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b. Determination of chemical formulae

One particularly useful result of a structure analysis is the determination of the unknown chemical formula of a compound. Three such examples of such determinations solely by crystallographic methods are penicillin which was shown to contain a $\beta$-lactam ring system, vitamin B12 which was known to contain cobalt but was shown by X-ray methods to have a modified porphyrin-like structure, and batrachotoxin, a potent poison (used by Colombian Indians for their arrow tips and isolated from a frog) for which only minute quantities could be isolated. Such structure determination then opened the doors for the study of the detailed chemistry (including synthesis), biochemistry and biology of these compounds.

References

1. Penicillin. Crowfoot, D., Bunn, C. W., Rogers-Low, B. W. and Turner-Jones, A., The Chemistry of Penicillin , Princeton, University Press (1949).

2. Vitamin B12. Brink, C., Hodgkin, D. C., Lindsey, J., Pickworth, J., Robertson, J. H. and White, J. G., Nature 174 (1954) 1169; Hodgkin, D. C., Pickworth, J., Robertson, J. H., Trueblood, K. N., Prosen, R. J. and White, J. G., Nature 176 (1955) 325; Hodgkin, D. C., Kamper, J., Mackay, M., Pickworth, J., Trueblood, K. N. and White, J. G., Nature 178 (1956), 64.

3. Batrachotoxin. Tokuyama, T., Daly, J., Witkop, B., Karle, I. L. and Karle, J., J. Amer. Chem. Soc . 90 (1968) 1917; Karle, I. L. and Karle, J., Acta Cryst . B25 (1969) 428.


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