IR Spectroscopy

Alcohol O-H

3200-3600 (Broad)

Carboxylic acid

2200-3600 (Very broad)

N-H bond

3350-3500

Hydrogen/triple-bonded carbon

~3300

Aldehyde C-H bond

2750 and 2850 (Two weak signals)

Aldehyde C=O bond

~1730

IR values will be _____ if the C=O bond is conjugated

LOWER

What does “conjugated” mean?

Resonance is possible

C=O double bond (general)

~1650-1820 (strong)

C=C bonds

1600-1700

Benzene rings

1450-1600 / 1650-2000

Carbon-carbon triple bond

2100-2200

CN triple bond

2200-2300

     |

— C — H

|

2850-3000

= C — H (note trigonal planar shape)

    |

3000-3100

O = C — O — (note trigonal planar shape)

|

1250-1350

     |

— C — O —

     |

1000-1100

C-N bond

1000-1200

C-Cl

600-800

C-Br

500-600

Anhydride, between ~1820 and ~1760

Acid chloride, ~1790

Ester, ~1735

Ketone, ~1720

Carboxylic acid, ~1715

Amide, ~1650