Definition of natural disaster : a sudden and terrible event in nature (such as a hurricane, tornado, or flood) that usually results in serious damage and many deaths The earthquake was one of the worst natural disasters of this century.
Synthesis, Chemical. the planned production of complex compounds from simpler compounds based on a knowledge of the reactantsâ chemical structure and reactivity. Chemical synthesis usually implies a sequence of several chemical processes (steps). In the early period in the development of chemistry, chemical synthesis was carried out mainly for inorganic compounds and was fortuitous in nature.
Total synthesis may be accomplished either via a linear or convergent approach. In a linear synthesisâoften adequate for simple structuresâseveral steps are performed one after another until the molecule is complete. The chemical compounds made in each step are called synthetic intermediates. For more complex molecules, a different approach may be preferable: convergent synthesis involves the individual preparation of several pieces (key intermediates), which are then combined to form the desired product.