Homework Help Forum: org. chem.

Posted by CM on Tuesday, October 6, 2009 at 5:23am.

A student who was isolating aspirin stopped the experiment after the filtration step with alumina. One week later, the methanol was evaporated and the experiment was completed. The melting point of the aspirin was found to be 110-115 degress Celsius. Explain why the melting point was low and why the melting range was so wide. My Answer:The melting point was low and the melting range was so wide because the aspirin partially decomposed. Therefore, it became impure and caused the melting range to widen. Due to the partial decomposition, the carbon backbone broke down some, which allowed the student’s aspirin to melt at a lower temperature. Is this correct? Please Help!

• org. chem. - Dr Russ, Tuesday, October 6, 2009 at 9:35am

  <<My Answer:The melting point was low and the melting range was so wide because the aspirin partially decomposed.>> this seems reasonable. Was the aspirin allowed to stand in the methanol? What happens if you allow an ester to stand in a large excess of an alcohol? Also what happens if you allow a carboxylic acid to stand in an excess of an alcohol? <>Therefore, it became impure and caused the melting range to widen.>> Agreed. << Due to the partial decomposition, the carbon backbone broke down some,>> you are guessing here!! what are the possible side products?

  
  

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