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Chapter 14 - Organic Molecules to Medicine

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Chapter 14 - Organic Molecules to Medicine Powered By Docstoc
					Chapter 14 – From Organic
 Molecules to Medicines
                             Aspirin
• Pharmaceutical products are often developed from substance
  found in a plant that has been used for traditional medicine.
• Aspirin is one of these products.
• Salicylic acid is the active substance that helps helps to reduce pain
  and fever.
• However, salicylic acid irritates the lining of the stomach.
• So when salicylic acid is reacted with ethanoic acid,it produces
  acetylsalicylic acid (aspirin).
• This reaction, however, is slow and the yield is low as the water
  formed tends to drive the reaction backwards.
• An alternative reaction pathway, that is faster and produces higerh
  yields, is one between ethanoic anhydride (acetic anhydride) and
  salicylic acid.
• Once the acid has passed through the stomach it reacts with water
  in the small intestine and returns to the more effective salicylic
  acid.
Reaction Pathways for Aspirin
              Soluble Aspirin
• Pure acetylsalicylic acid is not very soluble in
  water, despite have a –COOH functional
  group.
• Though converting the carboxylic acid
  functional group into the sodium salt changes
  the molecule into an ion and makes it much
  more soluble.
• Buffered aspirin provides further protection
  against stomach irritation.
             Identifying Aspirin - IR
• The analytical techniques IR, NMR and Mass Spectrometry can be used to
  analyse aspirin.
• The molecular structure of acetylsalicylic acid is shown below:
• There are two C=O groups present.
• One is part of an ester and the other is part of the carboxyl group.
• These correspond to the two absorptions at 1760 and 1770cm-1 in the IR
  spectrum.
       Identifying Aspirin - NMR
• There are four hydrogen around the benzene ring,
  three Hs in the CH3 group and one in the OH group.
• The four hydrogen attached to the benzene ring give
  four separate peaks.
• The three hydrogen atoms of CH3 all experience the
  same environment so they are the large peak.
• The single hydrogen atom in the COOH group would
  give a small peak, it is not shown in the spectrum
  over.
Identifying Aspirin cont…
  Identifying Aspirin – Mass Spec
• The peak at 180 is the molecular formula ion
  peak, this is the Mr of Aspirin.
• The masses of the various fragments are used
  to confirm the structural formula.

				
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posted:10/20/2012
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