Analytical techniques

• What happens when a molecule absorbs infrared radiation?

  It makes the covalent bond vibrate more in a stretching or bending motion
• What happens to bonds during infrared spectroscopy?

  Bonds absorb radiation that has the same frequency as their frequency of vibration
• What does missing infrared radiation indicate in a sample?

  It indicates the frequencies that have been absorbed, which can identify the compound’s functional group
• What do the peaks on an infrared spectrum represent?

  Absorbance of energy from the infrared radiation
• What is the m/z value of C₂H₅⁺?

  29
• What occurs to some molecules in a mass spectrometer?

  Some molecules lose an electron and form molecular ions
• What is the molecular mass of the molecular ion equal to?

  Relative molecular mass of the compound
• What is the symbol of a molecular ion?

  M+
• What happens inside a mass spectrometer?

  An organic compound is vaporised and passed through the spectrometer
• How is a molecular ion represented in mass spectrometry?

  It is the peak with the highest mass/charge ratio
• Is fragmentation predictable in mass spectrometry? Why?

  No, because it can happen anywhere in the molecule
• What does vibration cause in a molecular ion?

  Vibration causes the bond to weaken
• Will the molecular ion peaks of two isomers of the same compound be the same or different?

  Same
• What effect does excess energy from ionisation have on bonds?

  It makes the bonds vibrate more