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| common IR band frequencies | ||||||||||||||||||||
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List of common IR band frequencies and the corresponding molecular groups and examples for a quick spectral interpretation: Frequency (cm-1) Vibration Compound 3750-3100 O-H stretch phenolic/alcoholic 3450 and 3225 NH2 stretch primary amide 3326 N-H stretching PPTA (Kevlar) vibration 3069 C=C stretch styrene/butadiene copolymer 3050 C-H stretch aromatic 3000-2800 C-H stretch aliphatic 2918 and 2841 CH2 antisymmetric and symmetric arachidic acid stretching c-c-c=o \c-o-h 2916-2848 CH2 antisymmetric and symmetric stretching. Strong arachidic acid Intensities related to the alkyl chains tilted considerably from the surface normal. 2350 (near) CO2 carbon dioxide 2222 CN stretching TCNQ 2200 (near) CO 1944 C-O stretching band heme protein carbon monoxide with CO 1740 - 1730 C=O Stretching Hemicellulose and Cellulose -COOH, COOCH3 1700 (around) c=o stretching carboxylic group (a doublet suggests arachidic acid coexistence of cis and trans configuration.) (Also the frequency of the bands position suggest H-bonding. e.g. smaller frequency stronger H-bond) 1680 - 1660 Conjugated C=O Aromatic Units Stretching 1651 water(gas) 1650-1550 Amide transitions Heme protein 1640 C(=O)NH2 carbonyl absorption Primary amide 1639 Secondary amide Nylon 6/10 1636 C=O 1630 - 1635 Water 1605 C=C 1604 and 1556 C=C stretching benzene and thiophene ring 1595 C-H Stretch Aromatic Ring 1547-1531 C=C stretching modes. TCNQ Intensities related to orientation in the plain. 1510 C-H Stretch Aromatic ring 1510 Intense sharp peaks Functional characteristic of C=C groups in epoxy aromatic stretching. resin. 1470 to 1465 CH2 scissoring arachidic acid (singlet hexagonal subcell packing in which each hydrocarbon chain is freely rotated around its long axis) (The splitting is indicative of an orthorhombic subcell packing in which the hydrocharbon chains are packed alternatively) 1460-1450 CH3 deformation Cellulose, CH2 bending Hemicellulose CH2 scissoring Lignin 1435 C-O stretching coupled arachidic acid mode of the trans configuration. Intensities are related to increase trans stability. 1375 - 1365 C-H bending Cellulose Hemicellulose 1370 CH Cellulose Hemicellulose 1350 - 1150 CH2 wagging vibrations of the trans-zigzag arachidic acid hydrocarbon chain. 1302 OH in-plane bending vibrations of the arachidic acid trans configuration. Intensities are related to increase trans stability. 1270 - 1260 Ring Breading methoxyl or guaiacyl CO Stretching lignin 1264 and 1102 C-O stretch ester, polyethylene terphthalate 1246 C-O aromatic ether functional groups bending in epoxy resin. 1216 C-O ether linkage 1184 C-CH3 methyl epoxy resin deformation 1134 C-N stretching Aliphatic amine vibration curing agent DEH 26 1036 paradisubstituted epoxy resin benzene vibration 916 C-H deformation Epoxide ring 857 and 804 -C-H out of plain mode phenyl and thiophenyl rings 795 CCl4 730 or 720 A doublet do to crystalinity Polyethylene amorphocety 697 | |||||||||||||||||||
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