Pre-lab preparation

Notebook. This experiment involves a chemical preparation so you should set up your notebook according to the examples given in Padias and How to Keep a Lab Notebook.

Your chemical equation should not be a mechanism. Rather, show the material you will start with (methyl salicylate), important reagents (NaOH and H2O), important conditions ("reflux"), and the product that you expect to get (salicylic acid). Do not draw anything else.

Don't forget to include a table of physical properties for the substances that might appear in this experiment. This includes all starting materials, reagents, and product. A sample table with "?" indicating vital information is shown below.

Safety & Disposal. Wear gloves and goggles and carry out all operations in a fume hood. These are standard operating procedures, but they are especially important in this experiment. Any other hazards and warnings about safe handling should be entered in your notebook. Disposal procedures should also be entered for each reagent. Salicylic acid will be collected in a special container.

Online videos. Please review the following videos on lab procedures before lab (these are all from The Interactive Lab Primer):

	Simple Reflux (full video)
	Buchner (vacuum) Filtration (skip dessicator)
	Recrystallization (full video, but no 'hot' filtration for us)

Reaction

	Equipment
	50 mL round bottom flask
	lab jack + stirring motor
	magnetic stir bar
	ceramic heater + controller
	graduated cylinder
	screw clamps
	reflux condenser & water hoses
	funnel
	disposable pipettes

In your fume hood: place a stirring motor on top of a partially opened lab jack, then place a heater on top of the motor. Clamp the round bottom flask to the monkey bars in your fume hood so that it rests in the heater [NOTE 1]. Plug the heater into the controller, but do not turn on the controller (never plug a heater directly into a wall socket).

Transfer sufficient 6 M aqueous NaOH into a graduated cylinder so that you have 120 mmol of NaOH, then transfer this liquid to the round bottom flask using a funnel [NOTE 2]. Record the volume of aqueous NaOH that you actually use. Rinse your funnel and graduated cylinder with water to remove all traces of the reagent, and remove any stray drops of reagent from the ground-glass neck of your flask [NOTE 3].

Transfer about 21 mmol of methyl salicylate to your graduated cylinder [NOTE 2]. Record the volume that you actually use and transfer this material to the round bottom flask using a funnel. You should see a white gummy material form in your flask [NOTE 4].

Equip the flask with a stir bar, reflux condenser, and water hoses [NOTE 1]. Slowly flow water through the reflux condenser and adjust the controller voltage to initiate reflux [NOTE 5]. Reflux the mixture for 30 minutes, while stirring as best you can (the gummy material prevents the stir bar from working at first, but the material soon dissolves). Turn off the controller and remove the lab jack, motor, and heater. Allow the mixture to cool to room temperature before continuing [NOTE 6].

Workup

	Equipment
	150 mL beaker
	pH paper
	400 mL beaker (for ice water bath)
	250 mL filtering flask
	heavy-walled rubber hose
	Buchner funnel + neoprene adaptor
	filter paper

Pour the cooled mixture into a 150 mL beaker. Add sufficient 3 M aqueous H₂SO₄ to precipitate all of the salicylic acid [NOTES 7 & 8]. Place the beaker in an ice-water bath for several minutes, then collect your product by vacuum filtration [NOTE 9]. While still applying a vacuum, rinse the solids with a small amount of ice-cold water and let them air-dry for several minutes [NOTE 10].

Recrystallization [Note 11]

	Equipment
	Two 250 mL Erlenmeyer flasks
	boiling chips
	hot plate (stirring motor)
	disposable pipets + rubber bulbs

Place your crude salicylic acid and 5-10 mL of deionized water in a 250 mL Erlenmeyer flask ("acid" flask). Place about 80-120 mL of deionized water in a second flask ("water" flask). Add 2-3 boiling chips to each flask. Place the "water" flask on a hot plate and bring the water to a boil. Next, set the "acid" flask next to the "water" flask on the hot plate and bring the "acid" mixture to a boil as well. Transfer just enough boiling water from the "water" flask to the "acid" flask to dissolve all of the solids in the "acid" flask [NOTE 12]. Remove the "acid" flask FROM THE hot plate and let the solution cool slowly. Salicylic acid should crystallize spontaneously.

After the solution has cooled sufficiently, recover the product by vacuum filtration (use a clean filter flask and funnel). Set the product on a watch glass inside your laboratory cabinet to dry.

Characterization (Week 2)

After your product has dried for at least 12 hours, record its weight and its melting temperature [NOTE 13].