Coupling reactions and azo dyes

36 questions on Coupling reactions and azo dyes from the Amines and Aromatic Nitrogen Compounds chapter: 6 NEET level, 15 JEE Main, 15 JEE Advanced. Each one opens with its answer and solution.

• Benzenediazonium chloride is added to a cold alkaline solution of phenol (pH 9-10). The orange product is NEET level
• The group that links the two aromatic rings in azo dyes is NEET level
• Benzenediazonium chloride couples with aniline to give 4-aminoazobenzene in a medium that is NEET level
• Coupling of benzenediazonium chloride with phenol is carried out in mildly alkaline solution because JEE Main level
• Coupling of benzenediazonium chloride with N,N-dimethylaniline is carried out at pH 4-5 and not at pH 10 because at pH 10 JEE Main level
• Methyl orange is prepared by diazotising X and coupling the diazonium salt with Y in mildly acidic medium. X and Y are JEE Main level
• Benzenediazonium chloride is added to a cold alkaline solution of 2-naphthol. The intensely coloured product is JEE Main level
• Under identical conditions with alkaline phenol, which diazonium ion couples fastest? JEE Main level
• Benzenediazonium chloride is added to an alkaline solution of 4-methylphenol (p-cresol). The major product is JEE Main level
• Under the optimum pH for each, benzenediazonium chloride couples with which of the following? JEE Main level
• Nitrobenzene is treated with (i) Sn/HCl; (ii) NaNO2 / dil. HCl at 273-278 K; (iii) phenol in aqueous NaOH (pH 9-10). The major product is JEE Advanced level
• Assertion (A): Coupling of benzenediazonium chloride with phenol is done at pH 9-10 and not at pH 13-14. Reason (R): At very high pH the diazonium ion is conver... JEE Advanced level
• Methyl orange is made by diazotising sulfanilic acid and coupling with N,N-dimethylaniline at pH 4-5. Select the correct statements. JEE Advanced level
• 4-Nitroaniline is diazotised with NaNO2 / dil. HCl at 273-278 K and the cold solution is added to alkaline 2-naphthol. The major product is JEE Advanced level
• Benzenediazonium chloride couples with each of the following under suitable conditions. Select the pairs in which the stated major product is correct. JEE Advanced level
• The azo dye 4-hydroxyazobenzene is heated with excess Sn/HCl so that the N=N bond is completely cleaved and both nitrogens end up as amino groups. The organic p... JEE Advanced level
• Benzenediazonium chloride (1 equiv.) is allowed to couple with resorcinol (benzene-1,3-diol) in mildly alkaline solution. The major monoazo product is JEE Advanced level
• Match the coupling partner and conditions in List I with the azo product in List II. List I: (P) phenol, pH 9-10; (Q) aniline, pH 4-5; (R) 2-naphthol, aqueous N... JEE Advanced level
• Benzenediazonium chloride couples with phenol in mildly alkaline medium (pH 9-10) to give NEET level
• Benzenediazonium chloride is prepared from aniline by treatment with NaNO2 and dil. HCl at NEET level
• Azo dyes are characterised by the presence of the group NEET level
• Coupling of benzenediazonium chloride with phenol is carried out in mildly alkaline medium rather than in neutral or acidic medium because JEE Main level
• Benzenediazonium chloride is added to N,N-dimethylaniline in weakly acidic medium (pH 4-5). The main product is JEE Main level
• Which of the following does NOT undergo azo coupling with benzenediazonium chloride under mild conditions? JEE Main level
• Benzenediazonium chloride is added to an alkaline solution of 2-naphthol. The red-orange dye formed is JEE Main level
• Methyl orange is prepared by coupling the diazonium salt of one compound with a second compound. These two compounds are JEE Main level
• Benzenediazonium chloride is coupled in mildly alkaline medium with 4-methylphenol (p-cresol). The product is JEE Main level
• The rates of coupling with the same phenoxide (alkaline medium) of three diazonium ions, 4-nitrobenzenediazonium (X), benzenediazonium (Y) and 4-methoxybenzened... JEE Main level
• In the diazotisation C6H5NH2 + NaNO2 + HCl, the minimum number of moles of HCl consumed per mole of aniline according to the balanced equation C6H5NH2 + NaNO2 +... JEE Main level
• Complete reductive cleavage of the N=N bond of 4-hydroxyazobenzene (with Na2S2O4 or Sn/HCl) gives JEE Advanced level
• Aniline is first converted into acetanilide, nitrated (major product para), hydrolysed, then diazotised with NaNO2 / dil. HCl at 273-278 K, and the diazonium sa... JEE Advanced level
• Toluene is nitrated and the para isomer is isolated; this is reduced with Sn/HCl, diazotised with NaNO2 / dil. HCl at 273-278 K and coupled with phenol in alkal... JEE Advanced level
• Benzylamine, C6H5CH2NH2, is treated with NaNO2 / dil. HCl at 273-278 K, and the mixture is then added to alkaline 2-naphthol. Which observation is correct? JEE Advanced level
• Under suitable mild conditions, which of the following couple with benzenediazonium chloride to give azo compounds? JEE Advanced level
• Which statements about azo coupling are correct? JEE Advanced level
• Which reactions of benzenediazonium chloride give the stated main product? JEE Advanced level