What color is produced in Fehling's test for D-glucose?

Fehling's test is a qualitative analysis used to detect the presence of reducing sugars, such as D-glucose. When D-glucose is present, it reduces the blue copper(II) ions present in Fehling's solution to form copper(I) oxide, which precipitates out as a brick-red solid. This color change from blue to red is a key indicator of the reducing ability of glucose.

The blue color is attributed to the copper(II) complex in Fehling's solution, and when a reducing sugar like D-glucose interacts with it, the copper ions are reduced, leading to the formation of the brick-red precipitate. This red color confirms the presence of D-glucose in the solution, making it a vital aspect of Fehling's test.

Other colors, such as green or yellow, may appear in the test under different conditions or with varying concentrations of reducing sugar, but the definitive result for D-glucose is the conversion to red, highlighting it as a key characteristic of this test.