iyigunler
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i just dont understand it, wont go in my head
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n2001
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What don’t u understand about it?
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Claisen
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Image

As you will see, they have the same order of attachment but are arranged differently in space across a mirror plane. As shown above, they come often in pairs and are not superimposable. They won't go on top of eachother identically, like your hands. We refer to them as enantiomers.

Why are they called optical isomers? This is because they rotate plane polarised light in different directions (clockwise or anticlockwise). This means, if we have an equal mixture of each optical isomer (racemic mixture) there is no overall rotation.
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Bluejewel01
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Definition: two non-superimposobale mirror image structures.

E.g look at your hands. They are identical mirror images of each other but when you overlap them they aren’t the same no matter how many degrees you orientate your hand.
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Reality Check
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(Original post by iyigunler)
i just dont understand it, wont go in my head
It's also important to note that it only occurs when you have four different groups attached to the central carbon atom (if that's your example) - if two of the groups are the same, a H atom for example, you cannot produce two optical isomers.

Isomerisation can be a difficult topic to get your head round. The best way to understand it is to visualise it using a model kit. Ask at your school or college if you can use a model making set like a 'molymod' and practice making some optical isomers - use a central carbon atom and attach four different groups to it. Then try making its mirror image - that will be the stereoisomer.
Last edited by Reality Check; 1 year ago
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Claisen
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(Original post by Reality Check)
It's also important to note that it only occurs when you have four different groups attached to the central carbon atom (if that's your example) - if two of the groups are the same, a H atom for example, you cannot produce two optical isomers.

Isomerisation can be a difficult topic to get your head round. The best way to understand it is to visualise it using a model kit. Ask at your school or college if you can use a model making set like a 'molymod' and practice making some optical isomers - use a central carbon atom and attach four different groups to it. Then try making its mirror image - that will be the stereoisomer.
The first part is only true if there is no symmetry in the compound. Compounds can have a stereogenic centre but be symmetrical and therefore show no optical isomerism and are known as meso compounds.
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Reality Check
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(Original post by Acetyl)
The first part is only true if there is no symmetry in the compound. Compounds can have a stereogenic centre but be symmetrical and therefore show no optical isomerism and are known as meso compounds.
Advice is always great - but it needs tailoring to the OP bearing in mind the current level of the student, in this case an AS level. Sometimes things also need simplifying, rather than including lots of detail. If the OP is struggling with the basic concept of stereoisomerism, then talking about meso compounds is not going to be helpful to him - even when the information is technically correct. This isn't a criticism, but an observation designed to improve your otherwise excellent posts.

I am aware of what a meso compound is...
Last edited by Reality Check; 1 year ago
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