Label the different Hs with letters to make it easier to follow - you can do this in Paint


In Experiment 54, 3,4-dimethoxybenzaldehyde, 5-methylfurfurylamine, Benzylisocyanide, and Boc-Gly-OH are used with deuterated methanol to synthasize a Ugi adduct. H NMR spectra were taken of each of these components.

3,4-dimethoxybenzaldehyde (Veratraldehyde)

external image Veratraldehyde.jpg

The H NMR of Verataldehyde shows five major peaks. This corresponds to the five different kinds of protons present in the molecule. There is an aldehyde group (-CHO), -OCH3 groups, and three Ph-H protons. The aldehyde group is the least shielded of all the groups, meaning that it absorbs at a lower magnetic field. The -CHO peak is located at about 9.7 ppm, which is consistant with the typical 9-10 ppm position of aldehydes.
Moving upfield, there are a few peaks within close proximity of each other. These are the Ph-H groups, which are usually found around 7.2 ppm. The lowest field peak corresponding to the least shielded proton is that of the hydrogen located on the sixth carbon, at a ppm of about 7.44. This proton is split by the proton on the adjacent 5-carbon, resulting in a doublet. The next group is that of the hydrogen on the second carbon at 7.33 ppm. These two protons are deshielded by the adjacent aldehyde group, which also causes some splitting. The proton on the fifth carbon is more shielded and has a position of about 7.0. There is also a doublet due to the split with the C6 proton.
Further upfield is the peak for the -OCH3 groups at about 3.8 ppm. The typical position of these groups is between 3 and 4 ppm. This peak is also a doublet because there are two equal protons on adjacent carbon atoms. The peaks have an area ratio of 1:1. The peaks also have the greatest area due to the greater number of hydrogens in the group.


[(tert-butoxy carbonyl) amino] acetic acid (Boc-Gly-OH)

external image Malaria37-#13%20R1.jpg

Boc-Gly-OH has three major proton groups. The least shielded group is the carboxylic acid. Typical peak positions of carboxylic acids are between 10-12 ppm. The group is strongly deshielded by presence of both the carbonyl and oxygen. Moving upfield is the peak for the CH2 group next to the -COOH group. -CH2 groups can normally be found around 1.3 ppm. The electron-withdrawing oxygen atoms of the -COOH group causes the -CH2 to absorb at a lower field. The most shielded group is made up of the three -CH3 groups. -CH3 positions are usually around 0.9 ppm, but again, the oxygen atom in the molecule causes the group to be slightly less shielded. The area of the curves are also telling of the groups. The -COOH group has one proton and the smallest area. The -CH2 group contains two hydrogens and thus has a larger area. The -CH3 peak is the largest due to the much greater amount of protons.