Chemistry - STEREO ISOMERISM Question with Solution | TestHub
Just for fun, you might like to try and work out just how many diastereoisomers inositol has and how many of them are meso compounds.
Answer:
Solution:
Ans. Inositol has 9 stereoisomers in all : 8 diastereomeric forms, of which 7 are achiral (meso) and one is chiral, existing as a pair of enantiomers.
Sol. Start with all the OH groups on one side and gradually move them over. Moving one OH down gives a single five-up isomer; two down gives three isomers (1,2- 1,3- and 1,4-down, i.e. four-up); three down gives three isomers (1,2,3- 1,2,4- and 1,3,5-up).
all OHs up :
five OHs up :
four OHs up :
three OHs up :
That gives 1 + 1 + 3 + 3 = 8 diastereomeric forms. Every form except the last has at least one plane of symmetry (the all-up and 1,3,5-up forms have several), so 7 are meso. The last form (1,2,3-up) has no plane of symmetry and is chiral - it exists as a pair of enantiomers. Total : 9 stereoisomers, only one of them chiral.
