(R)and (S)Configuration: Breaking Ties In case of ties,use the next atoms along the chain of each group as tiebreakers. Examples H H CH3 CH2Br C-Br C>-C- CH3> C-CH3 >-CH2CH2CH2CH3 H CH3 2013 Pearson Education,Inc. Chapter 5 16
© 2013 Pearson Education, Inc. (R) and (S) Configuration: Breaking Ties In case of ties, use the next atoms along the chain of each group as tiebreakers. Chapter 5 16
(R)and (S)Configuration: Multiple Bonds Treat double and Re-c becomes H triple bonds as if break and duplicate each were a bond to a separate atom. R-C=N becomes RC break and duplicate R一C=C一H becomes RC CH break and duplicate OH OH R-C=0 becomes R break and duplicate 2013 Pearson Education,Inc. Chapter5 17
© 2013 Pearson Education, Inc. (R) and (S) Configuration: Multiple Bonds Treat double and triple bonds as if each were a bond to a separate atom. Chapter 5 17
(R)and(S)Configuration: Step 2 Working in 3-D,rotate the molecule so that the lowest priority group is in (R)enantiomer back. Draw an arrow from highest to lowest priority group. (S)enantiomer Clockwise =(R), Counterclockwise =(S) 2013 Pearson Education,Inc. Chapter 5 18
© 2013 Pearson Education, Inc. (R) and (S) Configuration: Step 2 • Working in 3-D, rotate the molecule so that the lowest priority group is in back. • Draw an arrow from highest to lowest priority group. • Clockwise = (R), Counterclockwise = (S) Chapter 5 18
Assign Priorities OH ② Counterclockwise (S) CH; NH2 ① alanine Draw an arrow from Group 1 to Group 2 to Group 3 and back to Group 1.Ignore Group 4. Clockwise =(R)and Counterclockwise =(S) 2013 Pearson Education,Inc. Chapter5 19
© 2013 Pearson Education, Inc. Assign Priorities Draw an arrow from Group 1 to Group 2 to Group 3 and back to Group 1. Ignore Group 4. Clockwise = (R) and Counterclockwise = (S) Counterclockwise (S) Chapter 5 19
Example OH CH2CH3 rotate 2 CHCH-CH CH3CH2CH OH Clockwise (R) When rotating to put the lowest priority group in the back, keep one group in place and rotate the other three. 2013 Pearson Education,Inc. Chapter 5 20
© 2013 Pearson Education, Inc. Example C OH CH3CH2CH2 H CH2CH3 1 2 3 4 C CH2CH3 CH3CH2CH2 OH H 1 2 3 4 rotate When rotating to put the lowest priority group in the back, keep one group in place and rotate the other three. Clockwise (R) Chapter 5 20