Lassaigne's Test: A qualitative test for detecting non-metallic elements (N, S, halogens) in organic compounds by fusing the compound with sodium metal and testing the aqueous extract.
Sodium Fusion: The process of heating an organic compound with sodium metal at high temperature to convert covalently-bonded non-metallic elements into water-soluble ionic compounds.
Prussian Blue: Fe4[Fe(CN)6]3 — ferric ferrocyanide. An intense blue pigment formed in the Lassaigne's nitrogen test. Named after the Prussian blue pigment used in paints.
NaSCN: Sodium thiocyanate. Formed in Lassaigne's test when both N and S are present. The thiocyanate ion (SCN-) contains both N and S, explaining the compound NaSCN.
Tollens' Reagent: Ammoniacal silver nitrate ([Ag(NH3)2]+ solution, prepared by adding excess NH3 to AgNO3). Gives silver mirror with aldehydes.
Fehling's Solution: A mixture of Fehling's A (CuSO4) and Fehling's B (NaOH + sodium potassium tartrate). Gives brick-red Cu2O precipitate with aliphatic aldehydes.
2,4-DNP: 2,4-Dinitrophenylhydrazine. Reagent that forms orange/yellow precipitates (2,4-dinitrophenylhydrazones) with compounds containing C=O groups.
Iodoform: CHI3 (triiodomethane). Yellow crystalline solid with SMILES C(I)(I)I. Produced by I2/NaOH from methyl ketones. Formerly used as antiseptic.
Self-Indicating Titration: A titration that does not require an external indicator because one of the reactants or products has a visible color change at the endpoint. KMnO4 titrations are self-indicating.
Primary Standard: A substance used to prepare solutions of accurately known concentration. It must be highly pure, stable, have a known composition, and be readily available. Oxalic acid (H2C2O4·2H2O) is a primary standard for KMnO4 standardization.
Nessler's Reagent: Alkaline K2[HgI4] (potassium tetraiodomercurate(II)). Gives brown precipitate with NH4+ (ammonium ion).
Autocatalysis: A reaction catalyzed by one of its own products. In KMnO4/oxalic acid titration, Mn2+ (product) catalyzes the further reaction, explaining why the reaction rate increases as the titration progresses.
Acetylation: Introduction of an acetyl group (CH3CO-) into a molecule. In preparation of acetanilide: aniline + acetic anhydride → acetanilide (NH2 → NHCOCH3).
Carbylamine Test: Test for primary amines using CHCl3 + KOH. Forms foul-smelling isocyanide (R-NC). Specific to primary amines.