Tests for the Functional Group Present in the Organic Compounds - MeitY OLabs

Tests for Unsaturation
📌 The disappearance of the orange-red color of bromine water indicates the presence of unsaturation.
🧪 Decolourisation of the pink color of KMnO₄ (Baeyer’s Test) also indicates unsaturation.
🧪 Saturation is confirmed if the colors of bromine water or KMnO₄ persist.

Tests for Alcoholic Group ($\text{R-OH}$)
🔥 The Sodium Metal Test confirms alcohols by producing effervescence (liberation of $\text{H}₂$ gas).
👃 The Ester Test involves reacting the compound with glacial acetic acid and concentrated $\text{H}₂\text{SO}₄$; a fruity smell indicates an alcohol group.
🔴 The Ceric Ammonium Nitrate Test produces a red coloration upon reaction with alcoholic compounds due to the formation of an alkoxy cerium ($\text{IV}$) complex.
💨 The Acetyl Chloride Test yields white fumes of ammonium chloride when a glass rod dipped in ammonium hydroxide solution is brought near the mouth of the test tube, indicating $\text{HCl}$ gas evolution.
🟡 The Iodoform Test results in the formation of a yellow precipitate of iodoform upon gentle warming after adding iodine solution and dilute $\text{NaOH}$.
🌡️ Lucas Test differentiates alcohols: Tertiary alcohols react instantaneously (cloudiness); Secondary alcohols react in 1–5 minutes; Primary alcohols require heating.

Tests for Phenolic Group
🔴 Phenol, being a weak acid, turns moist blue litmus paper red in the Litmus Test.
💜 The Ferric Chloride Test yields a violet color when phenol reacts with neutral ferric chloride solution.
🔵 The Liebermann’s Test produces a deep blue or green color with $\text{NaNO}₂$ and conc. $\text{H}₂\text{SO}₄$, which changes to red/brown upon adding water, and back to blue/green with excess $\text{NaOH}$.
🩷 The Phthalein Dye Test involves heating the compound with phthalic anhydride and conc. $\text{H}₂\text{SO}₄$; the resulting phenolphthalein gives a pink color with $\text{NaOH}$.

Tests for Aldehydic ($\text{RCHO}$) and Ketonic ($\text{RCOR'}$) Groups
🟠 The 2,4-Dinitrophenylhydrazine Test confirms carbonyl groups ($\text{C=O}$) by forming yellow or orange crystals.
⚪ The Sodium Bisulphite Test confirms the carbonyl group with the formation of a crystalline white precipitate.

Specific Tests for Aldehydes
🌸 Schiff’s Test confirms the aldehydic group by the appearance of a pink color.
🥈 Tollens’ Test confirms aldehydes by producing a silver mirror effect on the inner surface of the test tube upon warming.
🧱 Fehling’s Test confirms aldehydes by the reduction of $\text{Cu}(\text{II})$ ions to a red precipitate of copper ($\text{I}$) oxide upon warming.

Specific Tests for Ketones
🟣 The m-Dinitrobenzene Test indicates the ketonic group by the appearance of a violet color that slowly fades.
❤️ The Sodium Nitroprusside Test forms a red-colored complex when the ketone anion reacts with the nitroprusside ion after adding $\text{NaOH}$.

Tests for Carboxylic Group ($\text{RCOOH}$)
💨 The Sodium Bicarbonate Test confirms carboxylic acids by producing brisk effervescence due to $\text{CO}₂$ liberation.
👃 The Ester Test (heating with alcohol and conc. $\text{H}₂\text{SO}₄$) produces fruity smelling compounds.
🟥 Carboxylic acids are confirmed as turning blue litmus paper red in the Litmus Test.

Tests for Amino Group ($\text{R-NH}₂$/$\text{Ar-NH}₂$)
🔵 Amines are basic, thus they turn moist red litmus paper blue.
💧 Organic compounds with amino groups form soluble salts easily when reacted with acids like dil. $\text{HCl}$ (Solubility Test).
🤢 The Carbylamine Test confirms primary amines (aliphatic/aromatic) by producing an offensive smell (isocyanide) upon warming with chloroform and alcoholic $\text{KOH}$.
🔴 The Azo-Dye Test (diazotization followed by coupling with $\beta$-naphthol at $0-5^\circ\text{C}$) confirms aromatic primary amines by yielding a scarlet red dye.
💨 Nitrous Acid Test differentiates amines: Primary amines liberate nitrogen gas; Secondary amines form a yellow, oily nitrosamine; Tertiary amines form a soluble nitrite salt (no visual change).
⚗️ Hinsberg Test differentiation: Primary amine forms a soluble sulfonamide salt; Secondary amine forms an insoluble sulfonamide; Tertiary amine does not react but is insoluble.

Key Points & Insights
➡️ Perform controlled heating in water baths for reactions like the Ester Test for alcohols and the Tollens' Test for aldehydes to ensure proper reaction conditions.
➡️ Distinguish unsaturation using two complementary chemical tests (Bromine water and Baeyer’s Test) for robust confirmation.
➡️ Utilize the Lucas Test sequence (instant reaction, 5-minute reaction, heating required) as a rapid classification method for primary, secondary, and tertiary alcohols.
➡️ Confirm the presence of primary aromatic amines specifically via the Azo-Dye coupling reaction carried out strictly at $0-5^\circ\text{C}$.

📸 Video summarized with SummaryTube.com on Nov 08, 2025, 12:49 UTC