Home > Community > NMR spectrum of isomers of nitro bromobenzene
Upvote

VOTE

Downvote
+ Organic
Posted by
Lisa Ford

NMR spectrum of isomers of nitro bromobenzene

Dental Private  Follow
Quote from:
2D-nmr?

Unfortunately impossible at this point, this is an experiment from few weeks ago that I only have this data available from, and both uni and labs are closed due to the virus. Wish I could though!

Quote from:
Have you ruled out that any peaks might be starting material or be the result of a second nitration?

No, I haven't. All we did actually was cold conc. sulphuric and nitric acid with bromobenzene, kept below 65°, refluxed, added to ice-cold water, solid filtrated, washed with water, dried, recrystallised from hot ethanol (to give the first, apparently pure crop of crystals) and the liquid remaining after recrystallisation had solvent removed by rotary evaporation - this second product is what I have an NMR of. Quite likely that thos will be the impurities, not the meta isomer. In the video I was looking at the meta isomer appears to have wide-spread triplet, doublet, narrow triplet and a doublet, whereas in my spectrum it is at most a very narrow triplet and three doublets (looking from larger to lower chemical shift). Maybe rather than forcing the observations to fit my meta theory it's better to say that it's probably the impurities form further nitration.

Thanks everyone for the help so far!

More

Upvote

VOTE

Downvote
Donald Werve  Follow
1). Don’t worry, it often happens. Despite what simplifyingly figuring in many textbooks, little amounts of meta- derivatives are almost always formed during ortho/para directing electrophilic aromatic substitutions.
2). This does not work like that. Ortho/para protons to electron donating groups are upfielded, in contrast to ortho/para protons to electron withdrawing groups that are downfielded.

More

Upvote

VOTE

Downvote
Connie Francisco's Space  Follow
2D-nmr?

More

Upvote

VOTE

Downvote
Alexandre Omeyer  Follow
Have you ruled out that any peaks might be starting material or be the result of a second nitration?  I don't think that either possibility is all that likely, but one does not want to jump to conclusions, either.

More

Upvote

VOTE

Downvote
Dave Belyea  Follow
Yes indeed! Impurities by further nitration, may also be present.

More

Upvote

VOTE

Downvote