Selected Vitamins - Natural Products Chemistry: Sources, Separations, and Structures - page 128

OH

H

O

HO O

HO
Vitamin C (Ascorbic Acid)

OH

FIGURE 12.1 The structure of vitamin C (ascorbic acid). (R. B. Rucker, J. Zempleni,
J. Suttie, and D. McCormick, eds., 2007, Handbook of Vitamins , 4th ed., Taylor & Francis.)

ppm 5.5 5.0 4.5 4.0 3.5

FIGURE 12.2

1 H NMR spectrum (300 MHz) in D 2 O of vitamin C.

2

3

1

5

4

6

OH

O

HO O

5

4 4 1

2 3

HO OH

180 170 160 150 140 130 120 110 100 90 80 70 60

ppm

FIGURE 12.3

13 C NMR spectrum of vitamin C with carbon assignments.

carbon atoms. Upon integrating the peak ratios, these signals represent four protons
(Figure 12.2).
The 13 C NMR spectrum shown in Figure 12.3 indicates the presence of six car-
bon atoms. In the mass spectrum of Vit C (Figure 12.4), there is a strong molecular
ion indicating a m/z 178 mu, with subsequent loss of OH and C 2 H 4 O 2 fragment ions
consistent with the proposed structure.