chem assignment 11

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Experiment 11: CLASSIFICATION OF CARBOHYDRATES

Data Collection and Results Pages Name: __________________________ Date: ___________________ Pre-lab Preparations: Review the information in your textbook on carbohydrates (sugars). You may also use the Internet for assistance, if necessary. Allow plenty of time for your pre-lab preparation! 1. Fill in Table 11.1 based on the discussion provided in the Introduction prior to beginning the lab.

Table 11.1: What the Test Should Tell Us

TEST SELIWANOFF BARFOED BENEDICT What a Positive Result Should Look Like

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