User:Jonestj/Diastereomer

Lead
Diastereoselectivity is the preference for the formation of one or more than one diastereomer over the other in an organic reaction. ''In general, this stereoselectivity is contributed to the torsional and steric interactions in the stereocenter resulting from electrophiles approaching the stereocenter in reaction. ''

Physical Properties and Chemical Reactivity of Diastereomers Compared to Enantiomers
As mentioned before, some of the major differences between enantiomers and diastereomers are their individual relationships with physical properties and chemical reactivity. While enantiomers have mostly similar physical properties, physical properties like melting/boiling points, solubilities, and refractive indices of diastereomers vary to a decent extent as proven by several lab techniques: melting point analysis, thin-layer chromatography, gas-liquid chromatography, nuclear magnetic resonance spectrometry (NMR), and infrared spectroscopy.

Diastereomers differ not only in physical properties but also in chemical reactivity — how a compound reacts with others. Glucose and galactose, for instance, are diastereomers. Even though they share the same molar weight, glucose is more stable than galactose. This difference in stability causes galactose to be absorbed slightly faster than glucose in human body.

Multiple stereocenters
If a molecule contains two asymmetric centers, there are up to four possible configurations, and they cannot all be non-superposable mirror images of each other. The possibilities for different isomers continue to multiply as more stereocenters are added to a molecule. In general, the number of stereoisomers of a molecule can be determined by calculating 2n, where n = the number of chiral centers in the molecule.

''This holds true except in cases where the molecule has meso forms. These meso compounds are molecules that contain stereocenters, but possess an internal plane of symmetry allowing it to be superposed on its mirror image. These equivalent configurations cannot be considered diastereomers. ''

Applications
As stated previously, two diastereomers will not have identical chemical properties. This knowledge is harnessed in chiral synthesis to separate a mixture of enantiomers. This is the principle behind chiral resolution. After preparing the diastereomers, they are separated by chromatography or recrystallization. Note also the example of the stereochemistry of ketonization of enols and enolates.

One specific application is the use of diastereomer derivatization in optical isomer analysis. When studying conditions like short bowel syndrome, separating the optical isomers of a substance like lactic acid is important to help avoid any potential of seizures. Identifying and separating certain diastereomers within lactic acid will help assess which compounds are more helpful than another.

Distinguishing between diastereoisomers (another name for diastereomers) is important in cocaine studies, in which the different diastereoisomers will be studied using lab techniques like melting point analysis, microcrystalline tests, thin-layer chromatography, gas-liquid chromatography, high pressure liquid chromatography, infrared spectroscopy, nuclear magnetic resonance spectrometry, and electron impact mass spectrometry.