Lab: Determine Which Functional Groups In A Substance Essay, Research Paper

This lab used many test to determine which functional groups were present in certain substance. The Benedicts test was used to identify reducing sugars (glucose and fructose) based on their ability to reuce the Capric ions to cuprous oxide at high pH. The Cuprous oxide is reddish orange in color when shown to be at high levels by the test, and greenish when at low levels. In both the onion juice and glucose solution the reducing sugar levels were very high, because the test came back dark orange. The starch solution had relatively low levels of reducing sugar present and this was seen by the test coming back cloundy blue, green and brown.

Iodine is used to distinguish starch from mono/di/polysaccharides. In the test only two of the six solutions showed any signs of starch being present. The potato juice turned a brownish color with a precipitate indicating a slight presence of starch. The stach solution turned a dark blue/black color indicating a very high presence of starch in the solution. The presence of starch in the potato juice indicates that it does not have as high an amount of carbohydrates as onion juice, but a higher concentration of starch.

The Biuret test is used in identifing the bond between the amino group and carboxyl group in proteins. These bonds are found on adjacent amino acids and are called peptide bonds. In the test, peptide bonds in proteins complex with Cu in Biuret reagent and produce a violet color. Both the egg albumen and protein solution showed hi abundence of proteins. The egg albumen is rich in protein because it is the food source for the individual as it developes into its species.

Sudan IV is a test that functions by a lipid’s ability to selectively absorb pigments in fat-soluble dyes. In both instances the salad oil separated from the other solution (water and Sudan IV). The oil moved to the top of the test tube, while the water and Sudan IV moved under, not mixing. However, the oil, high in lipid content had absorbed much of the die when added to the Sudan IV test tube. The potato juice seemed to form a precipitate when mixed with Sudan IV, it was very cloudy and could not be seen through. Honey contains very little lipid, since there was no separation and a red tinted solution formed.

The grease -spot test shows how products high in lipids create a translucent mark on some kinds of paper. The results for this experiment were very predictable, the fatty products (salad oil, peanut butter, and margerine) all produce spots that when held to the light were somewhat transparent. Water produced no mark, it was just absorbed and then dried, not changing the transparency of the paper at all.

In each test controls are neccesary otherwise how would one tell if the test is actually working. The controls show if the test solution is working properly. It is always a good idea to use a control so that your data has more backup data, and it is allows for possible errors to be ruled out if the data seems to be inaccurate.

The results for the unkowns is very fragmented and inconsistant. These results make it very dificult to decide what beverage goes with what letter. Unknown A shows to be positive mainly only in the Sudan IV test showing that it has a high concentration of lipids. The only drink that has a has such a property is the cream soda, so by the data, I would think that unknown A is cream soda.