Organic analysis

• Describe the technique of infrared spectroscopy?

  • Certain groups in a molecule absorb IR radiation at characteristic frequencies
  • Complicated spectra can be obtained that provide information about the bonds present
• How do molecular ion peaks change if the compound contains chlorine/bromine?

  • There will be 2 molecular ion peaks
  • Chlorine exists as Cl35 and Cl37
  • Bromine exists as Br79 and Br81
• What is high resolution mass spectrometry?

  • When a high resolution mass spectrometer can measure atomic and molecular masses to extreme levels of accuracy
  • It is used for distinguishing between compounds that have the same Mr when rounded to the nearest whole number
• What is meant by "fingerprinting" in organic analysis?

  • Technique that allows for the identification of a particular molecule by comparison of spectra
  • Below 1500cm-1 part of the spectrum is unique for every compound so is used as a fingerprint
• Write out the equation for the equation of ethanal with Tollen's reagent

  CH3CH) + 2Ag+ + H2O -> CH3COOH + 2Ag + 2H+
• What is the test for alkenes?

  bromine water

  orange to colourless
• What are the tests for aldehydes

  1. Fehling's: blue to red ppt
  2. Tollens': silver mirror
• What is the test for carboxylic acids?

  sodium carbonate

  effervescence of CO2
• What is the test for primary and secondary alcohols?

  potassium dichromate

  orange to green
• What is the test for chloroalkanes?

  warm with silver nitrate

  slow formation of white ppt of AgCl