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Anonymous asked in Science & MathematicsChemistry · 11 months ago

Is this molecule R or S?

If you look at it from the front, the 4th priority is dashed into the page so it should be R. but if you turn the whole molecule to the right ( look at it from the right side), Br will go into the page ( dashed ), the ethyl group will be wedged and the methyl group/OH will be planar, it will still be R but since the 4th priority is not dashed, shouldnt we turn into S??

Please help thanks

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2 Answers

  • Anonymous
    11 months ago
    Favorite Answer

    It's R. The methyl group is lowest priority, then you've got the ethyl group as third, hydroxy group as second and bromine first (based on atomic numbers). The photo shows the correct orientation for working out whether it's R or S (as the lowest priority is going in to the page). The priorities from highest to lowest are clearly going clockwise so it's R.

    Similarly, you can have the lowest priority coming in to the page (wedged), work out whether the priorities are going clockwise or anticlockwise, and then flip the outcome. I think this is what you were getting at in the second part of your question, but you can only do it this way if the lowest priority substituent is coming INTO the page. (What you described ie. looking at the molecule from the right doesn't satisfy this, the methyl group isn't wedged but just pointing to the right)

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  • 11 months ago

    What is this wrong with this?

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