Synthesis of Triphenylmethanol Flashcards
purpose of experiment
the purpose of this experiment is to prepare and use a Grignard reagent to prepare triphenylmethanol in a 2-step synthesis
bromobenzene
starting material
methyl benzoate
reactant
magnesium
reactant part of grignard
magnesium sulfate anhydride
dehydrating agent
10% sulfuric acid
washing of the ether layer
NaCl
?
diethyl anhydride
drying agent
petroleum ether
washing of product
experimental set up
- *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)
Why must the apparatus be rigorously dry?
the water will react with the grignard, and we don’t want that to happen!
Formation of the Grignard reagent takes place at the surface of Mg. What is the purpose of grinding the Mg?
grinding the Mg will increase the surface area to react and create the grignard- it will get the reaction going
Why should the bromobenzene be added drop wise, a little at a time?
bromobenzene should be added drop wise to control the reaction from boiling over during reflux
How does the reaction mixture reflux without the application of heat?
the reaction mixture refluxes without heat because ether boils at a low temperature, and the reaction is very vigorous
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.
- Why is ice used?
- What reaction is occurring at this step?
- Why is only “ordinary” ether called for in this step?
- ice is used to stop the reaction and for recrystallization
- the reaction at this step is removing the grignard reagent
- only “ordinary” ether is used at this step because it was only needed as a solvent and not as a reagent.
week 2- what is the purpose of the saturated sodium chloride solution?
NaCl is used to wash the ether layer and remove the Mg
What is the difference b/t ether and petroleum ether?
the difference b/t ether and pet ether is that pet ether is not actually and ether b/c it lacks the ROR chain
Pre Lab ?’s:
- Be able to identify the major peaks on the IR spectrum of triphenylmethanol.
- What is the difference between ethyl ether and petroleum ether. That is, what type of functional group does each contain?
- Draw the structure of the product of step 5 of this procedure.
- see IR
- 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
- ?
