nrmoderately basic,ammonium ionsare bcthan alhol,ut not er eto thety of thert cer(K). Basicity of Amines to the electron-don um io 马a ines and imines ding ability gPhaaeoa9toaataga 21-5 Synthesis of Amines by Alkylation :NH,>R.C-NR'>RC=N: Amines can be derived from other amines aie8e3tonegctene5mpeah0esooeammomu N-proto s have pK, etimate to be7. 44 Amines are moderately basic, ammonium ions are weakly acidic. Amines are more strongly basic than alcohols, but not nearly as basic as alkoxides: The ammonium ions produced may be primary, secondary or tertiary and are named by attaching –ammonium to the substituent name followed by the name of the anion. The basicity of amines is related to the acidity of their conjugate acids, or ammonium salts. Ammonium salts are more acidic than water (pKa = 15.7) or alcohols, but much weaker than carboxylic acids (pKa=4-5). Due to the electron-donating character of alkyl groups, alkylammonium salts are slightly less acidic than ammonium ions and therefore the corresponding amines are more basic. The pKa values of alkyl ammonium salts do not vary in a regular way with increasing alkyl substitution. Factors affecting the pKa values are: •Changes in hydrogen-bonding ability •Disruption of the solvation shell The nitrogen lone pairs in arenamines and imines are less available for protonation. The electronic environment around the nitrogen atom affects the basicity of amines. Benzenamine (aniline) is considerably less basic than cyclohexanamine (and other primary amines). •The sp2 hybridization of the aromatic carbon attached to nitrogen renders the carbon relatively electron-withdrawing. •Resonance stabilization of the nitrogen lone pair into the aromatic ring is lost upon protonation. The hybridization of the nitrogen atom also affects basicity: Iminium ions have pKa values estimate to be 7–9. N-protonated nitriles have pKa values estimated to be less than -5. 21-5 Synthesis of Amines by Alkylation Amines can be derived from other amines. Direct alkylation of amines with haloalkanes to give ammonium salts generally results in multiple alkylations