Hints on Colun Chromatography柱色谱的提示.pptVIP

Spectroscopy IR Spectroscopy Vibrational Modes of Bonds Correlation Chart Correlation Chart * Lecture 11 IR Theory Next Class: Lecture Problem 4 due Thin-Layer Chromatography This Week In Lab: Ch 6: Procedures 2 3 Procedure 4 (outside of lab) Next Week in Lab: Ch 7: PreLab Due Quiz 4 Ch 5 Final Report Due 1H NMR: Determine bond connectivities/pieces of a structure, whole structure IR Use: Determine the functional groups present in a structure: -OH, C=O, C-O, NH2, C=C, C?C, C=N, C?N NMR (Nuclear Magnetic Resonance Spectroscopy): Uses radio waves (electromagnetic radiation) Interacts with sample’s nuclei in the presence of a magnet Effect: nuclei flip and relax (known as resonance) IR (Infrared Spectroscopy) IR radiation Interacts with molecule as a whole Effect: bond vibrations within molecule An IR Spectrum of Hexanol Main Use: To detect the presence or absence of a functional group (specific bonds) in a molecule How It Works: Bonds vibrate freely at specific wavelengths (wavenumbers) Want to cause the bonds to increase the magnitude of this vibrational frequency Subject compound to IR radiation, 4000-625 cm-1 cm-1 is the unit for wavenumber (n) (The numbers of waves within 1 cm) n is directly proportional to energy (unlike wavelength) 4. Bonds absorb energy equal to their natural vibrational energy - it is quantized. This absorption of energy causes a change in dipole moment for the bond. 5. Upon absorption, bonds stretch and/or bend; the IR measures this absorption. Specific bonds absorb specific IR radiation and signals will appear within certain wavenumber ranges (similar to NMR). Your lab notebook also has an IR correlation chart. Specific bonds absorb specific IR radiation and signals will appear within certain wavenumber ranges (similar to NMR). IR spectrum of hexanoic acid Different bond stretches what their signals look like in IR: A: O-H stretch (strong, broad) C: C-H stretch (strong, sharp) E: C?C or C?N stretch