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Lecture 24

Lecture 24. Gas Chromatography Refractive Index Polarimetry Next Lecture: Lecture Problem 8 Due Next Thursday: Quiz 7 in Lecture Next Week’s Office Hours: Tuesday from 3 to 5 pm! This week in lab: Ch 9 Final Report Due Synthetic #2 PreLab Due Next week in lab:

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Lecture 24

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  1. Lecture 24 Gas Chromatography Refractive Index Polarimetry Next Lecture: Lecture Problem 8 Due Next Thursday: Quiz 7 in Lecture Next Week’s Office Hours:Tuesday from 3 to 5 pm! This week in lab: • Ch 9 Final Report Due • Synthetic #2 PreLab Due Next week in lab: Synthetic #1 Final Report Due

  2. Nutmeg Oil GC-MS Data Mass Spectrum of A M+ at 192 Compound is:

  3. Chromatography • TLC & Column Chromatography • Stationary phase: silica gel (polar) • Mobile phase: organic solvent(s) (varying polarity) • Separation: based on differences in polarity of compounds • Gas Chromatography • Stationary phase: can be polar or nonpolar (choice of column) • Instrument Room GC uses a nonpolar stationary phase • Mobile phase: helium gas! • Separation: based on boiling points and/or size of compounds • Can vary the temperature - allows for better separation of • complex mixtures (low-boiling vs high-boiling components) • Flame ionization detector (FID) • Chapter 18 in Lab Guide

  4. Gas Chromatography FID Detector

  5. Gas Chromatography Injection site Control panel Capillary column

  6. Gas Chromatography Plotter

  7. Gas Chromatography • Info from chromatogram: • # of components in sample • Retention time of each component • Area of each signal - calculate % of each component in sample

  8. Refractive Index • An intrinsic property of a liquid compound • Defined as the ratio of the speed of light through a vacuum to • the speed of light through the liquid • Operational instructions are given in Chapter 20.

  9. Refractive Index Ideal reading Figures taken from Williamson, Minard & Masters MMOE, 5th edition

  10. Polarimetry • To determine the optical activity of a compound. Watch video • at http://www.colby.edu/chemistry/OChem/DEMOS/Chirality.html • Calculate the specific rotation of a chiral compound; see • Chapter 19 of the Lab Guide Cell for sample solution Digital display - results

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