Silver bromide behavior

All cell potentials reached equilibrium in 1 or 2 hr, except when the solvent was anhydrous terf-butanol, in which the electrodes reached equilibrium only in dilute soltuions of HBr and even then only in a sluggish manner. This sluggish behavior has been reported (27) for the silver-silver bromide electrode in anhydrous ethanol when the acid was concentrated. In the dilute hydrobromic acid solutions used here, this phenomena was not observed in anhydrous ethanol. It is estimated that the standard electrode potential of the silver-silver bromide electrode in anhydrous terf-butanol is accurate to only d=l mV. However, these data are reported to the same degree of precision found in the other tert-buta-nol-water solvents in order to facilitate comparisons of the emf s in the various dilutions of tert-butanol used. 

In Example Problem 12.2, we saw that cyanide ions precipitate with silver. Bromide ions show similar behavior. The two pertinent equilibria are... 

Kinetic experiments have been performed on a copper-catalyzed substitution reaction of an alkyl halide, and the reaction rate was found to be first order in the copper salt, the halide, and the Grignard reagent [121]. This was not the case for a silver-catalyzed substitution reaction with a primary bromide, in which the reaction was found to be zero order in Grignard reagents [122]. A radical mechanism might be operative in the case of the silver-catalyzed reaction, whereas a nucleophilic substitution mechanism is suggested in the copper-catalyzed reaction [122]. The same behavior was also observed in the stoichiometric conjugate addition (Sect. 10.2.1) [30]. 

The application of Konigs and Knorr s method of glycoside synthesis to acetyl-L-rhamnosyl bromide by Fischer, Bergmann and Rabe resulted in the formation of a mixture of one sirupy and two crystalline isomeric methyl rhamnoside acetates. When acetylrhamnosyl bromide was treated in anhydrous methyl alcohol with dry silver carbonate at room temperature, the solid part of the reaction product consisted of crystalline needles and cubes. The needles consisted of methyl 9-L-rhamnoside triacetate with the expected normal behavior toward alkaline deacetylat-ing agents. The cubes, consisting of 7-methyl L-rhamnoside triacetate ... 

Levene and Tipson studied the behavior of acetyl-n-ribosyl bromide in the Kflnigs-Knorr reaction. The reaction of methanol upon acetyl-n-ribosyl bromide in the presence of freshly prepared silver carbonate took place at room temperature in thirty minutes. The crystalline bromo-... 

Miss Frush and IsbelF used crystalline heptaacetyl-a-neolactosyl chloride in the Konigs-Knorr reaction under conditions identical with those described for pentaacetyl-a-D-(a)-guloheptosyl bromide, with the exception that the reaction time was increased to seventy-two hours. Acid and alkaline hydrolysis of the reaction solution showed that only about 70% of the original sugar was present, and that this was almost completely in the form of the orthoester. By extraction of the silver residues with chloroform, a halogen-free sirup was obtained, from which short rectangular crystals separated upon addition of methyl alcohol. This substance was methyl /3-neolactoside heptaacetate, which exhibited the expected normal behavior. 

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