- The three Hs within each methyl are homotopic, and the two Hs within each methylene are enantiotopic.
- Hence we get single absorptions for these groups, displaying the typical ethyl pattern of methyl triplet and CH2 quartet.
- Note the numerical values for the integration shown under the chemical shift scale, which fit the 3 : 2 ratio of CH3 to CH2.
- They are split to a triplet by the CH2 at (d).
- With a total of four equivalent neighbors (both (c) groups), (d) should be a quintet. The enlarged view shows this clearly.
- The apparent small additional couplings seen are probably artifacts. The integration values fit the 2 : 1 ratio of (c) to (d).
These are seen as a 5H "singlet" (ArH), two 2H triplets, a 2H quartet and a 3H triplet. Each triplet tells us that there are 2H in the adjacent position, and a quartet tells us that there are 3H adjacent.
(Think of it as the lines you see, L = n + 1, where n = number of equivalent adjacent H)
This tells us we that the peaks at 4.4 and 2.8 ppm must be connected as a CH2CH2 unit.
The peaks at 2.1 and 0.9 ppm as a CH2CH3 unit. Using the chemical shift charts, the H can be assigned to the peaks as below:
4.4ppm (2H) = CH2O;
2.8ppm (2H) = Ar-CH2;
2.1ppm (2H) = O=CCH2CH3 and
0.9ppm (3H) = CH2CH3
|If a given nucleus is spin-coupled to two or more sets of neighboring nuclei by different J values, the n+1 rule does not predict the entire splitting pattern. Instead, the splitting due to one J set is added to that expected from the other J sets. Bear in mind that there may be fortuitous coincidence of some lines if a smaller J is a factor of a larger J.|