Cathinones are differentiated by their ketone substitution around the beta carbon with the amphetamine skeleton, meaning they are ?-keto-amphetamines. 3-MMC has two methyl substitutions on its cathinone skeleton, a person at R3 in the phenyl ring, in addition to a 2nd at the nitrogen group RN.Mephedrone. "Not for human use. For complex use only. Pu