Spectroscopy

What is the electromagnetic spectrum (lowest energy to high energy)

radio, microwave, infrared, visible, ultraviolet, x-ray, gamma

IR spectroscopy

causes bonds to vibrate at different frequencies, shows which functional groups are present

UV spectroscopy

passing uv light through a chemical sample and plotting absorbance v wavelength

What does UV light do to molecules

provides energy for electronic transitions

IR is dependent on

change in dipole moment induced by vibrations

UV is dependent on

conjugation

batochromic shift

also known as red shift, when the absorption shifts to a lower energy

hypsochromic shift

A shift in the absorption maximum to shorter wavelength or higher energy, i.e., a blue shift.

why does a blue shift occur

when there is decreased conjugation, a nonpolar solvent, and removal of auxochromes

chromophore

the part of the molecule that absorbs light

auxochromes

groups attached to the chromophore

1 angstrom equals

10^-10 m

1 debeye equals

3.336 x 10^30 C x m

factors that affect IR frequency

dipole moment, bond strength, bond length, heavy atoms

IR frequency of carbonyls (C=O stretch)

strong intense 'V' around 1700 cm-1

IR frequency of C-H stretches

sp3: 3000-2850 cm-1

sp2: 3150-3000 cm-1

sp: 3300 cm-1

IR frequency of N-H stretch

3300 cm-1 sharp

two peak if primary

one peak if secondary

IR Frequency: O-H (alcohol)

3300 cm broad