Question

Identify the product (b) in the following sequence of reactions. \(\mathrm{CH}_{3}-\mathrm{CH}_{2}-\mathrm{CHO} \stackrel{\mathrm{H}_{2} \mathrm{NOH}}{\longrightarrow}(\mathrm{A}) \stackrel{\mathrm{P}_{+} \mathrm{O}_{\mathfrak{l}}}{\longrightarrow}(\mathrm{B})\) (a) \(\mathrm{CH}_{3}-\mathrm{CH}_{2}-\mathrm{CN}\) (b) \(\mathrm{CH}_{3}-\mathrm{CH}_{2}-\mathrm{CH}=\mathrm{NH}\) (c) \(\mathrm{CH}_{2}=\mathrm{CH}-\mathrm{CH}=\mathrm{NOH}\) (d) \(\mathrm{CH}_{3}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{NH}_{2}\)

Short answer

Question: Identify the structure of product B in the given reaction sequence: \(CH_3-CH_2-CHO\) reacts with \(H_2NOH\) to form product A, which then reacts with \(P_+O_l\) to form product B. The possible options for product B are: (a) \(CH_3-CH_2-CN\) (b) \(CH_3-CH_2-COOH\) (c) \(CH_3-CHO\) (d) \(\mathrm{CH}_3-\mathrm{CH}_2-\mathrm{NH}_2\) Answer: (a) \(CH_3-CH_2-CN\)

Step-by-step solution

Identify Intermediate Product (A)

The first reaction involves the conversion of an aldehyde (\(-CHO\)) to another functional group using \(H_2NOH\). This reagent is typically used to convert the carbonyl group of an aldehyde into an imine. Thus, the intermediate product (A) after this reaction will have the following structure: \(CH_3-CH_2-CH=NH\).

Identify Product (B)

The second reaction involves the conversion of intermediate product (A) using \(P_+O_l\). This reagent typically oxidizes imines to nitriles, which contain the -\(CN\) functional group. Considering the structure of the intermediate product (A), the final product (B) will have the following structure: \(CH_3-CH_2-CN\). Comparing this result with the given options, option (a) is the correct answer: (a) \(\mathrm{CH}_{3}-\mathrm{CH}_{2}-\mathrm{CN}\)

Key concepts

Aldehyde to Imine Conversion

In organic chemistry, transforming an aldehyde into an imine is a fundamental reaction that involves a nucleophilic addition followed by an elimination. To start with, an aldehyde is represented by the chemical group \[ \mathrm{R-CHO} \]where R can be any alkyl or aryl group. The carbonyl group (C=O) in an aldehyde is reactive due to the difference in electronegativity between carbon and oxygen.When hydroxylamine \( (H_2NOH) \) is introduced to an aldehyde, the oxygen in the carbonyl group forms a bond with one of the hydrogen atoms from the \( H_2NOH \), facilitating the nucleophilic attack of the nitrogen on the carbonyl carbon. This leads to the formation of a \[ \mathrm{C=N} \]imine bond after water is expelled. Imine formation is a reversible process and typically occurs in the presence of a dehydrating agent or under conditions that remove water from the reaction mix. This is a good example of **nucleophilic addition-elimination reactions**. Ultimately, the aldehyde \[ \mathrm{CH_3CH_2CHO} \]is converted into an imine: \[ \mathrm{CH_3CH_2CH=NH}. \]

Imine to Nitrile Oxidation

Once the imine is formed, it can be further transformed into a nitrile. This requires an oxidative reaction which modifies the imine \[ \mathrm{C=N} \]stretch into a triple-bonded nitrile group \[ \mathrm{C≡N}. \]In the given problem, the reaction uses \[ \mathrm{P}_+\mathrm{O}_l \]as an oxidation reagent to achieve this conversion.The conversion from an imine to a nitrile involves the oxidation of the *carbon-nitrogen double bond* into a *triple bond*. This alteration changes the electronic structure, making the molecule more stable by forming a straight chain of two carbons and a nitrogen. Oxidation reactions like this one decrease the hydrogen content, turning the molecule into a nitrile \[ \mathrm{CH_3CH_2-CN}. \]Nitriles are crucial in various chemical synthesis processes and industrial applications.

Functional Group Transformation

Functional group transformations play a central role in organic synthesis, allowing chemists to modify molecules' properties and functionalities. This sequence of reactions elegantly showcases how simple changes can lead to significant transformations.Initially, **aldehydes**, with their carbonyl functional groups, are moderately reactive due to their polarity. However, when transformed into **imines**, the compound's stability and functionality change dramatically, highlighting the significance of **functional group interconversion**.With further oxidative modification, imines become **nitriles**. Nitriles are characterized by their distinct **triple bonds** and are relatively less reactive under typical conditions, making them stable functional groups suitable for further chemical reactions or applications in materials science.Key takeaways include:- Recognizing the role of \( H_2NOH \)in transforming an aldehyde to an imine via nucleophilic addition.- Understanding how *oxidation* transforms an imine into a nitrile.- Realizing the importance of functional group transformations for tailor-making molecules with desired properties in organic chemistry.