Question

Experiment #6 Ester Synthesis PRE-LAB ASSIGNMENT This pre-lab assignment is worth 5 points for this Experiment and should be completed on a separate page and turned in at the beginning of lab. 1. Read the experiment carefully 2. Safety Considerations: Summarize O safety and health hazards for working with glacial acetic acid, butanoic acid and petroleum ether. 3. Procedure: Summarize the procedure using a bullet list. Assume you are summarizing the procedure to a fully qualified chemist, i.e. don't include details such as "record observations". 4 Pre-lab Question a. What IMFs do esters have? When esters have large alkyl groups, which functional group do they more closely resemble. b. How are we able to extract the ester out of the water in part A. with a non-polar solvent like petroleum ether?Draw the chemical structure of the ester made in part A and with the most common component of petroleum ether. What rule of thumb are we using and what IMFs are playing a role in dissolving the ester in petroleum ether? OBJECTIVES -To use acids to make esters. -To become familiar with small scale two-phase solvent extraction -To leam about drying agents -To identify an ester by the physical property of smell BACKGROUND Esters, derivatives of carboxylic acids, are found in a variety of natural sources. Simple esters generally have pleasant odors, and are the main components of many of the odors and flavors of fruits and flowers. Most odors and flavors are the result of a complex mixture, with one ester predominating. Because esters are easy to synthesize, flavor chemists often use esters, either one or several, to reproduce or enhance natural flavors. Although esters are often used as flavorings, they are rarely used as scents to be applied on the body. This is because esters are not highly stable, and can be hydrolyzed back to carboxylic acids and alcohols when exposed to perspiration. Since esterification is a reversible reaction, the addition of acid, water and heat (perspiration) favors hydrolysis. And, unfortunately, many simple carboxylic acids have a very unpleasant odor. For example, butyric acid (butanoic acid) is the main component responsible for the odor of rancid butter. Butyric acid is formed from hydrolysis of ethyl and methyl butanoate, esters that smell like pineapple and apple. Some esters are also bioactive. 3-methyl-1-butyl ethanoate, which smells like bananas, is also an alarm pheromone released by honey bees when they sting an intruder. The pheromone attracts other bees and incites them to attack the intruder. For these reasons, fragrances are more often made from essential oils (phenols, aldehydes, alkenes, etc.). Esters are the product formed in the reaction of an acid with an alcohol. The reaction is general and almost any acid can be combined with any alcohol - Adapted from Professor Steim's Chemistry 25 Laboratory Experiment 12 at Brown University. Modifications and additions by Ted Picciotto and Heather Colman, Portland Community College, 2012-2013