Question

Tough IR spectroscopy problem

Answer 1

Which one of the 4 compounds is represented by the IR spectrum? It's obviously not the 4th one, but I have no clue which of the other 3 it is...

http://i.imgur.com/FeshoeQ.jpg

Answer 2

Here are the IR charts I found online, even with the answers I have trouble figuring out the answer!!

2-bromoethylbenzene:
http://webbook.nist.gov/cgi/cbook.cgi?Spec=C103639&Index=0&Type=IR

butylbenzene:
http://www.chemicalbook.com/Spectrum/104-51-8_IR1.gif

styrene:
http://www.rod.beavon.clara.net/styreneIR.gif

Answer 3

@abb0t help meee :P

Answer 4

:O
Well, for these, I use my best educated guess. I haven't got a lot of experience with NMR since there were others more experienced with this in my research group that were far more experienced and not undergrads like me at the time...but I will help as much as i can.

Answer 5

The peak @ 3000-3050 (obviously) represents: Ar-H
You can rule out the alcohol because alcohols with their strong O-H bonds show a peak in the shape of an S, and it's very noticable, in or around 3500-3650, I believe.

Answer 6

That peak @ about 1600 also shows a C-C double bond. I don't see any other clear peak that shows an alkane. So I am going to say that it's the benzene with the double bond.

The third one.

Answer 7

But I believe all arenes have that :/ All arenes have the Ar-H at 3000-3100, those little bumps between 1700-2000 and C=C bonds 1450-1650 (according to my textbook).

The only thing I can think of is that there's a peak right before 1400 which means there's a terminal methyl group. The only compound with that is the 1st one...

Answer 8

IR is harddd

Answer 9

Anything below 1600 is unclear, from what I remember. It can mean a variable of things.

Answer 10

Exactly, the fingerprint zone! But my teacher wants us to use that specific one... Yeah I think that makes sense if I look at the IR spectrums that I posted the only one with a peak before 1400 is butylbenzene

Answer 11

Lol. IR is the easiest compared to C-NMR. For me, H-NMR was really tough.

Answer 12

Can't wait :P I'm pretty sure of this answer just'd like to check it: I got the ester

http://i.imgur.com/EsBCPEU.jpg

Answer 13

I'm not sure, but I think butylbenzene is not one of your choices.

Answer 14

and i think you may be confusing it with the first one. Which is actually: