University:
Boston University
Course:
CAS CH 641 | Physical Organic Chemistry
Academic year:

2020
Views:

67

Pages:

3
Author:

larbiwxcvbn

TP In the IR spectrum shown of CH3Br, the absorption near 3000 cm is due to … 0% 0% 0% 0% 1. 2. 3. 4. C C H H 1 Br stretch H stretch C Br symmetric stretch C Br antisymmetric stretch For today … • Infrared IR spectra • Atmospheric warming Resonance in light-matter interaction Infrared IR spectra Demonstration: Tale of three frequencies Frequencies match → … response energy transfer Frequencies do not match → … No response, “transparency” no energy transfer 1 What is being displayed in an IR spectrum? TP In the IR spectrum shown of CH3Br, the absorption near 3000 cm is due to … 0% 0% 0% 0% 1. 2. 3. 4. C C H H What is being displayed in an IR spectrum? 1 C2H6O: Dimethyl ether Br stretch H stretch C Br symmetric stretch C Br antisymmetric stretch 2 C2H6O: Ethanol Jiggling of bonded atoms O H is at about 3500 cm‒1 C H is at about 3000 cm‒1 This is reverse of what we predict based on mass. Quiz What motion must account for the absorption in the 3600 cm 0% 0% 0% 0% 0% 1. 2. 3. 4. 5. 1 region? CO stretch CC stretch CH stretch OH stretch Something else IR spectra detect function groups Lighter faster; stronger faster; dissimilar approaches lighter What could account for this reversal? 3

Infrared (IR) Spectra

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