Place these in order of decreasing priority according to the R-S convention
a) H, CL, Br, CH3
B) OH, CH3, CH2CL, CH3CH2
C) CH3, CH2CH3, CL, c6H5
http://science.uvu.edu/ochem/index.php/alphabetical/q-r/rs-convention/
To determine the priority of substituents using the R-S convention, we need to compare the atoms directly attached to the chiral center. The priority is determined by the atomic number of the atoms bonded to the chiral center.
a) For the first set (H, Cl, Br, CH3), we compare the atomic numbers:
H (1) < Cl (17) < Br (35) < CH3 (6)
Therefore, the order of priority in decreasing order would be: Br > Cl > CH3 > H.
b) For the second set (OH, CH3, CH2Cl, CH3CH2), we compare the atomic numbers:
OH (8) < CH3 (6) < CH2Cl (17) < CH3CH2 (6)
In this case, there is a tie between CH3 and CH3CH2 because both are carbon atoms and have the same atomic number. In such cases, we compare the atoms bonded to the carbon atoms until a difference is found. The atom bonded to the CH3 is hydrogen (H), while the atom bonded to CH3CH2 is another carbon (C). Since carbon has a higher atomic number than hydrogen, the order of priority in decreasing order would be: CH2Cl > CH3CH2 > CH3 > OH.
c) For the third set (CH3, CH2CH3, Cl, C6H5), we compare the atomic numbers:
CH3 (6) < CH2CH3 (6) < Cl (17) < C6H5 (6)
Again, we have a tie between CH3, CH2CH3, and C6H5 because they all have the same atomic number (carbon). In this case, we look at the atoms directly bonded to the carbon atoms. The atoms bonded to CH3 and CH2CH3 are hydrogen (H), while the atom bonded to C6H5 is a benzene ring (C6H5). Since the benzene ring has a higher atomic number than hydrogen, the order of priority in decreasing order would be: C6H5 > Cl > CH3 > CH2CH3.
Therefore, the final order of decreasing priority according to the R-S convention is:
a) Br > Cl > CH3 > H
b) CH2Cl > CH3CH2 > CH3 > OH
c) C6H5 > Cl > CH3 > CH2CH3