| Pages:
1
2
3
4
5 |
UnintentionalChaos
International Hazard
Posts: 1454
Registered: 9-12-2006
Location: Mars
Member Is Offline
Mood: Nucleophilic
|
|
That's why I used a small stoppered flask with a ST plug and keck clip and then transferred that to a sep. funnel to settle into two layers. Sep
funnels have this nasty habit of leaking just a little bit (in my experience) while shaking and I don't trust them with such nasties.
Department of Redundancy Department - Now with paperwork!
'In organic synthesis, we call decomposition products "crap", however this is not a IUPAC approved nomenclature.' -Nicodem
|
|
|
garage chemist
chemical wizard
Posts: 1803
Registered: 16-8-2004
Location: Germany
Member Is Offline
Mood: No Mood
|
|
Why not? I've shaken bromine with conc. H2SO4 in a sep funnel, it's really no problem.
And besides that, you can simply magnetically stir the two phases in a round-bottom flask instead of shaking them, and then pour the mix into the sep
funnel for separation only.
|
|
|
entropy51
Gone, but not forgotten
Posts: 1612
Registered: 30-5-2009
Member Is Offline
Mood: Fissile
|
|
"I've shaken bromine with conc. H2SO4 in a sep funnel, it's really no problem."
You get the Great Big Brass Pair award for that GC
|
|
|
Fleaker
International Hazard
Posts: 1252
Registered: 19-6-2005
Member Is Offline
Mood: nucleophilic
|
|
I've done it too. Just make sure that your bromine isn't horribly wet, and that it and your sulfuric acid are as cold a liquid as can be!!
When I tried this [EtBr via H2SO4/NaBr] reaction, I never had yields better than 50% even on a decent 1 mol scale. Why? Coolant water was not cold
enough!
[Edited on 11-7-2009 by Fleaker]
Neither flask nor beaker.
"Kid, you don't even know just what you don't know. "
--The Dark Lord Sauron
|
|
|
Sedit
International Hazard
Posts: 1939
Registered: 23-11-2008
Member Is Offline
Mood: Manic Expressive
|
|
That was my biggest fear when preparing to perform this but due to the volume of water my condenser handles and the fact that its comming right from a
well only a few feat away it proved to be plenty cold enough.
In the very beginning as they started to react wisp of presumably HBr vapors could be seen and if it was heated to distillation temperatures rapidly
after that it would all have been lost yeilds. I feel that I pushed the distillation along to fast and next time I will most definitly slow it down to
a crawl. I think that in doing so yeilds will be pushed up dramaticly and ether formation may also drop.
Knowledge is useless to useless people...
"I see a lot of patterns in our behavior as a nation that parallel a lot of other historical processes. The fall of Rome, the fall of Germany — the
fall of the ruling country, the people who think they can do whatever they want without anybody else's consent. I've seen this story
before."~Maynard James Keenan
|
|
|
entropy51
Gone, but not forgotten
Posts: 1612
Registered: 30-5-2009
Member Is Offline
Mood: Fissile
|
|
Sedit, I know well water is cold, but I really think you should try ice water in your condenser, even if not's not constantly flowing, but just
changed at intervals.
The reason is the HBr generated in the flask will carry some EtBr out of the condenser unless it contacts a very cold surface.
Try to rig up an adapter to run from the condenser outlet into the water in the receiver. Then the EtBr can't escape even if it all doesn't condense
in the condenser.
|
|
|
Sedit
International Hazard
Posts: 1939
Registered: 23-11-2008
Member Is Offline
Mood: Manic Expressive
|
|
Good idea.
I do have a thing for this already as I use it when using the condenser for steam distilling. The issue is its a rubber tube and I do not know the
full solvating power of EtBr just yet so I must stay a bit leary of that the first few times.
Knowledge is useless to useless people...
"I see a lot of patterns in our behavior as a nation that parallel a lot of other historical processes. The fall of Rome, the fall of Germany — the
fall of the ruling country, the people who think they can do whatever they want without anybody else's consent. I've seen this story
before."~Maynard James Keenan
|
|
|
entropy51
Gone, but not forgotten
Posts: 1612
Registered: 30-5-2009
Member Is Offline
Mood: Fissile
|
|
I wouldn't mix rubber and alkyl halides, I get HDPE (?) tubing at the hardward store that might be OK if the stuff wasn't heated. You could test a
sample of the tubing in a little EtBr in a test tube maybe.
I'll bet you could get several pieces of glass tubing for a few bucks. If you had some glassware you'd definitely be dangerous.
|
|
|
UnintentionalChaos
International Hazard
Posts: 1454
Registered: 9-12-2006
Location: Mars
Member Is Offline
Mood: Nucleophilic
|
|
It's not cheap, but FEP tubing is magical. Resistant to just about everything. I've only seen it ruined by high temperature oleum fumes.
Fleaker will back me up on this 
[Edited on 7-11-09 by UnintentionalChaos]
Department of Redundancy Department - Now with paperwork!
'In organic synthesis, we call decomposition products "crap", however this is not a IUPAC approved nomenclature.' -Nicodem
|
|
|
Lambda-Eyde
National Hazard
Posts: 860
Registered: 20-11-2008
Location: Norway
Member Is Offline
Mood: Cleaved
|
|
1-bromobutane
Yesterday I got 4 hours of free access to the school lab. I figured I'd make some 1-bromobutane (butyl bromide).
Pictures:
The setup. The addition funnel contains concentrated sulfuric acid.
You can clearly see the HBr fumes filling the apparatus and the deep red color of bromine, due to oxidation by the acid:
Here the two layers can be seen after the reaction. Top layer: BuBr and bromine along with unreacted 1-butanol. Probably some dibutyl ether too.
Bottom layer: H2SO4, NaHSO4, water.
I didn't have time for the workup, I'll probably do it on tuesday. The reaction mixture is sitting in a separatory funnel in a fume hood over the
weekend.
[Edited on 8-5-2010 by Lambda-Eyde]
|
|
|
rrkss
Hazard to Others
Posts: 193
Registered: 18-12-2009
Member Is Offline
Mood: No Mood
|
|
Interesting experiment with butyl bromide. Just curious what type of workup do you intend to run?
|
|
|
Lambda-Eyde
National Hazard
Posts: 860
Registered: 20-11-2008
Location: Norway
Member Is Offline
Mood: Cleaved
|
|
I'm following Vogel's prep for butyl bromide, which first involves distillation of the crude product. It is then washed with water, concentrated HCl,
sodium bicarbonate and then water again. If the color of the bromine persists I'll do a wash with a sodium thiosulfate solution as well. Lastly I'll
dry it over some calcium chloride and distill again.
|
|
|
DJF90
International Hazard
Posts: 2266
Registered: 15-12-2007
Location: At the bench
Member Is Offline
Mood: No Mood
|
|
Bromine on top?! Thats very odd?!
|
|
|
Lambda-Eyde
National Hazard
Posts: 860
Registered: 20-11-2008
Location: Norway
Member Is Offline
Mood: Cleaved
|
|
I figured it would go in the more apolar phase since it's not very water soluble. Also, there's much
H<sub>2</sub>SO<sub>4</sub> and NaHSO<sub>4</sub> in the bottom, polar phase, decreasing the solubility of
Br<sub>2</sub>.
If you think otherwise, please post what you think. I love to learn!
|
|
|
Sedit
International Hazard
Posts: 1939
Registered: 23-11-2008
Member Is Offline
Mood: Manic Expressive
|
|
When I made EtBr the bottom layer was the EtBr and the reaction mixture appeared abit like your upper layer although much lighter since I did all I
could to prevent oxidation of the NaBr by using a more dilute H2SO4 solution.
I may be wrong but assuming the density of BuBr is more then EtBr then I would have to think that your clear layer on the bottom is your BuBr and not
the dirty dark upper layer. The bottom layer in the picture also appears to refract light simular to what I experianced.
Knowledge is useless to useless people...
"I see a lot of patterns in our behavior as a nation that parallel a lot of other historical processes. The fall of Rome, the fall of Germany — the
fall of the ruling country, the people who think they can do whatever they want without anybody else's consent. I've seen this story
before."~Maynard James Keenan
|
|
|
Lambda-Eyde
National Hazard
Posts: 860
Registered: 20-11-2008
Location: Norway
Member Is Offline
Mood: Cleaved
|
|
But that just won't make sense. I used 55 mL 1-butanol in the synthesis, there's no way that would yield ~150 mL of 1-bromobutane!
The density of the 1-bromobutane is ~1,27 g/mL. The bottom layer with a large percentage of H<sub>2</sub>SO<sub>4</sub> and
NaHSO<sub>4</sub> probably has a higher density.
[Edited on 8-5-2010 by Lambda-Eyde]
|
|
|
Sedit
International Hazard
Posts: 1939
Registered: 23-11-2008
Member Is Offline
Mood: Manic Expressive
|
|
I never said the bottom was pure which given the densitys defined could account for the added bulk. Its easy enough to test. so ...... take it from
there and prove me wrong. I more thne likely am... iv mastered being wrong 
Knowledge is useless to useless people...
"I see a lot of patterns in our behavior as a nation that parallel a lot of other historical processes. The fall of Rome, the fall of Germany — the
fall of the ruling country, the people who think they can do whatever they want without anybody else's consent. I've seen this story
before."~Maynard James Keenan
|
|
|
Lambda-Eyde
National Hazard
Posts: 860
Registered: 20-11-2008
Location: Norway
Member Is Offline
Mood: Cleaved
|
|
Quote: Originally posted by Sedit  | I never said the bottom was pure which given the densitys defined could account for the added bulk.
|
But what would the impurities be? BuBr is completely insoluble in water.
But, you're right. I'll do some tests on tuesday prior to the workup; pH, density, smell, flammability etc.
|
|
|
Lambda-Eyde
National Hazard
Posts: 860
Registered: 20-11-2008
Location: Norway
Member Is Offline
Mood: Cleaved
|
|
I got about 45 minutes lab time today, enough to do a flammability test. The upper layer was not very flammable, but it definitely burned.
The lower layer would not burn at all.
A lot of the NaHSO<sub>4</sub> had crystallised in the separatory funnel over the weekend. I decanted the liquid from the funnel and
dissolved the NaHSO<sub>4</sub> in some water. I saved both solutions. The liquid without the majority of the
NaHSO<sub>4</sub> was put back in the separatory funnel, and I'll hopefully begin workup tomorrow.
Edit: The upper layer had a very dark purple, almost black color that was visible when I poured it (not bromine?). It had the most peculiar smell
(hard to describe), but the smell of unreacted alcohol was also easy to notice. I could not detect the smell of bromine.
The lower layer also had some of that peculiar, hard to describe smell.. Hmm.
I'll see what happens when I react the upper layer with some sodium thiosulfate.
[Edited on 10-5-2010 by Lambda-Eyde]
|
|
|
Sedit
International Hazard
Posts: 1939
Registered: 23-11-2008
Member Is Offline
Mood: Manic Expressive
|
|
It all seems a little complicated to go thru so many steps to try and determine which layer is the BuBr. Wouldn't it be just as easy to take two test
tubes filled with chilled water and add a few drops of each layer to different test tubes. The organic phase will sink to the bottom indicating which
layer is your BuBr. The aq phase so would just mix in with the water and not be noticed.
Once you got the right one then wash, seperate and distill.
Knowledge is useless to useless people...
"I see a lot of patterns in our behavior as a nation that parallel a lot of other historical processes. The fall of Rome, the fall of Germany — the
fall of the ruling country, the people who think they can do whatever they want without anybody else's consent. I've seen this story
before."~Maynard James Keenan
|
|
|
Lambda-Eyde
National Hazard
Posts: 860
Registered: 20-11-2008
Location: Norway
Member Is Offline
Mood: Cleaved
|
|
The flammability test along with the volume consideration does it for me. I'll check the densities tomorrow and hopefully do the first distillation.
|
|
|
mnick12
Hazard to Others
Posts: 404
Registered: 30-12-2009
Location: In the lab w/ Dr. Evil
Member Is Offline
Mood: devious
|
|
Propyl Bromide synthesis
Well after re-reading this thread and seeing all the good work done I thought I would have a go at n-propyl bromide. My Inspiration for this synthesis
was this thread, and it has been a while since I have contributed anything meaningful.
Before I start I feel I should post a brief waring.
Be careful propyl bromide is an alkylating agent, and probably carcinogenic.
Reactants
n-propyl alcohol 60.10gr
sulfuric acid 98.08gr
potassium bromide 119.00gr
So first I added the KBr to a 3 neck 500ml rbf. The KBr was really lumpy so I added 20ml of tap water to help break it up. Next I added all the
n-propanol to the mix, next I took a 125ml addition funnel and placed it in the middle neck of the flask. I poured the H2SO4 into the funnel and
adjusted it so that it took 1hr to add all of the H2SO4 into the mix. Once the acid was mixed in the solution sat for about an hour. Then I stoppered
off two of the necks, and in the third I placed a 200cm vigreaux column. I only had time to run it for an hour which normally would be enough, but it
was super super windy so the column got cooled really easily. Anyway the I ended up with 50ml of liquid, and I think there is about 2ml of water in
it. So I may try see if I can distill any more propyl bromide from the original mix, but I doubt that will yield anything more.
So in conclusion I would say this works pretty well, but the yields are kind of low. It would probably work better with pure HBr, but that would
require another step which can complicate things.
And now for the pics!
Here are the reactants from left to right, sulfuric acid, potassium bromide, and n-propyl alcohol.
Here is the finished product.
Sorry I dont have any other pictures, I actually took alot but for some reason they wont load into the attachment thing. These two were the only ones
that worked. So use you imagination to get the rest.
|
|
|
UnintentionalChaos
International Hazard
Posts: 1454
Registered: 9-12-2006
Location: Mars
Member Is Offline
Mood: Nucleophilic
|
|
My guess would be not enough water and needing of longer reflux.
A vigreux!? That's....a bizarre choice. That, the wind and the volatility of your product probably lead to significant losses. An efficient reflux
condenser would be recommended here.
See: http://www.orgsynth.org/orgsyn/orgsyn/prepContent.asp?prep=c...
Department of Redundancy Department - Now with paperwork!
'In organic synthesis, we call decomposition products "crap", however this is not a IUPAC approved nomenclature.' -Nicodem
|
|
|
Sedit
International Hazard
Posts: 1939
Registered: 23-11-2008
Member Is Offline
Mood: Manic Expressive
|
|
When I made the EtBr I added the H2SO4 first which forms an exothermic reaction with the alcohol atfirst then after this calmed down and I had EtSO4
<=> H2O IIRC I slowly added the NaBr after chilling the -OH acid mixture. I know there was a reason for me adding the acid first but I can not
for the life of me remember exactly what the mechanics behind it was but perhaps others could review my post or explain there own reason for why I did
this
Sorry my memory these days is short lived to say the lest.
Knowledge is useless to useless people...
"I see a lot of patterns in our behavior as a nation that parallel a lot of other historical processes. The fall of Rome, the fall of Germany — the
fall of the ruling country, the people who think they can do whatever they want without anybody else's consent. I've seen this story
before."~Maynard James Keenan
|
|
|
Arrhenius
Hazard to Others
Posts: 282
Registered: 17-8-2008
Location: US & A
Member Is Offline
Mood: Stochastic
|
|
Dissolving concentrated acids in anything will be exothermic. You're correct, there is an equilibrium between sulfuric acid, the alcohol, the
monoalkyl sulfate ester and the dialkyl sulfate ester. Surely there are competing mechanisms leading to the same product. I suspect the bromide
displacing the monoalkyl sulfate ester is the predominant reaction, though directly displacing water via the protonated alcohol may become dominant as
the reaction progresses (more water, Le Chatelier favors free alcohol + sulfuric acid). Regardless, the order of addition will not affect the
reaction, though it's probably safest to add the sulfuric acid to cold alcohol.
|
|
|
| Pages:
1
2
3
4
5 |
![[*]](images/xpblue/default_icon.gif){kind=icon}
