tert-Butyl peroxybenzoate

Tert-Butyl peroxybenzoate
Identifiers
614-45-9
PubChem 11966
Properties
C11H14O3
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

tert-butyl peroxybenzoate (TBPB) a chemical compound from the group of Peresters (compounds containing the general structure R1-C(O)OO-R2) which contains a phenyl group as R1 and a tert-butyl group as R2. It is often used as a radical initiator in polymerizations (for example ethene to LDPE) and for crosslinking (for example of unsaturated polyester resins).

Properties

tert-butyl peroxybenzoate is a clear light yellow liquid, which is little soluble in water but well in many organic solvents such as ethanol or phthalate.[1]

As peroxo compound, tert-Butyl peroxybenzoate contains about 8.16 wt% of active oxygen and has a so-called self-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.[2] tert-butyl peroxybenzoate should therefore be stored between minimum 10 °C (below solidification) and maximum 50 °C. Dilution with a high-boiling solvent increases the SADT. The half-life of tert-butyl peroxybenzoate, 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 and bases, as well as strong reducing and oxidizing agents accelerate the decomposition of tert-butyl peroxybenzoate even in low concentrations.[2] However, tert-butyl peroxybenzoate is one of the safest peresters or organic peroxides in handling.[3] The main decomposition products of tert-butyl peroxybenzoate are carbon dioxide, acetone, methane, tert-butanol, benzoic acid and benzene.[4]

Production

A standard procedure for the preparation of peresters is the acylation of tert-butyl hydroperoxide with benzoyl chloride.[5] In the reaction a large excess of tert-butyl hydroperoxide is used and the hydrogen chloride formed is removed in vacuo whereby a virtually quantitative yield is obtained.

Applications

Applications in polymer chemistry

Primarily, tert-butyl peroxybenzoate is used as a radical initiator, either in the polymerization of e.g. ethene (to LDPE), vinyl chloride, styrene or acrylic esters or as so-called unsaturated polyester resins (UP resins).[1] The quantity used for the curing of UP resins is about 1-2%.[1]

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).

Applications in organic chemistry

The protecting group 2-trimethylsilylethanesulfonyl chloride (SES-Cl) for primary and secondary amino groups is accessible by the reaction of vinyltrimethylsilane with sodium hydrogensulfite and tert-butyl peroxybenzoate (TBPB) to the sodium salt of trimethylsilylethanesulfonic acid and the subsequent reaction with thionyl chloride to the corresponding sulfonyl chloride.[3]

tert-butyl peroxybenzoate can be used to introduce a benzoyloxy group in the allyl position of unsaturated hydrocarbons.[6]

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 as Kharasch-Sosnovsky oxidation, generates racemic allylic benzoates in the presence of catalytic amounts of copper(I)bromide.[7]

A modification of the reaction utilizes copper(II)trifluoromethanesulfonate as a catalyst and DBN or DBU as bases to achieve yields up to 80% in the reaction of acyclic olefins with tert-butyl peroxybenzoate to allylic benzoates.[8]

Substituted oxazolines and thiazolines can be oxidized to the corresponding oxazoles and thiazoles in a modified Kharash-Sosnovsky oxidation with tert-butylperoxy-benzoate and a mixture of Cu(I) and Cu(II)salts in suitable yields.[9]

The carboalkoxy group at the C-4 position is essential a successful reaction.

Benzene and furans can be alkylated with olefins in an oxidative coupling under palladium salt catalysis, with tert-butyl peroxybenzoate as hydrogen acceptor.[10]

In the absence of Pd2+ salts, the aromatics are benzoxylated.

References

  1. 1 2 3 United Initiators, Technisches Datenblatt, TBPB
  2. 1 2 Organic Peroxide Producers Safety Division, SAFETY AND HANDLING OF ORGANIC PEROXIDES The Society of the Plastics Industry, 2012 edition
  3. 1 2 "2-Trimethylsilylethanesulfonyl chloride (SES-Cl)". Org. Synth. doi:10.15227/orgsyn.075.0161.
  4. ↑ PERGAN GmbH: Organische Peroxide für die Polymerisation
  5. ↑ N.A. Milas, D.G. Orphanos, R.J. Klein (1964), "The solvolysis of acid chlorides with t-alkyl hydroperoxides", J. Org. Chem. 29 (10): pp. 3099–3100, doi:10.1021/jo01033a525
  6. ↑ "3-Benzoyloxycyclohexene". Org. Synth. doi:10.15227/orgsyn.048.0018.
  7. ↑ M.S. Kharasch, G. Sosnovsky (1958), "The reactions of t-butyl perbenzoate and olefins – a stereospecific reaction", J. Amer. Chem. Soc. 80 (3): pp. 756–756, doi:10.1021/ja01536a062
  8. ↑ G. Sakar, A. DattaGupta, V.K. Singh (1996), "Cu(OTf)2 – DBN/DBU complex as an efficient catalyst for allylic oxidation of olefins with tert-butyl perbenzoate", Tetrahedron Lett. 37 (46): pp. 8435–8436, doi:10.1016/0040-4039(96)01911-9
  9. ↑ A.I. Meyers, F.X. Tavares (1996), "Oxidation of Oxazolines and Thiazolines to Oxazoles and Thiazoles. Application of the Kharasch−Sosnovsky Reaction", J. Org. Chem. 61 (23): pp. 8207–8215, doi:10.1021/jo.9613491
  10. ↑ J. Tsuji, H. Nagashima (1984), "Palladium-catalyzed oxidative coupling of aromatic compounds with olefins using t-butyl perbenzoate as a hydrogen accepter", Tetrahedron 40 (14): pp. 2699–2702, doi:10.1016/S0040-4020(01)96888-7
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