Isomers

Question 1

same formula but different chemical structure

Answer 1

isomers

Question 2

isomers that share only molecular formula

Answer 2

structural isomers (constitutional)

Question 3

isomers that share molecular formula and atom connectivity

Answer 3

stereoisomers

Question 4

stereoisomers that differ in rotation around single (sigma) bonds

Answer 4

conformational isomer

Question 5

stereoisomers that can be interconverted only by breaking bonds

Answer 5

configurational isomer

Question 6

if mirror image cannot be superimposed on original object, has handedness (a left and a right side), no internal plane of symmetry

Answer 6

chiral

Question 7

has mirror image that can be superimposed on original object

Answer 7

achiral

Question 8

an asymmetric core of optical activity; e.g. a C atom with four different ligands

Answer 8

chiral center

Question 9

formula representing possible number of stereoisomers

Answer 9

2^n (n = number of chiral centers)

Question 10

molecules that are non-superimposable mirror images of each other, have same atom connectivity but opposite configurations at EVERY chiral center, identical chemical and physical properties except optical activity and reactions in chiral environments

Answer 10

enantiomers

Question 11

molecules that are chiral and share same atom connectivity, but are not mirror images of each other, differ at SOME (but not all) of multiple chiral centers, have different chemical properties

Answer 11

diastereomers

Question 12

refers to rotation of plane-polarized light by a chiral molecule, enantiomers rotate plane-polarized light at same angle but in opposite directions;
d- or (+) = clockwise rotation, l- or (-) = counterclockwise rotation

Answer 12

optical activity

Question 13

specific rotation ([α])

Answer 13

[α] = α(obs) / (c * l)

where:
α(obs) = observed rotation in degrees
c = concentration in g/mL
l = path length in dm

Question 14

when (+) and (-) enantiomers are present in equal concentrations, rotations cancel out and no optical activity is observed

Answer 14

racemic mixture

Question 15

diastereomers in which substituents differ in their position around an immovable bond, in simple compounds we use cis and trans, in more complicated molecules with polysubstituted double bonds (E) and (Z) are used;
(Z) = zame zide, (E) = opposite sides

Answer 15

cis-trans isomers (geometric)

Question 16

a molecule with chiral centers that has an internal plane of symmetry, not optically active

Answer 16

meso compound

Question 17

spatial arrangement of atoms or groups in a stereoisomer

Answer 17

configuration

Question 18

a chiral molecules’ configuration in relation to another chiral molecule

Answer 18

relative configuration

Question 19

describes exact spatial arrangement of atoms or groups of a chiral molecule, independent of other molecules, R or S

Answer 19

absolute configuration

Question 20

steps to assign R vs S

Answer 20

1) assign priority to ligands by atomic number (4 doesn’t matter)
2) arrange lowest priority substituent in back
3) draw a circle around molecule from highest to lowest priority (skip 4)
4) clockwise = R, counterclockwise = S

Question 21

favored position of bulky groups on boat confirmation

Answer 21

equatorial (E)