Question

Acid amide is not obtained as a product in the reaction: (A) \(\mathrm{Me}_{2} \mathrm{CNOH} \stackrel{\text { Conc. } \mathrm{H}_{2} \mathrm{SO}_{4}}{\longrightarrow}\) (B) \(\mathrm{MeCOOH} \stackrel{\mathrm{N}_{3} \mathrm{H}}{\longrightarrow}\) (C) \(\mathrm{Me}_{2} \mathrm{CO} \frac{\mathrm{N}_{3} \mathrm{H}}{\mathrm{H}_{2} \mathrm{SO}_{4}}\) (D) \(\mathrm{MeCN} \frac{95 \%}{\mathrm{H}_{2} \mathrm{SO}_{4}}{\longrightarrow}\)

Short answer

Based on our analysis, reaction (A) does not produce an acid amide as a product: (A) \(\mathrm{Me}_{2} \mathrm{CNOH} \stackrel{\text { Conc. } \mathrm{H}_{2}\mathrm{SO}_{4}}{\longrightarrow}\)

Step-by-step solution

Identify the structure of acid amide

Acid amide molecules have the following general structure: RCONH2, where R can be any alkyl group.

Analyse reaction (A)

In reaction (A), we have dimethyl hydroximoyl chloride (Me2CNOH) reacting with concentrated H2SO4: \(\mathrm{Me}_{2} \mathrm{CNOH} \stackrel{\text { Conc. } \mathrm{H}_{2}\mathrm{SO}_{4}}{\longrightarrow} \) Concentrated H2SO4 is a dehydrating agent, so it will promote the loss of water to form the corresponding nitrile: \(\mathrm{Me}_{2}\mathrm{CNOH} \rightarrow \mathrm{Me}_{2}\mathrm{CN} + \mathrm{H}_{2}\mathrm{O}\) Here, the product is not an acid amide.

Analyse reaction (B)

In reaction (B), we have acetic acid (MeCOOH) reacting with hydrazoic acid (N3H): \(\mathrm{MeCOOH} \stackrel{\mathrm{N}_{3} \mathrm{H}}{\longrightarrow}\) This reaction can lead to the formation of an acyl azide: \(\mathrm{MeCOOH} + \mathrm{N}_{3} \mathrm{H} \rightarrow \mathrm{MeCON}_{3}\) Here, the product is not an acid amide.

Analyse reaction (C)

In reaction (C), we have acetone (Me2CO) reacting with hydrazoic acid (N3H) in H2SO4: \(\mathrm{Me}_{2} \mathrm{CO} \frac{\mathrm{N}_{3}\mathrm{H}}{\mathrm{H}_{2}\mathrm{SO}_{4}}\) Here, Me2CO reacts with N3H to form an imine which can undergo hydrolysis to form an acid amide: \(\mathrm{Me}_{2}\mathrm{C(OH)NH} + \mathrm{H}_{3}\mathrm{O}^{+} \rightarrow \mathrm{MeCONH}_{2} + \mathrm{H}_{2}\mathrm{O}\) So, in this reaction, an acid amide is formed.

Analyse reaction (D)

In reaction (D), we have acetonitrile (MeCN) reacting with 95% H2SO4: \(\mathrm{MeCN} \frac{95 \%}{\mathrm{H}_{2}\mathrm{SO}_{4}}{\longrightarrow}\) Here, MeCN reacts with H2SO4 and undergoes hydrolysis to form an acid amide: \(\mathrm{MeCN} + \mathrm{H}_{2}\mathrm{O} \rightarrow \mathrm{MeCONH}_{2}\) So, in this reaction, an acid amide is formed.

Conclusion

Based on our analysis, reactions (A) and (B) do not produce an acid amide. However, we are asked to identify the reaction that does not produce an acid amide as a product, which is reaction (A): (A) \(\mathrm{Me}_{2} \mathrm{CNOH} \stackrel{\text { Conc. } \mathrm{H}_{2}\mathrm{SO}_{4}}{\longrightarrow}\)

Key concepts

Dehydrating Agents

Dehydrating agents are chemicals used to remove water molecules from a compound. They are pivotal in various chemical reactions, especially in the conversion of some functional groups into nitriles by eliminating water. For example, in reaction (A) from the exercise:

• Dimethyl hydroximoyl chloride (\( \text{Me}_2\text{CNOH} \)) reacts with concentrated sulfuric acid (\( \text{H}_2\text{SO}_4 \)), a well-known dehydrating agent.
• This agent helps in removing water, transforming \( \text{Me}_2\text{CNOH} \) into its nitrile form, \( \text{Me}_2\text{CN} \).
• The reaction does not yield an acid amide because the dehydration leads to nitrile formation instead.

Concentrated sulfuric acid's role as a dehydrating agent is crucial as it facilitates the removal of water without forming an amide. Understanding the nature and function of these agents can help us predict and rationalize the products of chemical reactions.

Acyl Azide Formation

Acyl azides are functional groups formed in reactions such as that seen in reaction (B) with acetic acid (\( \text{MeCOOH} \)) and hydrazoic acid (\( \text{N}_3\text{H} \)). This process is key in organic synthesis for transforming carboxylic acids into various derivatives.

• The reaction of acetic acid with hydrazoic acid results in the formation of an acyl azide (\( \text{MeCON}_3 \)).
• Unlike the formation of acid amides, the azide group (\( \text{N}_3 \)) directly attaches to the carbonyl carbon, creating a new product that includes nitrogen-rich species.
• The formation of acyl azides can act as intermediates in further chemical transformations, yet do not lead to the formation of acid amides directly in this context.

The transformation to an acyl azide prevents the direct formation of an amide, illustrating the importance of understanding the chemistry of azide interactions in reaction mechanisms.

Hydrolysis

Hydrolysis is a chemical process where a compound reacts with water, leading to its decomposition into simpler substances. This mechanism is evident in reactions (C) and (D), where both ultimately yield acid amides.

• In reaction (C), acetone (\( \text{Me}_2\text{CO} \)) first reacts to form an intermediate imine, which upon hydrolysis converts into an acid amide (\( \text{MeCONH}_2 \)).
• Similarly, in reaction (D), acetonitrile (\( \text{MeCN} \)) undergoes hydrolysis facilitated by sulfuric acid to generate an acid amide.
• During hydrolysis, water acts as a reactant, demonstrating how it can cleave different functional groups, especially when catalysts or acids like sulfuric acid are present.

Understanding hydrolysis is fundamental in grasping how water can initiate or aid in transforming reactants like nitriles into acid amides, illustrating its role as both a catalyst and a participant in chemical reactions.