Assign(R)or(S) Working in 3D,rotate molecule so that lowest priority group is in back. Draw an arrow from highest to lowest priority group. Clockwise =(R),Counterclockwise=(S) rotate (S)enantiomer Copyright2005 Pearson Prentice Hall,Inc. 11
Chapter 5 11 Assign (R) or (S) • Working in 3D, rotate molecule so that lowest priority group is in back. • Draw an arrow from highest to lowest priority group. • Clockwise = (R), Counterclockwise = (S) =>
Properties of Enantiomers Same boiling point,melting point,density Same refractive index Different direction of rotation in polarimeter 。 Different interaction with other chiral molecules Enzymes Taste buds,scent Chapter 5 12
Chapter 5 12 Properties of Enantiomers • Same boiling point, melting point, density • Same refractive index • Different direction of rotation in polarimeter • Different interaction with other chiral molecules – Enzymes – Taste buds, scent =>
Plane-Polarized Light second polarizing filter, ·Polarizing filter first polarizing filter axis parallel to the first calcite crystals or plastic sheet. ·When two filters observer sees are used,the maximum light plane-polarized light amount of light transmitted second polarizing filter. first polarizing filter axis perpendicular to the first depends on the angle of the axes. observer see no light plane-polarized light Copyright2005 Pearson Prentice Hall,Inc. Chapter 5 13
Chapter 5 13 Plane-Polarized Light • Polarizing filter – calcite crystals or plastic sheet. • When two filters are used, the amount of light transmitted depends on the angle of the axes. =>
Polarimetry Use monochromatic light,usually sodium D Movable polarizing filter to measure angle Clockwise dextrorotatory d or (+ Counterclockwise levorotatory =or (- Not related to(R)and (S) 15°0-5 sodium monochromator polarizing sample cell analyzing detector > lamp filter filter filter Copyright 2005 Pearson Prentice Hall,Inc. 14
Chapter 5 14 Polarimetry • Use monochromatic light, usually sodium D • Movable polarizing filter to measure angle • Clockwise = dextrorotatory = d or (+) • Counterclockwise = levorotatory = l or (-) • Not related to (R) and (S) =>