post question 1 The possible carbohydrates in the following problems are limited

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post question 1

The possible carbohydrates in the following problems are limited to these: Arabise, glucose. fructose, maltose, sucrose, and starch. A carbohydrate solution gave a positive Molise test and negative Benedict. barged. Bial. and Seliwanoff teats. When treated with hydrochloric acid and boilod for several minutes, the solution showed positive Benedict, barged, and Seliwan off tests and a negative Bial test. Which carbohydrate was in the original solution? A solution containing: only one carbohydrate gave a Cu,0 precipitate with Benedict reagent Which of the carbohydrate* is present in the solution? Another sample of the solution from (b) failed to give a Cu_20 precipitate with Barfoed reagent. Which carbohydrate is present in the solution?

Explanation / Answer

Solution.

Arabinose, glucose, fructose, maltose, sucrose, and starch.

a) Molish test is a general test for carbohydrates. This is not a monosacharide, because of the negative Barfoed's test. The negative Bial test after hydrolysis says that the sacharide is formed by a hexoses. It can be starch or maltose.

b) Benedict's test is a test to determine whether or not the carbohydrate contains a free aldehyde or ketone group - reducing sugars. The predipitate says that we have a reducing sugar - it can be glucose or fructose, or even maltose.

c) Failed Barfoeds test says that the compound is a disacharide, therefore, it is maltose.

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