Today, I succesfully synthesized ethyl bromide (Bromoethane) from just 2 chemicals: ethanol and bromine.. I couldn't find a post about it on here, so
I thought I'd share, since in Europe sulfuric acid (or similar) are very hard to get or very expensive.
Synthesis of Ethyl Bromide
First, 30 g 95% Ethanol was added to a 3-neck RBF with a stopper, condenser and an addition funnel containing 26 g Bromine. The mixture was heated to
reflux, at which point, the bromine was added in around 3 portions, allowing time between the addition until the mixture became clear.
When the last portion of bromine was added, the mixture did not become clear, which probably means I added too much bromine, so a bit more ethanol was
added (through the condenser so the amount of ethyl bromide evaporating was minimized) until the mixtrure turned clear.
The mixture was boiled for 1 hour more. Afterwhich the ethylbromide was distilled off at around 40 C. The yield is about 50%, which is not a lot but
is expected. Sulfur can be added as catalyst, or the reaction can be done under UV-light, if I remember correctly.
Nice thread and method. I would think that reaction would still work well even without UV light since the alcohol can be oxidised to the carbonyl and
reducing Br2->2HBr. The patent gives different equations probably because they use UV light (but I didn't read it thoroughly yet). So in theory
(without UV light) for every mole of Br2 have 1.5mol of alcohol and perform yield calculation with respect to Br2 not alcoholchloric1 - 31-12-2024 at 19:37
When there is a will there is a way. I hate restrictions on chemicals. Not because it limits access to chemicals but because it’s stupid and
clever people find ways to work around it. Here’s an idea, focus on punishing people that do bad things not the chemicals they use. Seriously
it’s like punishing the rain for lives lost in flash floods!Maui3 - 1-1-2025 at 01:02
Thank you jackchem2001! Those are great points!
Chloric1, I definitely agree with you.Keras - 1-1-2025 at 01:20
Wouldn't HBr, which is freely available, give better yields? Besides dispensing with dealing with elemental bromine, which is never fun.Maui3 - 1-1-2025 at 01:43
Well then you'd have to use H2SO4 too, to dry the HBr. I geuss sodium bromide and sodium bisulfate could be used instead of H2SO4, but I am not sure..Keras - 1-1-2025 at 02:47
Yeah, using HBr with primary alcohols is possible, but Vogel says that without sulphuric acid the yield is less and the reaction time increased.
Strangely enough, alkyls chloride can be prepared from 36% HCl and ZnCl₂ in a somewhat satisfactory yield (~ ⅔).
Also you can try alkyl iodides from phosphoric acid and KI. Maui3 - 1-1-2025 at 02:52
Interesting, thanks!Metacelsus - 1-1-2025 at 10:15
How does the redox balance work in this reaction? Shouldn't something be getting oxidized here, since the bromine is getting reduced?AvBaeyer - 1-1-2025 at 19:23
Bromine will oxidize ethanol to tribromoacetaldehyde analogous to the preparation of chloral from chlorine and ethanol. In the process, considerable
hydrogen bromide will be formed which is available to produce bromoethane which is inert to further oxidation under the reaction conditions.
AvBMaui3 - 2-1-2025 at 01:26
I smelled bromal too.Metacelsus - 2-1-2025 at 08:47
Cool, makes sense.jackchem2001 - 2-1-2025 at 17:03
How does the redox balance work in this reaction? Shouldn't something be getting oxidized here, since the bromine is getting reduced?
I would draw an ionic mechanism a bit like this
And bromal (tribromoacetaldehyde) is from enol of acetaldehyde and Br2, which also gives HBr at each bromination.
Patent says SO2 helps yield since it will be oxidised to sulfuric acid. SO2 is quite soluble so maybe bubble in a bit from metabisulfite + acid
generator before adding the bromine to help yield
