experimental determination of structure 2

Question 1

what is infrared spectroscopy used for

Answer 1

infrared spectroscopy is used to identify certain functional groups in an organic compound

Question 2

infrared radiation comprises that part of the electromagnetic spectrum that lies….

Answer 2

between microwaves and visible light

Question 3

when infrared radiation is absorbed by organic compounds, the energy is sufficient to…

Answer 3

cause the bonds within the molecules to vibrate (stretch and bend) , but not enough to break the bonds

Question 4

• the wavelength of the infrared radiation that is absorbed when a bond vibrates depends on..
• light atoms joined by strong/stiff bonds absorb radiation of _____ wavelength , than heavier atoms joined by loose bonds

Answer 4

• the type of atoms that make up the bond and the stiffness (strength) of the bond
• shorter
  ( infrared spectroscopy makes use of these characteristics , can be used to identify certain bonds and functional groups in organic molecules.

Question 5

how is an infrared spectrum obtained

Answer 5

• infrared radiation is passes through the sample in a spectrometer. some wavelengths are absorbed , causing bond vibrations within the molecule
• the transmitted radiation then passes to a detector where the intensity at different wavelengths is measured , infrared spectrum is then obtained

Question 6

in an infrared spectrum , what does an absorption correspond to

Answer 6

corresponds to a peak pointing towards the bottom of the graph

Question 7

absorption is expressed in terms of….

Answer 7

wave number

Question 8

what is wavenumber and what are the units

Answer 8

reciprocal of wavelength - 1/wavelength , units are cm-1

Question 9

what are the molecules for

• absorption peak at 1700cm-1
• absorption peak at 2600-3400cm-1
• absorption peak at 2260-2215cm-1

Answer 9

• c–o
• o-h
• c—n