Lecture 8 - Principles of Stereochemistry

Question 1

stereoisomerism:

Answer 1

compounds that have the same connectivity, but a different arrangement of atoms in space (e.g. E-Z/cis-trans alkene isomers)

Question 2

two types of stereoisomerism:

Answer 2

enantiomers and diastereoisomers

Question 3

how can you tell if something is achiral?

Answer 3

construct the mirror image of an object if the mirror image is congruent (i.e., superimposable) with the original object it is achiral (i.e. not chiral)

Question 4

ONLY definition of chiral:

Answer 4

an object is chiral if it has a non-super impossible mirror image

Question 5

only test to see if something is chiral:

Answer 5

checking if it has a imposable/non-imposable mirror image

Question 6

achiral:

Answer 6

a molecule that has a superimposable mirror image

Question 7

what sort of propert is chirality:

Answer 7

chirality is a symmetry property

Question 8

how do we note chiral carbons [asymmetric centre]?

Answer 8

through an asterics [*] notation

Question 9

asymmetric centre:

Answer 9

any *carbon with 4 DIFFERENT groups [but doesn’t have to be JUST carbon, can also be phosphorous]

Question 10

many chiral molecules contain:

Answer 10

one or more asymmetric carbons

Question 11

an asymmetric carbon is a type of…

Answer 11

… stereocentre

Question 12

stereocentres [also known as a stereogenic atom]:

Answer 12

• an atom at which the interchange of two groups gives a stereoisomer

Question 13

what relationship do ENANTIOMERS concern:

Answer 13

the relationship between only 2 molecules

Question 14

molecules that have a non-superimposable (non-congruent) mirror image are:

Answer 14

chiral

Question 15

molecules that are non-congruent mirror images of one another are defined as:

Answer 15

enantiomers

Question 16

example of a macroscopic set of enantiomers:

Answer 16

our very own hands

Question 17

the configuration of an asymmetric carbon can be specified using the:

Answer 17

Cahn-Ingold-Prelog Rules

Question 18

Cahn-Ingold-Prelog Rules:

Answer 18

they are arranged into priorities using atomic number and viewed from opposite the low priority group

Question 19

how do we view our asymmetric centres?

Answer 19

we must view our asymmetric centre from opposite the low priority group

Question 20

where is the group of lowest priority always found?

Answer 20

the group of lowest priority is always away from the observer

Question 21

S configuration:

Answer 21

(lowest priority is behind) and remaining priorities descend in counterclockwise order

Question 22

R configuration:

Answer 22

(lowest priority is behind) and remaining priorities descend in clockwise order

Question 23

a molecule with a plane of symmetry is never…

Answer 23

… chiral

Question 24

what sort of bond should the low priority bond always lie on?

Answer 24

the lowest priority gourd should always be on a dotted fading bond

Question 25

properties of enantiomers:

Answer 25

enantiomers share identical physical properties EXCEPT for their interaction with plane polarised light

Question 26

a stereoisomer is named by:

Answer 26

indicating the configuration of each asymmetric carbon before the systematic name

Question 27

enantiomers and plane-polarised light:

Answer 27

Enantiomers rotate plane-polarized light in equal, but opposite directions

The sign of optical rotation is unrelated to R and S configuration of a compound