Module 4: Chapter 17 (Spectroscopy)

• identify the molecular mass of an organic compound 2. give further information about the structure

• in the spectrometer the molecule loses an electron to form a positive ion (ion is called the molecular ion) • m/z ratio detected of the ion and it shows up as the highest mass peak on the spectrum (the molecular ion peak) • assuming z = 1 its value will be equivalent to the molecular mass of the compound

• some molecular ions break down into smaller fragments • two species are formed; a positively charged fragment ion and an uncharged radical • peak heights reflect the likely hood of the particular fragmentation (the positively charged fragment, no the lost species)

• all molecule fragment in slightly different ways according to their structure, therefore a compound’s mass spectrum is unique and can be used to identify it (unknown compounds) • mass spectrometry is amongst the techniques used in sport to test urine samples for banned substances

• covalent bonds in molecule posses energy and have a natural vibration about a central point • they can absorb infrared radiation, this makes them vibrate more • vibrates can be stretches or bends (bends change bond angle) • only absorbs IR that has the same frequency as the natural frequency of the bond

• the mass of atoms (heavier = slower vibration) 2. the strength of bonds (stronger = faster vibration)

1 / wavelength in cm^3 • wavenumber is directly proportional to frequency

• used to monitor levels of localised pollution from nitrogen monoxide and hydrocarbons • IR-based breathalysers measure the ethanol levels in captured breath