Infrared spectroscopy

Bond variations

All bonds vibrate at a characteristics frequency

What does the frequency depends on?

The mass of the atoms in the bond

The bond strength

The type of vibrations

The frequencies at which they vibrate are in the infra- red region of the electromagnetic spectrum

What is infrared spectroscopy

It's an analytical technique that provides information about the functional groups present in a compound

Certain groups of atom absorb characteristics frequencies of infrared radiations as the bond between them undergo transitions between different vibrational energy levels

IR spectra

If the IR is passed through the compound it will absorb some or all the light at the frequencies at which it's bond vibrate

What are the wavenumber use as? ( cm -1 )

A measure of the wavelength or frequency of the absorption

What is the equation for calculating wavenmber?

Wavenumber =) 1 / wavelength ( cm )

What are the range for IR light absorption

4000 - 400 cm -1

What is the wavenumber for identifying functional groups

Above 1500 cm-1

What is the wavenumber used for fingerprint

Below 1500 cm-1

Alcohol

O - H stretch

Aldehyde or ketone

C = O stretch

Carboxylic acid

O - H and C = O stretch