Synthesis of Triphenylmethanol

Question 1

purpose of experiment

Answer 1

the purpose of this experiment is to prepare and use a Grignard reagent to prepare triphenylmethanol in a 2-step synthesis

Question 2

bromobenzene

Answer 2

starting material

Question 3

methyl benzoate

Answer 3

reactant

Question 4

magnesium

Answer 4

reactant part of grignard

Question 5

magnesium sulfate anhydride

Answer 5

dehydrating agent

Question 6

10% sulfuric acid

Answer 6

washing of the ether layer

Question 7

NaCl

Answer 7

?

Question 8

diethyl anhydride

Answer 8

drying agent

Question 9

petroleum ether

Answer 9

washing of product

Question 10

experimental set up

Answer 10

• *it is really important for all of the glassware in this experiment to be dry**
• this lab was a 2-part synthesis:
  1. magnesium and bromobenzene are reacted in order to make the grignard reagent phenylmagnesium
  2. the grignard is is combined w/ methyl benzoate (this is a nucleophilic substitution reaction)

Question 11

Why must the apparatus be rigorously dry?

Answer 11

the water will react with the grignard, and we don’t want that to happen!

Question 12

Formation of the Grignard reagent takes place at the surface of Mg. What is the purpose of grinding the Mg?

Answer 12

grinding the Mg will increase the surface area to react and create the grignard- it will get the reaction going

Question 13

Why should the bromobenzene be added drop wise, a little at a time?

Answer 13

bromobenzene should be added drop wise to control the reaction from boiling over during reflux

Question 14

How does the reaction mixture reflux without the application of heat?

Answer 14

the reaction mixture refluxes without heat because ether boils at a low temperature, and the reaction is very vigorous

Question 15

Step 4: this is the messy step-this is when ice and acid is added to the flask, and to this added to the reaction mixture.

1. Why is ice used?
2. What reaction is occurring at this step?
3. Why is only “ordinary” ether called for in this step?

Answer 15

1. ice is used to stop the reaction and for recrystallization
2. the reaction at this step is removing the grignard reagent
3. only “ordinary” ether is used at this step because it was only needed as a solvent and not as a reagent.

Question 16

week 2- what is the purpose of the saturated sodium chloride solution?

Answer 16

NaCl is used to wash the ether layer and remove the Mg

Question 17

What is the difference b/t ether and petroleum ether?

Answer 17

the difference b/t ether and pet ether is that pet ether is not actually and ether b/c it lacks the ROR chain

Question 18

Pre Lab ?’s:

1. Be able to identify the major peaks on the IR spectrum of triphenylmethanol.
2. What is the difference between ethyl ether and petroleum ether. That is, what type of functional group does each contain?
3. Draw the structure of the product of step 5 of this procedure.

Answer 18

1. see IR
2. the difference b/t ethyl ether and petroleum ether is that diethyl ether has methyl ends but petroleum ether has benzene rings as functional groups
3. ?