So basically what I need to know is how to do a bromination of nitrobenzene.
I have not been able to find any information on mechanisms or experimental procedures or anything. If anyone has any procedures, ideas, or places
that I could look for procedures and ideas that woud be fantastic.....thanks so much!unionised - 23-11-2003 at 14:49
Page 864 of the fifth edition of Vogel's textbook of practical organic chemistry(ISBN 0-582-46236-3)
How hard had you looked for this before you posted?Blind Angel - 24-11-2003 at 12:11
I would like to precise that not all of us has access to chem book, until this years the highest rank of chembook i had access, excepted for the PDF
found on some site, was high school chemistry handbook....unionised - 24-11-2003 at 14:20
Ok So you don't have much of a library. You do have google. If you want to brominate nitrobenzene you will obviously need bromine, nitrobenzene
and a flask.
Guess what you find if you google "bromine" "nitrobenzene" and "flask"?
Oh look a synthesis
"How hard had you looked before posting?" is still a valid question.squeeker50 - 24-11-2003 at 15:16
unionised-
Terribly sorry to be such a bother to you. For your information I have been looking on every search engine I can think of using many different key
words and phrases and have found a few mechanisms, lots of procedures for nitration of bromobenzene, but only one procedure for the bromination of
nitrobenzene that I am not capable of doing at my lab. I'm sorry, I go to a community college that doesn't have every chemistry book
published, but I did look and my proffesor has been looking and we havn't been very succesful. I found this site while searching on yahoo and
decided to give it a shot. I just thought that this was what it was for. Please forgive me, I will try not to make the misteak again of posting a
science question on a science discussion/question board. unionised - 24-11-2003 at 16:02
OK, Sorry.
I'm amazed that your prof hasn't got a copy of this book http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=257...
It has been the standard synthesis textbook since my dad did chemistry at university.BromicAcid - 24-11-2003 at 18:01
Quote:
how to do a bromination of nitrobenzene...... I have not been able to find any information on mechanisms or experimental procedures or anything
Well, because you are in college and doing synthesis you should know basic organic reactions pertaining to aromatics. Knowing that the nitro group
present will deactivate the ring toward electrophilic aromatic substitution. Let alone the fact that bromine will not normally react with benzene all
by its lonesome. Normally bromine is reacted with benzene in the presence of ferric or aluminum bromide in catalytic amounts. The same holds true
(mostly) for halogenating nitrobenzene. So take your nitrobenzene, add your aluminum or iron shavings or anhydrous aluminum or ferric bromide. Add
in slightly less then stoichiometric quantity of Br2 over a long period of time with efficent stirring and cooling if necessary to prevent bromination
from continuing beyond the first substitution (bromine is also deactivating but like the other halogens causes ortho-para substitution in spite of
this). After addition of all bromine gradually increase temperature and reflux gently for one hour or whatever being sure to exclude moisture from
the system but being sure not to close the system HBr will generate.
Then seperate, quick look at a chemical encyclopedia for differences will show there is a 46 C difference in BP, I really wouldnt go this way but,
check for azeotropes, distill off a majority of the nitrobenzene, wash what is left in flask with water (nitrobenzene slightly soluble in water plus
get rid of polar contaminates, then wash with saturated salt solution) then fraction off the bromonitrobenzene.
The nitro group will direct substitution to the meta position and a large yeild of your product will be 1 - bromo - 3 - nitrobenzene. I didn't
look up the reactions and I'm not totally sure if I'm correct but this just shows that basic organic chem, can give a decent idea of how to
perform this reaction then you can go from there and ask more pertinent questions like "Since the nitrobenzene is deactivated to its current
extent would a longer reflux then usual be necessary at higher temperatures to effectively convert all the nitrobenzene to bromonitrobenzene?"
As for the mechanism, that should be incredibly easy to find, the ferric bromide helps to turn the bromine into a stronger lewis acid which will allow
it to attack the benzene ring directly.
