Nitration Of Methyl Benzoate

2011-04-01 1:56 am

1) why were crystals formed washed with water before recrystallisation?

2) what happens during recrystillisation to:
a) impurities
b) the main product

3) how is the loss of the product kept to a minium during recrystallisation?

4) what are the usual stages in the purification of an organic solid?

very urgent !!! thanks alot !!!!

回答 (1)

己式庚辛

2011-04-03 1:55 am

✔ 最佳答案

these should have been learnt when you study recrystallization!
how come you don't know these when you're doing organic synthesis?

1.
to wash away / remove any soluble impurities, like salts and unreacted acids.

2.
impurities remain in the impure solution.
main product crystallizes to give large solid particles.

3.
use minimal amount of solvent; solubility of product is high at high temp., at vice versa.

4.
depends on the composition of matrix.
for example, if you're purifying acid from mixture of water-insoluble substances, first react with excess base. this turns acid into water-soluble salts.
then do solvent extraction to collect salt of acid.
recover by adding acid, followed by immediate recrystallization or further solvent extraction.
washing during filtering is a must.

👍 0 👎 0