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For more information, please see full course syllabus of Organic Chemistry
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Lecture Comments (4)

1 answer

Last reply by: Professor Starkey
Fri Sep 22, 2017 10:53 PM

Post by Maryam Fayyazi on September 20, 2017

Professor I have couple of questions about my lab;
1)given the structure of benzophone and biphenyl:
which structure would you be expected to have higer Rf value on a polar TLC plate(silica,alumina)why?

2)why is it recommended to spot the analyte on the TLC plate in the position that it will not be immersed eluent solvent?

3)why it is recommended to use pencil to mark your TLC plate instead of pen?
thanks alot

1 answer

Last reply by: Professor Starkey
Thu Mar 31, 2016 2:08 PM

Post by Tammy T on March 31, 2016

Why Silica gel SiO2 is polar? I drew out Lewis structure and VSEPR of SiO2, and the 2 dipole moments toward the 2 O on SiO2 molecule cancelled each other out. I thought SiO2 molecule has no net dipole moment overall. Please explain. Thank you great lecture!!

Introduction to TLC (Thin-Layer Chromatography)

Lecture Slides are screen-captured images of important points in the lecture. Students can download and print out these lecture slide images to do practice problems as well as take notes while watching the lecture.

  • Intro 0:00
  • Chromatography 0:06
    • Purification & Analysis
    • Types of Chromatography: Thin-layer, Column, Gas, & High Performance Liquid
  • Theory of Chromatography 0:44
    • Theory of Chromatography
  • Performing a Thin-layer Chromatography (TLC) Analysis 2:30
    • Overview: Thin-layer Chromatography (TLC) Analysis
  • Step 1: 'Spot' the TLC Plate 4:11
  • Step 2: Prepare the Developing Chamber 5:54
  • Step 3: Develop the TLC Plate 7:30
  • Step 4: Visualize the Spots 9:02
  • Step 5: Calculate the Rf for Each Spot 12:00
  • Compound Polarity: Effect on Rf 16:50
    • Compound Polarity: Effect on Rf
  • Solvent Polarity: Effect on Rf 18:47
    • Solvent Polarity: Effect on Rf
    • Example: EtOAc & Hexane
  • Other Types of Chromatography 22:27
    • Thin-layer Chromatography (TLC)
    • Column Chromatography
    • High Performance Liquid (HPLC)
    • Gas Chromatography (GC)
    • Preparative 'prep' Scale Possible