The identification and origin of N-H overtone and combination bands in the near-infrared spectra of simple primary and secondary amides

Authentication of liquid egg composition using ATR‐FTIR and NIR spectroscopy in combination with PCA

“…The last one, region E is located between 5083–4072 cm −1 and contains a combination of CH 2 vibrations of protein side chain, –CH=CH–, CH 3 , and CH 2 vibrations of the lipid substance . In addition, bands including combinations of bending and stretching each with amide II and amide III were identified in the region E (5000–4700 cm −1 ) . All regions in the NIR spectrum, the wavenumber range, the functional groups, and mode of vibrations of the molecules are provided in Table , where it can be seen that the combination modes of the molecules appear mostly in the last regions, whereas overtone modes of the molecules are more prevalent in the initial regions.…”

X-ray and vibrational studies of the complex betweenN-tert-butoxycarbonyl-L-phenylalanine and pyridine. Isotope effect

“…This absorption is assigned to the combination (C=O U )+2ϫamide II, observed in aliphatic amides. 30,31 Finally, the strong absorption at 4360 cm mode must be attributed to the (NH) vibration rather than the 3250 cm Ϫ 1 mode, which was assigned to the 2 (NH) overtone. 33,34 This lower frequency was interpreted as a strong NH bond weakening by proton transfer to the neighbouring oxygen.…”

Nondestructive Evaluation of Food Quality

“…Osborne and Douglas (1981) reported a similar effect in the case of wheat starch and the first two bands were observed at 1,450 and 1,540 nm by Law and Tkachuk (1977). The origin of amide absorption bands was proposed by Krikorian and Mahpour (1973). Secondary amines should have a single band at about 1,520-1,540 nm and 1,030 nm and aromatic primary amines at 1,460, 1,500 and 1,000 nm.…”

“…(vii) Nitrogen-hydrogen combination bands Krikorian and Mahpour (1973) reported bands at 1,960, 2,000, 2,050, 2,100 and 2,150 nm which they assigned to NH asymmetrically stretched plus amide II, NH symmetrically stretched plus amide II, NH asymmetrically stretched plus amide III, NH symmetrically stretched plus amide III and twice amide I plus amide III, respectively. Primary amines would be expected to have an NH stretched/ NH deformed combination band at about 2,000 nm.…”