CHM 2123 Lecture Notes - Lecture 1: Cold Finger, Porphyrin, Miscibility
17 Dec 2017
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Document Summary
Experiment 1 separation and purification of natural products. Tlc plate is a polar silica gel, usually placed into a development jar filled with a relatively non-polar solvent (ex, 60:40 hexanes:ethyl acetate) The purpose of the non-polar solvent, is to un-adhere the compound from the silica gel and transport it a certain length up the silica gel. Retention factor: (ratio) of distance the spot has travelled compared to the distance the solvent has travelled. If there is one hydrogen bond to the silica gel, but the compound contains a long hydrocarbon chain, the rf may be shown as higher than if the hydrocarbon chain was smaller. The number of hydrogen bonds also makes a difference. A hydroxyl group can form two hydrogen bonds; an aldehyde group can from only one and will have higher rf. Desired rf value for the target compound is ~ 0. 3. Increasing solvent polarity will increase the rf values of all compounds.
