Levorotation and dextrorotation

Levorotation and dextrorotation

Dextrorotation and levorotation (also spelled laevorotation)The first word component ' comes from Latin word for "right (as opposed to left)". Laevo or levo comes from the Latin for "left."] refer, respectively, to the properties of rotating plane polarized light clockwise (for dextrorotation) or counterclockwise (for levorotation). A compound with dextrorotation is called dextrorotary, while a compound with levorotation is called levorotary"'.

Compounds with these properties are said to have optical activity and consist of chiral molecules. If a chiral molecule is dextrorotary, its enantiomer will be levorotary, and vice-versa. In fact, the enantiomers will rotate polarized light the same number of degrees, but in opposite directions.

It is not possible to determine whether any chiral molecule will be levorotatory or dextrorotatory directly from its configuration, except via detailed computer modeling. [See, for example, [http://dx.doi.org/10.1016/S0009-2614(03)00968-0 this paper] , "Calculation of the gas phase specific rotation of (S)-propylene oxide at 355 nm", by Giorgioa et al.] In particular, both "R" and "S" stereocenters have the ability to be dextrorotatory or laevorotatory.


The prefixes "(+)-", "(-)-", "d-", "l-", "D-", and "L-"

A dextrorotary compound is often prefixed "(+)-", or (less often) "d-". Likewise, a levorotary compound is often prefixed "(-)-", or (less often) "l-". These "d-" and "l-" prefixes should not be confused with the "D-" and "L-" prefixes based on the actual configuration of each enantiomer, with the version synthesized from naturally occurring (+)-glyceraldehyde being considered the D- form. For example, nine of the nineteen L-amino acids commonly found in proteins are dextrorotatory (at a wavelength of 589 nm), and D-fructose is also referred to as levulose because it is levorotatory. See the article: Chirality (chemistry).

The prefixes "(R)-" and "(S)-"

There is no correlation between the (R) and (S) configuration of enantiomers and the direction of rotation of plane-polarized light.

pecific rotation

A standard measure of the degree to which a compound is dextrorotary or levorotary is the quantity called the specific rotation [α] . Dextrorotary compounds have a positive specific rotation, while levorotary compounds have negative. Two enantiomers have equal and opposite specific rotations.

The formula for specific rotation is:

[alpha] = frac{alpha}{c cdot l}

where: [α] = specific rotation
α = observed rotation
c = concentration of the solution of an enantiomer
l = length of the tube (Polarimeter tube)

The degree of rotation of plane-polarized light depends on the number of chiral molecules that it encounters on its way through the tube of polarimeter (thus, the length of the tube and concentration of the enantiomer). In many cases, it also depends on the temperature and the wavelength of light that is employed.


Solomons, T.W. Graham, and Graig B. Fryhle. Organic Chemistry. 8th. Hoboken: John Wiley & Sons, Inc., 2004.

Wikimedia Foundation. 2010.

Look at other dictionaries:

  • Dextrorotation and levorotation — (also spelled laevorotation)[1] refer, respectively, to the properties of rotating plane polarized light clockwise (for dextrorotation) or counterclockwise (for levorotation), seen by an observer whom the light is approaching. A compound with… …   Wikipedia

  • Optical rotation — (optical activity) is the turning of the plane of linearly polarized light about the direction of motion as the light travels through certain materials. It occurs in solutions of chiral molecules such as sucrose (sugar), solids with rotated… …   Wikipedia

  • Prefixes, medical — Medical words are often put together, cobbled from two or more building blocks. Among these building blocks are the prefixes. Examples of prefixes used in medicine include: {{}}a : Prefix much employed in the health sciences indicating “not,… …   Medical dictionary

  • L-DOPA — Systematic (IUPAC) name …   Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”

We are using cookies for the best presentation of our site. Continuing to use this site, you agree with this.