isomers

I get all the isomers. There are four cyclic isomers and seven non-cyclic isomers. According to Khan Academy, the answer for the total number of isomers with the formula c3h6o that are either cyclic or chiral is six. Four of them are the cyclic isomers: (R)-methyloxirane, (S)-methyloxirane...

Stuck on the answer for this one, and my Google Fu has failed me. A student measures the optical rotation of L-carnitine as -30 degrees and wonders if the optical rotation might actually be -390 degrees. Is it possible for the student to distinguish between the two possibilities by either...