Some carbonyl groups absorb above 1710cm",and this is characteristic of either esters,or strained cyclic ketones. Diagram 12-9c Characteristic absorptions of C-N bonds Carbon-nitrogen stretching frequencies are similar to carbon-carbon frequencies,except the absorptions are usually stronger. C-N Single bond 1200cm C=N Double bond 1600cm CN Triple bond >2200cm wavelength (um) 3.5 44.555566.57 891011121416 80 60 C=N 40 20 fingerprint region 3000 2500 200018001600 140012001000800 60 wavenumber(cm Summary It may seem like there is just too much data to learn,but just learn the general areas,and remember how strain and conjugation affects the frequencies. Diagram 12-11 and table 12-2.(SLIDES) IR spectroscopy is valuable since (a)it shows what functional groups are present (b)it indicates the absence of other functional groups (c)by comparison with an authentic sample,it can confirm the identity of a compound. Chl2 IR and MS Pagel3Some carbonyl groups absorb above 1710cm-1, and this is characteristic of either esters, or strained cyclic ketones. Diagram 12-9c Characteristic absorptions of C-N bonds Carbon-nitrogen stretching frequencies are similar to carbon-carbon frequencies, except the absorptions are usually stronger. C-N Single bond 1200cm-1 C=N Double bond 1600cm-1 CN Triple bond >2200cm-1 Summary It may seem like there is just too much data to learn, but just learn the general areas, and remember how strain and conjugation affects the frequencies. Diagram 12-11 and table 12-2. (SLIDES) IR spectroscopy is valuable since (a) it shows what functional groups are present (b) it indicates the absence of other functional groups (c) by comparison with an authentic sample, it can confirm the identity of a compound. Ch12 IR and MS Page13