Home >
Community >
Why is the addition of methanol during the prepartion of the liquid crystal cholesteryl benzoate necesary
Upvote
29
Downvote
+ Recrystallization
+ Chemistry
Posted by
Laszlo Petruska
Why is the addition of methanol during the prepartion of the liquid crystal cholesteryl benzoate necesary
Pyridinium hydrochloride and methyl benzoate are both soluble in methanol and thus will be washed through the filter leaving behind clean cholesteryl benzoate. If you don't use the methanol the solid you produce will be impure and sticky; the methyl benzoate and pyridinium hydrochloride will not pass through the filter but will bind to the product crystals.. Methanol also removes any excess of benzoyl chloride by reacting with it.
Pyridinium hydrochloride and methyl benzoate are both soluble in methanol and thus will be washed through the filter leaving behind clean cholesteryl benzoate. If you don't use the methanol the solid you produce will be impure and sticky; the methyl benzoate and pyridinium hydrochloride will not pass through the filter but will bind to the product crystals.. Methanol also removes any excess of benzoyl chloride by reacting with it.
The usual phrase is "work up" by addition of....whatever. This can be as simple as ammonium chloride soln to neutralise anions, or can be something to react with excess reagent and stop the reaction. However as you move forward into more complex procedures the problem of removing excess reagents and unreacted starting materials becomes far more significant.More
There is a pattern in all organic preparations that there is some kind of intermediate substance that is usually added in order to allow for better separation. In the british education system the reason for adding this intermediate substance (not an official name- just a term that I am using) is always just said to be added to react with some substance within the solution. Should I assume that the necessity of this is ALWYAS to allow you to separate away your desired product from most of the stuff within the mixture?More
It seems like just saying that we want to remove a certain substance within the mixture is a cruel oversimplification. As illustrated by your answer, this is only a proxy to the true reason, which is not to leave behinde a sticky substance that contains a complicated mixture that is not the cholesteryl benzoate that we want.More
It is certainly a simplification. Having a well-worked out procedure that delivers pure product is a rarity in synthetic chemistry. All too often getting hold of the clean desired product is far more challenging than running the reaction.More
Pyridinium hydrochloride and methyl benzoate are both soluble in methanol and thus will be washed through the filter leaving behind clean cholesteryl benzoate. If you don't use the methanol the solid you produce will be impure and sticky; the methyl benzoate and pyridinium hydrochloride will not pass through the filter but will bind to the product crystals.. Methanol also removes any excess of benzoyl chloride by reacting with it.
Pyridinium hydrochloride and methyl benzoate are both soluble in methanol and thus will be washed through the filter leaving behind clean cholesteryl benzoate. If you don't use the methanol the solid you produce will be impure and sticky; the methyl benzoate and pyridinium hydrochloride will not pass through the filter but will bind to the product crystals.. Methanol also removes any excess of benzoyl chloride by reacting with it.
More
VOTE
VOTE
VOTE
VOTE
VOTE