Mix sodium bicarbonate (NaHCO3
) and acid (especially HCl) SLOWLY! Otherwise you'll get a science-fair worthy volcano - potentially in your face. Wear safety goggles. (What do you suppose the products are of mixing sodium bicarbonate with a strong acid?)***SAFETY WARNING***
This statement is not technically correct:
we add an acid such as HCL, which will protonate aniline and create a salt, which is soluble in NaHCO3.
Let's look more closely at the various acid/base equilibria in this problem. We have several potential acids:
|(conj. acid of aniline)|
Remebering that acid/base equilibra favor the weaker acid (the compound with the highest pKa
, do you predict the following equilibra favor the right side of the arrow, or the left side of the arrow?
HCl + aniline --><-- aniline-H+ + Cl-
NaHCO3 + aniline --><-- aniline-H+ + NaCO3-
aniline-H+ + NaHCO3 --><-- aniline + H2CO3
With those answers in mind:
--What happens when you add aqueous HCl to a mixture of naphthalene/aniline in ether?
--Do you think your HCl/ether naphthalene/aniline mixture will be one phase or biphasic?
--What happens if you add NaHCO3
to that resulting mixture of HCl/ether naphthalene/aniline, as your "will be soluble in NaHCO3
" statement implies?
--What happens after you separate your aniline from the naphthalene (is the aniline in the water layer or the ether layer? Is the aniline protonated or not?)
--And what happens when you add NaHCO3
to that separated aniline? What if you added HCl to that separated aniline?
Hopefully these questions will help you understand exactly what is going on in your acid/base extraction. Enjoy the smell of mothballs