In organic chemistry, a ketone is a type of compound that features one carbonyl group (C=O) bonded to two other carbon atoms, i.e., R3CCO-CR3 where R can be a variety of atoms and groups of atoms. With carbonyl carbon bonded to two carbon atoms, ketones are distinct from many other functional groups, such as carboxylic acids, aldehydes, esters, amides, and other oxygen-containing compounds. The double-bond of the carbonyl group distinguishes ketones from alcohols and ethers. A carbon atom adjacent to a carbonyl group is called an -carbon. Hydrogen atoms attached to these -carbon centers are called -hydrogens. Ketones with -hydrogen centers participate in a so-called keto-enol tautomerism. The reaction with a strong base gives the corresponding enolate, often by deprotonation of the enol.