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).

 

[LudusRex]

The priority of functional groups in organic compounds is determined using the Cahn-Ingold-Prelog (CIP) system, which assigns priorities based on the atomic numbers of the atoms directly attached to the functional group. The higher the atomic number, the higher the priority.

To understand this better, let's take the example of COOH and COOCH3. In COOH, the carbon atom is bonded to an oxygen atom (atomic number 8) and a hydrogen atom (atomic number 1). In COOCH3, the carbon atom is bonded to two oxygen atoms (atomic number 8) and a hydrogen atom (atomic number 1). Since the atomic number of oxygen is higher than hydrogen, COOCH3 has a higher priority than COOH.

Similarly, in NH2 and OCOCH3, the nitrogen atom (atomic number 7) has a higher priority than the oxygen atom (atomic number 8), giving NH2 a higher priority.

In the case of C6H6, all six carbon atoms have the same atomic number (6), so the next step is to look at the atoms attached to each carbon atom. If we follow the CIP system, we would prioritize the atoms based on their atomic numbers. However, in the case of aromatic compounds like benzene (C6H6), the functional group with the highest priority is the one that has the largest number of atoms directly attached to the benzene ring. So, in this case, C6H6 would have the highest priority.

To summarize, the priority of functional groups is determined by the atomic numbers of the atoms directly attached to them, with higher atomic numbers having a higher priority. In cases where the atomic numbers are the same, the priority is based on the number of atoms directly attached to the functional group.