stereo Isomerism
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Azizur Rahman
Joined: 14/03/2013 - 16:46
Posts: 1
stereo Isomerism

Can anyone help me to understand optical isomers?

Joined: 10/06/2007 - 22:31
Posts: 347
This usually refers to

This usually refers to organic chemistry but can also be applied to certain transition metal complexes. I will only mention the organic ones here.

Each carbon atom has four bonds. Unless it has double or triple bonds, the single bonds point to the corners of a tetrahedron. If each of these bonds is to a different group (methyl and ethyl count as different, even though they would both be joined to the central carbon atom by a carbon)then the molecule will have two forms that are non-superimposable mirror images. These are called enantiomers. Enantiomers twist the plane of polarisation of plane-polarised light. This is a bit complicated to explain in words but think of a light wave coming towards you. It pulses (like a sine wave) in both up-and-down and side-to-side directions. The pulse can be modified by passing the light through polaroid. If this pulse was only in the vertical direction and then went through an optically active solution on its way to you, the pulse would no longer be in the vertical direction but would be at an angle. Each optical isomer twists the light by equal but opposite amounts if the path length and concentration are the same.

If you have equal concentrations of the two enantiomers mixed together, the plane of the light is unaltered. This is called a racemic mixture.

Hope this helps. Say if you need more.

Joined: 16/10/2012 - 12:44
Posts: 1

Can someone help me with this question M/J 2010, P11,q29

I don't understand why the answer for efficiency is in the units of force??