Bromide and benzene

Silver trifluoroacetate is used in a one step synthesis of bicyclo[3 2 2]nona-6,8-diene-3-one from 2-methoxyallyl bromide and benzene [50] (equation 23) Analogous reactions of toluene, p-xylene, and mesitylene yield the corre spending substituted bicyclo[3 2 2]noiia-6,8-diene-3-ones [50]... 

Analysis and mass spectrometry showed it to have the molecular formula C HeBrFa. This could have been formed by the addition of magnesium bromide to tetrafluorobenzyne followed by the elimination of magnesium bromide-fluoride to give bromotrifluorobenzyne (30) and hence the compound (31). Analysis of the 19F n.m.r. spectrum and more particularly the preparation of (31) from o-bromotetrafluorophenyl-magnesium bromide and benzene confirmed the suggested mechanism. In this latter reaction the ratio of (31) to (24) was 99 1 54>. 

A small amount of sodium benzenesulfinate was then added to react with the excess bromine. Filtration removed sodium bromide, and benzene was used to wash the filtrate (51 g. dry weight, 0.5 mole). Solvent was first removed from the filtered solution and combined washings on a rotary evaporator and finally by vacuum distillation. Vacuum distillation of the crude product (b.p. 76-78° at 0.17 mm.) gave 106.3 g. (92.2%) of benzenesulfonyl bromide.4... 

When the Pt loading was decreased from 1% to 0.5%, 0.3%, and 0.1%, activity test results showed that reducing the Pt metal loading on the support decreased the catalytic activity, as expected. However, 0.5% Pt/Zr02 had an activity only slightly less than that of 1% PhZr02. As shown in Figure 5, about 75% CO was oxidized at 200°C. More than 60% of methyl bromide and benzene were converted at 300°C. 

This reaction was initially studied by Anschutz between 1879 and 1886. It is the synthesis of anthracene from vinyl bromide and benzene in the presence of aluminum chloride. In addition, methyl phenyl carbinol or 1,1-diphenyl ethane can also be converted into anthracene derivative in the presence of aluminum chloride. 

In addition to the support materials, the effect of precious metal content on the catalyst performance was also studied. Pt loading has a strong impact on the catalyst activity when oxidizing methyl bromide and benzene. For other emissions, such as CO, methyl acetate, xylene, etc., lowering Pt content has little effect on the conversion. 

Copper 1) chloride, bromide and cyanide were used by Sandmeyer to introduce a chlorine, a bromine atom and a cyanide group respectively into a benzene ring by addition to the phenyl diazonium salt. 

Another method for the hydrogenoiysis of aryl bromides and iodides is to use MeONa[696], The removal of chlorine and bromine from benzene rings is possible with MeOH under basic conditions by use of dippp as a ligand[697]. The reduction is explained by the formation of the phenylpalladium methoxide 812, which undergoes elimination of /i-hydrogen to form benzene, and MeOH is oxidized to formaldehyde. Based on this mechanistic consideration, reaction of alcohols with aryl halides has another application. For example, cyclohex-anol (813) is oxidized smoothly to cyclohexanone with bromobenzene under basic conditions[698]. 

Violent reaetions have oeeuiTed between ozone and many ehemieals, a small seleetion being aeetylene, alkenes, dialkyl zines, benzene/mbber solution, bromine, earbon monoxide and etliylene, diethyl ether, hydrogen bromide, and nitrogen oxide. 

Swain and Eddy have queried the wide applicability of the S l and Sif2 mechanisms and favored a push-pull termolecular process for the reaction of pyridine with methyl bromide in benzene solution for example, they have suggested that the effects observed on the addition of methanol, phenol, p-nitrophenol, and mercuric bromide to the reaction mixture can be explained by an intermediate of type 168. ... 

By boiling allyl bromide and pyrogallol dimethyl ether with acetone and potassium carbonate, he obtained a dimethoxyphenyl allyl ether, which was converted into dimethoxyallyl phenol by heating to 220°. On methylation this yields trimethoxyallyl benzene, identical with elemicin. 

Stage 2 Preparation of 1 -[2-Phenyi-2-Methoxy]-Ethyi-Piperazine — 210 grams of 2-phenyl-2-methoxy-ethyl bromide and 260 grams of anhydrous piperazine are heated for 5 to 6 hours to reflux in 600 ml of ethanol, 500 ml of ethanol is then distilled off and finally the solvent is removed in vacuo. The residue is taken up in 250 ml of benzene and the piperazine hydrobromide is filtered off. The benzene is removed in vacuo. The oily residue is taken up by 450 ml of water and acidification is effected up to pH = 1 by concentrated HCI. 

Propyl-methyl-carbinyl allyl barbituric acid (also called allyl 1-methyl-butyl barbituric acid) may be prepared as follows 1 mol of propyl-methyl-carbinyl barbituric acid is dissolved in a suitable vessel In a 10 to 35% aqueous solution of 1 mol of potassium hydroxide. To this are added somewhat in excess of 1 mol of allyl bromide, and alcohol equal to about 10% of the total volume of the solution. The vessel Is agitated for 50 to 75 hours. At the end of this time, the solution, which may still exhibit two layers, is concentrated to about one-half its volume to remove the excess allyl bromide and the alcohol. On cooling, an oily layer, which is propyl-methyl-carbinyl allyl barbituric acid, separates out as a sticky viscous mass. It is dried, washed with petroleum ether, and dissolved in the minimum amount of benzene. Any unreacted propyl-methyl-carbinyl barbituric acid, which does not dissolve, is filtered off. The addition of petroleum ether to the clear filtrate causes the propyl-methyl-carbinyl allyl barbituric acid to precipitate as an oily mass. 

The knowledge of the valence tautomerization of benzene oxides to oxepins12 prompted several groups to synthesize oxepins by dehydrohalogenation of 7-oxabicyclo[4.1.0]heptane derivatives. Numerous examples have been described for the base-catalyzed elimination of hydrogen bromide from the 3,4-dibromo-7-oxabicyclo[4.1.0]heptane system. The reaction products are usually obtained as mixtures of oxepin 1 and benzene oxide 2. The 2,7-bis(hydroxy-methyl)oxepin 1 p obtained by this route can be converted to the 2,7-dicarbaldehyde with man-ganese(IV) oxide.23... 

Photolysis of ethyl l-azido-A-cyanoformimidate (21) (readily prepared by the treatment of 5-ethoxytetrazole with cyanogen bromide) in benzene produces a 1.17 1 mixture (not separated) of l-(jV-cyanoethoxycarbonimidoyl)-l//-azepine(22) and 2-ethoxy-l-phenylisourea-3-carboni-trile (23).166 More recently, a similar reaction has been reported under thermal conditions.293... 

The method described here is a modification of that of Schoeller.1 Diphenyl selenide has also been prepared from diazotized aniline and alkali monoselenides 2 by the Friedel-Crafts reaction with benzene and selenium tetrachloride3 or selenium dioxide 4 from diphenyl sulfone and selenium 5 from phenylmagnesium bromide and selenium,6 selenium dichloride,7... 

Robertson et al.261 measured rates of bromination of some aromatic hydrocarbons in acetic acid containing sodium acetate (to eliminate protonation of the aromatic by liberated hydrogen bromide) and lithium bromide (to reduce the rate to a measurable velocity ) at 25 °C, the second-order rate coefficients for 3-nitro-N,N-dimethylaniline and anisole being 14.2 and 0.016 respectively the former compound was thus stated to be about 1012 times as reactive as benzene (though no measurement of the latter rate coefficient, inferred to be 1.33 xlO-11, could be found in the literature) and this large rate spread gives one further indication of the unreactive nature of the electrophile. Other rates relative to benzene were ... 

Cross-alkylations have been reported on a number of occasions. Thus, ethylbenzene when treated with aluminium bromide and hydrogen bromide at 0 °C forms some benzene and diethylbenzene168, and in the sulphonation of durene some trimethyl- and pentamethyl-benzenesulphonic acids are formed as well as the tetra-methyl compound. It has been suggested169 that these transfer reactions involve an SN2 type process... 

Arenes are unsaturated but, unlike the alkenes, they are not very reactive. Whereas alkenes commonly take part in addition reactions, arenes undergo predominantly substitution reactions, with the TT-bonds of the ring left intact. For example, bromine immediately adds to a double bond of an alkene but reacts with benzene only in the presence of a catalyst—typically, iron(III) bromide—and it does not affect the bonding in the ring. Instead, one of the bromine atoms replaces a hydrogen atom to give bromobenzene, C H Br ... 

The reaction of 1-alkoxynaphtalenes with copper (II) bromide in benzene produced a mixture of 4-bromo-1-alkoxynaphtalenes and 4,4 -dialkoxy-l,l -binaphtyls. For instance, the reaction of 1-methoxynaphtalene 4 with copper(II) bromide in refluxing benzene for 2 h. gave a mixture of 4-bromo-1-methoxy-naphtalene 5 (47 %) and 4,4 -dimethoxy-l,l -binaphtyl 6 (45 %). In contrast, in similar reaction using alumina-supported copper(II) bromide at 30°C, only dimerization occurred and no brominated compounds were obtained. 

For example, while reaction of 2-butoxynaphtalene with copper(II) bromide in benzene at 50°C for 2 h. produced only 6 % yield of l-bromo-2-butoxynaphtalene, similar reaction with Kieselguhr-supported copper(II) bromide gave 86 % yield of the monobromide. On the other hand, reaction using alumina as a support in benzene proceeded completely even at 10°C in 1 h. to give in addition to the monobromide (77 %), the dibromide (21 %) and the binaphtyl (2 %). 

The reaction of 2-methylthionaphtalene with copper(II) bromide in benzene at 50°C yielded no detectable products after 5 h. In contrast, in similar reaction using alumina-supported copper(II) bromide, l-bromo-2-methylthionaphtalene was obtained in 92 % yield after 1 h. Although 1-methoxynaphtalene reacted with alumina-supported copper(II) bromide to give only the binaphtyl, reaction of 1-methylthionaphtalene with alumina-supported copper(II) bromide afforded only 4-bromo-l-methylthionaphtalene (75 %) and the dimerization did not take place. 

Bis(glyoximato)cobalt(II) complexes of the types Co(DH)2B2 and Co(DH)2B2 (DH = disubstituted glyoxime, B = base, e.g. pyridine or triphenylphosphine) reduce benzyl bromide in benzene and acetone solutions ... 

---