Amine Ko P飞 pK。of RaNH Trends ammonia 1.8×105 4.74 9.26 Primary alkyl amines methylamine 4.3×104 3.36 10.64 Ammonia weaker base than RNH2 ethylamine 4.4×104 3.36 10.64 n-propylamine 4.7×104 3.32 10.68 isopropylamine 4.0×10-4 3.40 10.60 cyclohexylamine 4.7×104 3.33 10.67 benzylamine 2.0×105 4.67 9.33 Secondary amines dimethylamine 5.3×104 3.28 10.72 diethylamine 9.8×104 3.01 10.99 RNH2,R2NH and R3N di-n-propylamine 10.0×10 3.00 11.00 about the same Tertiary amines trimethylamine 5.5×105 4.26 9.74 triethylamine 5.7×104 3.24 10.76 tri-n-propylamine 4.5×104 3.35 10.65 Aryl amines aniline 4.0×100 9.40 4.60 N-methylaniline 6.1×10-10 9.21 4.79 Aniline much weaker than cyclohexylamine N.N-dimethylaniline 1.2×109 8.94 5.06 p-bromoaniline 7×10-1 10.2 3.8 p-methoxyaniline 2×109 8.7 5.3 p-nitroaniline 1×103 13.0 1.0 Heterocyclic amines pyrrole 1×1015 -15 -1 Pyrrole very weak pyrrolidine 1.9×103 2.73 11.27 imidazole 8.9×108 7.05 6.95 pyridine 1.8×109 875 5.25 piperidine 13×103 2.88 11.12 Ch19 Amines(landscape) Page 11Ch19 Amines(landscape) Page 11 Trends Ammonia weaker base than RNH2 RNH2, R2NH and R3N about the same Aniline much weaker than cyclohexylamine Pyrrole very weak