[Bridiewms]

In an experiment we added potassium bromide, sulphuric acid and butan-1-ol to a flask and let them react. We then collected the distilate and added aqueous sodium carbonate to it in a seperating funnel and swirled the solution. we then collected the lower layer added drying agent and sent it off for IR analyisi.

What is the reason for adding sodium carbonate to the solution?

[ARGOS++]

[Bridiewms]

Would sodium sulfate and bicarbonate be produced...The bicarbonate would reduce the acidity of the solution?

What is the relavance of the pH of the solution thou?

[aldoxime_amine]

Somehow, i don't think this reaction is even feasible (preparation of bromobutane)

[macman104]

Somehow, i don't think this reaction is even feasible (preparation of bromobutane)

Sure it is.  Create a good leaving group, attack with a nucleophile...

[aldoxime_amine]

What gaurantees dehydration will not predominate?

[macman104]

It's possible and in reality you may get a mix, slight changes in procedure (such as concentration of reactants, or temperature) can help push it either way.

[azmanam]

I've made benzyl bromide this way (actually, I just mix benzyl alcohol with straight 48% HBr.  no chance for elimination, here, but I thought I'd throw in my 2 cents.

[ARGOS++]

[Bridiewms]

Yer thanks, you been a lot of help

[ARGOS++]

[Fleaker]

I've made benzyl bromide this way (actually, I just mix benzyl alcohol with straight 48% HBr.  no chance for elimination, here, but I thought I'd throw in my 2 cents.

That is a great procedure. It also works for benzyl chloride as well. Unfortunately, both of those are extremely irritating lachrymating agents.

In this case, it's a simple protonation of the alcohol by the sulfuric and then the bromide comes along.

There is also possibility of rearrangement and having the Br on the second carbon.

The sulfuric acid is not in concentration sufficient to cause dehydration to an alkene. These reactions work well and in high yields for alkyl chlorides and bromides. (ref. Vogel) It's a pity there is not an easy way to make iodobutane or iodoethane--the sulfuric acid will simple oxidize your halide salt to iodine and nothing will happen...


Also, the base, sodium carbonate removes any formed bromine in addition to neutralizing any acid traces.