CHE327lecture4

CHE327lecture4 - Announcements Your Distillation Experiment...

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Announcements Your Distillation Experiment Report is due at the beginning of lab this week. You need to take the melting point of your dimethyl fumarate from last week. (The procedure will be explained.) Print out a new part of the crystallization experiment. The crystallization of benzoic acid from Blackboard. acid from Blackboard. (To be posted by the end of the week. Chromatographic Separation β - Carotene β - Carotene is a member of the carotenoid family, compounds made up of isoprene units.It is made up of eight isoprene units, which are cyclized at each end.The long conjugated chain is responsible for the orange color. β - Carotene is the least polar among Isoprene spinach and paprika pigments. Column Chromatograph y ± Same principle as TLC ± Use SiO 2 or Alumina adsorbent ± Separation based mostly on polarity ± Differences from TLC ± Adsorbent is packed in a glass cylinder, rather than a plate. ± Larger scale What is the purpose of a column? ± Used to purify a compound that has significant impurities that cannot be significant impurities that cannot be removed by recrystallization or distillation distillation. ± Takes advantage of differences in polarity to separate an organic compound from a mixture of compounds. Column Chromatography Technique ± Still need TLC---- analytical tool ± To determine ~how many products ± To determine the solvent used for best separation. Advantages and Disadvantages ± Advantage: If a column is run properly under appropriate solvent conditions you under appropriate solvent conditions, you can separate (purify) your target compound with a near 100% recovery and with very with a near 100% recovery, and with very high purity. ± Disadvantage: Columns are expensive due to the use of large amounts of solvent and silica gel.
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Example of Separation Eluent: ligroin Packing the Column ± Add Cotton—not too tight. ± Add silica ge —don’t Add silica gel—don t breathe in. ± Wet column with eluent. ± Drain till top of silica gel. ± Load crude sample. ± Drain till top of silica gel. ± Add eluent and collect fractions. Isolation of β -Carotene From Spinach H 3 C H 3 C CH 3 CH 3 CH 3 CH 3 CH 3 H 3 C CH 3 CH 3 β -carotene H2C H3C CH3 H2C H3C CH3 N NN N CH3 Mg N N N N CH3 Mg O H3C ROOC CH3 O H3CO C H ROOC CH3 O H3CO O Chlorophyll a O Chlorophyll b Isolation of β -Carotene From Spinach ± Extract common green-plant pigments, such as chlorophylls and xanthophylls, from chopped spinach. ± From these crude pigment mixtures, isolate β -carotene isolate carotene. ± β -carotene is the most nonpolar of th i t these pigments. β -carotene is the most nonpolar of these pigments Clicker Question pigments.
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This note was uploaded on 11/26/2009 for the course CHE 327 taught by Professor Josephlauher during the Fall '08 term at SUNY Stony Brook.

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CHE327lecture4 - Announcements Your Distillation Experiment...

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