Sciencemadness Discussion Board

Replacing Sulfuric Acid with Sodium Bisulfate

DFliyerz - 3-4-2015 at 11:56

I know that in a fair number of reactions concentrated sulfuric acid can be replaced with solid sodium bisulfate due to it's low melting point, such as making nitric acid from nitrates and glacial acetic acid from sodium acetate, but can it be used in reactions such as esterification of carboxylic acids? What else can it be used in?

blogfast25 - 3-4-2015 at 13:04

Quote: Originally posted by DFliyerz  
[...] but can it be used in reactions such as esterification of carboxylic acids? What else can it be used in?


I doubt very much if bisulphate has enough protonating power to protonate carboxylic acids, as required by the Fisher esterification mechanism. Bisulphates will also not be soluble in or miscible with carboxylic acids which would lead to heterogeneous catalysis.

brubei - 3-4-2015 at 13:42

any other mineral acid work too, paratoluenesulfonic acid (APTS) is also a common organic acid suitable for esterification

[Edited on 3-4-2015 by brubei]

blogfast25 - 3-4-2015 at 13:48

Quote: Originally posted by brubei  
any other mineral acid work too, paratoluenesulfonic acid (APTS) is also a common organic acid suitable for esterification


Something tells me that someone clearly looking to replace sulphuric acid by a bisulphate won't have access to paratoluenesulfonic acid. ;)

papaya - 3-4-2015 at 13:50

Is it true that heating bisulphate yields sulfuric acid that can be distilled and collected, or was it only SO3 ?

DFliyerz - 3-4-2015 at 14:07

Also, it can be used to make hydrochloric acid from sodium chloride. So from what I can see, it's kinda like a sulfuric acid solid.

blogfast25 - 3-4-2015 at 14:08

Quote: Originally posted by papaya  
Is it true that heating bisulphate yields sulfuric acid that can be distilled and collected, or was it only SO3 ?


First it decomposes to sodium pyrosulphate, which around 500 C starts releasing SO<sub>3</sub>.

DFliyerz - 3-4-2015 at 14:44

Quote: Originally posted by blogfast25  
Quote: Originally posted by papaya  
Is it true that heating bisulphate yields sulfuric acid that can be distilled and collected, or was it only SO3 ?


First it decomposes to sodium pyrosulphate, which around 500 C starts releasing SO<sub>3</sub>.


Apparently though it doesn't need to decompose to make glacial acetic, and it's actually bad for it to decompose for that synthesis: https://www.youtube.com/watch?v=QQWvgLxtldc

blogfast25 - 3-4-2015 at 15:21

Quote: Originally posted by DFliyerz  

Apparently though it doesn't need to decompose to make glacial acetic, and it's actually bad for it to decompose for that synthesis: https://www.youtube.com/watch?v=QQWvgLxtldc


Well no. To displace acetic acid from sodium acetate with a stronger acid you basically need about 120 C, just above the BP of acetic acid.