216 W11-IR2-1 - and 1790~1740 cm-1(two peaks • acid...

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Chem 216 W11 Topic : ___Major IR Peaks __ page 1 of 2. Important IR Peaks Use only the 4000 – 1430 cm -1 region .” This is where most of the characteristic stretching vibration absorptions appear. I . 4000 – 3100 cm -1 (1) ν O-H: 3600 ~ 3200 cm -1 broad and very strong • Intermolecular H-bonding lower cm -1 3600 ~ 3500 cm -1 : dimeric; 3400 ~ 3200 cm -1 : polymeric • Intramolecular H-bonding lower cm -1 & sharper OH band (3) ν ≡ C-H: 3310~3200 cm -1 – strong; should also see ν C C (2140~2100 cm -1 )
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Chem 216 W11 Topic : ___Major IR Peaks__ page 2 of 2. II . 3100 ~ 2700 cm -1 : ν C-H (medium to weak intensity) • aromatic and alkenic ν C-H: 3100~3010 cm -1 • alkanic (sp 3 ) ν C-H: 2960~2850 cm -1 IV . 1850 ~ 1620 cm -1 : various ν C=O; very strong • acid anhydrides: 1850~1800
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Unformatted text preview: and 1790~1740 cm-1 (two peaks) • acid halides: 1830~1780 cm-1 • esters and six-membered lactones: 1750~1735 cm-1 • aldehydes: 1730~1720 cm-1 (slightly higher cm-1 than corresponding ketone ν C=O • ketones: 1715 cm-1 (1720~1705 cm-1 ) • carboxylic acid: 1720~1700 cm-1 • amides: 1680~1640 cm-1 Notes: (1) Conjugation lowers ν C=O by 30~20 cm-1 O O CH 3 O 1715 cm-1 1685 cm-1 1695 cm-1 α,β-unsaturated ketone aryl ketone (2) Ring strain raises ν C=O O O 1740 cm-1 O O O O 1775 cm-1 1832 cm-1 O 1715 cm-1 O O 1745 cm-1 1780 cm-1 V . 1680 ~ 1500 cm-1 : various ν C=C (intensity variable) & ν C=N ( strong ) Arom ν C=C: often 2~3 or more bands at ~1600, 1500, 1400 cm-1 ; can be very strong...
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216 W11-IR2-1 - and 1790~1740 cm-1(two peaks • acid...

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