Chemical substance In organic chemistry, there can be more than one chemical compound with the same composition and molecular weight. Generally, these are called isomers. Isomers usually have substantially different chemical properties, and often may be isolated without spontaneously interconverting. A common example is glucose vs. fructose. The former is an aldehyde, the latter is a ketone. Their interconversion requires either enzymatic or acid-base catalysis. However, tautomers are an exception: the isomerization occurs spontaneously in ordinary conditions, such that a pure substance cannot be isolated into its tautomers, even if these can be identified spectroscopically or even isolated in special conditions. A
Magic cube classes Frost referred to all but the simple class as Nasik cubes. <br>The smallest normal diagonal magic cube is order 5. See Diagonal magic cube. Minimum correct summations required = 3"m" + 6"m" + 4 All 4m pantriagonals must sum correctly (that is 4 one-segment, 12("m"-1) two-segment, and 4("m"-2)("m"-1) three-segment). There may be some simple AND/OR pandiagonal magic squares, but not enough to satisfy any other classification. <br>The smallest normal pantriagonal magic cube is order 4. See Pantriagonal magic cube. <br>Minimum correct summations required = 7"m". All pan-"r"-agonals sum correctly for "r" = 1 and 3. A cube of this class