A-Methyl styrene, oxidation

Methyltriphenylarsonium iodide, acetophenone and [ Hjwater gave a-methyl styrene oxide 82 (80%) labelled with tritium both in the oxirane ring and on the methyl group through the formation of a ylide intermediate 83 as shown in equations 58a,b,c. 85% yield colourless oil, b.p. 86°C/18 torr, radiochemical purity 98%, specific activity 5.44 mCimmoP ... 

One year later, the same authors studied the biohydrolysis of seven differently substituted a-methylstyrene oxide derivatives, including the para-bromo-a-methyl styrene oxide, using ten different EHs [14]. The best results were obtained with the... 

Kinetic hydrolytic resolution at high substrate concentration of para-bromo-a-methyl styrene oxide using an enzymatic extract of Aspergillus niger LCP 521. 

Preparative-scale synthesis of enantiopure para-trifluoromethyl-a-methyl styrene oxide using a partially purified recombinant EH from Aspergillus niger LCP 521 as a biocatalyst. 

Cleij, M., Archelas, A. and Furstoss, R. (1998) Microbiological transformations. Part 42 A two-liquid-phase preparative scale process for an epoxide hydrolase catalysed resolution of parfl-bromo-a-methyl styrene oxide. Occurrence of a surprising enantioselectivity enhancement. Tetrahedron Asymmetry, 9, 1839-1842. 

Hydroperoxide Process. The hydroperoxide process to propylene oxide involves the basic steps of oxidation of an organic to its hydroperoxide, epoxidation of propylene with the hydroperoxide, purification of the propylene oxide, and conversion of the coproduct alcohol to a useful product for sale. Incorporated into the process are various purification, concentration, and recycle methods to maximize product yields and minimize operating expenses. Commercially, two processes are used. The coproducts are / fZ-butanol, which is converted to methyl tert-huty ether [1634-04-4] (MTBE), and 1-phenyl ethanol, converted to styrene [100-42-5]. The coproducts are produced in a weight ratio of 3—4 1 / fZ-butanol/propylene oxide and 2.4 1 styrene/propylene oxide, respectively. These processes use isobutane (see Hydrocarbons) and ethylbenzene (qv), respectively, to produce the hydroperoxide. Other processes have been proposed based on cyclohexane where aniline is the final coproduct, or on cumene (qv) where a-methyl styrene is the final coproduct. 

If the side chain is in an iso form, a more complex aromatic olefin forms. Isopropyl benzene leads to a methyl styrene and styrene [70], The long-chain alkylate aromatics decay to styrene, phenyl, benzyl, benzene, and alkyl fragments. The oxidation processes of the xylenes follow somewhat similar mechanisms [71, 72],... 

Treatment of tt-methylstyrene oxide with f ri-butylmagnemuii chloride or phenylmagneaium bromide has been reported 24 171 p. yield 4,4-dimethyl 2phemyl-S-pentanol and 1.2-diphenyl-1-propanol respectively (Eq. 843). Both products presumably arise from methyl-phenylsoetsldehyde, formed by preliminary isomerization of a-mcthyl-styrene oxide. 

In some cases, oxidation of double bonds does not stop at the epoxide, but proceeds further to oxidative cleavage of the double bond. It was reported that the reaction of a-methyl styrene with H2O2 in the presence of TS-1 or TS-2 produces a-methyl styrene epoxide (15%), a-methyl styrene diol (10-40%) and acetophenone (40-60%) (Reddy, J. S. et al., 1992). However, results similar to those obtained with titanium silicates were obtained for many other catalysts, such as HZSM-5, H-mordenite, HY, A1203, HGa-silicalite-2, and fumed Si02. These materials have much different properties and differ significantly from titanium silicates thus, the results cast some doubt on the role of the catalyst in this reaction. Furthermore, the oxidation of styrene is reported to proceed with C=C cleavage and formation of benzaldehyde, in contrast to previous reports of the formation of phenylacetaldehyde with 85% selectivity (Neri et al., 1986). 

Anionic polymerization techniques and naphthalene chemistry were used by Teyssie et al. to prepare A2B miktoarm stars, where A is poly(ethylene oxide) (PEO) and B is PS, PI, poly(a-methyl styrene) or poly(tert-butyl styrene) [25]. The reaction sequence is shown in Scheme 7. 

Table 7 Asymmetric dihydroxylation of a-methyl styrene with different selenoxides as co oxidants ...

A block copolymer of styrene and ethylene oxide has also been prepared in this manner (70, 69). a-Methyl styrene in sodium-naphthalene-tetrahydrofuran also polymerized at — 78°. The polymerization is... 

Heterogeneous systems have also been developed for the cleavage of olefins with hydrogen peroxide.174,175 Titanium-containing zeolites can be used to cleave olefins.176 Adam and co-workers have recently shown that acetophenone, an oxidation product from the Ti-zeolite catalysed oxidation of a-methyl-styrene, derives from 2-hydroxyperoxy-2-phenylpropan-l-ol as an intermediate (which they detected and isolated) (Figure 3.34).177... 

In general, the above equations are best solved in a computer. Goto et al.9 obtained a solution to the case where species C is in excess so that the reaction is pseudo-first-order. They used the solution to analyze the efficiency of reaction systems such as oxidation of ethanol, hydrogenation of a-methyl styrene, and hydrogenation of aniline. They defined... 

METHYL STYRENE or 3-METHYL STYRENE or 4-METHYL STYRENE or m-METHYL STYRENE or p-METHYL STYRENE mixed Isomers (25013-15-4) C,H,o Flammable liquid. Forms explosive mixture with air (flash point 125°F/51°C). An inhibitor, usually 10 to 50 ppm of tert-butyl catechol, must be present in adequate concentrations to avoid explosive polymerization. Violent reaction with strong oxidizers, strong acids, peroxides and hydroperoxides. Incompatible with catalysts for vinyl or ionic polymers aluminum, aliuninum chloride, ammonia, aliphatic amines, alkanolamines, caustics, copper, halogens, iron chloride, metal salts (e.g., chlorides, iodides, sulfates, nitrates). The uninhibited monomer vapor may block vents and confined spaces by, forming a solid polymer material. On small fires, use dry chemical powder (such as Purple-K-Powder), foam, or CO extinguishers. a-METHYL STYRENE (98-83-9) C,H, Flammable liquid. Forms explosive mixture with air [explosion limits in air (vol %) 0.9 to 6.1 flashpoint 129°F/54°C autoignition temp 1066°F/574°C Fire Rating 2]. Easily polymerizable. Unless inhibited, forms unstable peroxides. Reacts with heat and/or lack of appropriate inhibitor concentration. Reacts with catalysts for vinyl or ionic polymerization, such as aluminum, iron chloride or 2,5-dimethyl-2,5-di(ieri-butylperoxy)hexane. Violent reaction with... 

Figure 3. C NEXAFS spectrum of polymers. PS polystyrene, PaMS Poly (a-methyl styrene), PDMPO poly(dimethyl p-phenylene oxide). The peaks 1 through 8 correspond to the C Is transitions into orbitals of C=C n (peak 1), bC=C (peak 2), C-H a (peak 3), C=C n (peak 4), ionization threshold (peak 5), C-C a (peak 6), bC-C a and C-O a (peak 7), and C=C a (peak 8). [Reprinted with permission of Elsevier Science from Kikuma and Tonner (1996)]...

Allylic olefins of higher molecular weight than propylene can also be converted to the corresponding a-3 unsaturated nitriles, aldehydes, and dienes by catalytic vapor phase oxidation and ammoxidatlon. Examples include the conversion of isobuthylene to methacrylonitrile ( eq. 14) or methacrolein ( eq. 16 ), a-methyl styrene to atroponitrile ( eq. 15 ) or atropoldehyde ( eq. 17), and 2-methylbutene to isoprene (eq. 18). 

Li and coworkers have reported BiuNI-catalyzed allylic sulfonylation of a-methyl styrene derivatives with sulfonyl hydrazides 143 using TBHP (Bu OOH) as the terminal oxidant (Scheme 4.73) [115]. The mechanism of this reaction involves the generation of sulfonyl radicals, Ts, from sulfonyl hydrazides 143 by the BU4NI/TBHP catalytic system, followed by the addition of Ts to a-methyl styrene derivatives 142 to give the corresponding allylic sulfones 144. 

Research in this area has resulted in the preparation of several comb polymers (Halasa, 1974 Folket al., 1044). The metallation technique is a useful and versatile method as it can be used with any polymeric material that contains a few double bonds. For example, ethylene-propylene was successfully grafted with norbornene. Similar reactions were performed on polymeric materials that contain aromatic rings, such as polystyrene, poly-a-methyl styrene, and polyphenylene oxide (PPO). 

Pseudo first order reactions with respect to the gaseous reactant, i,e, in case of large excess of B, have been studied in detail to describe systems as oxidation of ethanol, hydrogenation of a-methyl styrene, hydrogenation of aniline etc. Limiting cases, such as plug flow of both gas and liquid phases [46] or a constant concentration in the gas phase [48], were analysed as well as the general case of finite values of dispersion coefficients in both phases [52,58],... 

Conformational (steric) effects and ring strains contribute to strain energies. The quantity — E p is obtained experimentally from the difference between calculated and experimentally obtained enthalpies of polymerization. Steric effects shift the enthalpy of polymerization to more positive values, as can be seen from the examples of styrene/a-methyl styrene or ethylene oxide/propylene oxide (Table 16-13). 

---