13. Structure Determination
13. Structure Determination
The analysis of the outcome of a reaction requires that we know the full structure of the products as well as the reactants In the 1gth and early 20th centuries, structures were determined by synthesis and chemical degradation that related compounds to each other Physical methods now permit structures to be determined directly. We will examine mass spectrometry (Ms) infrared(IR) spectroscopy nuclear magnetic resonance spectroscopy (NMR) ultraviolet-visible spectroscopy (VIs)
• The analysis of the outcome of a reaction requires that we know the full structure of the products as well as the reactants • In the 19th and early 20th centuries, structures were determined by synthesis and chemical degradation that related compounds to each other • Physical methods now permit structures to be determined directly. We will examine: – mass spectrometry (MS) – infrared (IR) spectroscopy – nuclear magnetic resonance spectroscopy (NMR) – ultraviolet-visible spectroscopy (VIS)
13. 1 Infrared Spectroscopy and the Electromagnetic Spectrum Energy Frequency(v)in Hz 10 18 16 10 14 12 100 y rays X rays Ultraviolet Infrared Microwaves Radio waves 10-10 10-6 Wavelength ()in m Wavelength ()in m 380nm 500nm 600nm 700nm780nm 38×10-m 7.8×10-7m Thomson· Brooks Cole
13.1 Infrared Spectroscopy and the Electromagnetic Spectrum
Absorption Spectra Organic compound exposed to electromagnetic radiation, can absorb energy of only certain wavelengths(unit of energy) Transmits, energy of other wavelengths Changing wavelengths to determine which are absorbed and which are transmitted produces an absorption spectrum Energy absorbed is distributed internally in a distinct and reproducible way(See Figure 12-1
Absorption Spectra • Organic compound exposed to electromagnetic radiation, can absorb energy of only certain wavelengths (unit of energy) – Transmits, energy of other wavelengths. • Changing wavelengths to determine which are absorbed and which are transmitted produces an absorption spectrum • Energy absorbed is distributed internally in a distinct and reproducible way (See Figure 12-11)
Wavelength (um) 2.5 4 789101214162024 100 8c 40 40003500300026002200200018001600140012001000 800 Wavenumber(cm-1) 92004 Thomson /Brooks Cole