QUESTION: I need help calculating the theoretical yield of TPM (Triphenylmethano
ID: 564388 • Letter: Q
Question
QUESTION: I need help calculating the theoretical yield of TPM (Triphenylmethanol) and the crude and pure percent yields. Thanks!
MASS OF TRIPHENYLMETHANOL IS 0.008G. PLEASE REFER TO TABLE ON LAST PICTURE.
3.30.3 Unit 1: Grignard Synthesis and Analysis of Triphenylmethanol In this unit you will use techniques learned first semester to perform a multistep synthesis and purification and analyze your product for purity and to validate its identity Background and Chemistry of the Reaction: Read Williamson, Ch. 38, pp. 528-538. The chemistry will also be discussed in prelab. Precedure: This is a rather complex procedure which requires that great care be taken to keep all equipment and chemicals free of H0 until step 10, to avoid any unwanted side reaction which destroys the Grignard reagent. Once the product is formed, Hao is no longer a problem, The procedure below is essentially the same as in the text, but outlined in step-by-step fashion to make it a bit easier to follow Weeks ons Reaction 1: Making the Grignard reagent (Phenylmagnesium bromide) 1) Obtain from the drying oven the following equipment 2 needles 2 reaction tubes 2 vials I glass rod You will also receive the following items clean& dry: 1 syringe &2 rubber septa 0,033 2) Set up your Mg solution: Weigh out two pieces of Mg metal. The mass should be as close to 0.060g as possible or a bit more, but do record the exact mass. Transfer the Mg mctal to a dry reaction tube. Add 1.0 mL of dry diethyl ether using the syringe provided with the ether. Cap the tube with a rubber septum. 3) Set up your bromobenzene solution: Weigh out 0.330 g of bromobenzene (the best way to go about this is to convert this given mass of bromobenzene to volume by using the formula: density mass/volume; you will find the density of bromobenzene in catalog). Transfer the bromobenzene into one of the vials, add 0.7 mL of dry diethyl ether and cap the vial, 440 OML 4) As a vent for pressure, insert one of the needles in the septum covering the reaction tube containing the Mg. Use your dry syringe fitted with dry needle to transfer about a quarter of the bromobenzene/diethyl ether solution into the reaction tube slowly, in a drop-wise manner. Quickly remove the septum from the reaction tube and use the dry glass rod to crush the Mg pieces to get the reaction going (it should begin to boil). Cap it immediately and continue to slowly add the rest of the bromobenzene/diethyl ether solution. The solution should reflux at a moderate rate and begin to turn brown. 5) 6) Reflux mixture until as much Mg reacts as possible. If the reaction slows down, it may be warmed in a 35° water bath. If unreacted Mg remains at the bottom of the tube, try crushing it further or add another tiny drop of bromobenzene to the mixture. Try to maintain a solvent level of about 1.0 mL When it appears that no more Mg will react, proceed to the next step. What you have in the reaction tube at this point is your Grignard reagent.Explanation / Answer
For the given reaction,
benzophenone + phenylmagnesium bromide --> triphenylmethanol
1 mole of benzophenone reacts to form 1 mole of triphenylmethanol
moles of benzophenone = 0.002 mole
moles of triphenylmethanol formed = 0.002 mole
theoretical yield of triphenylmethanol = 0.002 mole x 260.336 g/mol = 0.521 g
Experimental yield of triphenylmethanol = 0.008 g
Percent yield = (0.008/0.521) x 100 = 1.54%