Somewhat like the parent amines, imines are mildly basic and reversibly protonate to give iminium salts: 
:RC=NR  +  H     [RC=NHR]
Alternatively, primary imines are sufficiently acidic to allow N-alkylation, as illustrated with benzophenone imine:
:(CH)C=NH  +  CHLi  →  (CH)C=NLi  +  CH
:(CH)C=NLi  +  CHI  →  (CH)C=NCH  +  LiI