tert-Butyl hydroperoxide

tert-Butyl hydroperoxide (TBHP) is a water-white liquid commonly commercially available as a 70% solution in water; 80% solutions are also available. It is used to initiate polymerization reactions and in organic syntheses to introduce peroxy groups into the molecule.

TBHP is an intermediate in the production of propylene oxide and t-butyl alcohol from isobutane and propylene. It is primarily used as an initiator and finishing catalyst in the solution and emulsion polymerization methods for polystyrene and polyacrylates. Other uses are for the polymerization of vinyl chloride and vinyl acetate and as an oxidation and sulfonation catalyst in bleaching and deodorizing operations. It is a strong oxidant and reacts violently with combustible and reducing materials, and metallic and sulfur compounds.

tert-Butyl hydroperoxide is used as an initiator for radical polymerization and in various oxidation process such as sharpless epoxidation. It is involved in osmium catalyzed vicinal hydroxylation of olefins under alkaline conditions. Furthermore, it is used in catalytic asymmetric oxidation of sulfides to sulfoxides using binaphthol as a chiral auxiliary and in the oxidation of dibenzothiophenes. It plays an important role for the introduction of peroxy groups in organic synthesis.

TBHP is produced by the liquid-phase reaction of isobutane and molecular oxygen or by mixing equimolar amounts of t-butyl alcohol and 30–50% hydrogen peroxide. TBHP can also be prepared from t-butyl alcohol and 30% hydrogen peroxide in the presence of sulfuric acid or by oxidation of tert-butylmagnesium chloride. The manufacturing process of TBHP is in a closed system.

Tert-butyl hydroperoxide is an alkyl hydroperoxide in which the alkyl group is tert-butyl. It is widely used in a variety of oxidation processes. It has a role as an antibacterial agent and an oxidising agent.

Watery odorless colorless liquid. Floats and mixes slowly with water.

Most alkyl monohydroperoxides are liquid. The explosivity of the lower members (e.g., methyl hydroperoxide, or possibly, traces of the dialkyl peroxides) decreasing with increasing chain length and branching [Bretherick 2nd ed. 1979 p. 10]. Though relatively stable, explosions have been caused by distillation to dryness [Milas, JACS 1946, 68, 205] or attempted distillation at atmospheric pressure [Castrantas 1965 p. 15].

tert-Butyl hydroperoxide is a strong irritant.Floyd and Stockinger (1958) observed thatdirect cutaneous application in rats did notcause immediate discomfort, but the delayedaction was severe. The symptoms were erythemaand edema within 2–3 days. Exposureto 500 mg in 24 hours produced asevere effect on rabbit skin, while a rinse of150 mg/min was severe to eyes.
It is moderately toxic; the effects aresomewhat similar to those of MEK peroxide.Symptoms from oral administration in ratswere weakness, shivering, and prostration.
LD₅₀ value, intraperitoneal (rats): 87 mg/kg
LD₅₀ value, oral (rats): 406 mg/kg.

tert-Butyl hydroperoxide is a flammable liquid and a highly reactive oxidizing agent. Pure TBHP is shock sensitive and may explode on heating. Carbon dioxide or dry chemical extinguishers should be used for fires involving tert-butyl hydroperoxide.

The general mechanism of transition metal-catalyzed oxidative Mannich reactions of N, N-dialkyl anilines with tert-butyl hydroperoxide (TBHP) as the oxidant consists of a rate-determining single electron transfer (SET) that is uniform from 4-methoxy- to 4-cyano-N, N-dimethylanilines. The tert-butylperoxy radical is the major oxidant in the rate-determining SET step that is followed by competing backward SET and irreversible heterolytic cleavage of the carbon–hydrogen bond at the α-position to nitrogen. A second SET completes the conversion of N, N-dimethylaniline to an iminium ion that is subsequently trapped by the nucleophilic solvent or the oxidant prior to the formation of the Mannich adduct[1].
Tert-butyl hydroperoxide could induce oxidative stress in liver mitochondria at low concentrations. The damaging effect of low concentrations of tBHP in the course of pyruvate oxidation in isolated liver mitochondria is caused by the opening of the nonspecific Ca²⁺-dependent cyclosporin A-sensitive pore in the inner mitochondrial membrane[2].

Moderately toxic by ingestion and inhalation. A severe skin and eye irritant. Mutation data reported. At highest dosage levels, symptoms noted were severe depression, incoordmation, and cyanosis. Death was due to respiratory arrest. Very dangerous fire hazard when exposed to heat or flame, or by spontaneous chemical reaction such as with reducing materials. Moderately explosive; may explode during distillation. Violent reaction with traces of acid. Concentrated solutions may ignite spontaneously on contact with molecular sieve. Mixtures with transition metal salts may react vigorously and release oxygen. Forms an unstable solution with 1,2-dichloroethane. To fight fire, use alcohol foam, CO2, dry chemical. When heated to decomposition it emits acrid smoke and fumes.

A study performed to evaluate the carcinogenicity of TBHP found it was not carcinogenic when applied to the skin of mice at 16.6% of the peroxide 6 times a week for 45 weeks. However, if its application was preceded by 0.05 mg of 4-nitroquinoline-1-oxide as a 0.25% solution in benzene applied 20 times over 7 weeks followed by TBHP (16.6% in benzene), then malignant skin tumors appeared between days 390 and 405 of the experiment . This supports the theory that peroxides are not complete carcinogens, but may act as promoters . The effects of TBHP on promotable and nonpromotable mouse epidermal cell culture lines were reported by Muehlematter et al. .

tert-butyl hydroperoxide should be stored in the dark at room temperature (do not refrigerate) separately from oxidizable compounds, flammable substances, and acids. Reactions involving this substance should be carried out behind a safety shield.

TBHP accelerates oxidation of glutathione and decreases the metabolism of sodium hexobarbital in rat livers and is a strong oxidation agent.

tert-Butyl hydroperoxide and concentrated aqueous solutions of TBHP react violently with traces of acid and the salts of certain metals, including, in particular, manganese, iron, and cobalt. Mixing anhydrous tert-butyl hydroperoxide with organic and readily oxidized substances can cause ignition and explosion. TBHP can initiate polymerization of certain olefins.

Excess tert-butyl hydroperoxide and waste material containing this substance should be placed in an appropriate container, clearly labeled, and handled according to your institution's waste disposal guidelines.

[1] Maxim O, et al. Mechanistic Investigation of Oxidative Mannich Reaction with tert-Butyl Hydroperoxide. The Role of Transition Metal Salt. Journal of the American Chemical Society, 2013; 135: 1549–1557.
[2] Fedotcheva N, et al. Mechanism of induction of oxidative stress in liver mitochondria by low concentrations of tert-butyl hydroperoxide. Biochemistry (Moscow), 2013; 78: 75–79.