Tris acetic acid preparation

Tris-acetic acid buffers have been proposed instead of Tris-hydrochloric acid buffers for preparative starch gel electrophoresis because the anodic solution does not drop to such low pH values (Pilz and Johann, 1966). Examples for use at 20°C are pH 7.3, four litres of 0.4m Tris plus 750 ml 2m acetic acid pH 8.6, 4.5 litres 0.4m Tris plus 280 ml 2m acetic acid. A recent paper describes buffers for the electrophoresis of enzymes on polyacrylamide gel (Orr et al., 1972). 

It follows therefore that ethyl malonate can be used (just as ethyl aceto- acetate) to prepare any mono or di-substituted acetic acid the limitations are identical, namely the substituents must necessarily be alkyl groups (or aryl-alkyl groups such as CjHjCHj), and tri-substituted acetic acids cannot be prepared. Ethyl malonate undergoes no reaction equivalent to the ketonic hydrolysis of ethyl acetoacetate, and the concentration of the alkali used for the hydrolysis is therefore not important. 

D) No general reaction can be cited for the preparation of crystalline derivatives of Class (iii). Triphenylamine, when nitrated in acetic acid with fuming nitric acid, gives tri-/>-nitrophenylamine, m.p. 280°. The presence of substituents in the phenyl groups may however complicate or invalidate nitration. 

Vicinal iodo carboxylates may also be prepared from the reaction of olefins either with iodine and potassium iodate in acetic acid/ or with N-iodosuccinimide and a carboxylic acid in chloroform. " A number of new procedures for effecting the hydroxylation or acyloxylation of olefins in a manner similar to the Prevost or Woodward-Prevost reactions include the following iodo acetoxylation with iodine and potassium chlorate in acetic acid followed by acetolysis with potassium acetate reaction with iV-bromoacetamide and silver acetate in acetic acid reaction with thallium(III) acetate in acetic acid and reaction with iodine tris(trifluoroacetate) in pentane. ... 

Glycosyl fluorides have also been prepared by treatment of per-O-acyl or partially 0-acylated sugars with hydrogen fluoride [liquid HF (for example, see Refs. 38 and 39) or HF in acetic acid or dichloromethane], as exemplified by 2,3,4-tri-O-benzyl-a-D-xylopyranosyl (18), a-D-glucopyranosyl (19), tetra-O-pivaloyl-a-D-glucopyranosyl (20), and 2,3,5-tri-O-acetyl-D-xylofur-anosyl fluorides (21) (see Table 1). Frequently, HF treatment - leads to... 

The present procedure represents a modification of two previously published procedures,2 3 and results in a safer, more convenient preparation of the title compound. In Step A, the ratio of reagents has been adjusted to allow for the formation of only pentaerythrityl tetrachloride and trichlorohydrin none of the dichlorinated product is produced. Thus work up of the reaction is easier the product can be filtered rather than extracted, so minimal solvent is used, and the crude products are used in Step B, thus avoiding a tedious distillation. Step B has also been modified to make it safer and more convenient. The crude material from Step A is used, and addition of nitric acid over a longer period reduces the hazards of this step. Previously, it was noted that after the nitric acid was added in one portion and the mixture was heated, "a reaction became apparent, whereupon the flask was lowered rapidly into a waiting cold bath and the operator withdrew. 2 Step C is a more detailed modification of the procedure reported by the Russian workers3 as an improvement to the original method of Mooradian and Cloke.2 The latter used quinoline to catalyze the conversion of tris(chloromethyl)acetic acid to 3-chloro-2-(chloromethyl)propene. 

Polymers containing pendant carbamate functional groups can be prepared by the reaction of phenyl isocyanate with poly(vinyl alcohol) in homogeneous dimethylsulfoxide solutions using a tri-ethylamine catalyst. These modified polymers are soluble in dimethyl sulfoxide, dimethylacetamide, dimethylformamide and formic acid but are insoluble in water, methanol and xylene. Above about 50% degree of substitution, the polymers are also soluble in acetic acid and butyrolactone. The modified polymers contain aromatic, C = 0, NH and CN bands in the infrared and show a diminished OH absorption. Similar results were noted in the NMR spectroscopy. These modified polymers show a lower specific and intrinsic viscosity in DMSO solutions than does the unmodified poly(vinyl alcohol) and this viscosity decreases as the degree of substitution increases. 

Another general method for the preparation of 19,19,19- and 20,20,20-trifluor-oretinals involves the aldol condensation of trifluoroacetone with an ethylenic aldehyde. When performed in the presence of acetic acid and piperidine, it affords an a, S-unsaturated ketone. Applied to cyclocitral and its homologues, the method leads to polyenic trifluoromethyl ketones. From these ketones, the various tri-fluorinated retinoids are prepared by known methods (Figure 4.24). ... 

Attempts66 to prepare the 2,3-anhydride from methyl 3-0-(methyl-sulfonyl)-/3-maltoside, using M sodium methoxide, resulted in the corresponding 3,6-anhydride 43. To circumvent the formation of 43, the reaction was performed with methyl 3-0-(methylsulfonyl)-6,6 -di-0-trityl-/3-maltoside. The desired product, methyl 2,3-anhydro-4-0-(2,3,4-tri-0-acetyl-6-0-trityl-a-D-glucopyranosyl)-6-0-trityl-/3-D-allopyrano-side (44), was obtained in 72% yield. Attempted detritylation of 44 by brief treatment with hydrogen bromide in glacial acetic acid, followed by conventional acetylation, gave methyl 2,6,2, 3, 4, 6 -hexa-0-acetyl-... 

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