Closely related to the concept of chirality, and particularly important in biological chemistry, is the notion of prochirality. A molecule is said to be prochiral if it can be converted from achiral to chiral in a single chemical step. For instance, an unsymmetrical ketone…
As noted previously, the most common cause of chirality in a molecule is the presence of four different substituents bonded to a tetrahedral atom. Although that atom is usually carbon, it doesn’t necessarily have to be. Nitrogen, phosphorus, and sulfur…
As noted on several previous occasions, isomers are compounds with the same chemical formula but different structures. We’ve seen several kinds of isomers in the past few chapters, and it’s a good idea at this point to see how they…
To end this discussion of stereoisomerism, let’s return for a last look at Pasteur’s pioneering work, described in Section 5.4. Pasteur took an optically inactive tartaric acid salt and found that he could crystallize from it two optically active forms having…
Let’s look at another example (Section 5.4) of a compound with more than one chirality center: the tartaric acid used by Pasteur. The four stereoisomers can be drawn as follows: The 2R,3R and 2S,3S structures are nonsuperimposable mirror images and therefore represent…
Molecules like lactic acid, alanine, and glyceraldehyde are relatively simple because each has only one chirality center and thus only two stereoisomers. The situation becomes more complex, however, with molecules that have more than one chirality center. As a general…
Structural drawings provide a visual representation of stereochemistry, but a written method for indicating the three-dimensional arrangement, or configuration, of substituents at a chirality center is also needed. The method used a set of sequence rules to rank the four groups attached to…
Little was done to build on Biot’s discovery of optical activity until 1848, when Louis Pasteur began work on a study of crystalline tartaric acid salts derived from wine. On crystallizing a concentrated solution of sodium ammonium tartrate below 28…
The study of chirality originated in the early 19th century during investigations by the French physicist Jean-Baptiste Biot into the nature of plane-polarized light. A beam of ordinary light consists of electromagnetic waves that oscillate in an infinite number of planes at…
A molecule that is not identical to its mirror image is said to be chiral (ky-ral, from the Greek cheir, meaning “hand”). You can’t take a chiral molecule and its enantiomer and place one on the other so that all atoms coincide. How can…