The reactivity of organometallic compounds increases with the percent ionic character of the carbon-metal bond. RLi and RMgX are of great importance in organic synthesis
1858 ~ 1861, Kekulé, Couper, and Butlerov, laid the basis for one of the most fundamental theories in chemistry: the structural theory. Valence(化合价): C — tetravalent; O — divalent; H — monovalent