Spectroscopic characterization and crystal structures of four hydrochloride cathinones: N-ethyl-2-amino-1-phenylhexan-1-one (hexen, NEH), N-methyl-2-amino-1-(4-methylphenyl)-3-methoxypropan-1-one (mexedrone), N-ethyl-2-amino-1-(3,4-methylenedioxyphenyl)pentan-1-one (ephylone) and N-butyl-2-amino-1-(4-chlorophenyl)propan-1-one (4-chlorobutylcathinone)