Hodgkin published the first full molecular structure of a steroid, cholesteryl iodide, solved entirely by X-ray crystallography.
In 1945, Dorothy Hodgkin published the complete three-dimensional structure of cholesteryl iodide, marking the first time the full atomic structure of a complex organic molecule had been determined entirely through X-ray crystallography.
Steroid chemistry had long been a contentious and difficult area, with chemists disagreeing over the correct structural formulas for cholesterol and related compounds based on chemical degradation studies alone. Hodgkin's crystallographic analysis provided definitive, unambiguous proof of the molecule's three-dimensional shape, resolving these disputes and validating X-ray crystallography as a powerful tool for elucidating complex organic structures that went far beyond simple inorganic salts.
This achievement required Hodgkin to develop and refine advanced mathematical and computational techniques for interpreting diffraction data from molecules containing dozens of atoms—an extraordinarily demanding task in an era before electronic computers, when Fourier syntheses had to be calculated largely by hand or with primitive mechanical aids.
The success of the cholesteryl iodide structure proved that no organic molecule, however complex, was beyond the reach of crystallographic analysis, directly paving the way for her subsequent, even more ambitious structural determinations of penicillin, vitamin B12, and insulin. It stands as one of the foundational achievements of structural chemistry in the twentieth century.