CLASSIFICATION OF CARBOHYDRATES

Type of Carbohydrate Expected to Test Positive

2. Draw the cyclic forms (not the Fischer projections) of glucose, fructose, sucrose, and lactose in the space below. Label each clearly by name, and identify each as an acetal, ketal, hemiacetal or hemiketal.

2 EXPERIMENT 11: CLASSIFICATION OF CARBOHYDRATES

3. Use check marks to classify each of the knowns in Table 11.2 prior to beginning the lab. You will fill out the last row after you have performed the experiment. (There should be more than 1 check mark in each row.)

Table 11.2 Carbohydrate Classification

Monosaccharide Disaccharide Aldohexose Ketohexose

Glucose

Fructose

Sucrose

Lactose

Unknown

During the Lab: 4. Fill in Table 11.3 during the lab period as the experiment is performed. (Observations – What do you see?)

Table 11.3: Actual Observations

SAMPLE SELIWANOFF TEST BARFOED’S TEST BENEDICT’S TEST

glucose

fructose

sucrose

lactose

UNKNOWN

EXPERIMENT 11: CLASSIFICATION OF CARBOHYDRATES 3

Post-lab Analysis: 5. Fill in Table 11.4 after the experiment has finished. Use your information from above sections to summarize observations by placing a “+” for a positive result and a “-“ for a negative result. Determine the identity of the unknown carbohydrate.

Table 11.4: Summary

SAMPLE SELIWANOFF TEST BARFOED’S TEST BENEDICT’S TEST

glucose

fructose

sucrose

lactose

In this assignment, you will write a discussion for the experiment performed. You will discuss your data and results in a well-organized paragraph (more than 5 complete sentences). Be sure to explain how you reached your conclusions. Your discussion should cover (in any order):

1) the identity of the unknown sugar;

2) the test results of the unknown analysis compared to each of the knowns;

3) what else these results tell us about the unknown sugar.