Problem 39 - Advanced Problems in Organic Chemistry for Competitive Examinations

Question

Identify incorrect matching in the following (a) Allyl alcohol-Prop-2-en-1-ol (b) Vinyl alcohol-Ethenol (c) Propargyl alcohol-But-3-yn-1-ol (d) Acrylaldehyde-2-Propenal

Step-by-Step Solution

Answer

Propargyl alcohol-But-3-yn-1-ol is incorrectly matched.

Step 1: Analyze Allyl alcohol

The chemical name for Allyl alcohol is Prop-2-en-1-ol, which is correct. This is because "allyl" refers to a 3-carbon chain with a double bond, matching the nomenclature Prop-2-en-1-ol.

Step 2: Analyze Vinyl alcohol

Vinyl alcohol is correctly named as Ethenol. This molecule consists of a 2-carbon chain (eth-) with a double-bond (vinyl) and an alcohol group, which matches the name Ethenol.

Step 3: Analyze Propargyl alcohol

The name Propargyl alcohol refers to a molecule with a 3-carbon chain with a triple bond on the first carbon, known as Prop-2-yn-1-ol. Therefore, naming it as But-3-yn-1-ol, which describes a 4-carbon chain with a triple bond at the third position, is incorrect.

Step 4: Analyze Acrylaldehyde

Acrylaldehyde is another name for Acrolein, which is correctly named 2-Propenal. It has three carbon atoms and a double bond, which matches the systematic nomenclature of 2-Propenal.

Key Concepts

Allyl Alcohol

Allyl alcohol is an important chemical compound in organic chemistry, often used as a precursor in the creation of other complex chemicals. Its structural makeup is simple yet crucial to understand:

• The term "allyl" denotes a 3-carbon chain, where one of the carbons is involved in a double bond.
• The molecular formula for allyl alcohol is \(C_3H_6O\).
• The systematic IUPAC name is Prop-2-en-1-ol.

The structure can be visualized as having the hydroxyl group (OH group) attached to the first carbon of the chain. The presence of the double bond between the second and third carbon atoms gives the compound its defining properties. This notation as Prop-2-en-1-ol accurately reflects the presence of both the alcohol group and the double bond in the structure.

Vinyl Alcohol

Vinyl alcohol, often less stable in its pure form, provides a unique look into functional groups and unsaturated carbon chains in organic chemistry. Here's what you need to know about its composition:

• The name "vinyl" suggests the presence of an ethenyl group, characterized by a carbon-carbon double bond.
• The compound can also be referred to as Ethenol based on IUPAC guidelines.
• Its molecular formula is \(C_2H_4O\).

Usually, vinyl alcohol rearranges into acetaldehyde, a more stable form, due to tautomerism—a process where hydrogen shifts between atoms within a molecule. This underscores the interesting yet fleeting existence of vinyl alcohol in a pure state. Its ability to tautomerize quickly enables applications in various synthesis processes.

Propargyl Alcohol

Propargyl alcohol is a key compound, featuring an intriguing combination of an alcohol group and a triple bond:

• This alcohol contains a 3-carbon backbone with a triple bond.
• Its proper IUPAC name is Prop-2-yn-1-ol, illustrating the position of the triple bond and the alcohol functionality.
• The molecule's formula is \(C_3H_4O\).

Propargyl distinctions lie in the triple bond starting at the first carbon, which offers high reactivity, particularly in nucleophilic addition reactions. This reactivity is valuable in synthesizing complex organic compounds, making it a staple in laboratories.

Acrylaldehyde

Acrylaldehyde, more commonly known in scientific studies as acrolein, plays a significant role in organic chemical reactions. Here are the highlights of its composition:

• The name Acrylaldehyde can be systematically defined as 2-Propenal.
• This name reflects its structure of a 3-carbon chain with an aldehyde group at the end and a double bond within the chain.
• Its molecular formula is \(C_3H_4O\).

Widely used in industrial applications such as creating acrylic acid and as a building block for several chemical syntheses, acrolein's reactivity arises from the polarity of its carbonyl group and its double bond. Understanding acrylaldehyde's properties can foster the efficient use of its reactive aldehyde group in various chemical transformations.