For example, hexane has a molecular formula of C
14 , or structurally CH
3 , implying that it has a chain structure of 6 carbon atoms, and 14 hydrogen atoms. However, the empirical formula for hexane is C
7 . Likewise the empirical formula for hydrogen peroxide , H
2 , is simply HO expressing the 1:1 ratio of component elements. Formaldehyde and acetic acid have the same empirical formula, CH
2 O . This is the actual chemical formula for formaldehyde, but acetic acid has double the number of atoms.
The Fischer projection is mostly used for linear monosaccharides . At any given carbon center, vertical bond lines are equivalent to stereochemical hashed markings, directed away from the observer, while horizontal lines are equivalent to wedges, pointing toward the observer. The projection is totally unrealistic, as a saccharide would never adopt this multiply eclipsed conformation. Nonetheless, the Fischer projection is a simple way of depicting multiple sequential stereocenters that does not require or imply any knowledge of actual conformation: