Test for sugars Reducing sugars give a red/brown precipitate with Benedict’s solution. The precipitate takes a while to settle in the tube. The colour you’ll see is likely to be simply red or brown. If there’s not much glucose present, the final colour may be green or yellow, or orange if there’s a little more.

Iodine is the fourth halogen, being a member of group 17 in the periodic table, below fluorine, chlorine, and bromine; it is the heaviest stable member of its group.

Iodine is a nonmetallic, nearly black solid at room temperature and has a glittering crystalline appearance. The molecular lattice contains discrete diatomic molecules, which are also present in the molten and the gaseous states. Above 700 °C (1,300 °F), dissociation into iodine atoms becomes appreciable.

Most of the world’s industrial iodine is obtained from brines (water strongly saturated in salt) associated with gas wells in Japan and from caliche ore mined in the Atacama Desert of northern Chile. In the United States, iodine is derived from deep well brines in northern Oklahoma.

In lab, we used Benedict’s reagent to test for one particular reducing sugar: glucose. Benedict’s reagent starts out aqua-blue. As it is heated in the presence of reducing sugars, it turns yellow to orange. The “hotter” the final color of the reagent, the higher the concentration of reducing sugar.

no reducing sugar

A positive test with Benedict’s reagent is shown by a color change from clear blue to brick-red with a precipitate.

Because both the Tollens’ and Benedict’s reagents are basic solutions, ketoses (such as fructose) also give positive tests due to an equilibrium that exists between ketoses and aldoses in a reaction known as tautomerism. Figure 14.5. 1: Benedict’s Test.

Sucrose

When Benedict’s solution and simple carbohydrates are heated, the solution changes to orange red/ brick red. This reaction is caused by the reducing property of simple carbohydrates. The copper (II) ions in the Benedict’s solution are reduced to Copper (I) ions, which causes the color change.

Benedict’s solution is blue but, if simple carbohydrates are present, it will change colour – green/yellow if the amount is low and red if it is high. A precipitate will also form if the sugars are present and the quantity of this gives an indication as to the quantity of sugars in the test sample.

Non-reducing sugar doesn’t contain an OH group attached to anomeric carbon and can’t reduce other compounds. Complete Answer: Maltose (malt sugar) is a reducing disaccharide while sucrose is a non-reducing one because of the absence of free aldehyde or ketone group in sucrose.

Glucose is a reducing sugar because it belongs to the category of an aldose meaning its open-chain form contains an aldehyde group. The aldehyde group is further oxidized to carboxylic group producing aldonic acid. Thus, the presence of a free carbonyl group (aldehyde group) makes glucose a reducing sugar.

Reducing sugars are sugars where the anomeric carbon has an OH group attached that can reduce other compounds. Non-reducing sugars do not have an OH group attached to the anomeric carbon so they cannot reduce other compounds. All monosaccharides such as glucose are reducing sugars.