Question

In comparison of IR spectrum between salicylaldehyde and salen H2, salicylaldehyde has a peak centred around 1640 cm^-1 while salen H₂ has a peak around 1610 cm^-1. Has it moved to higher or lower energy? What does this tell you about the strength of the C=O vs the C=N bond?

Answer 1

1640 cm-1 to 1610 cm-1 means lower in energy it is a frequency

E = hv

where v is the frequency which is directly proportinal to the energy

comming to the C=O and C=N

on basic point in IR spectroscopy is that energy required to strech the bond will depends on the strength of the bond

oxygen is more electro-ve than nitrogen so

C=O is more stronger than the C=N

as we discussed above stronger bonds will take more energy to strech the bonds than the

so C=O will require higher energy = 1640 cm-1 than the C=N whic is 1610 cm-1