Difference between revisions of "Chiral molecule"
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(no problem, I merely exploited the optical activity and 'rode' the light beam to the new location - no actual heavy lifting involved) |
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| − | A '''chiral molecule''' is a molecule that cannot be superimposed on its mirror image. Chiral molecules are optically active in the sense that they rotate the plane of polarized light. | + | A '''chiral molecule''' is a molecule that cannot be superimposed on its mirror image. Chiral molecules are optically active in the sense that they rotate the plane of [[polarized light]]. |
==Louis Pasteur== | ==Louis Pasteur== | ||
| − | [[Louis Pasteur]] encountered the phenomenon of optical activity in 1843, during his investigation of the crystalline sediment that accumulated in wine casks (a form of tataric acid called paratartaric acid - also called racemic acid, from the Latin racemus, "bunch of grapes"). He used fine forceps to separate two types of crystals identical in shape but mirror images of each other in structure. Both types proved to have all the chemical properties of tartaric acid, but in solution one type rotated plane-polarized light to the left (levorotatory), the other to the right (dextrorotatory). Pasteur later described the experiment and its interpretation: | + | [[Louis Pasteur]] encountered the phenomenon of optical activity in 1843, during his investigation of the crystalline sediment that accumulated in wine casks (a form of [[tataric acid]] called paratartaric acid - also called racemic acid, from the Latin racemus, "bunch of grapes"). He used fine forceps to separate two types of crystals identical in shape but mirror images of each other in structure. Both types proved to have all the chemical properties of tartaric acid, but in solution one type rotated plane-polarized light to the left (levorotatory), the other to the right (dextrorotatory). Pasteur later described the experiment and its interpretation: |
<blockquote> | <blockquote> | ||
Revision as of 15:33, December 18, 2008
A chiral molecule is a molecule that cannot be superimposed on its mirror image. Chiral molecules are optically active in the sense that they rotate the plane of polarized light.
Louis Pasteur
Louis Pasteur encountered the phenomenon of optical activity in 1843, during his investigation of the crystalline sediment that accumulated in wine casks (a form of tataric acid called paratartaric acid - also called racemic acid, from the Latin racemus, "bunch of grapes"). He used fine forceps to separate two types of crystals identical in shape but mirror images of each other in structure. Both types proved to have all the chemical properties of tartaric acid, but in solution one type rotated plane-polarized light to the left (levorotatory), the other to the right (dextrorotatory). Pasteur later described the experiment and its interpretation:
In isomeric bodies, the elements and the proportions in which they are combined are the same, only the arrangement of the atoms is differetn... We know, on the one hand, that the molecular arrangements of the two tartaric acids are asymmetric, and on the other hand, that these arrangements are absolutely identical, excepting that they exhibit asymmetry in opposite directions. Are atoms of the dextro acid grouped in the form of a right-handed spiral, or are they placed at the apex of an irregular tetrahedron, or are they disposed according to this or that asymmetric arrangement? We do not know.[1]
References
- ↑ From pasteur's lecture to the Societe Chimique de Paris in 1883, quoted in DuBos, R. (1976) Louis Pasteur: Free Lance of Science, p. 95, Charles Scribner's Sons, New York.