The correct order of priority for the given functional group is
−COOH>−SO3H>−
O
||
C
−NH2>−
O
||
C
−H
Functional group (priority order)
suffix(s)
prefix
(1)
−
O
||
C
−OH (Carboxylic acid)
Oic acid(when carbon(C) of this functional group present in the main chain)or Carboxylic acid (when carbon(C) of this functional group is not present in the main chain)
Carboxy
(2)
−
O
||
S
||
O
−OH (Salphonic acid)
sulphonic acid
sulpho
(3)
Anhydride
Oic anhydrid (when carbon(C) of this functional group present in the main chain) or
Carboxylic anhydride (when carbon(C) of this functional group is not present in the main chain)
-
(4)
esters
Oate (when carbon(C) of this functional group present in the main chain)or Carboxylate (when carbon(C) of this functional group is not present in the main chain)
-
(5)
Acid halides
Oyl halide (when carbon(C) of this functional group present in the main chain)or Carboxyl halide (when carbon(C) of this functional group is not present in the main chain)
haloflormyl
(6)
Amides R−
O
||
C
−NH2
amide (when carbon(C) of this functional group present in the main chain) or carbamide (when carbon(C) of this functional group is not present in the main chain)
carbamoyl
(7)
cynide (−C≡N)
nitrile (when carbon (C) of this functional group present in the main chain) or carbonitrile (when carbon(C) of this functional group is not present in the main chain)
cyano
(8)
−N
=
→
C
Carbylamine
isocyano
(9)
−
O
||
C
−H
al (when carbon(C) of this functional group present in the main chain) or Carbaldehyde (when carbon(C) of this functional group is not present in the main chain)
formyl(oxo)
(10)
−
O
||
C
−
one
oxo
(11)
−OH
ol
hydroxy
(12)
−SH
thiol
mercapto
(13)
−NH2
amine
amino
From this table you can see −COOH has highest priority and −NH2 has lowest priority among all functional group