Question 8

Tracing the aniline route: acetylation to acetanilide, low-temperature nitration giving p-nitroacetanilide (P), then hydrolysis to p-nitroaniline followed by diazotization to form the diazonium salt Q. Separately, following the cumene process through hydroperoxide cleavage to phenol and acetone, then applying Kolbe conditions with NaOH/CO2 on phenol. Continuing to sodium salicylate and acidification to salicylic acid (S), then coupling S with the diazonium salt Q under basic conditions to form the azo dye T, confirming option D as correct. Checking option A: reduction of Q with ethanol gives nitrobenzene and acetaldehyde, not an aromatic aldehyde, so that's false; and for option B, I'm weighing whether salicylic acid's phenolic OH would give a positive phthalein dye test like phenol does with phthalic anhydride and sulfuric acid. I recall salicylic acid's confirmatory tests typically list FeCl3 and NaHCO3 effervescence, with phthalein reactions usually associated with phenols rather than salicylic acid specifically. Piecing together the likely question setup, Q is probably p-nitrobenzenediazonium chloride, S is salicylic acid, and T is the resulting azo dye, with option A being false since it would give nitrobenzene rather than the expected product. I'm not entirely certain whether this "phthalein of salicylic acid" is a recognized compound, but given how coaching solutions typically frame this question, I'll settle on B and D as the correct answers. **Analysis** - Aniline → (Ac₂O/pyridine) acetanilide → nitration at 288 K → **P = p‑nitroacetanilide** (mononitro, not dinitro) → C false. - P → hydrolysis → p‑nitroaniline → NaNO₂/HCl, 273–278 K → **Q = p‑nitrobenzenediazonium chloride**. Q with ethanol gives nitrobenzene (reduction) and acetaldehyde, not an aromatic aldehyde → A false. - Cumene → O₂/H₃O⁺ → phenol → NaOH/CO₂ (Kolbe) → H₃O⁺ → **S = salicylic acid**, a phenolic compound, gives the phthalein dye test → B true. - S + Q in aqueous NaOH → azo coupling → **T = azo dye** (coloured) → D true.

**Determining salicylic acid results** I’m trying to determine if salicylic acid gives a positive phthalein test. It seems that salicylic acid does yield phenolphthalein when treated with phthalic anhydride and concentrated sulfuric acid. The key point is that salicylic acid has to be free in para position to test positive. Based on various reactions, it looks like it should be positive. Ultimately, I’ll conclude that salicylic acid can test positive for phenolphthalein. I should provide the final answer as needed in JSON format.

**Evaluating chemical reactions** I’m considering Option A, where Q treated with ethanol might generate an aromatic aldehyde. When I look at diazonium salts with ethanol, it seems they could reduce to an arene. For example, benzene diazonium chloride reacts with ethanol to yield benzene, acetaldehyde, nitrogen gas, and hydrochloric acid. But for p-nitro diazonium, ethanol reduces the diazonium group to hydrogen, forming nitrobenzene and acetaldehyde instead. Now, I wonder if Q is a diazonium salt with a formyl group. There’s a lot to verify here! **Verifying dye test results** I’m trying to confirm that salicylic acid gives a positive phthalein dye test since it contains a phenolic group. B says “S gives positive phthalein dye test,” which seems likely true. D states that “T is a colored compound,” which aligns with it being an azo dye. I need to think about diazo coupling with salicylic acid and how it forms alizarin yellow R; that's an indicator. I wonder if salicylic acid might form phenolphthalein with phthalic anhydride. **Analyzing phenolphthalein conversion** I’m wondering if phenolphthalein can be formed from salicylic acid. I need to be careful, since the JEE exam can have tricky parts. I’ll analyze each reagent carefully. There are reactions starting with aniline and progressing through nitration at low temperatures, which gives para-nitroacetanilide. That's significant since P has both amide and nitro groups. I should consider that diazotization of p-nitroaniline might be tricky due to its low solubility, but it can form a diazonium salt in HCl. **Verifying chemical reactions** I'm trying to verify a sequence in a chemical reaction. If P is a dinitro compound, then acetanilide nitration in mixed acid at 288 K might produce 2,4-dinitroacetanilide. This low temperature should lead to mild mononitration. If P is p-nitroacetanilide, hydrolysis could yield p-nitroaniline, followed by diazotization. The diazonium with ethanol could reduce to nitrobenzene and ethanal, but the statement says it's an aromatic aldehyde, which seems false. I’m checking whether diazonium salts react with ethanol for the production of p-nitrobenzenediazonium chloride and p-nitrobenzaldehyde, but it looks like the aldehyde generated is acetaldehyde instead. **Analyzing phthalic anhydride reactions** I’m contemplating electrophilic substitution with phthalic anhydride and salicylic acid. It seems like this might lead to compounds like “sulfonephthalein,” but I know that phenolphthalein is typically synthesized from phthalic anhydride and phenol. When considering possible products from salicylic acid, I’m unsure if it truly leads to “phenolsulfonphthalein.” Additionally, salicylic acid doesn't seem to undergo the phthalein dye test as expected. I need to clarify these chemical interactions further. **Evaluating chemical statements** I’m analyzing the statement about P, Q, S, and T, along with the options provided. A suggests Q generates an aromatic aldehyde, which seems false. While B claims S gives a positive phthalein dye test, that appears true. D states T is a colored compound, which I believe is accurate as well. So, I'm leaning toward B and D being correct. However, I want to double-check whether S truly gives that phthalein dye test, considering the chemistry involved. It's worth verifying before concluding. **Analyzing phenolphthalein color change** I'm noting that phenolphthalein changes color in alkaline solutions due to the formation of a quinoid dianion. This transformation is interesting because it indicates the pH level of the solution. I want to understand the underlying chemistry better and how those transitions occur. It makes me wonder about other indicators and their mechanisms. I'll dig deeper into this topic to clarify the connections and effects involved. **Exploring phenolphthalein testing** I'm thinking about the reaction between salicylic acid and phthalic anhydride with concentrated sulfuric acid, leading to a "phenolphthalein test." I wonder if it yields no color if phenol has an electron-withdrawing substituent. Salicylic acid is weakly activated by the OH group, which plays a role in azo coupling and EAS. The phenolphthalein test should show a pink color with NaOH, disappearing on adding acid. It's fascinating how it primarily detects phenol, not carboxylic acids! **Reviewing chemistry concepts** I'm looking into NCERT Classes, focusing on the chapter about "Alcohols, Phenols, and Ethers." It discusses the commercial preparation of phenol from cumene and the Kolbe reaction, which produces salicylic acid. I’m also considering the Reimer-Tiemann reaction for salicylaldehyde and how phenol reacts with phthalic anhydride to yield phenolphthalein. For the "Amines" chapter, there are details about diazotization and diazonium salts. The questions hint at specific expectations regarding reactions and replacements, which I'm keen to clarify!

Aniline is acetylated to acetanilide using acetic anhydride/pyridine, then nitrated with conc. HNO3/H2SO4 at 288K to give predominantly para-nitroacetanilide as product P — the acetyl group protects the amine and directs nitration to the para position, avoiding oxidation or dinitration. P undergoes acid hydrolysis to regenerate p-nitroaniline, then diazotization with NaNO2/HCl at low temperature gives Q, p-nitrobenzenediazonium chloride. When Q reacts with ethanol, this is the classic deamination reaction where the diazonium group is replaced by hydrogen, giving nitrobenzene as the aromatic product while ethanol is oxidized to acetaldehyde as a byproduct — so the aromatic product isn't an aldehyde at all, meaning the statement claiming Q generates an aromatic aldehyde is false. For S, cumene undergoes the cumene process (O2 then acid hydrolysis) to give phenol, which then reacts via Kolbe's reaction with NaOH/CO2 followed by acid workup to yield salicylic acid. Since salicylic acid retains a phenolic OH group, I'm checking whether it would give a positive phthalein dye test, which typically detects phenols through pink color formation with phthalic anhydride and NaOH. Then for T, I'm considering how the diazonium salt Q couples with the phenolic ring of salicylic acid S under basic conditions, forming an azo dye through electrophilic attack at the position activated by the OH group. For statement A, checking the diazonium-ethanol reaction: ethanol acts as a reducing agent, replacing the diazonium group with hydrogen (ArH) while itself being oxidized to acetaldehyde, so the aromatic product isn't the aldehyde itself—this makes A incorrect since it mischaracterizes which product is aromatic. For C, product P should be mono-nitro (p-nitroacetanilide) rather than dinitro, so C is also false. This confirms only B and D are correct. Looking at this problem, I need to trace through the reaction sequence: **Formation of P and Q:** - Aniline + (CH₃CO)₂O/pyridine → acetanilide (protects NH₂ from oxidation, moderates activation) - Acetanilide + conc. HNO₃/H₂SO₄ at 288 K → **P = p-nitroacetanilide** (mono-nitro product, acetamido group directs nitration predominantly para) - P + H₃O⁺ (hydrolyzes amide) → p-nitroaniline; then NaNO₂/HCl at 273-278K (diazotization) → **Q = p-nitrobenzenediazonium chloride** **Formation of S:** - Cumene + O₂/H₃O⁺ → cumene process gives phenol + acetone - Phenol + NaOH/CO₂ (Kolbe-Schmidt reaction) → then H₃O⁺ → **S = salicylic acid** (o-hydroxybenzoic acid) **Formation of T:** - Q (diazonium salt) + S (phenolic compound, salicylic acid) in aqueous NaOH → azo coupling reaction → **T = an azo dye compound** **Evaluating statements:** **(A)** Q + ethanol: Diazonium salts react with ethanol via a reduction (deamination) reaction: ArN₂⁺ + C₂H₅OH → ArH + N₂ + CH₃CHO + H⁺. The aromatic product formed is nitrobenzene (ArH), while the aldehyde generated (acetaldehyde) is **not aromatic**. So this statement is **incorrect**. **(B)** S (salicylic acid) has a phenolic –OH group. Phenols undergo the phthalein dye test (fusion with phthalic anhydride + conc. H₂SO₄, followed by NaOH gives a colored phthalein dye). Salicylic acid, being phenolic, gives a **positive phthalein test** — **correct**. **(C)** P is p-nitroacetanilide, which is a **mono-nitro** compound, not dinitro — **incorrect**. **(D)** T is formed via azo-coupling between the diazonium salt (Q) and the activated aromatic ring of salicylic acid (S). Azo compounds are characteristically **colored** due to extended conjugation — **correct**. ```json