L10a - This presentations objectives: Br2 ,h = heat h =...

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1 1 ©Dr. Kay Sandberg Δ ,h ν Br 2 Δ = heat h ν = light 0 1 2 PPM 1 H NMR spectrum of product 2 This presentation’s objectives: ©Dr. Kay Sandberg 1) Examine the chemist’s need and use of various characterization tools 2) Introduce 3 types of spectroscopy 3) Examine the theory behind NMR spectroscopy Spectroscopy & spectrometry Spectroscopy & spectrometry : techniques used to give evidence of the structure identification. How does a chemist prove that he/she synthesized a certain product? We can’t see individual molecules. 3 Match the spectrum 0 10 20 30 40 50 60 70 PPM 12 58 % 42 % 1. A 2. B ©Dr. Kay Sandberg reagent + Reactant 1-propanol 2-propanol 0 10 20 30 40 50 60 70 PPM 13 C NMR spectra OH OH A B 4 ©Dr. Kay Sandberg reagent + Reactant 1-propanol 2-propanol 0 10 20 30 40 50 60 70 PPM 0 10 20 30 40 50 60 70 PPM 13 C NMR spectra C C OH C H H HH H H H OH OH 5 molecule Section 13.2 What happens to the energy that gets absorbed by the molecule? lower energy state (E 1 ) higher energy state (E 2 ) before zap lower energy state (E 1 ) higher energy state (E 2 ) after zap Δ E Δ E = E 2 - E 1 ©Dr. Kay Sandberg 6 molecule Section 13.2 lower energy state (E 1 ) higher energy state (E 2 ) before zap lower energy state (E 1 ) higher energy state (E 2 ) after zap Δ E Δ E Only radiation whose photon has energy equal to the Δ E gets absorbed - all other is transmitted ©Dr. Kay Sandberg
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2 7 Section 13.2 Δ E = E photon = h ν photon lower energy state (E 1 ) higher energy state (E 2 ) Only radiation whose photon has energy equal to the Δ E gets absorbed - all other is transmitted Δ E in resonance = E 2 - E 1 ©Dr. Kay Sandberg 8 Section 13.2 energy states radio waves , infrared , light , or UV NMR (nuclear magnetic resonance) IR (infrared) UV -Vis (ultraviolet-visible) difference between nuclear spin states difference between vibrational states difference between electronic states ©Dr. Kay Sandberg MRI ~ NMR Magnetic resonance imaging “It is the same process, but the dreaded word ‘nuclear’ must be hidden from public view.” Maitland Jones 9 Match E gap Section 13.2 radio waves , infrared , light , or UV energy states NMR IR UV -Vis difference between nuclear spin states difference between vibrational states difference between electronic states NMR IR UV-Vis 1 E 2 E Δ E 1 E 2 E Δ E 1 E 2 E Δ E 1) G 2) P 3) Y Red martians invaded Venus using X-ray guns radio microwave infrared Visible light ultraviolet X-ray gamma Lo E Hi E ©Dr. Kay Sandberg 123 1% 2% 98% 10 radiation source sample detector % transmittance wavelength, or frequency 100 0 R O Y G B I V R O Y G B I V % absorbance 100 0 What is the physical basis for these spectroscopies?
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L10a - This presentations objectives: Br2 ,h = heat h =...

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