Methylphenidate (trade name: Ritalin) is prescribed for attention deficit hyperactivity di...

Methylphenidate (trade name: Ritalin) is prescribed for attention deficit hyperactivity disorder (ADHD). Ritalin is a mixture of R,R and S,S isomers, even though only the R,R isomer is active in treating ADHD. (The single R,R enantiomer, called dexmethylphenidate, is now sold under the trade name Focalin.) Draw the structure of the R,R and S,S isomers of methylphenidate.