In organic chemistry, a ketone is an organic compound with the structure R−C(=O)−R', where R and R' can be a variety of carbon-containing substituents. Ketones contain a carbonyl group −C(=O)−. The simplest ketone is acetone, with the formula (CH3)2CO. Many ketones are of great importance in biology and in industry. Examples include many sugars (ketoses), many steroids, and the solvent acetone.
Image: Oxidation of Ketone
Sugar is the generic name for sweet-tasting, soluble carbohydrates, many of which are used in food. Simple sugars, also called monosaccharides, include glucose, fructose, and galactose. Compound sugars, also called disaccharides or double sugars, are molecules made of two bonded monosaccharides; common examples are sucrose, lactose, and maltose. White sugar is a refined form of sucrose. In the body, compound sugars are hydrolysed into simple sugars.
Sugars (clockwise from top-left): white refined, unrefined, unprocessed cane, brown
German sugar sculpture, 1880
Sugar cane plantation
Two elaborate sugar triomfi of goddesses for a dinner given by the Earl of Castlemaine, British Ambassador in Rome, 1687