酯化反应

Before beginning esterification work, put on a lab coat, safety glasses, and nitrile gloves. Since many reagents are volatile or have unpleasant odors, you will handle them in a fume hood. Ensure glass and organic waste containers are available, and verify that each sink has paper towels for cleanup.

Tare a 10-mL glass vial on an analytical balance in a fume hood. Use a Pasteur pipette to measure the required mass of liquid carboxylic acid, or use a small spatula for solid compounds like anthranilic acid. Cap and label each vial with its assigned code. Prepare the specified number of vials for each carboxylic acid according to the lab protocol.

Students use a 3:1 molar ratio of alcohol to carboxylic acid in the esterification reaction. This means each group needs 0.21 moles of their assigned alcohol and 0.07 moles of their assigned carboxylic acid. The specific masses and volumes for each reagent are provided in the preparation table based on molecular weight and density.

Seven different ester products can be synthesized by combining three carboxylic acids with various alcohols. These include propyl acetate, isoamyl acetate, octyl acetate, butyl butyrate, ethyl butyrate, methyl butyrate, and methyl anthranilate. Each ester has a characteristic fruit scent, ranging from pear to grape, making the products easily identifiable.

Each station requires a lab stand, heating mantle with temperature controller, stir plate, 50-mL round-bottom flask, standard condenser, lab jack, and supporting equipment like clamps and tubing. Additionally, students need graduated cylinders, beakers, glass rods, Pasteur pipettes, and pH paper. A tube of vacuum grease and laboratory wipes should also be available for assembly and maintenance.

Bottles of saturated sodium bicarbonate and sulfuric acid should be placed in a dedicated fume hood along with plastic paraffin film and scissors. A large insulated cooler filled with crushed ice should be set up in a central area of the lab with an ice scoop for easy access by all student groups during the experiment.

Before students arrive, instructors should demonstrate how to safely waft vapors to smell chemical compounds without direct inhalation. This technique is essential because many esterification reagents are volatile or have strong odors. Once students understand proper vapor-wafting technique, they can safely receive their assigned carboxylic acid and alcohol vials for the reaction.