Potassium bisulfite, reduction

Potassium bisulfite reduces fluoroalkylnitroso compounds to the oximes, with the exception that the parent mtrosotnfluoromethane is converted to the corresponding hydroxylamine [90] (equation 72). ArylfluoroaJkylazo compounds are reduced to the hydrazo stage or the fluoroamine by zinc-add, depending on conditions [91] (equation 73) Of the various reagents tested tor selective reduction of ji-fluoroalkyl azides to P-fluoroalkylamines, triphenylphosphine was the best [92] (equation 74). 

Also obtained by reductive condensation of p-hydroxy-phenylglyoxal potassium bisulfite (CgH OgSK, preparation given) with methylamine in dilute ethanol under saturated hydrogen atmosphere and coohng with ice (71%) [4752],... 

Preparation by reductive condensation of 4-hydroxy-3-methoxyphenylglyoxal-potassium-bisulfite and benzylamine under hydrogen in the presence of Raney nickel in dilute ethanol at 45° for 1.75 h. Then, elimination of the catalyst and acidification of the mixture with hydrochloric add (76%) [4818]. 

A convenient laboratory route involves the reduction of an aqueous solution of nitrous acid or potassium nitrite with bisulfite under carefully... 

More definite evidence for the transient existence of the un-cyclized l-(jS-aminoethyl)-3,4-benzoquinones has been obtained recently by Kodja and Bouchilloux,77 78 who noted that a transient yellow color (Amax ca. 385 mp) was occasionally observed during the enzymic oxidations of catecholamines (particularly in unbuffered systems at low temperatures). This phenomenon was probably due to the formation of the transient o-quinones. (The absorption maximum of o-benzoquinone, the effective chromophore of the open-chain quinones, is known to occur at ca. 390 mp.79) An absorption maximum at 390 mp is characteristic of the formation of the dopa-quinone chromophore during oxidation of small C -terminal tyrosine peptides in the presence of tyrosinase.37 48 Similar spectroscopic features were observed when the oxidations were carried out with lead dioxide in sulfuric acid solutions (pH> 1). If the initial oxidation was carried out for a short period of time, it was possible to regenerate the original catecholamines by reduction (e.g. with sodium bisulfite, potassium iodide, and zinc powder) and to show that the 385 mp peak disappeared.77,78 Kodja and Bouchilloux were also able to identify 2,4-dinitrophenylhydrazones of several of the intermediate non-cyclized quinones by paper chromatography and spectroscopy (Amax n weakly acid solution ca. 350 mp with a shoulder at ca. 410 mp).77,78... 

The first report of the polymerization of tetrafluoroethylene was by Plunkett in 1941, who had a cylinder of tetrafluoroethylene cut open to see why the expected amount of gas was not released when the valve was opened. His perspicacity led to the discovery of an inert, white, opaque solid with a waxy feel. Various methods of polymerization were tried after the adventitious discovery and the preferred methods for polymerization now involve aqueous media and super-atmospheric pressures. Suitable initiators (Hanford and Joyce) include ammonium, sodium, or potassium persulfate, hydrogen peroxide, oxygen, and some organic peroxy compounds. Oxidation-reduction initiation systems involving the use of persulfate with either ferrous ion or bisulfite or the use of bisulfite with ferric ion are also useful and have been discussed by Berry and Peterson. 

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