2,4-Dinitrophenol

Chemical Properties

light yellow crystal powder

Uses

2,4-Dinitrophenol (DNP) can be used:

• As a reactant for catalytic reduction reactions.
• To activate carboxylic acids by converting them into dinitrophenyl (DNP) esters.
• To prepare the corresponding ester via acylation reaction using isobutyric anhydride catalyzed by hafnium triflate.
• As an effective cocatalyst to accelerate the activity and enantioselectivity of primary amine organocatalyst derived from natural primary amino acids for direct asymmetric aldol reaction.
• As an alternative activator to tetrazoles in the reaction of phosphoroamidites with nucleosides.

Production Methods

2,4-Dinitrochlorobenzene is hydrolyzed by heating with 6 % aqueous sodium hydroxide at 95 – 100 ℃ for 4 h. The product 2,4-Dinitrophenol is precipitated by addition of acid, filtered off, and washed to remove acid and also a small quantity of the more soluble 2,6-isomer. The yield is 95 %.

General Description

Solid yellow crystals. Explosive when dry or with less than 15% water. The primary hazard is from blast of an instantaneous explosion and not flying projectiles and fragments. slightly soluble in water and soluble in ether and solutions of sodium or potassium hydroxide.

Air & Water Reactions

Highly flammable. Slightly soluble in water.

Reactivity Profile

2,4-Dinitrophenol may explode if subjected to heat or flame. may explode if allowed to dry out. Forms explosive salts with alkalis and ammonia. Incompatible with heavy metals and their compounds. Also incompatible with strong oxidizing agents, strong bases and reducing agents. Reacts with combustibles.

Health Hazard

2,4-Dinitrophenol is a severely acute toxicant, exhibiting high toxicity in animals by all routes of administration. It can be absorbed through the intact skin. The toxic effects are heavy sweating, nausea, vomiting, collapse, and death. Ingestion of 1 g of solid can be fatal to humans. A 30-minute exposure to its vapors at a concentration of 300 mg/m³ was lethal to dogs (NIOSH 1986). Chronic effects include polyneuropathy, weight loss, cataracts, and dermatitis.
LD50 value, oral (rats): 30 mg/kg.

Fire Hazard

Combustible. May explode if subjected to heat or flame. POISONOUS GAS IS PRODUCED WHEN HEATED. Vapors are toxic. Can detonate or explode when heated under confinement.

Safety Profile

A deadly human poison by ingestion. An experimental poison by ingestion, inhalation, intravenous, intraperitoneal, subcutaneous, and intramuscular routes. Moderately toxic by skin contact. Experimental teratogenic and reproductive effects. Human systemic effects: body temperature increase, change in heart rate, coma. A skin irritant. Mutation data reported. Phytotoxic. A pesticide. An explosive. Forms explosive salts with alkalies and ammonia. When heated to decomposition it emits toxic fumes of NOx. See also NITRO COMPOUNDS of AROMATIC HYDROCARBONS.

Carcinogenicity

No teratogenic effects have been reported in limited developmental toxicity studies in rodents. Decreased fetal body weight and crown-rump length were noted in rats and mice after parenteral administration.
2,4-DNP was not genotoxic in most in vivo and in vitro studies.
An ACGIH threshold limit value (TLV) has not been established for 2,4-DNP.

Metabolic pathway

The bacterial strain RB1, which is isolated by enrichment cultivation with 2,4-dinitrophenol, degrades this phenol into two aliphatic acids. One metabolite results from the release of the 2-nitro group as nitrile, with the production of aliphatic nitro compound, 3-nitroadipate. Then, the 3-nitro group is released from this metabolite as nitrile. The other metabolite is 4,6-dinitrohexanoic acid possessing two nitro groups from 2,4-dinitrophenol.

Purification Methods

Crystallise it from *benzene, EtOH, EtOH/H2O or H2O acidified with dilute HCl, dry it, then recrystallise it from CCl4. Dry it in an oven and store it in a vacuum desiccator over CaSO4. The benzoate has m 132o (from EtOH). [Beilstein 6 IV 1369.]