Lab1 Recitation

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TLC

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Lab 1 RecitationThin-Layer ChromatographyKey Point SummariesGrading!!!Key Point SummariesStart with lab lecture notes! Then compare to procedure/resultsPractice good scientific writingFull sentences (try), no first person, active voice, and concise writingIt was determined that Standard II, which had an Rf value of 0.5, was a polar molecule because of its carboxylic acid group vs. Standard II (Rf = 0.5) is polar because of its carboxylic acid groupOne page text maximum, but Can have appendix for ChemBioDraw graphics (1 pg max) label as Figure 1, Table 2, Mechanism 2, Reaction 5, etc RecitationsWhat will they be? Real-life examples and applications of theory we learned in lecture and applied in controlled settings in lab. May help with post-lab quiz questions What will they not be? Your key point summaries in spoken form. Hi, group 2 spies!MandatoryYay!

HPLCHigh performance liquid chromatographyAccurateBetter reproducibilityHigher sensitivity (for smaller samples)InformativeMultiple detection techniques could follow (UV/Vis, mass spectrometry)ConvenientAutomaticImage Source: http://web.nmsu.edu/~kburke/Instrumentation/Agilent_HPLC.gif5HPLCImage Source: http://www.forumsci.co.il/HPLC/WEB-Pharm_Review/alkylphenones.gifhttps://sweepingthegarden.files.wordpress.com/2013/03/spongebob.jpghttp://www.extremescience.com/images/sailfish.jpghttps://s-media-cache-ak0.pinimg.com/736x/e7/b4/cc/e7b4cc5b29da05ef80bd8b395b940bab.jpg

Less polarMore polarTime6

HPLCHigh performance liquid chromatographyAccurateBetter reproducibilityHigher sensitivity (for smaller samples)InformativeMultiple detection techniques could follow (UV/Vis, mass spectrometry)ConvenientAutomaticImage Source: http://web.nmsu.edu/~kburke/Instrumentation/Agilent_HPLC.gif

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TLC before HPLCHPLC (high performance liquid chromatography)Quantitative, accurate, smartBut machine column can be difficult to clean out ($)Not disposableAND need lots of solvent for longer time and labor ($$$)TLCEasy set-up/disposableCost effectiveLow sensitivity but suitable for normal useImage Source: http://web.nmsu.edu/~kburke/Instrumentation/Agilent_HPLC.gif8Column ChromatographyStationary: Gel (usually polar)Mobile: Liquid (usually not as polar)Good for clean up (before HPLC) as well as simple separationSample: Mixed compoundsRed: polar Blue: not as polar

If all else failsSeparate using other techniquesDistillation (next week)Extraction (the week after)Crystallization (Chem 2321)Food for thoughtResults (high to low Rf): IbuprofenAspirinPhenacetinAcetaminophenCaffeineCan look at structure to justify resultsRf is related to polarity, and polarity is related to structure. Most to least polar

1. Caffeine2. Acetaminophen3. Phenacetin4. Aspirin5. Ibuprofen

Caffeine (most polar, lowest Rf)Dipole-dipoles from inductive withdrawal and resonanceNitrogen and Oxygen can act as H-bond acceptor

Ibuprofen (least polar, highest Rf)Has H-bond (polar), but has a really large nonpolar groupCompare to other molecules

Acetaminophen, PhenacetinBetween the two, Acetaminophen has 1 more H-bond donor (more polar)

AspirinEasily formed intramolecular H-bonding limits Aspirins ability to bond intermolecularly