Question

A hydrocarbon reacts with HI to give (X) which on reacting with aq. \(\mathrm{KOH}\) forms (Y). Oxidation of (Y) gives 3 -methyl-2-butanone, the hydrocarbon is (1) C=C(C)C (2) C=CC(C)C (3) CCC(C)(C)C (4) C#CC(C)C

Short answer

Option (4) C#CC(C)C

Step-by-step solution

Identify the product of HI addition

When adding HI to the hydrocarbon, we need to identify the primary product (X) of the reaction. HI will add across any multiple bonds in the hydrocarbon.

Reaction of (X) with KOH

Next, we need to understand the reaction of (X) with aqueous KOH. This generally leads to the formation of an alcohol (Y) by nucleophilic substitution.

Oxidation result analysis

The compound (Y) on oxidation yields 3-methyl-2-butanone. Recognize that oxidation typically converts an alcohol into a ketone or aldehyde.

Determine the structure of the original hydrocarbon

Since (Y) is oxidized to give 3-methyl-2-butanone, we need to trace back to find the original hydrocarbon structure that fits this oxidation pathway. Ensuring the given options, consider which one when adds HI forms the precursor alcohol for the ketone 3-methyl-2-butanone. Verify each option systematically.

Match with given options

Option (4) C#CC(C)C when reacted with HI followed by aqueous KOH and then oxidized, fits the description. It forms 3-methyl-2-butanone, confirming this as the correct hydrocarbon.

Key concepts

organic chemistry

Organic chemistry is the branch of chemistry that deals with the structure, properties, and reactions of organic compounds, which contain carbon. It is a vast and fascinating field that is crucial for understanding the natural and synthetic world. This particular problem showcases a simple hydrocarbon reacting through multiple steps to form complex products. The understanding starts with recognizing basic hydrocarbons and follows through their reactions with reagents such as hydroiodic acid (HI) and potassium hydroxide (KOH).

chemical reactions

Chemical reactions describe the process in which substances, called reactants, are transformed into different substances, called products. In this problem, we follow a hydrocarbon through a series of reactions:

• First, the hydrocarbon reacts with HI (hydroiodic acid) which adds across any multiple bonds present.
• Next, the resulting product reacts with aqueous KOH, typically leading to the formation of an alcohol.
• Finally, the alcohol is oxidized to form a ketone, specifically 3-methyl-2-butanone in this case.

Each step must be carefully analyzed to understand how the structure of the molecule changes.

ketones

Ketones are a class of organic compounds characterized by a carbonyl group (C=O) bonded to two carbon atoms. In this exercise, the final product is 3-methyl-2-butanone, a ketone. Recognizing the structure of ketones is important; they generally result from the oxidation of secondary alcohols. The identification process involves tracing back the oxidative pathways to determine the possible structure of the precursor alcohol and, hence, the starting hydrocarbon.

alcohol oxidation

Alcohol oxidation is a fundamental reaction in organic chemistry where an alcohol is converted into a carbonyl-containing compound, such as an aldehyde or a ketone. In the given problem:

• The alcohol (Y) generated from the reaction of hydrocarbon with HI and then KOH is oxidized.
• Through oxidation, an alcohol (OH group) is transformed. Primary alcohols become aldehydes, and secondary alcohols become ketones.
• The final product, 3-methyl-2-butanone, results from such an oxidation of a secondary alcohol.

Understanding this oxidation process helps in identifying and confirming the structural transitions taking place in sequential reactions.