Gas ChromatographyRefractive IndexPolarimetry

Next Lecture: Lecture Problem 8 DueNext Thursday: Quiz 7 in LectureNext 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

Lecture 24

Nutmeg Oil GC-MS Data

Mass Spectrum of A

M+ at 192

Compound is:

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O

O

OCH3

Allyl methoxybenzodioxoleFW = 192

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

Gas Chromatography

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FID Detector

Gas Chromatography

Capillary column

Injection site

Control panel

Gas ChromatographyPlotter

Gas Chromatography

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

Refractive Index

• An intrinsic property of a liquid compound• Defined as the ratio of the speed of light through a vacuum tothe speed of light through the liquid

Operational instructions are given in Chapter 20.

Refractive Index

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Figures taken fromWilliamson, Minard & MastersMMOE, 5th edition

Ideal reading

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; seeChapter 19 of the Lab Guide

Cell for sample solution

Digital display -results