Synthesis of 3-methyl-3-pentanol

[forpoker21]

Homework Statement

A student wants to synthesize 3-methyl-3-pentanol. They react 2.3 equivalents of ethyl magnesium bromide with ethyl acetate, and then quench the reaction with sulfuric acid.

1. what is the product of the dimerization reaction?
2. What is the product from the reaction of ethyl magnesium bromide and water?
3. What two side products can potentially form from quenching the 3-methyl-3-pentoxide magnesium bromide salt with hydrochloric acid?
4. What can we use to quench the reaction to eliminate the formation of one of these products? Explain.
5. A student can't find any ethyl acetate, and decides to use acetic acid instead. Upon addition of acetic acid, he observes a vigorous reaction and he quenches his reaction with sulfuric acid. What product(s) are formed in this reaction?
6. Show a purification scheme for the reaction described in the problem statement.

Homework Equations

The Attempt at a Solution

1. So here, I think I am determining what the product is when ethyl magnesium bromide reacts with ethyl magnesium bromide. Is it butane?
2. Ethyl magnesium bromide + water -> propane + Mg(OH)Br?
3. Not sure here.
4. Maybe HCl?
5. I don't know where to start.

 

[nate808]

1. The product of the dimerization reaction is 3-methyl-3-pentanol, as stated in the problem statement.
2. The reaction of ethyl magnesium bromide and water would produce ethane and magnesium hydroxide.
3. The two side products that can potentially form from quenching the 3-methyl-3-pentoxide magnesium bromide salt with hydrochloric acid are methane and magnesium chloride.
4. We can use a weaker acid, such as acetic acid, to quench the reaction instead of hydrochloric acid. This would eliminate the formation of magnesium chloride as a side product.
5. The addition of acetic acid to the reaction would lead to the formation of acetyl chloride and methane as products. The vigorous reaction observed is due to the formation of a Grignard reagent from the reaction of acetic acid with magnesium.
6. Purification scheme:
a. First, the reaction mixture is neutralized with a weak acid, such as acetic acid, to remove any remaining Grignard reagent.
b. The mixture is then extracted with a polar solvent, such as water, to remove any water-soluble impurities.
c. The organic layer is then dried with anhydrous salt, such as magnesium sulfate, to remove any remaining water.
d. The product, 3-methyl-3-pentanol, can be isolated by distillation.
e. Any remaining impurities can be removed through recrystallization or column chromatography.