Xylenes, as solvents

Acetone in conjunction with benzene as a solvent is widely employed. With cyclohexanone as the hydrogen acceptor, coupled with toluene or xylene as solvent, the use of higher reaction temperatures is possible and consequently the reaction time is considerably reduced furthermore, the excess of cyclohexanone can be easily separated from the reaction product by steam distillation. At least 0 25 mol of alkoxide per mol of alcohol is used however, since an excess of alkoxide has no detrimental effect 1 to 3 mols of aluminium alkoxide is recommended, particularly as water, either present in the reagents or formed during secondary reactions, will remove an equivalent quantity of the reagent. In the oxidation of steroids 50-200 mols of acetone or 10-20 mols of cyclohexanone are generally employed. 

Yields obtained from catalyst prepared from 125 gm of aluminum-nickel alloy. In xylene as solvent. 

Schrader prepared the ester (38) in 60% yield by reaction of sodium p-nitrophenate with diethyl chlorophosphate, using xylene as solvent for the reaction. He made it, but in lower yields, from p-nitrophenol and diethyl chlorophosphate, using, respectively, pyridine and sodium cyanide as acceptors for hydrogen chloride. Schrader also prepared it in 96% yield by nitrating diethyl phenyl phosphate at 0° C. or below. Under the conditions he used, Schrader claims that the nitro group is directed to the para position. No yield is given for the diethyl phenyl phosphate, which he presumably made from sodium phenate and diethyl chlorophosphate. Diethyl chlorophosphate may be prepared in high yield (30) from diethyl phosphite and chlorine. 

This reaction is applicable to a dithienotropone synthesis starting from tropone 2,7-bis(thioether). An earlier attempt at rearrangement of 2-(allylthio)tropone with xylene as solvent failed (59MI2). 

With hot xylene as solvent, compound 81 was obtained as the sole product. In this latter case the reaction proceeds via a Diels-Alder addition of 79 with DMAD followed by elimination of a nitrile (R CN). In aprotic polar solvents an imidazo[l,2-fl]pyridine (82) is formed. This reaction can be considered to be a 1,3-dipolar cycladdition of 84 with 2 mol DMAD via a 1,4-dipolar intermediate. 

Tetrabenzoylethane (315) and freshly prepared phosphorus pentaselenide were reacted in both pyridine and xylene as solvents. In either case, only the reduced selenides (316) (cis/trans) were formed, along with minor amounts of the substituted selenophenes (317) and (318 Scheme 109) (77CS(l2)li). 

However, it has been shown67-69 that the structure of the final product may depend on the experimental procedure. For example, if phenylacetylene reacts with 5-phenyl-l,2-dithiole-3-thione in xylene in the presence of hydrochloric acid, the l,3a IV,4-trithiapentalene is obtained but by using neutral dry xylene as solvent, a l,6,6a IV-trithiapentalene is formed which can also be obtained by heating the l,3aiSIV,4-isomer with phosphorus pentasulfide in tetrahydronaph-thalene (Scheme 14).67,68... 

There are two types of enamels, industrial and household. Industrial enamels are produced with toluene or xylene as solvents household enamels, with petrol or butylacetate. Silicone enamels are attractive, tough, atmosphere-resistant, durable and exceptionally hard. 

Similar observations were made with TBHP-S02-initiated polymerization of MMA at 50 °C. using benzene, toluene, and xylene as solvents and at 60°C. using chloroform as the solvent (Figure 7). Among the three aromatic hydrocarbons used, the rate enhancement is of the order xylene > toluene > benzene. 

A practical examle of this kind of measurement is the study by Sato and Otsu of di-tert. -butyl peroxalate decomposition in p-xylene as solvent in the presence of vinyl monomer and 2-methyl-2-nitrosopropane (at room temperature the initiator is decomposed into Me3CO and C02). Due to repulsive forces, the spin-trapping agents reluctantly react with oxyl radicals. Therefore the following reactions mutually compete... 

Silphenylenes, aromatic-containing silicon monomers, can be produced in 50 88% yields by the reaction of halo- and dihalobenzenes with chloro- and alkoxysilanes under Barbier conditions. Iodine, bromine, and cuprous chloride are used as initiators with THE, TMEDA, toluene, or xylene as solvents. Shavings or powdered magnesium can be used [Eqs. (66) and (67) 134,135]. 

The checkers report that evaporation of decane is excessively slow. They found that the synthesis works equally well using xylenes as solvent, and the evaporation is more efficient. 

The kinetic experiments were carried out with VO-TPP and o-xylene as solvent in a 250 ml batch autoclave. Approximately 80 mg of catalyst (pellet diameter 63 -160 pm) was weighed and introduced in the reactor. The catalyst was sulfided in situ for two hours with dimethyldisulfide (623 K, 6.0 MPa Hj). After sulfiding, VO-TPP dissolved in o-xylene (total reaction volume 125 ml) was introduced. The reactor was filled to 0.34 MPa with a mixture of 15 mol % HjS in Hj. Next Hj was added to a total pressure of 5.0 MPa and the reactor was heated to a temperature of 553 K. 

To evaluate the effect of molecular solvents, the above mentioned reactions were carried out using methanol, water, acetonitrile, and xylene as solvents and the reactions were found to be very slow (10 0%) even after 12-24 h. It is important to note that in water, no reaction took place, even after 24 h. Acceleration of these oxidation reactions in [bmim][Br] can be demonstrated by its ability to act as both a phase transfer catalyst and a solvent. Most importantly, [bmim][Br] and CoPc could be recycled and reused in further reactions for six runs. 

A bis-borane adduct of selenium is formed in reaction (27) (in xylene as solvent). 

In dehalogenating the phenylaluminum chlorides with sodium it is best to work with xylene as solvent. The complex salts which are formed as an intermediate react further at above 100°C. Triphenylalane is obtained in high yield in this way from the corresponding phenylaluminum chlorides, but the compound usually contains some chlorine. A substantially better method for preparing pure triphenylalane is by the reaction of dimethyl-aluminum chloride with sodium phenyl the resulting dimethylphenylalane disproportionates on distillation at reduced pressure to pure triphenylalane and trimethylalane (171) ... 

Player and coworkers have developed a facile parallel synthesis of a 48-membered library of benzoxazoles using two efficient methods in solution. Both methods involve the use of 2-aminophenol, acid chloride, with dioxane (or xylene) as solvent in a sealed reaction vessel for a reaction time of 15 min at 210 °C (or 250 °C). All benzoxazoles were obtained in good to excellent yields (46-98%) [47]. The use of... 

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