The Double Bond Region 2000-1500 cm

The principal bands in this region are due to C=C and C=0 stretching. Carbonyl stretching is one of the easiest absorptions to recognise in an infrared spectrum. It is usually the most intense band in the spectrum, and depending on the type of C=0 bond, occurs in the region 1830-1650 cm i. It should be noted, however, that metal carbonyls may absorb above 2000 cm.  

The C=C stretching band is much weaker and occurs at around 1650 cm i. This band is often absent for symmetry or dipole moment reasons. The C=N stretching band also occurs in this region and is usually stronger.- 

The N—bending vibration in amines occurs between 1630 and 1500 cmy and- is usually strong. Before assigning a band, always check the N—stretching region above 3000 cm i in order to avoid any possible confusion. 

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The double bond region (2000-1500 cm 1), where in catalytic studies bridge-bonded CO, as well as carbonyl groups in adsorbed molecules (around 1700 cm 1), absorb,... 

I The region from 2000 to 1500 cm"1 is where double bonds (0=0, C=N, and C=C) absorb. Carbonyl groups generally absorb in the range 1680 to 1750 cm-1, and alkene stretching normally occurs in the narrow range 1640 to 1680 cm-1. 

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