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Vibrations of Free Molecules - 2. Forms of Vibration of the Methyl Group in Propene

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Vibrations of Free Molecules - Vibration of the Methyl Group in Propene This is the formula of a more complicated molecule: propene. Since the molecule contains nine atoms, 21 normal vibrations are possible. In each

00:31

propene molecule the nearest hydrogen atom of the methyl group lies in the plane of the molecule.The C= C double

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bond stretching vibration is infrared- and Ramanactive.You may observe the

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large variations in the length

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of the C= C double bond and also the simultaneous changes in many bond angles.The methyl group has nine possible vibrations: There are three stretching vibrations, three scissors vibrations, and two rocking vibrations. Two of each type of vibrations are degenerate; that is, they have the same frequency. There is also one twisting vibration.At about 3000 wave numbers we find a symmetric and two degenerate

02:25

stretching vibrations of the methyl

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group. Let us now look at one of the degenerate stretching vibrations. The motions of the CH-bonds nearest to and farthest from us are outof-phase.The

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CH 3 scissors vibrations occur at about 1400 wave numbers. We

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shall first observe the symmetric scissors vibration.You can clearly see that the length of the neighbouring C-C bond also vary. All the atoms move a little.This is one of the degenerate deformations of the methyl group.While the angle between the two CH-bonds pointing away from

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us increases, the angle with the CH--bond pointing towards us

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decreases and vice versa. The rocking vibration ist only visible in the infrared spectrum.Apart from

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the rocking motion of the CH 3 group, you can sec that the CH 2 group on

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the left moves in the

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opposite direction. The intensity of

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the torsional vibration of the CH 3 group is extremely small in the infrared and the Raman spectrum.You can see clearly

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that the left und right

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hand parts of the molecule execute a torsional motion in opposite directions.

Spracherkennung
Texterkennung
Bildinhalt

00:00

Molekülstruktur

Deformierung

Edelstein

Setzen <Verfahrenstechnik>

Ordnungszahl

Computeranimation

Doppelbindung

Raman-Spektroskopie

Infrarotspektroskopie

Raman-Effekt

Infrarotspektroskopie

Bewegung

Torsio

Chemische Formel

Chemische Bindung

Methylgruppe

Linker

Molekül

Funktionelle Gruppe

Insulinkomabehandlung

Molekül

Propen

Metadaten

Formale Metadaten

Titel	Vibrations of Free Molecules - 2. Forms of Vibration of the Methyl Group in Propene
Alternativer Titel	Schwingungen freier Moleküle - 2. Schwingungsformen der Methylgruppe in Propen
Autor	Schrader, Bernhard Schneider, Richard
Lizenz	CC-Namensnennung - keine kommerzielle Nutzung - keine Bearbeitung 3.0 Deutschland: Sie dürfen das Werk bzw. den Inhalt in unveränderter Form zu jedem legalen und nicht-kommerziellen Zweck nutzen, vervielfältigen, verbreiten und öffentlich zugänglich machen, sofern Sie den Namen des Autors/Rechteinhabers in der von ihm festgelegten Weise nennen.
DOI	10.3203/IWF/C-1210eng
IWF-Signatur	C 1210
Herausgeber	IWF (Göttingen)
Erscheinungsjahr	1976
Sprache	Englisch
Produzent	IWF
Produktionsjahr	1975

Technische Metadaten

IWF-Filmdaten

Film, 16 mm, LT, 71 m ; F, 6 1/2 min

Inhaltliche Metadaten

Fachgebiet	Chemie
Abstract	The movement of the atoms during the more important normal vibrations of propene are shown in perspective representation: the stretching vibrations of the C=C double bond and the stretching and bending vibrations of the CH[3]-group. The in-phase and out-of-phase movements as well as the concept of characteristic vibrations become clear in the process.
Schlagwörter	molecular structure oscillations / in molecules