Chapter 27: Problem 205
p-cresol reacts with chloroform in alkaline medium to give a compound 'A' which on reacting with hydrogen cyanide gives, compound 'B'. The latter on acidic hydrolysis, gives chiral carboxylic acid. The structure of the carboxylic acid is [2005]
Short Answer
Expert verified
The chiral carboxylic acid is 2-hydroxy-3-methylbenzoic acid.
Step by step solution
01
Identify the starting reactant
The starting compound is p-cresol, which is a phenol derivative with a methyl group at the para position. Its chemical structure can be represented as C7H8O or C6H4(OH)CH3.
02
Apply Reimer-Tiemann Reaction
p-cresol is undergoing a Reimer-Tiemann reaction with chloroform (CHCl3) in an alkaline medium, which typically results in the formation of a formyl group. The product (Compound A) is 4-hydroxy-3-methylbenzaldehyde, also known as 4-formyl-m-cresol.
03
React Compound A with Hydrogen Cyanide
4-Hydroxy-3-methylbenzaldehyde (Compound A) reacts with hydrogen cyanide (HCN) to form a cyanohydrin. This reaction adds a -CN group to the carbonyl carbon, resulting in the intermediate Compound B, which is 4-hydroxy-3-methyl-2-(hydroxymethyl)benzonitrile.
04
Conduct Acidic Hydrolysis
The cyanohydrin (Compound B) undergoes acidic hydrolysis, converting the nitrile group (-CN) into a carboxylic acid group (-COOH). This process transforms Compound B into the corresponding chiral carboxylic acid, which is 4-hydroxy-3-methyl-2-(hydroxymethyl)benzoic acid.
05
Identify the Structure
The final structure of the chiral carboxylic acid is 2-hydroxy-3-methylbenzoic acid, also known as o-hydroxy-p-toluic acid which is chiral due to the presence of a stereocenter at the benzylic position.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Reimer-Tiemann Reaction
The Reimer-Tiemann reaction is a classic organic chemical reaction primarily used to introduce formyl groups into aromatic compounds such as phenols. It provides a straightforward method to convert phenols into aromatic aldehydes. The reaction involves the use of chloroform (CHCl₃) and a strong base, usually sodium hydroxide (NaOH).
- When p-cresol, a type of phenol derivative, is reacted with chloroform under these conditions, a new carbon-to-carbon bond is formed, attaching a formyl group to the aromatic ring.
Cyanohydrin Formation
Cyanohydrin formation is a significant step in organic synthesis involving the addition of hydrogen cyanide (HCN) to aldehydes or ketones. This reaction results in the creation of a new cyanohydrin compound, which includes both a hydroxyl group (-OH) and a nitrile group (-CN) on the same carbon atom.
- Compound A, 4-hydroxy-3-methylbenzaldehyde, reacts with HCN, resulting in Compound B, a cyanohydrin, formally named 4-hydroxy-3-methyl-2-(hydroxymethyl)benzonitrile.
Acidic Hydrolysis
Acidic hydrolysis is a crucial conversion process in organic chemistry where a nitrile group is transformed into a carboxylic acid group. This reaction involves treating the nitrile compound with an acid and water to break down and replace the -CN group with a -COOH group, releasing ammonia.
- For the compound in our process, 4-hydroxy-3-methyl-2-(hydroxymethyl)benzonitrile (Compound B), acidic hydrolysis converts it to a chiral carboxylic acid.
p-Cresol Reactions
p-Cresol is a phenolic compound that serves as a starting material for various chemical transformations. In reactions, its phenolic group (the -OH) enables it to engage in electrophilic substitution reactions, facilitating the introduction of additional functional groups. In the context of this exercise, p-cresol first undergoes a Reimer-Tiemann reaction to introduce an aldehyde group.
- This transformation produces 4-hydroxy-3-methylbenzaldehyde, setting the stage for subsequent reactions like cyanohydrin formation and hydrolysis.
- Eventually, this pathway leads to the formation of a chiral carboxylic acid, demonstrating how p-cresol's reactivity can be exploited to create sophisticated organic structures with potential applications in pharmaceuticals and materials science.