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Preparation of Phenylazo-beta-naphthol | MSc Chemistry Lab DU

‪@GeneralDiscussionwithArvind‬ Preparation of Phenylazobeta-Naphthol (Azo Dye) Phenylazobeta-naphthol is an azo dye, formed by the diazotization of aniline followed by coupling with beta-naphthol. The process involves two key reactions: diazotization and coupling. Materials Required: Aniline Sodium nitrite (NaNO₂) Hydrochloric acid (HCl) Beta-naphthol Sodium hydroxide (NaOH) Ice Water Procedure: Diazotization of Aniline: Dissolve aniline (C₆H₅NH₂) in dilute hydrochloric acid in a beaker. Cool the solution using an ice bath to maintain the temperature between 0–5°C. In a separate container, dissolve sodium nitrite (NaNO₂) in water. Slowly add the sodium nitrite solution to the cooled aniline hydrochloride solution, ensuring the temperature remains low. This reaction forms benzenediazonium chloride (C₆H₅N₂Cl). Preparation of Beta-Naphthol Solution: Dissolve beta-naphthol (C₁₀H₇OH) in sodium hydroxide (NaOH) solution to form a clear sodium beta-naphthoxide solution. Cool this solution to maintain a temperature close to 0–5°C. Coupling Reaction: Gradually add the benzenediazonium chloride solution to the beta-naphthol solution, while stirring the mixture in an ice bath. The mixture will form a red-orange precipitate of phenylazobeta-naphthol (C₆H₅N=N-C₁₀H₆OH) as the azo coupling reaction proceeds. Stir the solution well and allow it to settle. Filtration and Washing: Filter the precipitate and wash it with cold water to remove any impurities like excess sodium chloride and unreacted beta-naphthol. Dry the product thoroughly. Recrystallization (Optional): For purification, recrystallize the crude product using ethanol or another suitable solvent to obtain pure phenylazobeta-naphthol. Reaction Equation: The resulting phenylazo-beta-naphthol is an orange-red azo dye commonly used as a pH indicator or in textile dyeing. Safety Notes: Perform the reaction in a well-ventilated area or fume hood. Use protective gloves and safety glasses to avoid contact with chemicals. Keep the reaction temperature low to prevent decomposition of the diazonium salt. Maintain low temperature (0–5°C) throughout the diazotization process to prevent decomposition. Always use an ice bath for both the diazotization and coupling reactions. Add sodium nitrite solution slowly to avoid side reactions during diazotization. Keep the solution well-stirred to ensure even distribution of reagents. Use freshly distilled aniline to prevent impurities that can interfere with diazotization. Check the pH of the solution before diazotization; it should be acidic (around pH 1-2). Cool the beta-naphthol solution to 0–5°C before adding the diazonium salt. Sodium hydroxide should be in excess when dissolving beta-naphthol to ensure complete ionization. Avoid adding the diazonium salt too quickly; slow addition prevents overreaction and side products. Use distilled water to avoid contaminants affecting the reaction. Ensure the sodium nitrite is fully dissolved before adding it to the aniline hydrochloride solution. Monitor the temperature continuously during the diazotization step to prevent the breakdown of the diazonium ion. Stir continuously during both the diazotization and coupling reactions for uniform results. Use a cold filtration setup to filter the precipitate and avoid dissolving the product. Use cold water to wash the precipitate thoroughly to remove unreacted beta-naphthol. For better yields, optimize the stoichiometry of the aniline and sodium nitrite. Always recheck concentrations of solutions before adding to avoid under- or over-reaction. Check for complete dissolution of aniline hydrochloride before adding sodium nitrite. #OrganicChemistry #AzoDyeSynthesis #Diazotization #BetaNaphthol #ChemicalReactions #PhenylazobetaNaphthol #ChemistryTips #LabSafety #CouplingReaction #SodiumNitrite #AnilineSynthesis #ChemistryHacks #ChemicalEngineering #OrganicSynthesis #LabWork #ChemistryExperiments #ChemicalPrecipitation #ChemicalPurification #Recrystallization #LabTechniques #ChemicalSynthesis #ResearchChemistry #ChemistryEducation #MScChemistry #ChemistryLab #ReactionMechanism #ChemistryStudents #DyeChemistry #AzoDyes #ChemicalPreparation #OrganicLab #ScienceInLab #ChemicalReactions101 #LabSkills #ResearchLab #ChemistryHacks #ChemicalEquation #ChemistryTutorial #SyntheticChemistry #ChemistryResearch #ExperimentalChemistry #LabExperiments #DiazotizationReaction #CouplingMechanism #ChemistrySafety #ChemistryInnovation #OrganicChemLab #SynthesisProcedure #ChemistryFacts #LabTech File PDF Link: https://drive.google.com/file/d/113T7...