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 Units Septet, 1.34 ppm Signal b, 12 units Triplet, 0.91 ppm C 3 H 8 EoU=0 2 signals, 2 types of H Ratio is 1:3 or 2:6 a is a septet, so 6 H’s adjacent b is a triplet, so 2 H’s adjacent a is at 1.3 ppm: CH 2 ? b is at 0.9 ppm: CH 3 ? Structure is CH 3 CH 2 CH 3

C 4 H 8 O 2, EoU=1 a, quartet 4 units b, singlet 6 units c, triplet 6 units 3 signals, 3 types of H Ratio is 4:6:6 (or 2:3:3) a is a quartet, adjacent to 3H b is a singlet, adjacent to 0H c is a triplet, adjacent to 2H a at 4.1 ppm, CH 2 O? b at 2.0 ppm, CH 3 C=O? c at 1.4 ppm, CH 3 ? Structure is CH 3 C(O)OCH 2 CH 3

Mass Spectrometry Three things happen to molecules inside a mass spectrometer: 1. The molecules are energized in some way to create ions. 2. The ions are separated based on their mass/charge ratio. 3. The ions are detected. < mm Hg

Electron Impact Ionizaton Generate electrons: heated filament Accelerate electrons through a potential difference (voltage). Commonly: electron kinetic energy is 80 eV. (conversion 1 eV = 96.5 kJ/mole) Enough energy to ionize and cause extensive fragmentation.

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