IR Spectroscopy

Infrared (IR) Spectroscopy

Identifies functional groups in compounds.

IR Region

Wavelength range of 1,000-15,000 nm.

C=O Peak

Strong peak at 1660-1820 cm^-1.

C-C (alkane)

Observed at 1200 cm^-1.

C=C (alkene)

Occurs at 1650 cm^-1.

C≡C (alkyne)

Found below 2200 cm^-1.

Aromatic C=C Peak

Typically around 1600 cm^-1.

C≡N

2250

Aromatic compound

~1600

R-O-H (alcohol)

Appears between 3300-3600 cm^-1.

N-H Peak

Located at 3300-3600 cm^-1, less broad. How every many peaks= how many N-H bonds

O-H Peak in Carboxylic Acid

Broad peak at 2400-3400 cm^-1.

Aldehyde Peaks

Appear at 2750 and 2850 cm^-1.

sp2 Hybridized Carbon

Peak at 3050 cm^-1.

sp Hybridized Carbon

Peak at 3300 cm^-1.

Mass Spectroscopy (MS)

Determines molecular weight of compounds.

Radical Cation

Molecular ion M^+ with a positive charge.

Base Peak

Tallest peak in mass spectrum.

Molecular ion peak

Peak that represents the molecule.

Bromine Isotopes

Equal peaks at 79 and 81 amu.

Chlorine Isotopes

3:1 ratio peaks at 35 and 37 amu.

Odd Molecular Weight

Indicates presence of nitrogen in compounds.

Alcohol Fragmentation

Loses water, M-18 peak due to loss.

Nuclear Magnetic Resonance (NMR)

Reveals carbon skeleton and connectivity.

Ultraviolet (UV) Spectroscopy

Analyzes bonding patterns in compounds.

Carboxylic Acid

2200-3600

Amine

3350-3500

Ester

1700-1750

Ketone

1680-1750

Amide

1650-1700

Iodine isotopes

127 amu