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Organic Chemistry II Separations

Organic Chemistry II Separations. Dr. Ralph C. Gatrone Department of Chemistry and Physics Virginia State University. Structure Determination. We need to know The structures of the starting reagents The structures of the products How is this done? MS – molecular weight

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Organic Chemistry II Separations

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  1. Organic Chemistry IISeparations Dr. Ralph C. Gatrone Department of Chemistry and Physics Virginia State University

  2. Structure Determination • We need to know • The structures of the starting reagents • The structures of the products • How is this done? • MS – molecular weight • IR – functional groups • UV-Vis – conjugated pi system • NMR – C and H framework

  3. Separation of Organic Molecules • Before you can determine the structure of an organic molecule you must isolate it from its matrix. • This is done using a separation technique.

  4. Matter • Anything that has mass • and occupies space. • Phases of Matter • Solid – definite shape and volumeLiquid – definite volume but changes shape • Gas – changes volume, changes shape • Plasma – matter present in stars

  5. Matter’s Properties Physical • Color, hardness, density, phase • Changes do not produce a different substance • Frozen water and liquid water = water Chemical • Matter is changed from one substance into a different substance • Methane burns giving carbon dioxide and water • Change involves rearrangement of how atoms are bonded • Chemical reaction takes place • Methane reacts with oxygen

  6. Matter • Pure substances and Mixtures • Pure Substances • Elements • Compounds • Separation accomplished by chemical methods.

  7. Mixtures • Most matter exists as mixtures • Two or more substances combined • Each retains its properties • salt and pepper; sugar and water • Heterogeneous – composition varies in sample • Homogeneous – composition is constant throughout the sample • Separation by physical methods

  8. Mixtures • Heterogeneous Mixtures • Sand and water • Oil and water • Sand and salt • Dirt • Homogeneous Mixtures • Solution – all components are in the same phase • Salt water, sugar water • Suspension – components are in different phases • Milk, fog, blood

  9. Separations • Pervasive in industry • Purify products • Remove hazardous materials from waste • Essential to all manufacturing processes • Efficiency of method selected often determines final cost of product

  10. High Priority Research Needs(National Research Council) • Improved selectivity among solutes • Concentration of solutes • Understanding interfacial phenomena • Increase rate and capacity • Research will impact upon • Biotechnology • High technology materials • Critical and strategic metals • Alternative fuels • Waste effluents

  11. Available Separation Methods • Distillation/condensation • Dissolution/precipitation • Sublimation • Chromatography • Solvent Extraction • More detail provided in analytical chemistry

  12. Distillation/Condensation • Boiling point = temperature where vapor pressure of the liquid equals the pressure in the liquid • Types • Simple; fractional; steam; and vacuum • Contributes approximately 50% of cost

  13. Simple Distillation

  14. Fractional Distillation

  15. Steam Distillation

  16. Steam Distillation

  17. Vacuum Distillation

  18. Dissolution/Precipitation • Solute contacted with a solvent • Solution forms • If solvent is reduced, we can • Precipitate the solute • Precipitation is determined by solubility • Solute is collected by filtration

  19. Sublimation • Transition of a substance • Solid to gas • Without going through liquid phase • Endothermic process • Occurs at temperatures and pressures below the substance’s triple point

  20. Chromatography • Solute is partitioned between two phases • Stationary • Mobile • Differences in absorption and desorption between these phases effect a separation.

  21. Types • Column • Solid stationary phase is held in a tube • Mobile phase is a liquid • Planar • Paper • Solid stationary phase is paper • Mobile phase is liquid

  22. Types • Planar • Thin layer • Solid phase is supported on glass or plastic slide • Mobile phase is a liquid solvent

  23. Column Chromatography

  24. Planar Chromatography

  25. Types • Gas Liquid Chromatography • Stationary phase is a liquid • Mobile phase is a gas • Liquid Chromatography • Stationary phase is a solid • Mobile phase is a liquid solvent

  26. Gas Chromatography

  27. Columns (packed)

  28. Columns (capillary)

  29. Liquid Chromatography

  30. Liquid Chromatography Columns • Normal phase • Silica or alumina • Organic solvents • Reverse phase • Hydrocarbon coated silica • Water or water alcohol solvents

  31. Solvent Extraction • Simplest separation process • Very efficient • Potentially continuous • Simple apparatus

  32. Centrifugal Contactor (Continous Process)

  33. Solvent ExtractionHistorical Highlights • 1706 – Philips patented separatory funnel • 1842 – Peligot extracted uranyl nitrate into ether • 1882 – Rothe extracted ferric chloride into ether • 1900 – physical chemistry of distribution law • 1925 – Fischer introduced dithizone • 1934 – Meuiner introduced cupferon • 1939 – Sandell introduced dimethylglyoxime • 1943 – Moeller introduced 8-hydroxyquinoline • Post war expansion occurred due to atomic energy programs

  34. Solvent ExtractionNuclear Fuel Cycle • Especially suited process because • Multi-stage operation • Continuous process • Easily engineered for remote control • Generates smaller volume of waste • Solvent degradation products are easily removed

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