Assigning Priorities R, S

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Aletheia

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I'm a little confused with assigning priority. I know you're supposed to assign it at the FIRST point of difference. So, for example, if we have:
1. CH3
2. CH2SH
3. NH3
4. COO

The N is highest priority, but because there are three other Cs does this mean that that is not the first point of difference. Ie: are we looking for the point of difference so that all of them are different? So, provided that we assign priority 1 to NH3, I would assign priority 2 to CH2SH because of the S and Hs bound to the Carbon, then to COO because of the two OO groups and then, finally CH3. Is my reasoning correct?

Thank you kindly.
 
I'm a little confused with assigning priority. I know you're supposed to assign it at the FIRST point of difference. So, for example, if we have:
1. CH3
2. CH2SH
3. NH3
4. COO

The N is highest priority, but because there are three other Cs does this mean that that is not the first point of difference. Ie: are we looking for the point of difference so that all of them are different? So, provided that we assign priority 1 to NH3, I would assign priority 2 to CH2SH because of the S and Hs bound to the Carbon, then to COO because of the two OO groups and then, finally CH3. Is my reasoning correct?

Thank you kindly.

Looks correct to me.
 
Yes. But by the way, double bonds count as 2 single bonds. So the COO has 3 oxygens.
 
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