# Dr.Bob the question Ihad reposted (NOT the old one

posted by on .

Yes...another calculation problem.

Rxn:

1ml isopentyl alcohol + 1.5ml glacial acetic acid + 3 drops sulfuric acid=> isopentyl acetate

to calculate the theoretical yield..

I know that the acetic acid is in excess but how would I calculate the theoretical yield?
is it just find moles acetic acid (know excess) and then since I do know that the ratio is 1:1 then I can just find theoretical yield directly?

Another question is...

1) What catalyst is used in the experiment?
I say it's the sulfuric acid.

2) since one method of formation of ester is to add excess acetic acid. What is another way to form the ester which will favor the formation fo ester

I said that you could add excess isopentyl alcohol

3) Why is it easier to remove excess acetic acid from products than excess isopentyl alcohol?

Thank you

Some Lab Question (s) - ~christina~, Saturday, March 8, 2008 at 11:45pm
Is the last question with the "why is it easier to remove excess acetic acid from products than excess isopentyl alcohol?"

because I can just use sodium bicarbonate to remove the acid?

Is there a method to remove the isopentyl alcohol though?

• Dr.Bob the question Ihad reposted (NOT the old one - ,

1ml isopentyl alcohol + 1.5ml glacial acetic acid + 3 drops sulfuric acid=> isopentyl acetate

to calculate the theoretical yield..

I know that the acetic acid is in excess but how would I calculate the theoretical yield?
is it just find moles acetic acid (know excess) and then since I do know that the ratio is 1:1 then I can just find theoretical yield directly?
Find theoretical yield by 1 mol isopentyl alcohol gives 1 mol of the ester. If you are not positive that acetic acid is in excess, you can determine theoretical yield (1:1 again) using acetic acid as the starting material. You will then have two theoretical yields for isopentyl acetate; take the smaller one and that will be the limiting reagent. Since both isopentyl alcohol and acetic acid are liquids, you will need density in order to convert mL to grams.

Another question is...

1) What catalyst is used in the experiment?
I say it's the sulfuric acid.

I think that is correct.

2) since one method of formation of ester is to add excess acetic acid. What is another way to form the ester which will favor the formation fo ester

I said that you could add excess isopentyl alcohol
That will work since either reactant in excess will shift the equilibrium to the right and favor the formation of the ester. However, my educated gues is that the prof will consider that the same KIND of shift (adding either one in excess). I suspect the prof may be looking for the removal of isopentyl acetate. How would you do that? By distillation but look up the boiling points of the alcohol, ester, acetic acid, etc to check it out. Several books on synthesis of esters talk about sifting the equilibrium by distilling the ester as it is formed.

3) Why is it easier to remove excess acetic acid from products than excess isopentyl alcohol?
NaHCO3 is the way to go for removal of the two acids. To try to separate two organic compounds, one an alcohol and the other an ester would be MUCH tougher. So we take the easier route.

• Dr.Bob the question Ihad reposted (NOT the old one - ,