Given the molecular formula, calculate the degree of unsaturation for the following compounds. Suggest at least three possible structures consistent with the degree of unsaturation for each compound.
1) C7H14O2
Degree of unsaturation = 1. Therefore, it has a carbonyl or a ring or a double bond. Some examples are below.
2) C4H10O
Degree of unsaturation = 0. It has no double bonds or rings. Some examples:
3) C9H10O
Degree of unsaturation = 5. It is likely to have an aromatic ring (4 degrees of unsaturation) plus a carbon-carbon double bond or a carbonyl or a ring. Some examples:
4) C8H9NO3 (Special case: a nitro group, –NO2, has a degree of unsaturation of 1)
Omit the N and one hydrogen (rule 3), omit the oxygen (rule 2), then 8–4+1 = 5, so the degree of unsaturation = 5. Since the nitro group counts as one of these degrees of unsaturation, possible structures include:
5) C4H6O2
Degree of unsaturation = 2. Thus, it has 2 of some combination of rings, carbon-carbon double bonds, or carbonyl groups. Examples:
6) C7H10Cl2
Replace the Cl’s by hydrogens to get C7H12 (rule 1), then 7–6+1 = 2, so the degree of unsaturation = 2. Examples:
Nine compounds are drawn below. The NMR spectrum for each is among the nine spectra on the following 3 pages.
1) Match each compound with its NMR.
2) Draw the structure above the corresponding spectrum and show clearly which NMR peak corresponds to which proton(s) in the molecule.
3) Write down one or two bands which you would look for in the IR spectrum of the compound to verify your assignment.
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The structures of ethyl butanoate and propyl butanoate are drawn below. Note how each has an ethyl group and a propyl group; the only difference is how they are orientated around the ester functional group. The NMRs for these two compounds are on the next page.
1) Match each compound with its NMR.
2) Draw the structure above the spectrum and indicate clearly which proton(s) correspond to which NMR peak.
Note: Esters are named from their parent carboxylic acid. For example, ethyl butanoate is derived from butanoic acid and propyl propanoate is derived from propanoic acid.
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The eight spectra on the following pages represent mono, di, and trisubstituted aromatic compounds. An example of each type of disubstituted compounds is represented: ortho, meta, and para subsituted. The structures of the compounds which correspond to the eight spectra are drawn below.
1) Match each compound with its NMR. (You probably will not be able to tell an ortho from a meta subsituted compound; you will not be marked off if you have these wrong. You will be marked off if you mix up a para with an ortho or meta substituted compound.)
2) Draw the structure above the spectrum and indicate which proton(s) correspond to which NMR peak. You do not have to assign each proton on the aromatic ring to a specific peak in the NMR aromatic region—simply indicate that they are “somewhere” in the aromatic grouping of NMR peaks.
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