[anilin]

what does "para substitution out of the plane" mean in interpretation of IR spectroscopy? for example for P-aminophnol which bonds correspond to para substitution out of the plane in its IR diagram? do we get two peaks or one for that? could you recommend a book on this problem?
Thanks

[KritikalMass]

Imagine you are standing up with your arms at your side. If you raise your arms out to the sides that would be like in plane bending. If you raised your arms out in front of you that would be like out of the plane bending.

So if you look at the molecule, then in plane bending would be the amino and hydroxyl groups wagging left to right. Out of plane bending would be the amino and hydroxyl groups moving toward you and away from you.

The para just refers to the orientation of the substituents with respect to one another on the ring. Para they are arranged opposite, meta they are diagonal, and ortho they are side by side on adjacent carbons. In the picture below the first one is ortho, the 2nd one is meta, the last one is para.

In the IR spectra not sure how many peaks you would get, would guess two since you have to different functional groups on the ring.

Hope that helped and hope I didn't confuse you!

[Darwin]

In the IR spectrum you'll only see one band for para-substitution (C-H out-of-plane bending vibration). This band normally lies just to the left of 800 cm^-1 (815 - 800 cm^-1), but it can be shifted to either side depending on the substituents.