i am here presenting a platform for the discussion on the stereochemistry.
These are the compounds that are made of the same atoms and same number too, but vary in the 3D structure. These do not interchange.
So here chirality is an important factor.
CHIRALITY is nothing but a carbon attached to 4 different groups. and so it is not superimposable on its mirror image.
Chirality is one of the factor for optically active compounds (the ability to rotate the plane polarized light).
this doesn't mean that all the molecules that are chiral are optically active.
ENANTIOMERS are mirror images that are non-superimposable.
they generally have same physical and chemical properties.
These two forms rotate the plane polarized light to the same extent but in opposite directions.
when they react with achiral substanes, they react at the same rate. but when react is a chiral compound, or if a chiral solvent or catalyst is present than the reaction rate will be altered.
some criterias for optical activity:
-absence of plane of symmentry
-absence of center of symmentry
the extent of the rotation of plane polarized light depends upon
-the type of solvent
-the concentration of the sample
Direction of the rotation can be altered if we change the wavelength, solvent or sometimes the concentration.
WHAT KIND OF COMPOUNDS ARE OPTICALLY ACTIVE ?:
1.if there is a stereogenic carbon and if there is a small variation in the compounds that are attached to the carbon, then the compound can show optical activity.
2.if there is an atom that has 4bonds, forming a tetrahedron, then they can show the optical activity.
3.In the above case, 4th bond is analogous to lone pair of electrons, they can also show the optical activity.
4.if the bridge headed atom in the adamantanes has 4 different groups, they are capable to be optically active.
5.some helical shaped compounds are optically active. e.g.hexahelicene
We can have further discussion on this interesting and important topic.
Jerry March Advanced Organic Chemistry, 6th edition, wiley publishers, pg no 136 to 152
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