Dextro- prefix

Prefix lev/levo-Prefix ar-Prefix dex/dextro-Prefix es-... 

The small capital letter prefix refers to configuration, related to n glyceraldehyde, and not to the direction of optical rotation. The sign of optical rotation is expressed as (+) and (—) or as d and I or by the words dextro and Uuvo. Th is we have n.( —)-fructose and ,-(+).arabinose. 

In solution, enantiomers rotate the wave plane of linearly polarized light in opposite directions hence they are refered to as dextro"- or levo-rotatory , designated by the prefixes d or (+) and 1 or (-), respectively. The direction of rotation gives no clue concerning the spatial structure of enantiomers. The absolute configuration, as determined by certain rules, is described by the prefixes S and R. In some compounds, designation as the D- and L-form is possible by reference to the structure of D- and L-glyceraldehyde. 

The biological consequences of molecular shape can be dramatic. Look at the structures of dextromethorphan and levomethorphan, for instance. (The Latin prefixes dextro- and levo- mean "right" and "left," respectively.) Dextromethorphan is a common cough suppressant found in many over-the-counter cold medicines, but its mirror-image, levomethorphan, is a powerful narcotic pain-reliever similar in its effects to morphine. The two substances are chemically identical except for their shapes, yet their biological properties are completely different. 

Optical isomerism is when two molecules are nonsuperimposable mirror images of each other (Think of a pair of gloves. They can only stack palm to palm, not one on top of the other.) Such molecules are termed asymmetric or chiral. (Note Chiral carbons have 4 different substituents.) Two optical isomers can be distinguished in their names by the prefixes dextro- or levo- according to whether a solution of the compound rotates a beam of polarized light to the right or the left. The abbreviations d- and l- are commonly used for dextro- and levo-. A new system of naming uses R- (rectus) and S- (sinister). 

The prefixes dextro- and leva- are synonymous with dextrorotatory and levorotatory and refer to rotation only. 

COOH, —NH2, — CH3, and —H. There are two ways in which four different groups can be arranged in a tetrahedral structure about a central atom (see Fig. 7.9). The two optical isomers of alanine are designated by the prefixes L- and D- for leva and dextro (Latin for left and right, respectively). 

If an optically active compound rotates the plane of polarization clockwise, it is called dextrorotatory, indicated by (+). If an optically active compound rotates the plane of polarization counterclockwise, it is called levorotatory, indicated by (—). Dextro and levo are Latin prefixes for to the right and to the left, respectively. Sometimes lowercase d and I are used instead of (+) and (—). 

The active forms of dihydroxysuccinic acid are named dextro-tartaric acid and levo-tartaric acid. The former occurs widely distributed in nature, and is usually called tartaric acid, the prefix being omitted. The inactive acid which is a mixture of... 

The following prefixes and interpolations are not treated as part of the name ortho- (o-), meta- (m-), para- (p-), alpha- (a), beta- (p), gamma- (y) etc. primary- (prim-), secondary- (sec-), tertiary- (tert-), cis-, trans-, dextro- (d-), levo- (I-), normal (n-), N- (- bond to nitrogen atom). 

Rotation of the plane of polarized light in the clockwise sense is taken as positive (+), and rotation in the counterclockwise sense is taken as a negative ( —) rotation. Older terms for positive and negative rotations were dextrorotatory and levorotatory, from the Latin prefixes dextro- ( to the right ) and levo- ( to the left ), respectively. At one time, the symbols d and / were used to distinguish between enantiomeric forms... 

Enantiomer i- nan-te-o-mor [Gk enangtios + E -mer] (ca. 1929) n. Either of a pair of chemical compounds whose molecular structures have a mirror-image relationship to each other. An asymmetric molecule that is the mirror image of its stereoisomer. The two isomers are given the prefixes dextro-and leva-, e.g., d- and Mactic acid. The physical properties of pure enantiomers are equal within experimental error, yet mixtures of the two, called racemic mixtures, may have different properties. For example, 50-50 d/ -lactic acid melts 20°C lower than its pure enantiomers. 

There are several conventions used to designate specific enantiomers. Dextro- and fevD- prefixes refer to the direction of rotation of polarized light. R and S, the most commonly used designations, are assigned based on the "priority" assigned to each of the four groups attached to the chiral carbon—something that is beyond the scope of this text. 

Much confusion has arisen from the indiscriminate use of the small prefix d or Z to denote chemical relationship as well as optical rotation, and to avoid mistakes it is now usual to employ the prefix (+) or (—) to indicate if a compound is dextro- or laevo-rotatory, the large capital D or L being used to denote lineal descent from the (+) or (—) chemical ancestor. 

There are a number of dmgs such as dextrorophan and levorphan which are prefixed by dextro- or levo- to indicate... 

The prefixes dextro and leva are derived from the Latin words dexter, "right," and leva, "left."... 

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