Water of crystallization degree of hydration can be critical to the resulting chemical properties. For example, anhydrous RhCl is not soluble in water and is relatively useless in organometallic chemistry whereas RhCl•3HO is versatile. Similarly, hydrated AlCl is a poor Lewis acid and thus inactive as a catalyst for Friedel-Crafts reactions. Samples of AlCl must therefore be protected from atmospheric moisture to preclude the formation of hydrates. Crystals of hydrated copper(II) sulfate consist of [Cu(HO)] centers linked to SO ions. Copper is surrounded by six oxygen atoms, provided by two different sulfate groups and four molecules of water. A fifth water resides elsewhere
Descriptor (chemistry) the arrangement of atoms, usually of carbon atoms in carbon skelets. "n", "iso" and "neo" are no longer used in the systematic nomenclature, but still frequently in trivial names and in laboratory jargon. The prefix "n" describes a straight-chain carbon skeleton without branches, whereas "iso" describes a branched skeleton, without specifying any further details. More generally, "iso" is a compound which is isomeric to the "n" compound (a compound in which individual atoms or atomic groups are rearranged) "neo" is a non-specific term for "new", usually synthetically produced substances or isomers of long-known "n" compounds or natural substances (for example