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8B-handout-jan7 - Chem 8B Winter 2009 Outline of Concepts...

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Chem 8B, Winter 2009 - Outline of Concepts and Skills for Lectures on Jan 7 and 9 Lecture Topic: What properties allow us to detect, separate, and determine structures of organic molecules Why is it important to be able to separate and detect molecules? Examples include: 1) detecting soil, air, and water contaminants, 2) crime scene investigation, 3) analysis of blood and urine samples for drug metabolites or disease markers, 4) detecting/analyzing vitamins and nutrients in a food product, 5) detecting the presence of explosives or chemical warfare agents for national security, and 6) to assess and purify pharmaceutical molecules or proteins for research. To be effective, scientists often need to be able to separate and detect parts per million, or even parts per trillion of a molecule. There are 5 general laboratory techniques used to separate organic molecules: 1) Extraction – separation based on solubility by dissolving a compound into solvent or water (see lab experiment #8 for week 5). 2) Distillation – separation based on boiling point 3) Crystallization – separation based on the physical property of some molecules to form solid crystals, while others will remain a liquid or oil and can be washed away 4) Electrophoresis – separation based on charge using electric current (usually amino acids or proteins) 5) Chromatography – one of the most important and commonly used techniques (see lab experiment #9 for week 2). Chromatography is a general term for the separation of mixtures of compounds based on a partition between stationary (non-mobile) phase and a mobile phase (gas or liquid). (Historically, it was used for the separation of colored compounds, thus the origin of “chroma”). The stationary phase can be a gel, paper, silica, alumina, or many others. When separating a mixture of compounds with chromatography, a
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