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Organic Chemistry II Separations

Organic Chemistry II Separations

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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