Phenylethyl bromide , reaction

The same idea will explain an experiment in which a styrene phial (20 mmole) was broken at -10 °C into 100 ml of a 6 x 10 3 M solution (C104" content) of the coloured ionic reaction product between AgC104 and 1-phenylethyl bromide (see above). Because of the rather slow initial mixing, the colour of the solution was not completely discharged by the styrene, and a violent polymerisation ensued, at least 100 times faster than the reaction catalysed by an equivalent amount of perchloric acid would have been. 

Since we could not prepare a stable solution of the ester, we attempted its preparation in the styrene solution to be polymerised. Silver perchlorate was dissolved in this and the reaction was started by the crushing of a phial containing 1-phenylethyl bromide (under our conditions styrene was not polymerised by the silver perchlorate alone). The solutions became cloudy because of the formation of colloidal silver bromide, but no colour formation could be observed until the end of the polymerisation then the solutions became yellow, very like the reaction mixtures in which perchloric acid had been used as catalyst. The ester was found to be as effective a catalyst as anhydrous perchloric acid. Equal concentrations of the ester and the acid produced very similar polymerisations as shown in the Figure. The accelerating parts of the curves obtained with the ester as catalyst are readily explained by the fact that the reaction between silver perchlorate and 1-phenylethyl bromide is not instantaneous and therefore a steady increase in catalyst concentration characterises the first part of the polymerisation. 

The ester hypothesis is supported by experiments in which the ester was formed in situ by the reaction of 1-phenylethyl bromide with silver perchlorate in the presence of styrene. These gave results in close agreement with those obtained with perchloric acid [6]. Propagation by the ester is envisaged as addition of the two parts of the ester across the double bond of the monomer in modern terminology this is an insertion . 

Figures 3-21 and 3-22 show results in the ATRP polymerization of styrene using 1-phenylethyl bromide as the initiator, CuBr as catalyst (activator), and 4,4-di-5-nonyl-2,2 -bipyridine as ligand [Matyjaszewski et al., 1997]. Figure 3-21 shows the decrease in monomer concentration to be first-order in monomer, as required by Eq. 3-223. The linearity over time indicates that the concentration of propagating radicals is constant throughout the polymerization. The first-order dependencies of Rp on monomer, activator, and initiator and the inverse first-order dependence on deactivator have been verified in many ATRP reactions [Davis et al., 1999 Patten and Matyjaszewski, 1998 Wang et al., 1997].

The present procedure is that of Ing and Manske1 and avoids the troublesome preparation of potassium phthalimide. Diphthalimide-propane and a-bromopropyl phthalimide are conveniently prepared by the same general procedure. In a similar manner, /3-phenylethyl bromide gives a 76 per cent yield of /3-phenylethyl phthalimide while only a very small amount of styrene is formed in the reaction. The only other feasible preparative method for benzyl phthalimide is from benzyl chloride and potassium phthalimide.2... 

Racemic a-phenylethyl bromide is carbonylated under phase-transfer conditions with 5 N NaOH and dichloromethane containing bis-(dibenzylideneacetone)Pd(O) and a chiral 2-substituted 3,1,2-oxaza-phospholane to give a-phenylpropionic acid in moderate ee (Scheme 83) (196). The reaction involves kinetic resolution of the bromide with a discriminative slow oxidative addition step. 

The procedure given above is an adaptation of the methylation method first used by Sommelet and Ferrand3 and developed more fully by Clarke, Gillespie, and Weisshaus.2 /3-Phenylethyldi-methylamine has been prepared from /9-phenylethylamine by alkylation with dimethyl sulfate 4 by the reaction of fi-phenyl-ethylamine and of N-methyl- S-phenylethylamine with formaldehyde 6 by catalytic reduction of phenylacetonitrile in the presence of dimethylamine 3 by the reaction of dimethylamine with /3-phenylethyl chloride 7 8 9 and with /3-phenylethyl bromide 9 and by the reaction of phenylacetaldehyde with dimethylamine.10... 

When this reaction was interrupted, and unconsumed jS-phenylethyl bromide recovered, it was found by mass spectrometric analysis to contain no deuterium. Similar experiments with other systems have given similar results in typical second-order elimination reactions there is no hydrogen-deuterium exchange. 

Here the process is truly a simultaneous one and does not proceed in the stepwise manner which is indicated. This has been shown by an experiment carried out with 0-phenylethyl bromide in a solution of C2H6OD containing sodium ethylate. After the elimination of hydrogen bromide was about half completed, the still unreacted organic bromide was found to contain no deuterium.2 If reactions 1 and 2 proceeded faster than 3, the starting material would have been equilibrated with deuterium at this point by the reactions ... 

The kinetic resolution of racemic 1-phenylethyl bromide was examined in the alkylation of benzoic acid using trisubstituted monocyclic guanidines as chiral sources [67]. (R)-Excess ester was obtained in 96% yield even with 15% ee, when the reaction was carried out in benzene with l,3-dimethyl-(45,55)-diphenyl-2-[(15)-phenylethylimino]imidazolidines [27a] (Scheme 4.25). 

Thus, direct determination by EPR of coppa Il) species was reported by Matyjaszewski and coworkers [139] in the case of styrene ATRP. The polymerization proceeds by monomer addition to free radicals reversibly generated by an atom transfer process from dormant polymer chains with halide end-groups. In these reactions, a small amount of copper(II) species was used as a deactivator which moderates rates and keeps low polydispersity. An example of time-dependent EPR signals of copper species in the ATRP of styrene in toluene, initiated by 1-phenylethyl bromide (styrene/l-phenylethyl bromide/CuBr/ dNbipy=l(X)/l/l/2) at 110°C is shown in Figure 10.7 [139]. 

The reaction of an organostibanyl anion, which was reduc-tively generated from the diorganostibanyl bromide and sodium metal, with 1-phenylethyl bromide afforded the organostibanyl transfer agent Sb-1. However, due to the difficulty in generating the stibanyl anions and their low reactivities, the synthetic scope of this route is limited. 

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