Laboratory Techniques in Organic Chemistry
Laboratory Techniques in Organic Chemistry
4th Edition
ISBN: 9781464134227
Author: Jerry R. Mohrig, David Alberg, Gretchen Hofmeister, Paul F. Schatz, Christina Noring Hammond
Publisher: W. H. Freeman
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Chapter 21, Problem 4Q
Interpretation Introduction

Interpretation:

The product obtained by distillation should be identified on basis of its boiling point and its IR spectrum.

Concept introduction:

IR spectroscopy is spectroscopic method to identify the structure of organic compounds. When IR is passed through the sample, different bonds vibrate at different frequencies of IR by absorbing IR light. In IR spectrum energy in terms of wavenumber( cm-1 ) is the horizontal axis and intensity is the vertical axis.

As different molecules have different bonds of varying strength so they absorb IR light of different frequencies. This results in different absorption bands in the IR spectrum characteristic to that bond.

IR region is divided into 3 regions, near, mid and far IR region. The mid-IR region extends from 4000600cm-1 and it is the most important region as approximately all organic compounds absorb in this region.

The allowed vibrational energy levels for IR transition is as follows:

  E=hνο(ν+1)

Where,

  • E is IR energy absorbed by a molecule.
  • h is Planck's constant.
  • νο is zero point vibrational level.
  • ν is vibrational level with integer value of 1,2,3,4.....

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34. Figure 3 shows Van Deemter plots for a solute molecule using different column inner diameters (i.d.). A) Predict whether decreasing the column inner diameters increase or decrease bandwidth. B) Predict which van Deemter equation coefficient (A, B, or C) has the greatest effect on increasing or decreasing bandwidth as a function of i.d. and justify your answer. Figure 3 Van Deemter plots for hydroquinone using different column inner diameters (i.d. in μm). The data was obtained from liquid chromatography experiments using fused-silica capillary columns packed with 1.0-μm particles. 35 20 H(um) 큰 20 15 90 0+ 1500 100 75 550 01 02 594 05 μ(cm/sec) 30 15 10

Chapter 21 Solutions

Laboratory Techniques in Organic Chemistry

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