Pre-Lab Preparation

Read our general advice regarding pre-lab preparation, and the overview and background sections for this experiment.

Reading note. The procedures in this manual regularly refer to material in Making the Connections: A How-To Guide for Organic Chemistry Lab Techniques by Anne B. Padias. These references appear as Padias p. X. Similarly, references to your lecture textbook appear as Loudon p. X.

Prepare your notebook. After you have read the preliminary material (see above), read the procedure that follows and make all appropriate entries [NOTE 1] in your notebook (see How to Keep a Notebook). Remember: you must bring a prepared notebook to lab. Students who do not prepare their notebook in advance will be unable to start the experiment.

This lab combines experimental work with computer modeling. Each part should require no more than 2 hours to complete.

Solubility measurements

Wear goggles.

Choose a partner and do all work in pairs. Take turns performing operations and making measurements so that both partners get experience in all phases of the experiment. Also, both partners need to record the procedure and observations in their respective notebooks. Do not use one person as the lab worker and the other as the data recorder.)

	Equipment
	3 large test tubes (clean, dry, Padias p. 18)
	50 mL beaker (clean, Padias p. 18 )
	graduated cylinder (clean)
	stirring device (spatula or glass rod)
	addition devices (buret, disposable pipet)
	Organic liquids
	hexane, ethyl acetate, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-2-propanol, 3-methyl-1-butanol

Initial measurements. Test the solubility of hexane in water by placing about 5-7 mL of distilled water [NOTE 2] in a large test tube and adding to it about 5-7 mL of hexane. Stir the liquids well. Note whether hexane dissolves in water (an undissolved liquid might appear as a film floating on the water, or as many small droplets, or as a well-distinguished layer). In a similar fashion, test the solubility of ethyl acetate in water, and the solubility of 2-propanol in water. Make sure you start with a clean (but not necessarily dry) test tube for each measurement.

You should not have any trouble establishing the bulk solubilities of hexane, ethyl acetate, and 2-propanol in water. It is possible, however, that a seemingly "insoluble" liquid actually dissolves in water to a small extent. Test this possibility as follows: place about 10 mL of distilled water in a test tube and add one drop of the "insoluble" liquid. If the added liquid fails to dissolve, stir the solution well, and then let it sit for 30 seconds. How many drops can you add before undissolved material is detected? Do your measurements establish a lower or upper bound on the solubility of these liquids in water?

Alcohol solubility measurements. The preceding measurements were intended to give you a feel for the properties of three important organic liquids, and also a feel for the experimental difficulties you will encounter when trying to measure the solubility of a partially soluble/insoluble liquid in water. The remaining measurements are intended to establish the solubilities of a variety of alcohols in water. Some of the alcohols are completely soluble, while others are only partially soluble.

Measure the solubility of each alcohol by placing 25 mL of distilled water [NOTE 2] in a clean beaker. Add a small amount of the alcohol [NOTE 3] using a buret (Padias p. 21-22) (burets containing different alcohols will be stationed around the lab). After each addition, notice if you can see any undissolved alcohol. If you can, stir the solution, then let the solution sit undisturbed for 30 seconds. If you still see undissolved material, the water layer is saturated with alcohol. Record the volume of alcohol added and stop adding alcohol. If you cannot saturate the water layer with 20 mL of alcohol, consider the alcohol to be completely soluble.

Data handling. If an alcohol is only partially soluble (or insoluble) in water, convert the volume of added alcohol to mass of added alcohol. Then calculate the percentage of alcohol by weight ("wt%") in the final saturated solution using the following equation:

Disposal

Alcohols (pure) - place these in the organic waste container. Organic materials should never go down the sink (see 3.4 Waste Disposal in the Reed College Chemical Safety Manual).

Water-organic mixtures - since these contain a substantial amount of water, place these in the special waste container that will be provided. Just as organics should never go down the sink, large amounts of water should not go into the organic waste container (the collected organic wastes are sent to an incinerator and water prevents efficient burning) so we will separate the water and organic layers before disposing of the organics.

Note: A variety of wastes are created in this experiment. It is vital to put materials in the appropriate waste container. These containers may (or may not) be located in the same fume hood, but they will always be clearly labeled. Please read the label on the collection bottle before disposing of your waste.

Molecular modeling

After you complete your solubility measurements [NOTE 4 ], go to the computational chemical laboratory (Rm. 203) to build molecular models and obtain data on molecular properties that might affect solubility. Instructions for building models and obtaining relevant properties will be distributed in lab. A copy of the instructions can also be downloaded.