ROD 2 - 1. Diastereomers are stereoisomers that are not...

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1 . Diastereomers are stereoisomers that are not enantiomers . 2. Meso compounds are achiral molecules (they contain a plane of symmetry) that have two or more stereocenters. 3. To distinguish between enantiomers and diastereomers among molecules with more than one chiral center, assign each chiral center as R or S, then compare the designations (i.e. R,R and R,S are diastereomers, R,.R and S,S are enantiomers, etc.). This is easier than trying to look for mirror images, mirror planes, and superimposablility. 4. You need to draw molecules in their most symmetric possible conformation with looking for symmetry, (do not worry about strain for this). Use eclipsed conformations if you need to. When analyzing ring compounds containing two or more stereocenters, look for planes of symmetry (when the cyclohexanes are drawn flat) to identify which compounds are chiral and which ones are not. 5. Fischer projections are a useful way to display a chiral center. 6. Enantiomers have identical properties measured in an achiral way, but diastereomers have different properties measured in any fashion. 7. We are chiral because our proteins, carbohydrates, DNA etc. are chiral l , so different enantiomers of the same constitutional isomer may taste/smell differently to us. Also, for most chiral drugs, only one enantiomer usually has the desired effect. 1. . We are chiral because our proteins, carbohydrates, DNA etc. are chiral l , so different enantiomers of the same constitutional isomer may taste/smell differently to us. Also, for most chiral drugs, only one enantiomer usually has the desired effect. Click here for an interesting story about a famous chiral drug. 2. When analyzing ring compounds containing two or more stereocenters, look for planes of symmetry (when the cyclohexanes are drawn flat) to identify which compounds are chiral and which ones are not. 3. Fischer projections are a useful way to display a chiral center. 4. Enantiomers have identical properties measured in an achiral way, but diastereomers have different properties measured in any fashion. 5. We are chiral because our proteins, carbohydrates, DNA etc. are chiral, so different enantiomers of the same constitutional isomer may taste/smell
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differently to us. Also, for most chiral drugs, only one enantiomer usually has the desired effect. 6. Samples of enantiomers rotate the plane of plane polarized light to an equal extent, but in opposite directions. 7. There is no absolute link between "R" and "S" and "+" and "-" . Sometimes the R enantiomer rotates plane polarized light in the "+" direction, and for other molecules, the S enantiomer rotates plane polarized light in the "+" direction. 8. A one-to-one mixture of enantiomers is called a racemic mixtur e , and a racemic mixture will not rotate the plane of plane polarized light since the effects of the two enantiomers are equal and opposite, so they cancel. 9.
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ROD 2 - 1. Diastereomers are stereoisomers that are not...

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