R S Configuration Assigning Priorities

[Nitin_Naudiya]

The Order of priority of few elements is given Below

OCOCH₃ > NH₂ > COOCH₃ > COOH > COCH₃ > C₆H₆

Can anyone 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 anyone 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 couldn't 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]

The Order of priority of few elements is given Below

OCOCH₃ > NH₂ > COOCH₃ > COOH > COCH₃ > C₆H₆

Can anyone 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 anyone 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 couldn't 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.

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.

If we consider C₆H₆ ...out of the 6 Carbon Atoms which one should i choose...

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).