Alkaline Cupric Tartrate

Reducing sugars Accurately weigh 7 g of sorbitol and transfer to a 400 mL beaker with 35 mL of water and mix. Add 50 mL of alkaline cupric tartrate test solution, and cover the beaker. Heat so that it boils in approximately 4 minutes and boil for 2 minutes. Collect the precipitated cuprous oxide in a tared filtering crucible previously washed with hot water, alcohol, and ether, and then dried at 105 C for 30 minutes. Wash the cuprous oxide on the filter Avith hot water, then with 10 mL of alcohol, and then 10 mL of ether. Dry at 105 C for 30 minutes. The weight of the cuprous oxide should not exceed 50 mg. 

A. A 1 50 aqueous solution slowly reduces alkaline cupric tartrate TS at 25°, but more readily upon heating. 

A. Add 5 mL of sulfuric acid TS to 10 mL of a 2% aqueous suspension of sample, heat in a boiling water bath for 30 min, and cool. Neutralize the mixture with barium carbonate, and centrifuge it at 900 g for 10 min. Add 1 mL of the supernatant to 5 mL of hot alkaline cupric tartrate TS. A copious red precipitate of cuprous oxide forms. 

Identification Add a few drops of a 1 20 aqueous solution to 5 mL of hot alkaline cupric tartrate TS. A copious red precipitate of cuprous oxide forms. 

Reducing Sugars Dissolve 500 mg of sample in 10 mL of water, warm, and make the solution alkaline with 1 mL of 6 N ammonium hydroxide. Pass hydrogen sulfide gas into the solution to precipitate the iron, and allow the mixture to stand for 30 min to coagulate the precipitate. Filter, and wash the precipitate with two successive 5-mL portions of water. Acidify the combined filtrate and washings with hydrochloric acid, and add 2 mL of 2.7 N hydrochloric acid in excess. Boil the solution until the vapors no longer darken lead acetate paper, and continue to boil, if necessary, until the solution has been concentrated to about 10 mL. Cool, add 5 mL of sodium carbonate TS and 20 mL of water, filter, and adjust the volume of the filtrate to 100 mL with water. Add 2 mL of alkaline cupric tartrate TS to 5 mL of filtrate, and boil for 1 min. No red precipitate forms within 1 min. 

Identification Add 5 mL of 1 N sodium hydroxide to 5 mL of a hot, saturated solution of sample, and gently warm the mixture. The liquid turns yellow and, finally, brown-red. Cool to room temperature, and add a few drops of alkaline cupric tartrate TS. A red precipitate of cuprous oxide forms. 

Alkaline Cupric Tartrate TS (Fehling s Solution) See Cupric Tartrate TS, Alkaline. 

Algin, 24, 54,312, 351 Alginates Assay, 768 Algin Derivative, 331 AlginicAcid, 19 Alkaline Borate Buffer, 848 Alkaline Cupric Citrate TS, 851 Alkaline Cupric Tartrate TS, 849 Alkaline Mercuric-Potassium Iodide TS, 850... 

In this experiment, benzil is prepared by the oxidation of an a-hydroxyketone, benzoin. This experiment uses the benzoin prepared in Experiment 32A and is the second step in the multistep synthesis. This oxidation can be done easily with mild oxidizing agents such as Fehling s solution (alkaline cupric tartrate complex) or copper sulfate in pyridine. In this experiment, the oxidation is performed with nitric acid. 

The nonstoichiometric sugar oxidation process in the presence of alkali is used for both qualitative and quantitative determination of reducing sugars (Fehling s reaction with alkaline cupric tartrate Nylander s reaction with alkaline trivalent bismuth tartrate or using Benedict s solution, in which cupric ion complexes with citrate ion). Hydroxyaldehydes and hydroxyketones are formed by chain cleavage due to retroaldol reaction under nonoxidative conditions using dilute alkali at elevated temperatures or concentrated alkali even in the cold. 

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