What Is Indoline?
Indoline is a heterocyclic compound known as 2,3-dihydro-1H-indole or 2,3-dihydroindole. It appears as a colorless to dark brown liquid with the chemical formula C8H9N and a molecular weight of 119.16. Its CAS number is 496-15-1, and it is structurally similar to indole (C8H7N) but with a reduction at positions 2 and 3.
The isomer of indoline with the nitrogen atom at position 2 is known as isoindoline.
Properties of Indoline
Indoline has a boiling point of 220°C, a melting point of -21°C, and a specific gravity of 1.063 g/mL at 25°C. It is highly soluble in ethanol and nearly insoluble in water. Compared to indole, indoline is more basic due to its unreduced nitrogen atom, with an acid dissociation constant (pKa) of 5.2.
Uses of Indoline
Indoline is primarily used as an intermediate in the synthesis of pharmaceuticals, agricultural chemicals, dyes, photo-functional materials, and functional resins. It is particularly notable in the production of pigments and dyes and is utilized in electronics, such as in dye-sensitized solar cells.
Other Information on Indoline
1. Production Method
Indoline can be synthesized via the catalytic reduction of indole. It is obtained by distilling and purifying coal tar, using metal catalysts such as copper chromite, raney nickel, and nickel-titanium. When stored, it should be kept in a well-ventilated, cool place, in a light-shielded, tightly sealed glass container.
2. Precautions for Use
Flammability: Indoline is a flammable liquid. Keep it away from heat, sparks, and open flames. In case of fire, use carbon dioxide, powder extinguishers, water spray, foam, or fire sand to extinguish it.
Health Hazards: Indoline is corrosive and irritating to the skin and eyes. Protective clothing, gloves, and eyewear should be worn when handling it. In case of contact, wash the affected area with soap and water and seek medical attention if irritation persists. Use it in a well-ventilated area or a draft chamber to avoid inhalation of vapors.