SCH4U: Preparation of Esters Lab

SCH4U: Preparation of Esters Lab Introduction: Esters are responsible for the “fruity” odours and flavours of many naturally occurring products. Chemists can reproduce these odours or flavours in the lab by mixing the right alcohol and carboxylic acid together; thus, producing “artificial” or “synthetic” versions of these naturally occurring compounds. In this lab activity you will create a number of different esters and attempt to identify the odour of each ester created.

Materials: Alcohols Acids A. Methanol W. Salicylic acid B. Ethanol X. Acetic acid (ethanoic) C. 1-propanol D. 2-propanol E. Isobutyl F. Isopentyl G. Isoamyl H. 1-octanol

Procedure: 1) Set up a 400mL beaker, half full with water, on a hot plate to act as a hot bath (75o-80oC) (Do not allow water to boil). 2) Obtain two clean test tubes. Into one test tube add approximately 1mL of the desired alcohol; into the second test tube add approximately 1mL of the desired carboxylic acid. Carefully, waft the vapours of each tube towards your nose and record the odour of each reactant. 3) Mix the contents of the two test tubes together. Using a dropper add 5 drops of concentrated sulphuric acid to the mixture. Carefully, mix the solution. 4) Place the test tube containing the reactants into the hot bath for about 5 minutes. Do not let the water or the contents of the test tube boil. 5) Remove the test tube from the water bath and carefully waft the vapours towards your nose. If you have trouble detecting the odour of the ester follow the next step. 6) Add approximately 20mL of warm water to a 250mL beaker. Pour the contents of your test tube into the beaker containing warm water.* Carefully, waft the vapours towards your nose and smell the odour emanating from the beaker. 7) Name the ester and describe its odour. 8) Discard the contents of your beaker into the organic waste jar.

** Why would putting the ester reaction mixture in water help us smell the ester? Observations

Ester #1 Alcohol Carboxylic Acid Ester

Using structural formula, show the reaction that occurred:

Teacher Key

Alcohol Acid Ester produced Smell

Methanol Butanoic acid Methyl butanoate Pineapple

Methanol Benzoic acid Methyl benzoate Marzipan

Methanol Salicylic acid Methyl salicylate Wintergreen

Ethanol Methanoic acid Ethyl methanoate Raspberry/rum

Pear drops/nail-varnish Ethanol Ethanoic acid Ethyl ethanoate remover

Ethanol Butanoic acid Ethyl butanoate Pineapple

Propan-1-ol Ethanoic acid Propyl ethanoate Pear

Pentan-1-ol Ethanoic acid Pentyl ethanoate Banana

Pentan-1-ol Butanoic acid Pentyl butanoate Apricot/pear

Pentan-1-ol Pentanoic acid Pentyl pentanoate (Pine)apple

3-methylbutan-1-ol Ethanoic acid 3-methylbutyl ethanoate Banana/bee alarm pheromone (isoamyl alcohol)

Octan-1-ol Ethanoic acid Octyl ethanoate Orange

Phenylmethanol Ethanoic acid Benzyl ethanoate Peach (benzyl alcohol)