Assign(R)or(S) R)enantiomer (S)enantiomer 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 11
Chapter 5 11 Assign (R) or (S) • 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)
Assign Priorities ③CH3 《H④ ② NH, Atomic number:F N C H Once priorities have been assigned,the lowest priority group (#4)should be moved to the back if necessary. Chapter 5 12
Chapter 5 12 Assign Priorities Atomic number: F > N > C > H Once priorities have been assigned, the lowest priority group (#4) should be moved to the back if necessary
Assign Priorities CH; Counterclockwise (S) K? 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) Chapter 5 13
Chapter 5 13 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)
Example 3 OH CH2CH3 rotate 2 CH:CH2CH2 CH2CH3 CH:CH2CH OH Clockwise (R) When rotating to put the lowest priority group in the back, keep one group in place and rotate the other three. Chapter 5 14
Chapter 5 14 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)
Treatment of Multiple Bonds HH R becomes R- break and duplicate H H R-C=N becomes break and duplicate R一C=C一H becomes R C一H break and duplicate OH OH R一C=O becomes R- break and duplicate O Copyright2010 Pearson Prentice Hall,Inc. Chapter 5 15
Treatment of Multiple Bonds Chapter 5 15