Interpreting NMR Spectra•Calculate elements of unsaturation (1/2(2C+2-H), ignore O, halogens count as H’s•Count number of signals (equals number of types of H)•Check integration to determine ratio of types of H•Check splitting to determine connectivity•Use chemical shift table to identify types of H•Work out fragments•Assemble fragments, remembering rules of bonding•Check result to make sure it matches formula and number of types of H.

Signal a, 4 UnitsSeptet, 1.34 ppm

Signal b, 12 unitsTriplet, 0.91 ppm

C3H8 EoU=0

2 signals, 2 types of H

Ratio is 1:3 or 2:6a is a septet, so 6 H’s adjacentb is a triplet, so 2 H’s adjacent

a is at 1.3 ppm: CH2?b is at 0.9 ppm: CH3?

Structure is CH3CH2CH3

C4H8O2, EoU=1

a, quartet4 units b, singlet

6 unitsc, triplet6 units

3 signals, 3 types of H Ratio is 4:6:6 (or 2:3:3)

a is a quartet, adjacent to 3Hb is a singlet, adjacent to 0Hc is a triplet, adjacent to 2H

a at 4.1 ppm, CH2O?b at 2.0 ppm, CH3C=O?c at 1.4 ppm, CH3?

Structure is CH3C(O)OCH2CH3

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Magnetic Sector Mass Spectrometer

Important Isotopes

Isotopes in MS

Branched Hydrocarbons

The MS for branched saturated hydrocarbons are similar, except certain fragments become more prominent.

IR Spectrometer

• Lightsource, sample, wavelength selector, detector

• CW and FT