Chemical Forums
Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: Braden126 on October 07, 2015, 12:25:12 PM
-
Having trouble matching the following compounds to their corresponding IR bands.
I think for Biphenyl that it's number 1.
Also I think Benzamide corresponds to number 7.
I am not sure on Benzonitrile.
Any assistance is appreciated. Thank you
-
Well, benzonitrile is probably the easiest because the C≡N group has a fairly characteristic medium-strong stretching vibration.. where? :)
Amide carbonyl is also fairly characteristic, especially because it's accompanied by some N-H stretching and bending modes. The bending modes are fairly low frequency, which rules out 7. Because it's an unsubstituted amide, you should also expect two high frequency stretches, one stronger than the other.
For biphenyl, my first thought would be to look for a really low frequency dihedral wag. Not sure where that would show up, maybe lower than what's reported here. Mostly what you'll have is C-H stretch (3000ish) and bends (1400is), plus maybe some aromatic breathing modes (low freq).