Benzoyl peroxide ketones

Derivative Formation. Hydrogen peroxide is an important reagent in the manufacture of organic peroxides, including tert-huty hydroperoxide, benzoyl peroxide, peroxyacetic acid, esters such as tert-huty peroxyacetate, and ketone derivatives such as methyl ethyl ketone peroxide. These are used as polymerization catalysts, cross-linking agents, and oxidants (see Peroxides and peroxide compounds). 

The reaction rate of fumarate polyester polymers with styrene is 20 times that of similar maleate polymers. Commercial phthaHc and isophthaHc resins usually have fumarate levels in excess of 95% and demonstrate full hardness and property development when catalyzed and cured. The addition polymerization reaction between the fumarate polyester polymer and styrene monomer is initiated by free-radical catalysts, commercially usually benzoyl peroxide (BPO) and methyl ethyl ketone peroxide (MEKP), which can be dissociated by heat or redox metal activators into peroxy and hydroperoxy free radicals. 

Organic Peroxides — (R-O-O-R) are very hazardous. Most of the compounds are so sensitive to friction, heat, and shock that they cannot be handled without dilution. As a result, organic peroxides present a serious fire and explosion hazard. Commonly encountered organic peroxides include benzoyl peroxide, peracetic acid, and methyl ethyl ketone peroxide. 

About 8,000 metric tons of peroxides were consumed in 1972. This consumption was strongly stimulated by the rapid growth in reinforced plastics (Ref 23). The largest volume product is benzoyl peroxide which is used in polystyrene and polyester markets for such items as toys, automobiles, furniture, marine, transportation and mil requirements. Also, methyl ethyl ketone peroxide is used in large volumes to cure (as a catalyst) styrene-unsatur-ated polyester adhesive resins used in mil ammo adhesive applications, as well as in glass fiber reinforced plastic products such as boats, shower stalls, tub components, automobile bodies, sports equipment, etc. The monoperesters are growing slowly because of some substitution of the peroxydicarbonates and azo compds (Refs 8,9 23)... 

The polyester product is first dissolved in styrene at a level of 60 % polyester and 40 % styrene. The initiators, either benzoyl peroxides (BPOs) or methyl ethyl ketone peroxide (MEKP), with appropriate co-catalysts, are added. The mixture is then poured into a glass mold and cured at room temperature for the MEKP system or at 100 °C for the BPO systems. A post-cure at 100 °C or 130 °C, respectively, for 5 h is then carried out. Blending experiments were carried out by using a dicyclo pentadiene (DCPD) resin, 61-AA-364, from GLS Fiberglass (Woodstock, IL, USA). This sample is pre-promoted , so we could only use the MEKP system. 

PEER polymers can be cured with traditional radical initiators such as methyl ethyl ketone (MEK) peroxides and benzoyl peroxide (BPO). Curing can be carried out either at room temperature or at elevated temperature. A PEER polymer containing 30 % maleic anhydride can be cured at room temperature with MEK peroxides in 10 to 60 min, depending on the type of peroxide used (Table 22.2). To cure a PEER resin with MEK peroxides at room temperature, a co-catalyst is needed. The commonly used cobalt naphthenate works very well in this case, while another co-catalyst, dimethyl aniline, is very efficient for the BPO system. 

Halogens are frequently used as oxidation agents and, under two-phase conditions, they can either be employed as ammonium complex halide salts [3], or in the molecular state with or without an added quaternary ammonium catalyst [4]. Stoichiometric amounts of tetra-n-butylammonium tribromide under pH controlled conditions oxidize primary alcohols and low-molecular-weight alkyl ethers to esters, a,cyclic ethers produce lactones [3], and secondary alcohols yield ketones. Benzoins are oxidized to the corresponding benzils (80-90%) by the tribromide salts in acetonitrile in the presence of benzoyl peroxide [5]. 

The a-halo ketone has also been prepared in situ (NBS, benzoyl peroxide, light) [89IJC(B)500]. Similarly, imidazo[2,l-b][l,3,4]thiadiazoles are accessible from 2-amino-l,3,4-thiadiazoles and acetophenones in the presence of hydroxy(tosyloxy)iodobenzene (HTIB). This latter method has been proposed as more convenient and versatile than the reaction of 2-amino-1,3,4-thiadizoles with a-halo ketones [94IJC(B)686, 94JCR(S)38, 94MI5],... 

Cyclohexanol and cyclohexanone are made by the air oxidation of cyclohexane (81%) with a cobalt(II) naphthenate or acetate or benzoyl peroxide catalyst at 125-160°C and 50-250 psi. Also used in the manufacture of this mixture is the hydrogenation of phenol at elevated temperatures and pressures, in either the liquid or vapor phase (19%). The ratio of alcohol to ketone varies with the conditions and catalysts. 

The most recent work210 on sensitized decomposition of peroxides dealt primarily with ketones (cf. Section III.C.3) although it was also demonstrated that anthracene could sensitize decomposition of benzoyl peroxide. In view of the earlier work206,209 and the fact that benzoyl peroxide quenches anthracene fluorescence at a rate of 1.0 x 1010M 1 sec-1 in benzene,211 a singlet exciplex mechanism is strongly implicated. 

While most vinyl ketones readily undergo radical polymerization, and can only be stored in the monomeric state if an inhibitor is present, this enone failed to polymerize with either benzoyl peroxide or azobisisobutyronitrile under a variety of conditions. Examining the C-13 NMR spectrum of the monomer provides some insight into the lack of reactivity displayed by this unsaturated ketone. 

Benzoyl Peroxide and Azobisisobutyronitrile-Initiated Graft Copolymerization. Cellulose nitrate (CN) (10 g) was dissolved in methyl isobutyl ketone (90 ml) in a three-necked flask and to this solution methyl methacrylate (10 ml) and benzoyl... 

Oxybenzoylation of enamines of cyclic ketones by benzoyl peroxide was performed in the early sixties51,52. The corresponding 2-benzoyloxycycloalkanones were formed (Scheme 35). 

Oxalyl chloride yields COCl radicals on photolysis and this reaction has been used to directly substitute alkanes with the chloroacyl group (equation 30). Similarly, biacetyl reacts with alkanes in a benzoyl peroxide-initiated chain reaction to give ketones in ca. 60-70% yield (equation Cyanogen... 

Preformed enolates are susceptible to further methods of oxygenation. For example treatment with LTA in benzene effects a-acetoxylation at lower temperature and more rapidly than the corresponding enol examples. Similarly a-benzoylation using benzoyl peroxide is possible for both lactones and 3-keto esters and presumably could be used for less-activated ketones. 

Racemic kjellmanionone (123) has also been prepared by direct oxidation of the potassium enolate of die ketone (122) with MCPBA and, if general, this would represent a convenient procedure. Oxidation of ketones with benzoyl peroxide is of no synthetic value (vide supra), but the process becomes useful if enolates are employed. Treatment of enone (126) with LDA in THF at 0 C followed by quenching with... 

Benzoyl peroxide, C HsCO-O-O-COCtHg, or methyl ethyl ketone peroxide, CH3C2Hs-C(0-0) CCzH5 CH3 is used as a catalyst. To initiate the reaction at room temperature it is necessary to add another substance ouch as cobalt naphthenate, (Cdimethyl aniline, C H (CH3), to produce an initiator, e.g. free radicals C6H C 00(benzoil radical). 

---