2.3 Relative and Absolute Configurations

Question 1

absolute configuration: R and S forms (STEPS)

Answer 1

step 1: assign priority (by atomic number) to 4 substituents surrounding the chiral center

step 2: if the lowest priority group is on a dash, go directly to step 3; if the lowest priority group is on a wedge, the answer is the OPPOSITE of step 3

step 3: draw a circle connecting substituents 1→3 (clockwise = R, counterclockwise = S)

Question 2

Fischer projections

Answer 2

a method to represent 3D molecules

horizontal lines represent wedges (out of the page)

vertical lines represent dashes (into the page)

Question 3

configuration

Answer 3

refers to the spatial arrangement of the atoms or groups in a molecule

Question 4

relative configuration

of a chiral molecule

Answer 4

a chiral molecules configuration in relation to another chiral molecule

used to determine whether molecules are enantiomers, diastereomers, or the same molecule

Question 5

absolute configuration

of a chiral molecul

Answer 5

describes the exact sptial arrangement of the atoms or groups in a chiral molecule, independent of other molecules

Question 6

(E) and (Z) nomenclature is used for ….

Answer 6

compounds with polysubstituted double bonds (multiple substituents that are not just hydrogen)

Question 7

when is cis-trans used, and when is E/Z used

Answer 7

cis-trans: when there are only 2 substituents other than H
E/Z: when therea re 3 or more substituents other than H

check…

Question 8

how to determine (E) vs (Z) form

Answer 8

1. find the groups with the highest priority on each side of the double bond
2. (Z) if both are on the same side; (E) if both are on oppsite sides