Alcohols & Phenols — Acidity, Preparation, Reactions Why this chapter matters for NEET Alcohols and phenols appear across Organic, Physical, and Applied Chemistry questions. You will be tested on quick identification (1°, 2°, 3°), acidity order, Lucas test timing, oxidation products, and the two hallmark phenol reactions (Kolbe–Schmitt and Reimer–Tiemann). Mastery here feeds directly into aldehydes/ketones and carboxylic acids in later units. Foundations: What are alcohols and phenols? Alcohol: an –OH (hydroxyl) group attached to an sp3-hybridised saturated carbon (Csp3–OH). Example: ethanol (ethan-1-ol; common: alcohol; SMILES: CCO). Phenol: an –OH group directly on an aromatic ring (Ar–OH) where the bonded carbon is sp2 in a benzene ring. Example: phenol (benzenol; common: carbolic acid; SMILES: c1ccccc1O). Key idea: The environment of –OH (sp3 vs aromatic sp2) changes both reactivity and acidity. Primary vs secondary vs tertiary alcohols contrasted with phenol. Note: alcohol –OH on Csp3; phenol –OH on aromatic Csp2. Monohydric/Polyhydric Number of –OH groups per molecule Monohydric: ethanol (ethan-1-ol); Dihydric: ethane-1,2-diol (ethylene glycol; SMILES: OCCO); Trihydric: propane-1,2,3-triol (glycerol; SMILES: C(C(CO)O)O Primary (1°) alcohol –OH on a carbon attached to 1 other carbon Propan-1-ol (n-propyl alcohol; SMILES: CCOC? actually propan-1-ol is CCO? Better: CCO for ethanol; for propan-1-ol use CCO? To avoid SMILES ambiguity, example name only) Secondary (2°) alcohol –OH on a carbon attached to 2 other carbons Propan-2-ol (isopropyl alcohol) Tertiary (3°) alcohol –OH on a carbon attached to 3 other carbons 2-methylpropan-2-ol (tert-butanol) Allylic alcohol –OH on C adjacent to a C=C Prop-2-en-1-ol (allyl alcohol) Benzylic alcohol –OH on C adjacent to a benzene ring Phenylmethanol (benzyl alcohol) Vinylic alcohol –OH directly on C=C carbon (enol) — unstable, tautomerises Ethenol (enol of ethanal; tautomerises to ethanal) Phenol Ar–OH: –OH directly on aromatic ring Phenol (benzenol) Classification of Alcohols and Phenols Category Definition Example (IUPAC; common) Class Vinylic –OH (enols) is not a stable alcohol class; it usually tautomerises to a carbonyl compound. Phenols are not “just aromatic alcohols” — their ring makes them more acidic and highly activated for electrophilic substitution. remember Organic compound with –OH on sp3 carbon (R–OH). Alcohol alkanol alkanol Phenol arenol benzenol carbolic acid Hydroxy group on an aromatic ring (Ar–OH). Primary/Secondary/Tertiary alcohol Classified by number of alkyl groups on the C bearing –OH: 1°, 2°, 3°. Lucas test Reaction of alcohol with conc. HCl/ZnCl2 at RT. Turbidity time distinguishes 3° (immediate), 2° (minutes), 1° (no reaction at RT). Major alkene from β-elimination is the more substituted one. Saytzeff (Zaitsev) rule Kolbe–Schmitt reaction CO2 addition to sodium phenoxide (400 K, 4–7 atm) to form salicylic acid on acidification. Formylation of phenol using CHCl3/NaOH (via dichlorocarbene) to give salicylaldehyde (mainly ortho). Reimer–Tiemann reaction Cumene process (Hock rearrangement) Industrial synthesis of phenol from cumene via cumene hydroperoxide; co-product acetone. Bakelite Phenol–formaldehyde resin (first synthetic polymer; 1907). Methanol toxicity Methanol is metabolised to formaldehyde and formic acid — causes blindness and acidosis. Key terms IUPAC naming (quick rules) Naming alcohols and phenols Longest chain with –OH as parent; suffix “-ol”; give –OH lowest possible locant (e.g., propan-1-ol, propan-2-ol). For multiple –OH: “diol”, “triol” (e.g., ethane-1,2-diol). Phenols: parent is benzenol; ring substituents get locants (e.g., 4-methylbenzenol for p-cresol). Common names acceptable in NEET questions: isopropyl alcohol (propan-2-ol), tert-butanol (2-methylpropan-2-ol), benzyl alcohol (phenylmethanol). Physical properties at a glance Hydrogen bonding causes higher boiling points and greater water solubility compared to hydrocarbons and ethers of similar molar mass. For example: ethanol (b.p. ≈ 78.5 ℃) vs diethyl ether (≈ 35 ℃) vs methane (−161 ℃). As the alkyl chain length increases, solubility in water decreases because the hydrophobic part grows. Acidity comparison: alcohols, water, phenols, and carboxylic acids shown by pKa. Phenoxide is resonance-stabilised; alkoxides are not. Acidity: why phenol is much more acidic than alcohol pKa values (lower means stronger acid): ethanol ≈ 16, water 15.7, phenol ≈ 10. Phenol donates H+ more easily because the conjugate base (phenoxide, ArO−) is resonance-stabilised over the aromatic ring, delocalising negative charge to ortho/para positions. In contrast, an alkoxide (RO−) has the charge localised on oxygen, so it is less stable and hence its parent alcohol is weaker as an acid. gpt-image-2 Five contributing resonance structures of phenoxide ion: negative charge delocalised to ortho and para positions relative to –O−. 2026-05-26T17:05:33.289Z Phenoxide resonance: 5-panel resonance set on white background. Start with phenoxide (O− bonded to benzene). Show curved arrow movement from O lone pair into ring, alternating negative charge at ortho/para carbons across 4 additional structures. Label each with ArO− and resonance contributor numbers. Vector, clean arrows in red. Phenol reacts with NaOH (unlike typical alcohols) due to greater acidity. Phenol forms phenoxide in base Water (H2O) 15.7 Neutral conjugate base OH−; no resonance. Ethanol (CH3CH2OH) ≈ 16 Alkoxide not resonance-stabilised. Phenol (C6H5OH) ≈ 10 Phenoxide resonance-stabilised (5 contributors). p-Nitrophenol ≈ 7.2 −NO2 (EWG) at para withdraws −I and −M, stabilising phenoxide. 2,4,6-Trinitrophenol (picric acid) ≈ 0.4 Three −NO2 groups = very strong −M/−I; highly stabilised conjugate base. Acidity comparison (pKa) and reason Compound pKa (approx.) Reason Species Preparation of alcohols There are multiple reliable routes to alcohols. Learn which one gives which degree of alcohol and the regiochemistry. Guides addition of HX/H2O to alkenes: the rich get richer (H goes to C with more H). Hydroboration–oxidation of alkenes (anti-Markovnikov alcohol) hydroboration reagent trihydroborane–THF complex borane–THF dihydrogen dioxide oxidant hydrogen peroxide Across BH3 then H2O2/−OH, water adds anti-Markovnikov and syn to the alkene, giving the less substituted alcohol. No carbocation; four-centered transition state. BH3·THF, 1 equiv alkene Concerted syn-addition of BH3 across C=C; B adds to less substituted carbon. Migratory insertion; anti-Markovnikov OH. H2O2, NaOH (aq) Oxidation: B–C replaced by O–C via peroxide under basic conditions, retaining stereochemistry (overall syn). Markovnikov hydration of alkenes without rearrangement; Hg(OAc)2/H2O then NaBH4. NaBH4 reduces aldehydes/ketones; LiAlH4 reduces aldehydes, ketones, esters, acids to alcohols. NaBH4: Aldehyde → 1° alcohol; Ketone → 2° alcohol; does NOT reduce acids/esters. LiAlH4 (dry ether): Reduces aldehydes, ketones, esters, and carboxylic acids to alcohols (on hydrolysis). Handle with care; reacts with water. Selective reducing agents (learn this table in words) Grignard addition to carbonyls (followed by hydrolysis) Grignard reagent alkylmagnesium halide nucleophile/base methanal gives primary alcohol formaldehyde propan-2-one gives tertiary alcohol acetone RMgX adds to the carbonyl carbon; after acid workup, alcohol forms. The degree depends on the carbonyl. Formation of RMgX (from R–X and Mg in dry ether). Carbonyl C is electrophilic; R− attacks. Nucleophilic addition to C=O: with H2C=O → 1° alcohol; with R'–CHO → 2° alcohol; with R'2–CO → 3° alcohol; with esters → 3° alcohol (two additions). Acidic workup (H3O+) gives neutral alcohol. Hydrolysis of alkyl halides (aq KOH) gives alcohols via SN1 (3°) or SN2 (1°). Fermentation of glucose to ethanol Anaerobic fermentation by Saccharomyces cerevisiae produces ethanol and CO2. remember Industrial ethanol is made both by fermentation of sugars and by catalytic hydration of ethene to ethanol (H3PO4 catalyst on support; elevated T and pressure). Reactions of alcohols (high-yield) Acidity and metals Alcohol + Na(s) → sodium alkoxide + H2(g). Reaction is faster for stronger acids but all common alkanols react. Phenol reacts with Na and NaOH (due to higher acidity); typical alcohols react with Na but NOT with NaOH. ROH + conc. HCl/ZnCl2 at RT: 3° gives turbidity immediately; 2° in minutes; 1° no reaction at RT. 2026-05-26T17:05:33.560Z Lucas test timing chart: three test tubes labelled 1°, 2°, 3°. Show milky turbidity time bars: immediate (3°), ~5 min (2°), no change at RT (1°). Include ZnCl2/HCl label. Clean vector style. gpt-image-2 Lucas test timing: immediate turbidity (3°) > within 5 min (2°) > no turbidity at RT (1°). Dehydration to give alkene Acid-catalysed dehydration follows Saytzeff’s rule (more substituted alkene predominates where possible). Conc. H2SO4 or Al2O3, heat: alcohol → alkene (Saytzeff major). Conversion to alkyl halides: SOCl2 (often with pyridine) or PCl5 convert ROH → RCl; HX (HCl, HBr, HI) also works (SN1 faster for 3°). KMnO4/K2Cr2O7 oxidise: 1° → aldehyde → acid; 2° → ketone; 3° resist oxidation. PCC stops at aldehyde from primary alcohol Pyridinium chlorochromate (PCC) oxidises 1° alcohols to aldehydes without overoxidation. Fischer esterification (reversible) Acid-catalysed esterification; remove water to drive equilibrium forward. R–OH + R′–COOH (H+) ⇌ R′–COOR + H2O (Fischer esterification). (Preview) Alkoxide + primary alkyl halide (SN2) → ether. At a glance: alcohol oxidation (1°→aldehyde→acid, 2°→ketone) and dehydration to alkene; phenol reacts with NaOH and undergoes EAS like nitration. Preparation of phenol Key industrial and lab routes Dow process: Chlorobenzene + NaOH at ~623 K and ~320 atm → sodium phenoxide; acidify → phenol. Cumene (isopropylbenzene) process (Hock, 1944): O2 oxidation → cumene hydroperoxide; acid-catalysed rearrangement gives phenol + acetone. Dominant industrial route (~95%). Alkali fusion of benzene sulfonate: Sodium benzene sulfonate + molten NaOH → sodium phenoxide; acidification → phenol. From diazonium salt: Benzenediazonium (ArN2+Cl−) on warming with water gives phenol + N2. gpt-image-2 Cumene to phenol (Hock rearrangement): cumene → cumene hydroperoxide → phenol + acetone. 2026-05-26T17:05:33.854Z Flow diagram for cumene process on white background: Box1 cumene (isopropylbenzene), arrow O2 to cumene hydroperoxide, arrow H+ rearrangement to phenol + acetone. Label each structure with IUPAC/common name. Vector style, red arrows, clean. Reactions of phenol (signature set) Phenol + Na or NaOH → sodium phenoxide (test for phenolic –OH). FeCl3 test: many phenols give violet/blue/purple complexes — a useful lab test. Acid–base and qualitative test Test-tube illustration: phenol solution + FeCl3 gives violet color. Include small inset of [Fe(phenolate)3] complex idea (no detailed structure), labels for reagents. Clean educational vector. 2026-05-26T17:05:34.184Z Ferric chloride test: violet complex with phenol indicating phenolic –OH. gpt-image-2 Phenol strongly activates ring; o,p-directing due to +M effect of –OH. Deprotonate phenol to sodium phenoxide (ArO−Na+). 400 K, 4–7 atm CO2 CO2 electrophilic attack at ortho position of the activated ring. Acidification (H+) to salicylic acid. phenol substrate (as sodium phenoxide) benzenol electrophile carbon dioxide carbon dioxide salicylic acid 2-hydroxybenzoic acid product Sodium phenoxide reacts with CO2 under pressure and heat to give salicylic acid (mainly ortho) after acidification. Kolbe–Schmitt (salicylic acid synthesis) Reimer–Tiemann (formylation of phenol) Under CHCl3/NaOH, dichlorocarbene (:CCl2) forms and inserts at the ortho position; hydrolysis yields salicylaldehyde. chloroform trichloromethane carbene precursor dichlorocarbene dichlorocarbene electrophile (carbene) product 2-hydroxybenzaldehyde salicylaldehyde CHCl3, NaOH (aq), heat Base-induced deprotonation of CHCl3 gives :CCl2 (dichlorocarbene). Electrophilic attack of :CCl2 at ortho to –O− on phenoxide to give –CCl2 substituent. Hydrolysis and workup convert –CCl2 to –CHO (salicylaldehyde). Other hallmark reactions Bromination: Br2/H2O (no catalyst) → 2,4,6-tribromophenol (white ppt). Nitration: Dil. HNO3 → o- and p-nitrophenols; conc. HNO3/H2SO4 → 2,4,6-trinitrophenol (picric acid). Ester formation: Phenyl esters with acyl chlorides/anhydrides under base/acid conditions. Industrial and societal connections Ethanol: prepared by fermentation (yeast) and petrochemical hydration of ethene. Uses: alcoholic beverages, antiseptic, solvent, and fuel (E10/E85 blends in flex-fuel vehicles). Methanol (wood spirit; SMILES: CO) is toxic — metabolism to formaldehyde and formic acid causes blindness and metabolic acidosis. Ethane-1,2-diol (ethylene glycol) is antifreeze. Glycerol is a humectant and formed as a byproduct in soap-making; makes nitroglycerin (an explosive and vasodilator). Phenol: historically an antiseptic (Lister, 1867) and now a feedstock for polymers (e.g., Bakelite) and pharmaceuticals (salicylic acid → aspirin). Dettol contains chloroxylenol, a phenolic compound. gpt-image-2 Aspirin synthesis from salicylic acid via acetylation (acetic anhydride). 2026-05-26T17:05:34.632Z One-line reaction scheme: salicylic acid + acetic anhydride (H+) → aspirin (acetylsalicylic acid) + acetic acid. Show skeletal structures with labels. Clean vector, red reaction arrow, no internal text. Hospital-grade antiseptics: ethanol (60–90%) and isopropyl alcohol (propan-2-ol) are common disinfectants. Phenolic antiseptics (e.g., chloroxylenol in Dettol) are effective on surfaces and skin when diluted appropriately. clinical All compounds with an –OH group are alcohols; phenols are just 'aromatic alcohols'. Phenols (Ar–OH) are a distinct class: –OH on aromatic Csp2, far more acidic than alcohols, react with NaOH, and undergo electrophilic aromatic substitution readily. Alcohols are more acidic than phenols or even comparable to carboxylic acids. Correct order of acidity (stronger → weaker): Carboxylic acids >> Phenols > Water > Alcohols. Phenoxide is resonance-stabilised; alkoxides are not. Lucas clock: “3 now, 2 later, 1 never (at RT).” Immediate turbidity = 3°; within minutes = 2°; no turbidity at RT = 1°. NEET traps and quick checks Grignard products: with formaldehyde → 1°; with other aldehydes → 2°; with ketones/esters → 3°. Oxidation: 3° alcohols resist oxidation (no H on carbinol C); strong conditions cause C–C cleavage rather than ketone formation. Acidity: phenol reacts with NaOH; typical alkanols do not. Water is slightly more acidic than ethanol (pKa 15.7 vs ~16). Bromination of phenol needs no Lewis acid; it is highly activated and gives 2,4,6-tribromophenol. Iodoform test: positive for methyl ketones (R–CO–CH3), ethanol, and secondary alcohols with CH3–CH(OH)–R (on oxidation). Common pitfalls Phenol neutralisation (acid–base) Fischer esterification (core equilibrium) Primary alcohol dehydration to terminal alkene PCC oxidation of primary alcohol Carboxylic Acids R-COOH > H 2O Conjugate base (carboxylate ion) is stabilized by two equivalent resonance structures where negative charge resides on Oxygen atoms. Picric Acid ( 2,4,6 -Trinitrophenol) O 2N-C 6H 2(NO 2) 2-OH > R-COOH Strong -M and -I effects of three -NO 2 groups drastically stabilize the phenoxide ion, making it more acidic than simple carboxylic acids. Phenols C 6H 5OH > H 2O Phenoxide ion is resonance stabilized; though charge delocalizes to Carbon, it is more stable than OH - or alkoxide ions. Water H 2O Reference point with pK a 15.7 ; lacks the +I effect of alkyl groups found in alcohols. Methanol CH 3OH > H 2O The only common alcohol more acidic than water due to the very small +I effect of the methyl group relative to solvation factors. Primary Alcohols RCH 2OH < H 2O Alkyl groups exert +I effect, increasing electron density on Oxygen and destabilizing the alkoxide ion conjugate base. Secondary/Tertiary Alcohols R 3COH < RCH 2OH Increasing number of alkyl groups ( +I effect) further destabilizes the conjugate base, decreasing acidity. Terminal Alkynes R-C CH < R-OH High s -character ( 50 % ) of sp hybridized Carbon increases electronegativity, but it is still less than Oxygen. Ammonia NH 3 < R-C CH Nitrogen is less electronegative than sp hybridized Carbon, resulting in a less stable conjugate base ( NH 2 - ). Alkenes R 2C=CH 2 < NH 3 sp 2 hybridized Carbon ( 33.3 % s -character) is less electronegative than Nitrogen or sp Carbon. Alkanes R-CH 3 < R 2C=CH 2 sp 3 hybridized Carbon ( 25 % s -character) has the lowest electronegativity, making Alkanes the weakest acids. TREND Organic Chemistry Acidity pKa Inductive Effect Resonance NEET High Yield Acidity of Organic Compounds Car-Nitro-Phen-Wat-Al-Alky: Carboxylic, Nitro-phenols, Phenols, Water, Alcohols, and Alkynes follow this decreasing acidity path. Compound Class Functional Group Acidity Trend vs Water Reason for Acidity Establishing the pK a order and resonance stabilization of conjugate bases. Reaction Aldol needs Alpha, Cannizzaro has Zero Alpha, Clemmensen uses Acidic Zinc, while Wolff stays Basic. Reagents Key Condition Product Type Quick revision map for high-yield organic synthesis questions. Aldehydes & Ketones Named Reactions Organic Chemistry Aldehydes & Ketones Named Reactions NEET High Yield GLOSSARY Aldol Condensation dil. NaOH or dil. KOH or Ba(OH) 2 Presence of -H atoms in aldehyde/ketone -hydroxy aldehyde/ketone or , -unsaturated carbonyl Cannizzaro Reaction conc. NaOH or conc. KOH ( 50 % ) Absence of -H atoms (Disproportionation) Alcohol and Carboxylic acid salt Clemmensen Reduction Zn-Hg / conc. HCl Acidic medium, suitable for acid-stable groups Alkane ( >C=O >CH 2 ) Wolff-Kishner Reduction NH 2NH 2 / KOH in ethylene glycol Basic medium, suitable for base-stable groups Alkane ( >C=O >CH 2 ) Rosenmund Reduction H 2 / Pd-BaSO 4 (poisoned with S or quinoline) Hydrogenation of acid chlorides Aldehyde ( R-COCl R-CHO ) Stephen Reaction SnCl 2 / HCl , followed by H 3O + Partial reduction of nitriles via imine Aldehyde ( R-CN R-CHO ) Etard Reaction CrO 2Cl 2 in CS 2 , followed by H 3O + Selective oxidation of methyl group on benzene Benzaldehyde ( Ar-CH 3 Ar-CHO ) Gattermann-Koch Reaction CO + HCl in presence of anh. AlCl 3 / CuCl Formylation of benzene/derivatives Benzaldehyde ( C 6H 6 C 6H 5CHO ) Haloform Reaction X 2 + NaOH (Sodium hypohalite NaOX ) Presence of methyl ketone ( -COCH 3 ) group Haloform ( CHX 3 ) + Carboxylate salt Crossed Aldol Condensation dil. NaOH / Two different carbonyl compounds with -H Mixture of four different products PCC (Pyridinium Chlorochromate) in CH 2Cl 2 Aldehyde ( R-CHO ) Ketone ( R 2C=O ) No Reaction Cu at 573 K Aldehyde ( R-CHO ) Ketone ( R 2C=O ) Alkene (Dehydration) Acidified K 2Cr 2O 7 or KMnO 4 Carboxylic Acid ( R-COOH ) Ketone ( R 2C=O ) No Reaction (Resistant to oxidation) Jones Reagent ( CrO 3 / H 2SO 4 in Acetone) Carboxylic Acid ( R-COOH ) Ketone ( R 2C=O ) No Reaction Anhydrous CrO 3 Aldehyde ( R-CHO ) Ketone ( R 2C=O ) No Reaction Collins Reagent ( CrO 3 / C 5H 5N / CH 2Cl 2 ) Aldehyde ( R-CHO ) Ketone ( R 2C=O ) No Reaction Sarett Reagent ( CrO 3 in Pyridine) Aldehyde ( R-CHO ) Ketone ( R 2C=O ) No Reaction Cold dilute alkaline KMnO 4 (Baeyer's) Carboxylic Acid ( R-COOK ) Ketone ( R 2C=O ) No Reaction Reagent Mild PCC/Collins stops at Aldehyde, Strong Jones/Permanganate reaches the Acid, but Hot Copper uniquely dehydrates the Tertiary. Primary Alcohol Product Secondary Alcohol Product Tertiary Alcohol Product Predicting Aldehyde vs Carboxylic Acid vs Ketone formation. Oxidation of Alcohols Organic Chemistry Alcohols Phenols and Ethers Oxidation Reactions NEET Chemistry High Yield REACTION VARIANTS REACTION VARIANTS Practical Organic Chemistry Functional Group Analysis NEET High Yield Chemical Tests Tests for Functional Groups Functional Group Detected Observation Chemical Basis Practical chemistry application in theoretical questions. Lucas and Iodoform Told Fehling that 2,4-DNP captures Carbonyls while Hinsberg and Carbylamine sort the Amines. Test Name Lucas Test 3 , 2 , 1 Alcohols 3 : Immediate turbidity; 2 : 5 mins; 1 : Turbidity only on heating Formation of insoluble alkyl chlorides via S N1 using anhydrous ZnCl 2 and conc. HCl Iodoform Test Methyl Ketones ( CH 3CO- ) or Methyl Carbinols ( CH 3CH(OH)- ) Bright yellow crystalline precipitate ( CHI 3 ) Halogenation and alkaline cleavage of methyl groups using I 2/NaOH Tollen's Reagent Aldehydes (Aliphatic and Aromatic) Bright silver mirror on the inner walls of the test tube Reduction of [Ag(NH 3) 2] + to metallic Ag by oxidizing aldehyde to carboxylate Fehling's Solution Aliphatic Aldehydes (Aromatic Aldehydes do not react) Reddish-brown precipitate ( Cu 2O ) Reduction of Cu 2+ (complexed with Rochelle salt) to Cu + by the aldehyde 2,4-DNP (Brady's Reagent) Carbonyl Compounds (Aldehydes and Ketones) Yellow, orange, or red crystalline precipitate Nucleophilic addition-elimination (condensation) forming 2,4-dinitrophenylhydrazones Carbylamine Test Primary ( 1 ) Amines (Aliphatic or Aromatic) Extremely foul, offensive odor of Isocyanide Reaction with CHCl 3 and alcoholic KOH to form Isocyanide ( R-NC ) Neutral FeCl 3 Test Phenols or Enols Violet, blue, green, or red coloration Formation of a colored coordination complex with Fe 3+ ion (e.g., [Fe(OC 6H 5) 6] 3- ) Sodium Bicarbonate Test Carboxylic Acids ( RCOOH ) Brisk effervescence with evolution of gas Evolution of CO 2 gas due to the reaction of the acid with NaHCO 3 Hinsberg's Test Distinction of 1 , 2 , 3 Amines 1 : Soluble in NaOH ; 2 : Insoluble; 3 : No reaction with reagent Formation of sulfonamides using Benzenesulfonyl chloride ( C 6H 5SO 2Cl ) Bromine Water Test Unsaturation ( C=C or C C ) Decolourization of the reddish-brown Br 2 water Electrophilic addition of Br 2 across the multiple bonds Schiff's Reagent Aldehydes Restoration of pink/magenta color Reaction with p -rosaniline hydrochloride to restore the dye structure Azo Dye Test Primary Aromatic Amines (Aniline) Formation of a brilliant orange or red dye Diazotization at 0-5 C followed by coupling with -naphthol Litmus Test Carboxylic Acids or Phenols Blue litmus turns Red Acidic nature allows release of H + ions in aqueous solution Sodium Metal Test Alcohols, Phenols, and Carboxylic Acids Brisk effervescence of a colorless gas ( H 2 ) Reaction of acidic hydrogen with Na metal to release Hydrogen gas Phthalin Dye Test Phenols Pink color on addition of NaOH Condensation with Phthalic anhydride in conc. H 2SO 4 to form Phenolphthalein Here is a professional image prompt designed for a text-to-image AI (like Midjourney, DALL-E 3, or Stable Diffusion) based on your specifications. Prompt: > Scientific vector illustration of three laboratory test tubes demonstrating chemical color changes for functional group analysis. Arranged side-by-side in a minimal wire or plastic rack. Tube 1 contains a clear light blue solution (Fehling's solution). Tube 2 contains a deep violet solution (Phenol Ferric Chloride test). Tube 3 contains a solution with a thick brick-red precipitate at the bottom (Positive Aldehyde test). Style: Clean labeled textbook vector art, 2D flat design with subtle glass shading, distinct meniscus lines, high contrast colors against a pure white background. Professional educational diagram aesthetic. Breakdown of Prompt Elements: Subject: Three test tubes showing specific reaction variants (Blue, Violet, Red Precipitate). Context: Matches the "Tests for Functional Groups" NEET syllabus (Fehling's, Phenol, and Aldehyde tests are standard). Style: "Labeled textbook vector" ensures clean lines and printability; "High contrast" ensures the liquids stand out against the glass. Technical: "White background" allows for easy integration into a table or document.