Organic Analysis

• What can high resolution mass spectrometry determine?

  The molecular formula of a compound
• What does the peak with the highest mass/charge ratio represent?

  It represents the molecular ion
• Why is the mass/charge ratio equal to Mr for the molecular ion?

  Because the charge of the ion is +1
• What is the molecular formula of butane?

  C4H10
• What is a molecular ion?

  A molecule with one electron knocked off
• How many decimal places can high resolution mass spectroscopy measure?

  5 decimal places
• Why is high resolution mass spectroscopy useful?

  It differentiates compounds with similar Mr
• What is the accurate mass of hydrogen?

  1. 0078
• What is the accurate mass of carbon?

  12.0000
• What is the accurate mass of oxygen?

  15.9949
• What is the accurate mass of nitrogen?

  14.0031
• How can a more precise Mr help in identifying molecular formulas?

  It can differentiate compounds with similar Mr
• What is the Mr of CH3CH2OH?

  $46.0417$
• What is the Mr of H2NCH2NH2?

  $46.0530$
• Which compound corresponds to the Mr of 46.0417?

  CH3CH2OH
• What happens when a compound contains chlorine or bromine atoms?

  Two molecular ion peaks will occur
• What is the m/z value of CH3Cl?

  50
• What is the ratio of heights for CH3Cl's M:M+2 peaks?

  1. 1
• What is the m/z value of CH3Br?

  94
• What is the ratio of heights for CH3Br's M:M+2 peaks?

  1. 1
• What happens if a compound contains two chlorine or bromine atoms?

  A M+2 and a M+4 peak will occur
• What is the m/z value of C2H4Cl2?

  98
• What is the ratio of heights for C2H4Cl2's M:M+2:M+4 peaks?

  1. 6:1
• What is the m/z value of C2H4Br2?

  186
• What is the ratio of heights for C2H4Br2's M:M+2:M+4 peaks?

  1. 2:1
• What is the m/z value of C2H3Cl3?

  132
• What is the ratio of heights for C2H3Cl3's M:M+2:M+4:M+6 peaks?

  27:27:9:1
• What is the purpose of infrared spectroscopy?

  • Absorb infrared radiation at characteristic frequencies
  • Identify types of bonds in a molecule
  • Provide unique "fingerprint" for compounds
• What is the fingerprint region in infrared spectroscopy?

  Below 1500 cm-1 with unique signals
• What is the range for C=O bonds in IR spectroscopy?

  1680 – 1750 cm-1

  
• How is the fingerprint region used in spectroscopy?

  To identify compounds against a database
• What does a trough between 2500-3000 cm-1 indicate?

  Presence of O-H bond in an acid
• What is the result of adding sodium carbonate to a carboxylic acid?

  Effervescence of CO2 evolved
• What are the results of test-tube reactions for functional groups?

  • Alkene: Orange colour decolourises with bromine water
  • Aldehyde: Blue to red precipitate with Fehling’s solution
  • Aldehyde: Silver mirror with Tollens’ reagent
  • Carboxylic acid: Effervescence with sodium carbonate
• What is Tollens’ reagent used for?

  To oxidize aldehydes to carboxylic acids
• What happens when aldehydes react with Tollens’ reagent?

  A silver mirror forms in the test tube
• What is the result of aldehydes reacting with Fehling’s solution?

  Blue solution changes to red precipitate
• What is the mechanism of the greenhouse effect?

  CO2 absorbs infrared radiation, warming the atmosphere
• What are the steps in the greenhouse effect process?

  1. UV radiation heats Earth's surface
  2. Earth radiates infrared radiation
  3. CO2 absorbs infrared radiation
  4. Atmosphere warms due to energy transfer