4-Nitrophenylacetonitrile (CAS 555-21-5) is a yellow crystalline powder primarily used as a versatile intermediate in organic synthesis, particularly for the production of pharmaceutical compounds and cyanostilbenes. It is known for acting as a radical inhibitor in polymerization and a key building block for p-nitrophenylacetic acid. 

Key Information and Properties

CAS Number: 555-21-5

Molecular Formula: C8H6N2O2

Molecular Weight: 162.15 g/mol

Appearance: Cream to yellow crystalline solid/powder

Melting Point: 113-115 °C (lit.)

Boiling Point: 195–197 °C at 12 mmHg

Solubility: Insoluble in water, soluble in organic solvents like ethanol and ether

Flash Point: 157.2 °C

Density: ~1.32 g/cm³

Common Synonyms

p-Nitrophenylacetonitrile

4-Nitrobenzyl cyanide

p-Nitro-α-tolunitrile

(p-Nitrobenzene)acetonitrile

4-Nitrobenzeneacetonitrile

2-(4-Nitrophenyl)acetonitrile

NSC 5396

Uses and Applications

Organic Synthesis: Used as a versatile building block for the synthesis of various complex organic compounds.

Pharmaceutical Intermediates: Acts as a key starting material or intermediate in the synthesis of pharmaceutical compounds.

Chemical Manufacturing: Used in the preparation of p-nitrophenylacetic acid.

Material Science: Used in the preparation of cyanostilbenes.

Polymerization Inhibition: Employed as a radical inhibitor in the polymerization of vinyl acetate, helping control the reaction rate.

Safety and Hazards

Toxicity: Classified as toxic if swallowed (Category 3) and harmful in contact with skin or if inhaled (Category 4).

Irritation: Causes skin irritation (Category 2), serious eye irritation (Category 2), and may cause respiratory irritation.

Handling: Keep in a tightly closed container in a cool, dry, well-ventilated area.

Incompatibilities: Incompatible with strong acids, bases, and oxidizing agents.

Exposure: May cause headache, dizziness, nausea, and contact dermatitis.