Question

Please, fill in first table for Seliwanoff's Test for Ketoses. Additional info is found in the images following table. (Second table is info and image following).

Part C: Seliwanoff's Test for Ketoses Seliwanoff's Test Results Test Tube Sample Prediction Ketose? (Y/N) Observations Distilled water Peach / no change Glucose Peach to red slowly Fructose deep red solution very quickly Sucrose deep red solution quickly Lactose Peach to red slowly Starch Peach to red very slowly Mystery sample Peach to red slowly * Note: Prediction should be expected result based on structure (shown on page 483)

Answer 1

Seliwanoff's Test for carbohydrates mostly done to differentiate between aldoses and ketoses.

SAMPLE	PREDICTION	OBSERVATION	KETOSE(Y/N)
Distilled water	This does not contain any sugar molecules that might appropriately show positive or negative result	Peach/no change	No
Glucose	This is technically an aldose hence it may develop red coloration but not instantly	Peach to red slowly	No
Fructose	This is a ketose sugar which might provide a chance for it to show positive result	Deep red solution very quickly	Yes
Sucrose	It is a disaccharide made of an aldose(glucose) and a ketose(fructose). Hence the red coloration will occur because of the presence of fructose as seliwanoff reagent will react quickly with it	Deep red solution quickly	Yes
Lactose	Disaccharide made of glucose and galactose, both being aldose hence the test might be negative	Peach to red slowly	No
Starch	It is a poolysaccharide made of glucose molecules, hence reaction will be very slow and negative result might occur	Peach to red very slowly	No
Mystery sample		Peach to red slowly	No