Chapter 20.7: Stereoisomerism II: Configurational Isomerism

Question 1

define stereoisomers

Answer 1

molecules in which the atoms are bonded in the same order, but have different spatial arrangement

Question 2

define configurational isomersim

Answer 2

a type of stereoisomerism in which atoms or functional groups are connected in the same sequence, but there is a difference in spatial locations of atoms or groups

Question 3

the only way to interconvert configurational isomers is to…?

Answer 3

break the covalent bonds

Question 4

What are the two categories configurational isomers can be divided into?

Answer 4

Enantiomers

Diastereomers

Question 5

define enantiomers

Answer 5

two molecules that are nonsuperimposable mirrior images of one another

Question 6

define diastereomers

Answer 6

configurational isomers that are not mirror images

Question 7

cis means…?

Answer 7

same side

Question 8

trans means…?

Answer 8

opposite sides

Question 9

define cis-trans isomersim

Answer 9

cis-isomers have the same functional group on the same side of a bond and trans-isomers have the same functional groups on opposite sided of the bond

Question 10

what type of isomers are cis and trans isomers?

Answer 10

diastereomers (under the broader category of configurational isomers)

Question 11

define E, Z system

Answer 11

the protocol for assigning stereochemical configuration of an alkene with three or more different groups

Question 12

what are the priority of substituents determined by?

Answer 12

by Cahn-Ingold-Prelog rules

Question 13

what are the three Cahn-Ingold-Prelog rules?

Answer 13

1. priority is first determined on the basis of the atomic mass of the atoms that are directly bonded to the carbons in the double bond
2. if the atoms are directly attached to a double-bonded carbon atom are the same, then the second atoms of the substituents are compared. again the priority assigned on the basis of atomic mass. if there is no difference in priority among the second atoms, then third atoms are considered, and so on.
3. if a substituent contains a double or triple bond, then multiply bonded atom is treated as if it were two or three atoms bonded atom is treated as if it were two or three atoms bonded to the same carbon atom.

Question 14

define chirality

Answer 14

the type of isomersim in which molecules are nonsuperimposible

Question 15

define chirality center

Answer 15

a carbon atom with 4 different substituents in a tetrahedral arrangement

Question 16

define optical activity

Answer 16

the ability of chiral compounds to rotate the plane of plane-polarized light

Question 17

define dextrorotary isomer (the d isomer)

Answer 17

the enantiomer that rotates plane-polarized light CLOCKWISE

Question 18

define levorotatory (the l isomer)

Answer 18

capable of rotating the polarization of light COUNTER CLOCKWISE

Question 19

define racemic mixture

Answer 19

an equimolar mixture of two enantiomers that does not rotate the plain of polarization at all

Question 20

what is the only physical property that is not identical between enantiomers?

Answer 20

the way they interact with plain polarized light

Question 21

define absolute configuration

Answer 21

the exact three-dimensional spatial arrangement of atoms at a chirality center

Question 22

define R, S system

Answer 22

the protocol for assigning stereochemical configuration of a chirality center

Question 23

what is the configuration if 1-3 is clockwise according to the R, S system?

Answer 23

R

Question 24

what is the configuration if 1-3 is counterclockwise according to the R, S system?

Answer 24

S