-i totally do not understand.
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Here's an analogy, hope it helps!
Imagine you are sitting at a dinner table. Across from you is your friend Aaron. Sitting next to you are your friends Becky and Chuck. From this information, even though we know Aaron is across from you, it is impossible to tell who is to your left or to your right - Becky or Chuck? So that's like relative configuration - we know who you are sitting next to (i.e. the atoms attached), but that's it.
In an absolute configuration, the order is known. For determining priority, the Cahn-Ingold-Prelog rules are used, but for this analogy, ABC order should get the point across. For instance, if Becky is to your left and Chuck to your right, going in ABC order would be counterclockwise (S configuration). If the opposite is true (if Becky and Chuck were to switch seats), the ABC order would be clockwise (R configuration). Remember though, Cahn-Ingold-Prelog rules do NOT use ABC order, it's a bit more complicated than that and involves the atomic numbers of the atoms attached (the "friends" in the example).
Also, the 3-D aspect of configuration is a little more complicated in that the atoms don't all sit at a flat "table", but it makes the analogy easier to understand that way.
Imagine you are sitting at a dinner table. Across from you is your friend Aaron. Sitting next to you are your friends Becky and Chuck. From this information, even though we know Aaron is across from you, it is impossible to tell who is to your left or to your right - Becky or Chuck? So that's like relative configuration - we know who you are sitting next to (i.e. the atoms attached), but that's it.
In an absolute configuration, the order is known. For determining priority, the Cahn-Ingold-Prelog rules are used, but for this analogy, ABC order should get the point across. For instance, if Becky is to your left and Chuck to your right, going in ABC order would be counterclockwise (S configuration). If the opposite is true (if Becky and Chuck were to switch seats), the ABC order would be clockwise (R configuration). Remember though, Cahn-Ingold-Prelog rules do NOT use ABC order, it's a bit more complicated than that and involves the atomic numbers of the atoms attached (the "friends" in the example).
Also, the 3-D aspect of configuration is a little more complicated in that the atoms don't all sit at a flat "table", but it makes the analogy easier to understand that way.
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Configuration is relative arrangement of atoms or groups around a particular atom. Stereoisomers differ in their configuration. However it is generally not possible to determine the relative arrangement from properties or by inspecting the molecule. Scientific Rosanoff suggested that we arbitrarily assign a particular configuration to optical isomers of glyceraldehyde and correlate all other isomers with respect to it. This way of assigning configuration is relative configuration.
With the development of assymmetric x-ray crystallography and pther techniques it is now possible to find actual configuration of isomers which is absolute configuration. It is expressed in terms of R-S system.
However the arbitrary choice of Rosanoff was correct and so both are now interchangeable.
With the development of assymmetric x-ray crystallography and pther techniques it is now possible to find actual configuration of isomers which is absolute configuration. It is expressed in terms of R-S system.
However the arbitrary choice of Rosanoff was correct and so both are now interchangeable.