Ch 2: Isomers (12%)

structural/constitutional isomers, stereoisomers

name the 2 divisions of ISOMERS

conformational isomers, configurational isomers

name the 2 divisions of STEREOISOMERS

enantiomers, diastereomers

name the 2 divisions of CONFIGURATIONAL ISOMERS

structural/constitutional isomers

the least similar of all isomers; only thing the 2 molecules have in common is their molecular formula

stereoisomers

isomers that not only share the same molecular formula but also share the same atomic connectivity

conformational isomers

the most similar of all isomers; isomers that are the same molecule but differ in rotation about single (sigma) bonds

configurational isomers

isomers that can only change from one form to another by breaking and reforming covalent bonds

optical

configurational isomers can also be considered _________ isomers because the different spatial arrangement of groups in these molecules affects the rotation of plane-polarized light

enantiomers

isomers that have the same connectivity but opposite configurations at every chiral center in the molecule; have identical physical and chemical properties, except for optical activity in which they are opposites

magnitude, direction, right, clockwise, left, counterclockwise

At the molecular level, one enantiomer will rotate plane-polarized light to the same ____________ but in the opposite ___________ of its mirror image. A compound that rotates the plane of polarized light to the _____, or ____________, is dextrorotatory (d-) and is labeled (+). A compound that rotates light toward the _____, or ______________, is levorotatory (l-) and is labeled (-).

optically active

compounds that are able to rotate plane-polarized light are considered to be this

racemic mixtures

solutions when both (+) and (-) enantiomers are present in equal concentrations and their rotations cancel each other out, so no optical activity is observed

diastereomers

isomers that have two or more chiral centers and differ at some, but not all, of those centers; have different chemical and physical properties

2^n

for any molecule with n chiral centers, there are ___ possible stereoisomers

meso compounds

molecules with chiral centers yet an internal plane of symmetry, making the molecule not optically active; the molecular equivalent of racemic mixtures

Z

(E) vs. (Z) Absolute Conformation

alkenes where the two highest-priority substituents on each carbon are on the same side of the double bond

E

(E) vs. (Z) Absolute Conformation → Polysubstituted Double Bonds

alkenes where the two highest-priority substituents on each carbon are on opposite sides of the double bond

S (to the left)

(R) vs. (S) Absolute Conformation → Chiral Centers

Molecules where the order of substituents, when drawn from highest-lowest priority, creates a circle going counterclockwise

R (to the right)

(R) vs. (S) Absolute Conformation → Chiral Centers

Molecules where the order of substituents, when drawn from highest-lowest priority, creates a circle going clockwise