♦ Tension =CH: 3100 cm -1
♦ Tension -C=C-: 1600 and 1475 cm -1
♦ Flexion =CH out of plane: 900-690 cm -1
The oop vibrations together with the overtones and combination bands that appear between 2000 and 1667 cm -1 allow us to know the degree of substitution of benzene.
IR spectrum of toluene
It is convenient to remember the shape of the combination bands and the two Flexion bands oop at 750 and 690 cm -1 that indicate the presence of a single substituent on benzene (monosubstituted).
IR spectrum of ortho-xylene
Ortho-disubstituted benzenes present a bending band oop in the range 770-735 cm -1
Observe in detail the combination bands that allow us to identify this type of substitution.
IR spectrum of meta-xylene
Meta-disubstituted benzenes present two oop bending bands in the ranges 811-750 cm -1 and 725-680 cm -1
Note the combination bands for this substitution.
IR spectrum of para-xylene
Para-substituted benzenes present a bending band oop in the range 860-780 cm -1
combination bands
