R and S Configuration and Optical Activity

Two mirror-image molecules share one name. How do we tell them apart? The R and S system, and how polarised light reveals the difference.

Rank the groups, orient and trace to assign R or S, how enantiomers behave, the polarimeter and racemic mixtures, and why R and S are not the same as plus and minus.

Study: General Organic Chemistry →   Watch on YouTube

In this video

• 0:00The naming problem
• 0:30Step 1: rank the groups
• 1:06Steps 2 and 3: orient and trace
• 1:26Exam trap: group 4 towards you
• 1:36How enantiomers behave
• 2:09The polarimeter
• 2:38Exam trap: R and S vs plus and minus
• 2:54Recap