Expt. 14.1 A The Grignard Synthesis of Triphenylmethanol Week 2

Reaction Review Step 1: Preparation of Grignard Reagent Step 2: Reaction of Grignard Reagent with the ketone

Reaction Step 3: Hydrolysis to form the alcohol

Competing Reactions

Pre-lab Preparation – week 2 Construct a flowchart for the isolation, and purification of triphenylmethanol Template has been provided in lab; fill in the parts that are missing. All the things in the top box have to find a home in the boxes below. Some of the things can be in more than one box. Hint: the unreacted organic starting materials are fairly soluble in benzene. Benzene is non-polar – as is pet ether (a mixture of low boiling alkanes). Week 2 procedures must be in your notebook

Week 2 in the Lab - Tips When you left off, you had two layers in the capped centrifuge tube. You may need to add a little more ether. Also recheck the pH. Add more HCl if needed. Should have two clear layers (upper is light yellow) With all the ether extractions, the aqueous layer will be on the ____________ Diethyl ether is VERY volatile. Shake easily. Vent often.

Week 2 in the Lab - Tips When you dry the ether layer, use a 10 or 25 mL Erlenmeyer flask, not the centrifuge tube. It will take a fair amount of sodium sulfate. How do you know when it’s dry? When you evaporate the ether, use a LOW heat setting on the hot plate. After you add the pet ether, stir it thoroughly to expose all the solid. And if you don’t? Be sure to get the weight of the crude product. Take about 10 mL of isopropanol. Add in SMALL quantities. Start with ~3 mL. (5-6 mL total usually).

Workup Sequence Starting with the two layers in the centrifuge tube: We separate the two layers. The aqueous layers are extracted with ether. Why? The ether layers are washed with water. Why? Why do we have to dry the ether layer if we used anhydrous ether in the first place? We will NOT be doing any TLC analysis. We will NOT be isolating the biphenyl side product. Remember to weigh the crude product (so you can calculate the % recovery). Allow the recrystallized product to dry overnight. Determine final weight and MP.

After Lab Calculations in notebook Results and Discussion in notebook theoretical yield based on actual amounts used percent yield % recovery (from crude yield) % error of the MP Results and Discussion in notebook Identify product & evaluate purity based upon melting point range Draw the structure of your final product Complete datasheet (watch units!!)