How could you distinguish between cyclohexane and cyclohexene using Infrared Spectroscopy only?
How could you distinguish between 1-hexene and 1-hexyne using IR only?
Its all here is this site.
http://wwwchem.csustan.edu/Tutorials/INFRARED.HTM
To distinguish between cyclohexane and cyclohexene using Infrared (IR) Spectroscopy, we need to analyze the functional groups present in each compound.
Cyclohexane is a saturated hydrocarbon, meaning it contains only single bonds (C-C) and lacks any functional groups. On the other hand, cyclohexene is an unsaturated hydrocarbon with a double bond (C=C) present, making it an alkene.
Infrared Spectroscopy measures the absorption of infrared light by the functional groups in a molecule. Alkenes, like cyclohexene, typically show a strong absorption peak in the range of 1600-1680 cm-1, which corresponds to the stretching vibration of the C=C bond. In contrast, cyclohexane will not exhibit a peak in this region because it lacks a C=C bond.
By comparing the IR spectra of the sample to the known characteristic absorption ranges of different functional groups, you can identify the presence or absence of a C=C bond, thus distinguishing between cyclohexane and cyclohexene.
Similarly, to differentiate between 1-hexene and 1-hexyne, we need to consider their functional groups.
1-hexene is an alkene, containing a C=C double bond. As mentioned earlier, alkenes typically show a strong absorption peak between 1600-1680 cm-1 in IR spectra due to the C=C bond stretching vibration.
In contrast, 1-hexyne is an alkyne and contains a C≡C triple bond. Alkynes have a unique triple bond stretching vibration in the IR region, which causes a prominent absorption peak in the range of 2100-2260 cm-1. This absorption is absent in alkenes like 1-hexene.
Therefore, by observing the IR spectra of the sample compounds and analyzing the characteristic absorption peaks in the relevant ranges, you can differentiate between 1-hexene and 1-hexyne.