 | |
| Names | |
|---|---|
| Preferred IUPAC name tert-Butyl benzenecarboperoxoate | |
| Other names tert-Butyl perbenzoate | |
| Identifiers | |
| |
3D model (JSmol) | |
| ChemSpider | |
| ECHA InfoCard | 100.009.440 |
| UNII | |
| |
| |
| Properties | |
| C11H14O3 | |
| Molar mass | 194.230 g·mol−1 |
| Density | 1.034 g/cm3 |
| Melting point | 8-9 °C |
| Boiling point | 112 °C (decomposes) |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
tert-Butyl peroxybenzoate (TBPB) anorganic compound with the formulaC6H5CO3CMe3 (Me = CH3). It is the most widely producedperester; it is an ester ofperoxybenzoic acid (C6H5CO3H). It is often used as aradical initiator inpolymerization reactions, such as the production ofLDPE fromethylene, and forcrosslinking, such as for unsaturated polyester resins.[1]
TBPB, which is pale yellow, is exclusively encountered as a solution in solvents such as ethanol or phthalate.[2]
As peroxo compound, TBPB contains about 8.16wt% of active oxygen and has aself accelerating decomposition temperature (SADT) of about 60 °C. The SADT is the lowest temperature at which self-accelerating decomposition in the transport packaging can occur within a week, and which should not be exceeded while storage or transportation.[3] TBPB should therefore be stored between minimum 10 °C (belowsolidification) and maximum 50 °C. Dilution with ahigh-boiling solvent increases the SADT. The half-life of TBPB, in which 50% of the peroxy ester is decomposed, is 10 hours at 104 °C, one hour at 124 °C and one minute at 165 °C. Amines,metal ions,strong acids andbases, as well as strongreducing andoxidizing agents accelerate thedecomposition of TBPB even in low concentrations.[3] However, TBPB is one of the safest peresters or organic peroxides in handling.[4] The main decomposition products oftert-butyl peroxybenzoate arecarbon dioxide,acetone,methane,tert-butanol,benzoic acid andbenzene.[5]
A standard procedure for the preparation of peresters is theacylation oftert-butyl hydroperoxide withbenzoyl chloride.[6] In the reaction a large excess oftert-butyl hydroperoxide is used and thehydrogen chloride formed is removedin vacuo whereby a virtually quantitativeyield is obtained.
Primarily, TBPB is used as aradical initiator, either in the polymerization of e.g. ethylene (to LDPE), vinyl chloride, styrene or acrylic esters or as so-called unsaturated polyester resins (UP resins).[2] The quantity used for the curing of UP resins is about 1-2%.[2]
A disadvantage, particularly in the production of polymers for applications in the food or cosmetics sector, is the possible formation of benzene as a decomposition product which can diffuse out of the polymer (for example, an LDPE packaging film).
Theprotecting group 2-trimethylsilylethanesulfonyl chloride (SES-Cl) for primary and secondaryamino groups is accessible by the reaction ofvinyltrimethylsilane withsodium hydrogensulfite and TBPB to the sodium salt of trimethylsilylethanesulfonic acid and the subsequent reaction with thionyl chloride to the corresponding sulfonyl chloride.[4]
TBPB can be used to introduce abenzoyloxy group in the allyl position of unsaturated hydrocarbons.[7]
From cyclohexene, 3-benzoyloxycyclohexene is formed with TBPB in the presence of catalytic amounts of copper(I)bromide in 71 to 80% yield.
This allylic oxidation of alkenes, also known asKharasch-Sosnovsky oxidation, generatesracemic allylic benzoates in the presence of catalytic amounts ofcopper(I)bromide.[8]
A modification of the reaction utilizescopper(II) trifluoromethanesulfonate as a catalyst andDBN orDBU as bases to achieve yields up to 80% in the reaction of acyclic olefins with TBPB to allylic benzoates.[9]
Substitutedoxazolines andthiazolines can be oxidized to the correspondingoxazoles andthiazoles in a modified Kharash-Sosnovsky oxidation with TBPB and a mixture of Cu(I) and Cu(II) salts in suitable yields.[10]
The carboalkoxy group at the C-4 position is essential a successful reaction.
Benzene andfurans can be alkenylated with olefins in an oxidative coupling under palladium salt catalysis, with TBPB as hydrogen acceptor.[11]
In the absence of Pd2+ salts, the aromatics are benzoxylated.
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