Chapter 5 Chirality

Question 1

stereoisomer

Answer 1

same molecular formula, same connectivity, atoms arranged differently in space

geometric or cis/trans and optical

Question 2

enantiomers

Answer 2

stereoisomers that are non-superimposible mirror images of each other

aka. optical isomer

Question 3

diastereomers

Answer 3

stereoisomers that are not mirror images of each other

Question 4

chiral

Answer 4

molecules that exist in two enantiomeric forms

have no plane of symmetry

Question 5

achiral

Answer 5

molecule identical to its mirror image; has a plane of symmetry

Question 6

stereogenic center

Answer 6

carbon atom bonded to four different groups

Question 7

chirality test

Answer 7

check superimposibility w/ mirror image

check for a plane of symmetry

if no stereogenic centers, usually achiral

Question 8

optical activity

Answer 8

physical properties of enantiomers are identical

enantiomers rotate plane-polarized light differently

Question 9

+ & - denotation

Answer 9

if +, enantiomer rotates right clockwise, dextrorotatory

if -, enantiomer rotates light counter-clockwise, levorotatory

+ & - are experimental values

Question 10

R & S nomenclature

Answer 10

cahn-ingold-prelog

if priority atoms go clockwise, “R” rectus

if priority atoms go counter-clockwise, “S” sinister

Question 11

cis-trans isomers

Answer 11

cis & trans are not mirror images of eachother, and therefore are diastereomers

Question 12

physical properties of diastereomers

Answer 12

different physical properties, easily separated

Question 13

meso compounds

Answer 13

have stereogenic centers, but are not chiral due to a plane of symmetry

Question 14

2+ stereocenters

Answer 14

max # = 2^n rule, n=number of stereocenters

n=2 then 2^2 = 4 possible stereoisomers

Question 15

t.s. of enantiomers

Answer 15

enantiomers have an identical E pathway as intermediates in t.s, form @ identical rates

Hammond postulate-t.s has radical char

racemic mixture is not optically active