What to do, and why.

Both ¹³C NMR and IR spectroscopy can be used to identify alkenes, and subtle differences can identify the substitution pattern of H atoms and alkyl groups on the C=C carbon atoms.

Examine the ¹³C NMR spectra of carvone by accessing the resource.

How many non-equivalent C atoms are there that are part of C=C functional groups? How many signals should these give in the ¹³C NMR spectrum, and where should they come in chemical shift?

Examine the IR spectra of the alkenes hex-1-ene, α-pinene, and cyclohexene by accessing the resource.

In each case identify the number of H-atoms that are substituted on the C=C bond. Then find the out-of-plane bending vibration for each alkene and note the wavenumber at which that vibration occurs in each case. How easy would it be to tell alkenes with different substitution patterns apart based on these out-of-plane bending vibrations? Now consult Figure 9.22 again in your text and identify the out-of-plane bending vibrations for these cis and trans isomers of pent-2-ene.

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