Vibrations of Free Molecules - 1. Stretching and Deformation Vibrations of Ethylene
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| License | CC Attribution - NonCommercial - NoDerivatives 3.0 Germany: You are free to use, copy, distribute and transmit the work or content in unchanged form for any legal and non-commercial purpose as long as the work is attributed to the author in the manner specified by the author or licensor. | |
| Identifiers | 10.3203/IWF/C-1209eng (DOI) | |
| IWF Signature | C 1209 | |
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| Production Year | 1975 |
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| IWF Technical Data | Film, 16 mm, LT, 78 m ; F, 7 min |
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00:00
EthyleneDeformityMolecule
00:11
EthyleneMoleculeEthylene
00:29
Raman scatteringAlkeneInfrarot-SpektrumFunctional groupRaman spectroscopy
02:02
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Motion (physics)Phase (waves)Kohlenstoff-14Ionenbindung
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Kohlenstoff-14IonenbindungRaman scatteringActivity (UML)
04:18
Phase (waves)DoppelbindungFunctional groupMotion (physics)Raman scattering
04:50
Infrarot-SpektrumRaman scatteringFunctional group
05:08
IonenbindungMoleculeMolecular geometry
05:39
TamoxifenInfrarot-SpektrumMoleculeMolecular geometryRaman scatteringRaman spectroscopy
06:00
MoleculeEmission spectrumWursthülleIonenbindung
06:32
GasverflüssigungNitrosamine
Transcript: English(auto-generated)
00:03
Vibrations of free molecules, stretching and deformation vibrations of ethylene. The ethylene molecule has six atoms. Therefore, there are three times six minus six, that is 12 normal vibrations.
00:33
Above is the infrared spectrum of ethylene, and below it you see the Raman spectrum.
00:44
Five of the normal vibrations can be seen as bands in the infrared spectrum. A further six are visible in the Raman spectrum.
01:04
The position of one of these bands is uncertain. The twelfth normal vibration is inactive in both spectra. The vibrations can be divided into stretching vibrations and bending vibrations.
01:25
There is one CC stretching vibration, and there are four CH stretching vibrations. In addition, there are four in-plane bending vibrations, and three out-of-plane bending vibrations of the CH2 groups.
01:48
The stretching vibration of the carbon-carbon double bond is only visible in the Raman spectrum. It occurs at 1623 wavenumbers.
02:05
Here is the ethylene molecule drawn in perspective. You will now see vibrations of this molecule excited by one energy quantum, H nu. For the sake of clarity, the amplitudes of the vibrations
02:22
have been magnified by a factor of five. You can see the large variations in the distance between the carbon atoms. In phase, with this motion, the angle between the CH bonds in the CH2 group also varies.
02:54
The four CH stretching vibrations are visible as four bands in the infrared and Raman spectra at about 3,000 wavenumbers.
03:02
The two symmetric stretching vibrations of the CH2 group occur at lower frequencies than the anti-symmetric vibrations. Here is the Raman active symmetric stretching vibration of the CH2 group.
03:25
In this vibration, all the CH bonds stretch simultaneously. The bond between the carbon atoms also stretches slightly, but out of phase with the motions of the CH bonds. Two of the in-plane bending vibrations, the so-called scissors,
04:01
occur at about 1,400 wavenumbers in the Raman and infrared spectra. This is the Raman active scissors vibration.
04:21
In this vibration, the CH2 angles in both groups vary simultaneously. The length of the double bond also varies, but out of phase.
04:53
The two other in-plane bending vibrations are called rocking vibrations. Both give only very weak bands.
05:05
Here is the Raman active rocking vibration. In this vibration, only bond angles in the plane of the molecule change.
05:43
The wagging vibrations are very strong in the infrared, but very weak in the Raman spectrum. You will now see the infrared active vibration.
06:11
The wagging vibration also causes only changes in bond angles, but in this case perpendicular to the plane of the molecule.