Bromine treatment

Most microbes in cooling systems can be controlled by chlorine or bromine treatment if exposed to a sufficient residual for a long enough time. A free chlorine residual of 0.1—0.5 ppm is adequate to control bulk water organisms if the residual can be maintained for a sufficient period of time. 

In a Hunsdiecker reaction, the silver salt of an aromatic carboxylic acid is converted by bromine treatment to an acyl halide. 

The syntheses of 74 and 75 is outlined in Scheme 20. Bromination of o-xylene, using a catalytic amount of iodine, afforded 4,5-dibromo-o-xylene 71 as a crystalline solid after recrystallization from methanol [141]. The appearance of only one singlet for the aromatic hydrogen atoms in the H NMR spectrum of 71 confirms the regiochemical outcome of the bromination. Treatment of 71 with... 

An acidic solution of 2,4-dinitrophenylhydrazine reacts with N-p-chlorophenyl-sulfonyl-3-ethoxy-l,2-thiazetidine 1-oxide to give (80%) the bis-2,4-dinitrophenyl-hydrazone of glyoxal. The adduct of A-sulfinyl-p-chlorophenylsulfonamide with dihydropyran is inert to catalytic hydrogenation and bromination. Treatment of two l,2-thiazetidine-3-one 1-oxides (e.g., 421) with hydriodic acid results in ring-cleavage and loss of sulfur. They are not oxidized to 1,1-dioxides by peracetic acid, ° but m-chloroperbenzoic acid accomplishes this oxidation. The unstable adducts with ketene decompose to amides with loss of hydrogen sulfide and sulfur dioxide or may be trapped by reaction with aromatic amines as shown for thiazetidine 1-oxide 422.An aldol-type condensation has been reported for A -cyclohexyl-1,2 thiazetidine-3-one 1-oxide and p-(A(A"-dimethylamino)benz-aldehyde. " Sulfur monoxide is lost in the flash-vacuum thermolysis of 422a. ... 

It is also possible to use the Negishi coupling for the polymerization of dibromo furans. First, 3-octylfuran is converted to 2,5-dibromo-3-octylfuran (44) upon addition of bromine. Treatment of this material with Rieke zinc followed by tetrakis provides a 40% yield ofpoly(3-octylfuran) (45) [55]. 

A very different, but similarly effective, auxiliary is the chiral carbonyl(t/5-cyclopentadienyl)(tri-phenylphosphine)iron moiety. When the z./i-unsaturated acyl-iron complex ( -)-(/ )-11 is treated by a modified Simmons Smith reagent, a 91 9 mixture of cyclopropane diastereomers is isolated in good yield73. Precomplexation of the starting iron complex by the Lewis acid zinc(II) chloride seems to be necessary to obtain good selectivity. The chiral iron moiety can then be removed oxidatively by bromine treatment, and the intermediate acyl bromides converted into amides by reaction with (/ )- -phenylethylamine. 

I-Alkyl-7-azaisatins. 7-Azaindoles are brominated at C-3 with bromine. Treatment of the products with NBS in DMSO transforms them into the isatins. 

Ichthyopterin, a blue fluorescent substance i occurs in fish scales or skin along with isoxanthopterin and isoxanthopterin carboxyhc acid. The latter two compounds appear on the basis of paper chromatography to be formed upon reduction and oxidation, respectively, of ichthyopterin, and periodate oxidation gives isoxanthopterincarboxaldehyde. Ichthyopterin shows remarkable similarities to 7-hydroxybiopterin, synthesized from 6-acetonylisoxanthopterin by bromination, treatment of the bromo derivative with potassium acetate, hydrolysis of the resulting acetate and reduction of the hydroxy ketone to the dioPi . On the basis of Rf values in ten different solvents, the two appear to be identical . 

Bromination of dibutyl vinylboronate at low temperature readily affords a stable di-bromo derivative [2, 3]. Similarly, ( )-alkenylboronic acids or their catechol esters yield the corresponding substituted compound by stereospecific trans addition of bromine. Treatment with base induced anti elimination of the boronic group and the bromine ion. The final result of this sequence was the replacement of boron by bromine with inversion of olefin geometry in excellent yields and 99% stereochemical purities (Scheme 9.1) [4]. 

As mentioned above, the ability to synthesize the 11-epitrichothecenes is an added bonus of this methodology. Scheme 19 outlines how this was accomplished from the intermediary ketone (194). After introduction of bromine, treatment with fluoride ion yielded the novel 11-epitrichothecene (199), the structure of which was confirmed by X-ray analysis. In an effort... 

The ORR on PtML/PdgCo/C showed the Pt mass activity is 2-3-fold higher that of commercial Pt/C. However, upon the operating conditions, the Co component is subject to diffusion out of the nanoparticles, which engenders more low-coordination sites and so inflicts the catalytic activity. Like Pd-C nanoparticles, PdjCo/C can also be surface tailored by bromine treatment to remove the low-coordination sites and improve the ORR. 

Dithiazoles.—1,2,4-Dithiazolium salts (703) are formed from thioamides ArCSNHa by the action of perchloric acid or bromine. Treatment of benzo-l,2,3-dithiazolium chloride (704) with diethylamine yields compound (705). The S-dioxide (707) is formed on heating the azide (706). ... 

Br2 Bromination Treatment with an alkene gives an anti addition of Br and Br across the alkene. 

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