GreenD - 13-7-2011 at 13:25
NaBr (actually I think I have KBr), ethanol, H2SO4 and a small amount of water have been mixing for quite some time.
I used the same molar ratios as http://www.youtube.com/watch?v=7Jn0z5BGpR0 who is from this board, although about a 10th of the scale.
After about 1 hour the solution turned a light yellow / orange. After about 4 hours it seemed to maintain the same yellow/orange color, and assumed no
more reaction was going to take place.
I added a slight bit more H2SO4, nothing.
I added a slight bit more ethanol, nothing.
After 12 hours - nothing changed, still lots of solid KBr. Added quite a bit of ethanol, H2SO4 and a small amount of H2O. Still not
much change.
Is the other product of this reaction NaOH, which would be quenched by the H2SO4 to make H2O and Na(x)SO4? I'm wondering why the video uses almost a
1:1 ratio of water to reagents if H2O is a product of the reaction, wouldn't this be unfavorable for product?!
AndersHoveland - 14-7-2011 at 09:26
Phosphoric acid is preferable over sulfuric acid to avoid oxidation, but sulfuric acid can still be used.
(bottom of page)
http://sites.google.com/site/energeticchemical/organic-precu...
An alternative method is to react ethane with bromine vapor in sunlight for several hours, but the bromoethane will be contaminated by dibromoethanes.
garage chemist - 14-7-2011 at 14:36
It is completely normal that the crystalline NaBr does not dissolve during the reaction. It just slowly turns into solid NaHSO4 without change in
appearance.
And you have to distill off the EtBr as it is formed, and then properly work up the distillate! Is anything distilling?
Do not add more ethanol or acid, the reagent ratios in the video seem fine to me.
We have an excellent thread on the preparation of alkyl bromides here, where I have also described my experience making EtBr and BuBr. Search for it.