Spektroskopi IR: Perbedaan antara revisi
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Molekul diatomik sederhana hanya mempunyai satu ikatan, which may stretch. More complex molecules have many bonds, and vibrations can be conjugated, leading to infrared absorptions at characteristic frequencies that may be related to chemical groups. For example, the atoms in a CH<sub>2</sub> group, commonly found in [[organic compound]]s can vibrate in six different ways: '''symmetrical and antisymmetrical stretching''', '''scissoring''', '''rocking''', '''wagging''' and '''twisting''': |
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Revisi per 30 Desember 2008 04.12
Molekul diatomik sederhana hanya mempunyai satu ikatan, which may stretch. More complex molecules have many bonds, and vibrations can be conjugated, leading to infrared absorptions at characteristic frequencies that may be related to chemical groups. For example, the atoms in a CH2 group, commonly found in organic compounds can vibrate in six different ways: symmetrical and antisymmetrical stretching, scissoring, rocking, wagging and twisting:
| Symmetrical stretching |
Antisymmetrical stretching |
Scissoring | Rocking | Wagging | Twisting |
|---|---|---|---|---|---|
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The infrared spectrum of a sample is collected by passing a beam of infrared light through the sample. Examination of the transmitted light reveals how much energy was absorbed at each wavelength. This can be done with a monochromatic beam, which changes in wavelength over time, or by using a Fourier transform instrument to measure all wavelengths at once. From this, a transmittance or absorbance spectrum can be produced, showing at which IR wavelengths the sample absorbs. Analysis of these absorption characteristics reveals details about the molecular structure of the sample.