Problem 92 - A Complete Resource Book in Chemistry for JEE Main

Question

At higher temperature, iodoform reaction is given by (a) \(\mathrm{CH}_{3} \mathrm{CO}_{2} \mathrm{CH}_{3}\) (b) \(\mathrm{CH}_{3} \mathrm{CO}_{2} \mathrm{C}_{6} \mathrm{H}_{5}\) (c) \(\mathrm{CH}_{3} \mathrm{CO}_{2} \mathrm{C}_{2} \mathrm{H}_{5}\) (d) \(\mathrm{C}_{6} \mathrm{H}_{3} \mathrm{CO}_{2} \mathrm{CH}_{3}\)

Step-by-Step Solution

Answer

None of the given options will give an iodoform reaction.

Step 1: Understanding the Iodoform Reaction

The iodoform reaction occurs when a compound containing a methyl ketone (an R-CO-CH3 group) is treated with iodine (I2) and a base like sodium hydroxide (NaOH). The presence of the active group results in the formation of iodoform (CHI3), which is a yellow precipitate. We are looking for a compound that will give this reaction.

Step 2: Analyzing Option (a)

Option (a) is \( \mathrm{CH}_{3} \mathrm{CO}_{2} \mathrm{CH}_{3} \). This is methyl acetate. Upon hydrolysis, it forms acetic acid, which does not contain the necessary methyl ketone group. Thus, it will not give the iodoform reaction.

Step 3: Analyzing Option (b)

Option (b) is \( \mathrm{CH}_{3} \mathrm{CO}_{2} \mathrm{C}_{6} \mathrm{H}_{5} \). This is phenyl acetate. Like methyl acetate, it does not have a methyl ketone group, so it will not produce an iodoform reaction.

Step 4: Analyzing Option (c)

Option (c) is \( \mathrm{CH}_{3} \mathrm{CO}_{2} \mathrm{C}_{2} \mathrm{H}_{5} \). This is ethyl acetate. While it may undergo hydrolysis, it does not contain a methyl ketone, therefore it will not yield an iodoform reaction.

Step 5: Analyzing Option (d)

Option (d) is \( \mathrm{C}_{6} \mathrm{H}_{3} \mathrm{CO}_{2} \mathrm{CH}_{3} \). This compound is methyl benzoate, which also lacks the methyl ketone group. Therefore, it will not give an iodoform reaction.

Step 6: Conclusion

None of the given options contain a methyl ketone moiety that would allow them to participate in the iodoform reaction at higher temperatures. However, if we've interpreted the question correctly, it's possible that the correct structure was related closely to one of these in a form not provided.

Key Concepts

Methyl Ketone

Methyl ketones are a specific kind of ketone where there is a methyl group
(-CH₃) directly attached to the carbonyl group (C=O). These structures are represented as R-CO-CH₃.
In simpler terms, they are a subtype of ketones with a very reactive site. This makes them very
eager participants in various chemical reactions, notably the iodoform reaction.
This reaction is especially important in organic chemistry because it is a method used to identify the presence
of methyl ketones in a given compound.

• Methyl ketones have a significant role in organic synthesis.
• They can be formed through several reactions, including oxidation of secondary alcohols.
• Methyl ketones are essential for various industrial applications.

The key feature for a methyl ketone to undergo an iodoform reaction is the possession of a specific
grouping that includes a carbonyl group adjacent to a methyl group.

Organic Chemistry Reactions

Organic chemistry reactions involve changes between organic compounds,
often involving the breaking and forming of covalent bonds.
The iodoform reaction is a classic organic reaction which serves as an important chemical test for
detecting methyl ketones.
It involves treating the compound with iodine (I₂) and a base usually sodium hydroxide (NaOH).
During this reaction, if a methyl ketone is present, a product called iodoform (CHI₃) forms, which is
yellow and usually solid.

• The iodoform test is specific to methyl ketones and certain alcohols.
• This reaction is one of the few organic chemistry reactions that produces a visible, solid product.
• It highlights the importance of functional groups in organic reaction mechanisms.

Being a test reaction, the iodoform reaction sets a pathway for many analytical methods in labs to
denote specific structural elements within larger molecular frameworks.

Hydrolysis in Chemistry

Hydrolysis is a chemical process where molecules are broken down by reaction with water.
In organic chemistry, this process often leads to the breaking of bonds to generate acids, bases,
or different organic compounds.
In the context of our discussion, though methyl acetate and similar esters
undergo hydrolysis, they do not yield methyl ketones.

• Hydrolysis reactions are guided by the nature of the molecule and reaction conditions.
• It is an essential process in biochemical and industrial applications.
• Not all hydrolysis processes lead to
  iodoform reactions; instead, they can yield different types of products.

Understanding the hydrolysis of different substances plays an
important role in identifying the end products of organic reactions and correctly predicting reaction
pathways.