Steppe
a term applied to one of those extensive plains which, with the occasional interpolation of low ranges of hills, stretch from the Dnieper across the S. E. of European Russia, round the shores of STEREOSCOPE known where two compounds are found to consist not only of the same atoms but of the same groups of atoms, and yet they differ in their properties, both chemical and physical. For instance, both fumaric acid and maleic acid have the chemical formula C4H4O4, and the atoms are grouped in this manner:
COOH.CH: CH.COOH. The two compounds are known as isomers, and the fact that two substances could exist with the same structural formula, and yet be entirely different and distinct compounds for a long time remained unexplained.
The solution to the problem was offered by stereo-chemistry. Following the theories of Van't Hoff, the carbon atom is conceived as being situated at the center of a regular tetrahedron, the groups combined with it being located at the angles. The differing pro g properties of isomers is explained by the theory that the arrangement of the groups at the corners, relative to one another, differs in the two compounds. For instance, if a projection were made of the "solid formula" of the two compounds given above, they would appear as:
H-C-COOH 11 H-C-COOH Maleic Acid H-C-COOH II COOH-C-H Fumaric Acid