Chapter 17 (spectroscephy)

• identify molecular mass of an unknown or known compound

molecular ion (m+): the organic compound that is put into the mass spec, loses an electron and forms a positive ion

• The molecular ion breaks down into smaller pieces (fragments) • other peaks in mass spec are caused by fragment ions formed from the breakdown of the molecular ion • fragment ions are always positively charged • when molecular ions fragment non charged radicals form which are not detected by the mass spec

• 4 steps: ionisation, acceleration, deflation, detection • molecule is ionised and fragmented • the base peak is the most abundant peak

E.g ethanol: - M + at m/z = 46 - small m + 1 peak at m/z = 47 - link fragments to orignal molecule

• IR causes covalent bonds to vibrate more and absorb energy • molecules will absorb IR energy at a frequency corresponding to the frequency of the bond natural vibration • IR spec detects how the absorption of a sample of a sample varies with wave number • it used to identify functional groups that are present in a molecule

• absorption of IR radiation by atmospheric gasses containing C-O, O-H, C-H • vibrating bonds in the bonds re-emit the absorbed energy from the sun as radiation that increases the temperature of the atmosphere, this leads to global warming

• the strength of the covalent bond • mass of the atoms in the bonds, heavier atoms vibrate at a lower frequency, e.g C-Br absorbs a lower frequency than C-Cl

• measure carbon monoxide, carbon dioxide and hydrocarbons • breathalysers, determine levels of alcohol