MCAT Organic Chemistry Review 2018-2019

Proton  NMR is  good    for:

Now let’s move on to Hb. Because both hydrogens are attached to the same carbon, which can freely
rotate, they will be magnetically identical. These hydrogens are three bonds away from one other
hydrogen, Ha. This means that they will appear as a doublet. Because there are two of them, the
integration for the doublet representing Hb will be larger than the triplet for Ha.

Table 11.2 shows the ratios for up to seven adjacent hydrogens, but it isn’t necessary to memorize
this table for the MCAT. Just remember to follow the n + 1 rule for the proton of interest to
determine the number of peaks. In addition, peaks that have more than four shifts will generally be
referred to generically as a multiplet.

Table 11.2. Area Ratios for Peaks Split by Adjacent Hydrogens

Number  of  Adjacent    Hydrogens Total Number  of  Peaks Area  Ratios

0 1 1

1 2 1:1

2 3 1:2:1

3 4 1:3:3:1

4 5 1:4:6:4:1

5 6 1:5:10:10:5:1

6 7 1:6:15:20:15:6:1

7 8 1:7:21:35:35:21:7:1

Table 11.3 indicates the chemical shift ranges of several different types of protons. It is unnecessary
to memorize this table, as it is fairly low-yield information. The values that are useful to memorize
are the outliers like the deshielded aldehyde at 9 to 10 ppm, and the even more deshielded
carboxylic acid between 10.5 and 12 ppm. Another popular peak on the MCAT is the hydrogen of an

Determining the relative    number  of  protons and their   relative    chemical    environments

Showing how many    adjacent    protons there   are by  splitting   patterns

Inferring   certain functional  groups