Riboflavin (Vitamin B2) consists of the sugar alcohol D-ribitol attached to 7,8 - dimethyl isoalloxazine. The coenzymes are flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD). Good luck! Solution Riboflavin (Vitamin B2) consists of the sugar alcohol D-ribitol attached to 7,8 - dimethyl isoalloxazine. The coenzymes are flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD). Good luck!.