Spectroscopic Analysis of Amines

Of the seven dyes approved for coloring foods, these three are azo dyes. All are sold as their sodium salts. 

The official names of these dyes are FD C Red No. 40, FD C Yellow No. 5, and FD C Yellow No. 6, where FD C stands for Food, Drug, and Cosmetic, which is both the name of the law under which these dyes are regulated and the purposes for which they are approved. 

Infrared The absorptions of interest in the IR spectra of amines are those associated with N—H vibrations. Primary alkyl- and arylamines exhibit two peaks in the range 3000-3500 cm which are due to symmetric and antisymmetric N—H stretching modes. 

The infrared spectrum of butylamine has peaks for N —H stretching at 3290 and 3370 cm T One corresponds to a symmetrical stretch of the two N —H bonds, the other to an antisymmetrical stretch. The peak at 1600 cm is for NH2 bending (scissoring). 

The 200-MHz NMR spectra of (a) 4-methylbenzylamine and ib) 4-methylbenzyl alcohol. The singlet corresponding to CH2N in (a) is more shielded than that of CH2O in ib). 

NMR Similarly, carbons that are bonded to nitrogen are more shielded than those bonded to oxygen, as revealed by comparing the C chemical shifts of methylamine and methanol. 

Mass Spectrometry A number of features make amines easily identifiable by mass spectrometry. 

Bacteria require p-aminobenzoic add in order to biosynthesize folic acid, a growth factor. Structurally, sulfanilamide resembles p-aminobenzoic acid and is mistaken for it by the bacteria. Folic acid biosynthesis is inhibited and bacterial growth is slowed sufficiently to allow the body s natural defenses to effect a cure. Since animals do not biosynthesize folic acid but obtain it in their food, sulfanilamide halts the growth of bacteria without harm to the host. 

Identification of the mechanism by which Pron-tosil combats bacterial infections was an early triumph of pharmacology, a branch of science at the in- 

We tend to take the efficacy of modern drugs for granted. One comparison with the not-too-distant past might put this view into better perspective. Once sulfa drugs were introduced in the United States, the number of pneumonia deaths alone decreased by an estimated 25,000 per year. The sulfa 

The colors of azo compounds vary with the nature of the aryl group, with its substituents, and with pH. Substituents also affect the water-solubility of azo dyes and how well they bind to a particular fabric. Countless combinations of diazonium salts and aromatic substrates have been examined with a view toward obtaining azo dyes suitable for a particular application. 

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