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    So what I like about Chemistry is how small changes can cause much larger repercussions. For example, how r-thalidomide is a good sedative but s-thalidomide causes malformations; the difference in these two molecules is that the other is an optical isomer. Where else does this principle apply in Chemistry?
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    Another example along the same lines (with geometrical instead of optical isomerism) is trans fats - as the name suggests, they are trans isomers of fats which should be cis in nature, which means that they cannot be processed properly, and lead to increased cholesterol levels and heart disease. Although this isn't as dramatic as the effects of thalidomide, I think it's another intersting example of the importance of stereoisomerism.

    You could also give the example of methanol and ethanol. The only difference between them is the 1 carbon difference in chain length (ethanol has 2, methanol has 1), and yet methanol leads very rapidly to blindness, nausea, kidney failure, and death in even small doses, whereas ethanol is much more tolerated by the body. This could also be used to show where chemical processes are significant (distillation) to separate these two very different products and avoid accidental human consumption of methanol.
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    (Original post by lizardlizard)
    Another example along the same lines (with geometrical instead of optical isomerism) is trans fats - as the name suggests, they are trans isomers of fats which should be cis in nature, which means that they cannot be processed properly, and lead to increased cholesterol levels and heart disease. Although this isn't as dramatic as the effects of thalidomide, I think it's another intersting example of the importance of stereoisomerism.

    You could also give the example of methanol and ethanol. The only difference between them is the 1 carbon difference in chain length (ethanol has 2, methanol has 1), and yet methanol leads very rapidly to blindness, nausea, kidney failure, and death in even small doses, whereas ethanol is much more tolerated by the body. This could also be used to show where chemical processes are significant (distillation) to separate these two very different products and avoid accidental human consumption of methanol.
    AH thank you!! This is exactly what I was looking for!
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    (Original post by haes)
    So what I like about Chemistry is how small changes can cause much larger repercussions. For example, how r-thalidomide is a good sedative but s-thalidomide causes malformations; the difference in these two molecules is that the other is an optical isomer. Where else does this principle apply in Chemistry?
    maybe not in this bad way thalidomide got well known in the public. I know just some isomers with different properties:

    L-Valine and D-Valine for instance are different in taste. L-Valine is bitter, while D-Valine is sweet. L-Carvon smells of caraway, whileD-Carvon smells of mint. By looking for the internet, I really have found another isomers out which are similar in repercussion: beta blocker.The one thing has a selective effect on heart, the other thing the same on cell membranes of eyes. One of them, D-penicillamine, is toxic.
 
 
 
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