Qualitative Organic Analysis – Key Tests and Solubility Rules

Vocabulary flashcards summarizing common qualitative organic tests and solubility rules for functional-group identification.

Bromine/CCl4 Test

Immediate loss of bromine color shows an alkene (unsaturation).

Aromatic Flame Test

Black sooty smoke (aromatic); rapid clean burn (high-O); sparking (high-N); yellow smoky flame (aromatic/unsaturated/high-MW aliphatic); yellow non-smoky (low-MW aliphatic); clear bluish (very O-rich).

Belstein Test

Green flame indicates a halogen (Cl, Br, or I) in alkyl or aryl halides; F gives no response.

Silver Nitrate Test

Room-temperature precipitate signals halide: white (Cl), pale yellow (Br), yellow (I). Carboxylic acids may give false positives.

Chromic Acid Test

Instant blue-green color means aldehyde or 1°/2° alcohol; ketones remain orange.

Lucas Test

Cloudy ppt timing diagnoses alcohol class: <2 min (benzylic, allylic, 3°); ~10 min (2°); none (1°).

Ferric Chloride Test

Red, blue, purple, or green solution indicates phenol (esters or 1,3-dicarbonyls can interfere).

Bromine-Water Test

Loss of yellow bromine color after mixing implies phenol (electrophilic bromination).

2,4-DNP Test

Red-orange-yellow precipitate detects carbonyls: yellow (non-conjugated), orange/red (conjugated) aldehydes or ketones.

Tollens Test

Silver mirror or black Ag ppt confirms an aldehyde (reduces Ag⁺).

Iodoform Test

Yellow CHI₃ precipitate reveals a methyl ketone (RCOCH₃) or ethanol-type 2° alcohols after oxidation.

Sodium Bicarbonate Test

Effervescence (CO₂) when the sample dissolves shows a carboxylic acid.

Hinsberg Test

Differentiates amines: 1° gives soluble sulfonamide (stays clear with HCl); 2° yields insoluble solid (insoluble in HCl); 3° shows no reaction but dissolves in HCl.

Hydroxylamine/Ferric Chloride Test

Deep red-purple complex after hydroxylamine treatment indicates an ester; if color appears without hydroxylamine, a phenol is present.

Iron(II) Hydroxide Test

Brown or red-brown ppt within 1 min identifies nitro groups via reduction to hydroxylamine.

Water Solubility – Basic Compounds

Low-molecular-weight amines dissolve, giving basic aqueous solutions.

Water Solubility – Neutral Compounds

Low-molecular-weight alcohols, aldehydes, and ketones dissolve without affecting pH appreciably.

Water Solubility – Acidic Compounds

Low-molecular-weight carboxylic acids dissolve, producing acidic solutions.

Phenol Solubility Pattern

Phenols are insoluble in water and NaHCO₃ but dissolve in aqueous NaOH (form phenoxide).

Carboxylic Acid Solubility Pattern

Carboxylic acids are insoluble in water, soluble in NaHCO₃ and NaOH (form carboxylate).

Amine Solubility Pattern

Amines are insoluble in water/NaOH but become soluble in aqueous HCl (form ammonium salts).

Neutral/Non-basic Insoluble Group

Alcohols, esters, aldehydes, ketones, ethers, halides, and hydrocarbons are insoluble in water, NaOH, and HCl.