CHEM-C127 Aspirin Notes
CHEM-C127 Aspirin Notes Chemistry C127
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This 1 page Class Notes was uploaded by Kathryn Brinser on Thursday April 14, 2016. The Class Notes belongs to Chemistry C127 at Indiana University taught by Dr. Norman Dean in Fall 2016. Since its upload, it has received 52 views. For similar materials see Principles of Chemistry and Biochem I Lab in Chemistry at Indiana University.
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Date Created: 04/14/16
C127 Lecture 12 Notes- Aspirin 4-14-16 Essentially: salicylic acid + acetic anhydride + heat = acetylsalicylic acid Decomposes into acetic acid and salicylic acid over time Learning Goals o Use qualitative test to assess purity of a sample o Use melting point determinations to assess purity of a sample o Use Thin Layer Chromatography to assess purity of a sample Safety o All liquid/solid waste should go in waste bottle o Dispose of all glass in broken glass bucket o Make sure melting point apparatus turned off at end Melting Point o Every chemical compound has unique point o Intermolecular forces between molecules in crystal lattice control melting point o Impurities weaken intermolecular forces and lower melting point o Can identify and assess purity of a compound Salicylic acid has different melting point than aspirin- if measured value closer to salicylic’s melting point than aspirin’s, substance decomposed badly Temperature at melting point identifies compound present Size of temperature range over which melting occurs tells about purity of sample- broader range less pure, smaller range (2-3℃) higher purity When given expected melting point, melting should occur within the 2-3℃ range of that value o Ex. Made-up value for to show comparison: Expected Melting Point Measured Melting Range Pure Aspirin 149℃ 147-150℃ Impure Aspirin 149℃ 140-148℃ (lower and broader) o Melting starts with first drop of liquid you see in tube; finishes when no more solid present Thin-Layer Chromatography o Identifies compound, assesses purity o Interaction of molecules with a solid phase and a moving liquid phase When molecule interacting with solid, it does not move When molecule interacting with solvent, it moves with liquid o Different molecules have different “preferences” for liquid/solid phases, so they travel different distances on TLC plate Characterized by unique
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