1. Basic Chemical Building Blocks (Intermediates) ...

1. Basic Chemical Building Blocks (Intermediates) These are organic compounds that form the base structure of dyes. Chemical Type Examples Purpose Aromatic Amines Aniline, o-Toluidine, p-Toluidine For azo dye formation Aromatic Hydrocarbons Benzene, Toluene, Naphthalene Starting point for sulfonation/nitration Phenols Phenol, Resorcinol, α-Naphthol Used in acid and disperse dyes Naphthols 1-Naphthol, 2-Naphthol For azo coupling reactions Nitro Compounds Nitrobenzene, dinitrotoluene For reduction to amines ⚗️ 2. Functional Reagents These help introduce specific dye properties. Reagent Type Examples Purpose Sulfonating Agents Oleum, Sulfuric acid Water solubility (acid dyes) Diazotizing Agents Sodium nitrite + HCl Diazotization of aromatic amines Coupling Agents β-Naphthol, Phenol derivatives Azo dye coupling Alkalis Sodium carbonate, Caustic soda Neutralization or pH control Oxidizing Agents Sodium dichromate, potassium permanganate Used in vat and sulfur dyes Reducing Agents Sodium hydrosulfite, glucose Vat dyes and sulfur dye solubilization 🧪 3. Solvents & Carriers Used to dissolve or transport intermediates during reactions. Water – Primary solvent Alcohols – Methanol, Ethanol (for solubilization) Acetic Acid – As buffer in dye baths Benzene / Toluene – Organic reactions (now limited due to toxicity) 🌿 4. Natural Raw Materials (used in eco-friendly dyes) Indigo – From Indigofera plant (now also synthetic) Henna (Lawsone) – Natural dye for skin/hair Turmeric (Curcumin) – Yellow dye Madder Root – Alizarin red Logwood, Walnut husks – Tannins and dark shades 🌈 5. Dye-Specific Raw Materials Dye Class Raw Materials Needed Azo Dyes Aromatic amines + coupling components (like phenols) Vat Dyes Indigo, Anthraquinone + reducing agents Reactive Dyes Cyanuric chloride, Vinyl sulfone Sulfur Dyes Aromatic amines + sulfur + sodium sulfide Disperse Dyes Mono/di amino benzene derivatives + esters or ketones Acid Dyes Aromatic amines + sulfonated intermediates 📦 Additives and Finishers Leveling agents – Ensure even dyeing Fixing agents – Improve fastness Softening agents – Improve feel of fabric