Process for producing 2,5-dimethyl-2,5-dihydroperoxyhexane

Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing

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C07C40900

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058565868

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BRIEF SUMMARY
This application is a 371 of PCT/EP95/02985, filed Jul. 27, 1995.


BACKGROUND OF THE INVENTION

The present invention is in a process for the preparation of 2,5-dimethyl-2,5-dihydroperoxyhexane by the reaction of 2,5-dimethyl-1,5-hexadiene with hydrogen peroxide in an acidic medium.
2,5-Dimethyl-2,5-dihydroperoxyhexane (DHHP) is an important starting material for the preparation of cross-linking peroxides (dialkyl peroxides, such as e.g. 2,5-dimethyl-2,5-di-tert.-butylperoxyhexane, or perketals, such as 3,3,6,6,9,9-hexamethyl-1,2,4,5-tetraoxacyclonotane)(cf. GB-PS 936008), as well as of highly reactive bifunctional peresters.
In FR-PA 1291965 discloses the preparation of 2,5-dimethyl-2,5-di-tert.-butylperoxyhexane from 2,5-dimethyl-1,5-hexadiene by reaction with tert.-butylhydroperoxide. However, the yield of 26% thereby obtained is very unsatisfactory and, furthermore, according to this process, only dialkylperoxides but no perketal or perester derivatives of DHHP are obtained.
From the prior art, a process for the preparation of 2,5-dimethyl-2,5dihydroperoxyhexane (DHHP), from 2,5-dimethylhexane with oxygen is known.
EP-A-0513711 describes a process for the preparation of aliphatic hydroperoxides, e.g. of 2,5-dimethyl-2,5dihydroperoxyhexane (DHHP), by the reaction of a corresponding tetrahydrofurane derivative with hydrogen peroxide.
U.S. Pat. No. 4,154,768 describes a general process for the preparation of tert.-alkylhydroperoxides from asymmetric secondary olefins by reaction with hydrogen peroxide in a reaction mixture containing a strong acid.
According to JP-A-3215468 and JP-A-3190856, hydroperoxides are obtained by the reaction of an olefin or alcohol with hydrogen peroxide in the presence of a strong acid.
Usually, the preparation of 2,5-dimethyl-2,5dihydroperoxyhexane (DHHP) takes place by the reaction of 2,5-dimethylhexane-2,5-diol with hydrogen peroxide in the presence of an acidic catalyst, in general using sulphuric acid (cf. Rust, J. Am. Chem. Soc. 79 (1957) 4000, 4002; L. Criegee, Erdol und Kohle, 15 (1962) 523, 524, 528; Criegee and Paulig, Chem. Ber., 88 (1955), 712, 716; Criegee and Dietrich, Liebigs Ann. Chem. 560 (1948) 141; L. Dulog and A. Sanner, Tetrahedron Letters, 51 (1966) 6353-6358). According to these processes, the dosing of the diol takes place as a solid, which is a disadvantage. Another disadvantage of this process is the easy formation of cyclisation products (e.g. 2,2,5,5-tetramethyltetrahydrofuran) from the diol under the influence of acids which gives poor yields of dihydroperoxide and a contaminated product.
Therefore, there was still a great need for a process for the preparation of 2,5-dimethyl-2,5-dihydroperoxyhexane (DHHP) which can be carried out in a simple and technically advantageous way, and by which the DHHP is obtainable in high yield.
This problem has been solved by the process of the present invention.


THE INVENTION

The subject of the present invention is a process for the preparation of 2,5-dimethyl-2,5-dihydroperoxyhexane (DHHP) according to claim 1 by reaction of 2,5-dimethyl-1,5-hexadiene with hydrogen peroxide in an acidic medium.
At ambient reaction temperatures, almost no reaction takes place between 2,5-dimethyl-1,5-hexadiene and an aqueous mixture of hydrogen peroxide and sulphuric acid. However, after addition of a small amount of a suitable emulsifier or of a solvent which is miscible with water, a rapid reaction to DHHP takes place.
Therefore, the reaction is preferably carried out in an acidic aqueous medium and with addition of an emulsifier or of a water-miscible solvent.
As water-miscible solvent there can be used: triethyl phosphate, tetrahydrofuran, 1,4-dioxane, glycols or glycol ethers, of which triethyl phosphate is especially preferred.
Especially suitable emulsifiers are non-ionic oxyethylates of aliphatic fatty alcohols or oxoalcohols with 10 to 18 carbon-atoms, such as C.sub.13 /C.sub.15 -oxoalcohols with 8 to 10 mol ethylene oxide; C.sub.10 -oxoalcohol with 6 to 7 mol ethylene oxide; C.sub.13 -oxoalcohol with 8 mol ethylene oxi

REFERENCES:
patent: 2996549 (1961-08-01), Mageli
patent: 4154768 (1979-05-01), Leveskis
Chemische Berichte vol. 88, pp. 712-716, Criegee, May 1955.
Mar. "Advanced Organic Chemistry" p. 617, 1968.
Morrison and Boyd "Organic Chemistry" 3rd edition, pp. 166-171, 1975.

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