A primary amine, RNH2 can be reacted with CH3—X to get secondary amine, R—NHCH3 but the only disadvantage is that 3o amine and quaternary ammonium salts are also obtained as side products. Can you suggest a method where RNH2 forms only 2o amines?

Primary amines show carbylamine reaction in which two H-atoms attached to N-atoms of NH2 are replaced by one C-atom. On catalytic reduction, isocyanide (formed) produces secondary amine and not tertiary or quaternary salts.