when exposed to certain conditions, such as the presence of a halogen and a base.
• Iodoform reaction requires at least one methyl group adjacent to the carbonyl.
• Analyzing the formula \( \mathrm{C}_3 \mathrm{H}_3 \mathrm{O} \) suggests a structure that can fit these requirements.

The iodoform test is selective for methyl ketones, providing a definitive indicator through the formation of yellow iodoform.
This shows how specific functional groups are targeted in organic reactions to yield characteristic products.

Chemical Tests

Chemical tests are experiments conducted to determine the chemical composition of a substance or to identify specific chemical compounds.
Such tests utilize specific reactions to generate a recognizable outcome, like a color change, which supports identification. The iodoform test in organic chemistry is a classic example of using chemical tests to identify compounds like methyl ketones and secondary alcohols.

• Involves the use of iodine and a base to test for the presence of certain functional groups.
• Positive results typically produce a yellow precipitate of iodoform, a key distinguishing feature.
• This test is useful in quickly assessing the presence of specific types of organic compounds in a mixture.

Historically, chemical tests like these provide a simple, yet effective way to perform qualitative analysis without complex equipment.
It is not only functional in educational settings but also in practical scenarios where rapid testing is required.