R S Configuration Assigning Priorities

Nitin_Naudiya

The Order of priority of few elements is given Below

OCOCH₃ > NH₂ > COOCH₃ > COOH > COCH₃ > C₆H₆

Can any one explain me how these priority were assigned.

If we consider C₆H₆ ....out of the 6 Carbon Atoms which one should i choose ... and if i choose any one of the Six then i should add their Atomic Numbers of the neighbouring elements and then find out the Largest and that would have the highest Priority. I tried this method with all the atoms but couldnt understand .What approach should i take.

Please Explain me atleast 3 of the above mentioned compounds so that i can get an idea of how to go about it.

chemisttree

I think the C6H6 is an error and should actually be -C6H5... that is if you are determining the priority of an attached benzene group.

Nitin_Naudiya

Yes it is C₆H₅

Sorry for the Error

chemisttree

Well, that answers the following.
When assigning priorities, you count double bonds the same way you do for alkanes. So for benzene you would consider the attached group as a carbon attached to three other carbons in the same way that a tertiary carbon of an alkane is attached to three other carbons. If you were to rank benzene against t-butyl, you would choose benzene as higher ranking than t-butyl because the methyl groups of t-butyl are of lower rank (carbon attached to three hydrogens) than the adjacent carbons in the benzene ring (carbon attached to one hydrogen and two carbons).