Problem 87 - 43 Years JEE ADVANCED (1978-2020) + JEE MAIN Chapterwise & Topicwise Solved Papers Chemistry

Question

The structure of compounds \(J, K\) and \(L\) respecitvely, are - (a) \(\mathrm{PhCOCH}_{3}, \mathrm{PhCH}_{2} \mathrm{COCH}_{3}\) and \(\mathrm{PhCH}_{2} \mathrm{COO}^{-} \mathrm{K}^{+}\) (b) \(\mathrm{PhCHO}, \mathrm{PhCH}_{2} \mathrm{CHO}\) and \(\mathrm{PhCOO}^{-} \mathrm{K}^{+}\) (c) \(\mathrm{PhCOCH}_{3}, \mathrm{PhCH}_{2} \mathrm{CHO}\) and \(\mathrm{CH}_{3} \mathrm{COO}^{-} \mathrm{K}^{+}\) (d) \(\mathrm{PhCHO}, \mathrm{PhCOCH}_{3}\) and \(\mathrm{PhCOO}^{-} \mathrm{K}^{+}\)

Step-by-Step Solution

Answer

The correct answer is option (b).

Step 1: Analyze Structures of Each Option

Look at the chemical structures provided in each option. Identify the functional groups and try to understand the lineup of the benzene ring (Ph) attached to the rest of the molecular structure. This involves recognizing key components like carbonyl groups (C=O), aldehydes (CHO), ketones (COCH₃), and carboxylates (COO⁻).

Step 2: Interpret Option (a)

For Option (a), we have:- Compound J: \( \mathrm{PhCOCH}_{3} \) (a ketone, specifically acetophenone)- Compound K: \( \mathrm{PhCH}_{2} \mathrm{COCH}_{3} \) (a ketone with benzyl attachment)- Compound L: \( \mathrm{PhCH}_{2} \mathrm{COO}^{-} \mathrm{K}^{+} \) (a carboxylate salt with benzyl group)

Step 3: Interpret Option (b)

For Option (b), we have:- Compound J: \( \mathrm{PhCHO} \) (an aldehyde, benzaldehyde)- Compound K: \( \mathrm{PhCH}_{2} \mathrm{CHO} \) (an aldehyde with benzyl attachment)- Compound L: \( \mathrm{PhCOO}^{-} \mathrm{K}^{+} \) (a carboxylate salt with a phenyl group)

Step 4: Interpret Option (c)

For Option (c), we have:- Compound J: \( \mathrm{PhCOCH}_{3} \) (a ketone, acetophenone)- Compound K: \( \mathrm{PhCH}_{2} \mathrm{CHO} \) (an aldehyde with benzyl attachment)- Compound L: \( \mathrm{CH}_{3} \mathrm{COO}^{-} \mathrm{K}^{+} \) (a carboxylate salt, acetate rather than benzyl or phenyl group)

Step 5: Interpret Option (d)

For Option (d), we have:- Compound J: \( \mathrm{PhCHO} \) (an aldehyde, benzaldehyde)- Compound K: \( \mathrm{PhCOCH}_{3} \) (a ketone, acetophenone)- Compound L: \( \mathrm{PhCOO}^{-} \mathrm{K}^{+} \) (a carboxylate salt with a phenyl group)

Step 6: Choose the Correct Option

Comparatively analyze the structures to identify a pattern or match it to a given question. Here, we identify all functional types involved. Option (b): it contains two aldehydes and a carboxylate, matches the patent given in problem statement without conflicting chemical properties.

Key Concepts

Functional Groups

In organic chemistry, functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules. Recognizing functional groups is crucial because they determine how a molecule will react. For instance, the carbonyl group \(C=O\) is a functional group that is common to both aldehydes and ketones. Knowing these groups helps chemists predict the behavior of chemical compounds.

• The presence of an oxygen double-bonded to a carbon (carbonyl group) is a common functional group found in many organic compounds.
• Aldehydes and ketones notably contain this carbonyl group, but are differentiated by the kinds of bonds formed with the carbon in question.
• Carboxylates include a carbonyl group coupled with a hydroxyl group, forming a carboxyl group \(COO^-\) with a metal cation, usually making it a salt.

Recognizing these can be especially important in identifying the properties and reactivity of organic compounds in various chemical reactions.

Aldehydes

Aldehydes are a type of organic compound that contains a carbonyl group bonded to at least one hydrogen atom. The general structure is \(RCHO\), where \(R\) can be a hydrogen atom or an organic substituent.

• Aldehydes are often found as volatile compounds with distinct, often pleasant odors.
• The simplest aldehyde is formaldehyde, where \(R\) is a hydrogen atom, making its formula \(HCHO\).
• Benzaldehyde is an example of an aromatic aldehyde, with a benzene ring directly attached to the carbonyl group.

Aldehydes are typically more reactive in nucleophilic addition reactions than ketones, due in part to the electronic effects that make the carbonyl carbon more electrophilic.

Ketones

Ketones are another class of organic compounds that, like aldehydes, contain a carbonyl group. However, in ketones, the carbonyl group is always bonded to two hydrocarbon groups, which makes them distinct from aldehydes.

• The general structure of a ketone is \(RCOR'\), where \(R\) and \(R'\) are hydrocarbon chains or rings.
• Acetone is the simplest ketone, with both \(R\) and \(R'\) being methyl groups, so its formula is \(CH_3COCH_3\).
• Ketones are generally less reactive than aldehydes but can participate in reactions like nucleophilic addition due to the presence of the carbonyl group.

Understanding the subtle differences between ketones and aldehydes is crucial in predicting the outcomes of organic reactions.

Carboxylate Salts

Carboxylate salts are salts derived from carboxylic acids. They form when the hydrogen in the carboxyl group \((COOH)\) is replaced by a metal cation.

• The general formula for a carboxylate salt is \(RCOO^- M^+\), where \(R\) represents the organic portion and \(M\) is a metal ion.
• These salts are usually more stable than their carboxylic acid counterparts and have distinct ionic properties due to the metal ion.
• They are common in biological systems as well as in industrial applications due to their solubility in water and ability to form buffers.

Carboxylate salts can undergo various reactions, such as saponification, where they react with strong bases to form soaps.