Rectus Sinister System of notation of optical isomers.
Key points: •Rectus Sinister system •Rectus – right handed, clockwise •Sinister – left handed, counter-clockwise •Identify each chiral centre (sp3 C atom 4 different atoms or groups attached) •Assign the priority as high as 1, as low as 4 based on the atomic number. •Low priority group is away from you. •Determine the relative direction of the priority order 1 to 2 to 3. •If this is clockwise it is R •If the is counter clockwise it is S. •If there is more than one stereocentre, the location needs to be included with the locant, e.g. 2R •
CIP priority rule ( Cahn-Ingold-Prelog)
•If the first atom of two groups is the same, consider the second atom(s) in the same way as the first. • • • • •If this does not assign priority, consider the next atoms until there is a difference.
Reference book for Organic Chemistry
Organic Chemistry by Morrison and Boyd, 7th Edition
