Spectroscopy

empirical formula calculation

# of element = (percentage)/(molecular mass)

• for ratio divide all elements by lowest #

*always assume oxygen unless stated otherwise

IR spectroscopy

gives information about what functional groups are present in a molecule

NMR Spectroscopy

gives information about structure and bonding in a molecule

H NMR signals

- chemical shifts = location of peaks (connectivity of H to elements)

- determine the # of different types of H atoms

H NMR splitting

- N+1, where N is the # of protons on the adjacent carbon

shorter

higher frequencies have a ______ wavelength

stretching frequencies

- bonds to H have higher stretching than those to heavier atoms

- double bonds lower stretching frequency

degrees of unsaturation

(2C+2-H-hal+N)/2

C-H

around 3000cm^-1

O-H

- broad rounded tip, around 3300cm^-1

N-H

- broad sharp tip, around 3300cm^-1

R2-NH

- broad w/ one sharp tip, around 3300cm^-1

N-H2

- broad w/ two sharp tip, around 3300cm^-1

C=O

- around 1710cm^-1

Aldehyde

two C-H signals around 2700cm^-1