Chapter 5

Question 1

Stereochemistry is the study of _______ structure of molecules

Answer 1

3D

Question 2

_______: any atom at which the interchange of 2 groups gives a stereoisomer

Answer 2

Stereocenter

Question 3

Chiral Centers must have __ different groups

Answer 3

4

Question 4

Corollary: if 2 groups are the same. the molecule is ________

Answer 4

achiral

Question 5

_______: non-superimposable mirror images

Answer 5

enantiomers

Question 6

What are the 3 situations where you know that a normal chiral center is not possible?

Answer 6

1) CH2
2) CH3
3) Double or triple bond

Question 7

Molecules that have chiral centers and an internal plane of symmetry are _______ and called _______

Answer 7

achiral
meso compounds

Question 8

When assigning (R) and (S) configurations (according to Chan-Ingold-Prelog):
1) number atoms attached to the chiral center, the highest atomic number has _______ priority
2) if tied, look at _______ point of difference
3) double and triple bonds are treated as if each is constructed from _______ bonds

(Br,H,H)>(O,O,H)

Answer 8

1) higher
2) first
3) single

Question 9

When assigning (R) and (S) configurations (according to Chan-Ingold-Prelog):
4) orient group ___ away from you and connect 1,2,3
5) if arrow moves clockwise: _______
if arrow moves counterclockwise: ________

Answer 9

4) 4
5) (R)
(S)

Question 10

The lowest priority group (#4) needs to be in the back. IF priority group #4 is in front, determine the absolute configuration and then _______ your answer.

Answer 10

flip

Question 11

Polarimetry is used to distinguish between enantiomers (chiral molecules) based on their ability to rotate the _______ light with same magnitude, but in _______ direction

Answer 11

plane-polarized
opposite

Question 12

Compounds that rotates p/p-light are said to be _______

Answer 12

optically active

Question 13

If p/p-light is rotated clockwise, it is considered to be _______ or (__)

Answer 13

dextrorotatory (d)
(+)

Question 14

If p/p-light is rotated counterclockwise, it is considered to be _______ or (__)

Answer 14

levelrorotary (l)
(-)

Question 15

Racemic mixtures (or racemate): contain _______ mixture of enantiomers with an overall rotation of __

Answer 15

50:50
0°

Question 16

The _______, which is sometimes called enantiomeric excess, can be determined if a mixture is neither optically pure or racemic

Answer 16

optical purity (op)

Question 17

The optical purity is the _______ in one enantiomer from the race mixture

Answer 17

excess
40 %(S)
40% (R)
op: 20 %(S)

Question 18

What are the 2 exceptions to chiral compounds without asymmetric atoms?

Answer 18

1) biphenyls (staggered)
2) allenes (end C with Dif groups)

Question 19

_______: stereoisomers that are not mirror images. (_______ but not _______ chiral centers inverted)

Answer 19

diastereoisomers
some
all

Question 20

Enantiomers: _______ chemical and physical properties in achiral environment

Answer 20

identical

Question 21

Diastereomers: _______ chemical and physical properties

Answer 21

different

Question 22

to find the max number of stereoisomers:

Answer 22

2^(# of chiral centers) - (lines of symmetry)

Question 23

Cis-trans isomerism on double bonds are _______

Answer 23

diastereomers

Question 24

_______ have different physical properties, so we can separate them by ordinary means such as distillation, recrystallization, and chromatography

Answer 24

Diastereomers

Question 25

_______ have similar physical properties, so their separation is a more difficult process. This type of separation is called _______

Answer 25

enantiomers
resolution

Question 26

_______ Resolution: the reaction of a pure enantiomer of one compound with a racemic mixture of another compound produces a mixture of diastereomers. Separation of the diastereomers, followed by hydrolysis, gives the resolved enantiomers

Answer 26

chemical

Question 27

_______ Resolution: the enantiomers of the racemic compound form diastereomeric complexes with the chiral material on the column packing. One of the enantiomers binds more tightly than the other, so it moves slowly through the column

Answer 27

chromatographic

Question 28

A chiral atom doesn’t necessarily have to be a carbon. it can also be _______, _______, _______

Answer 28

N
P
S

Question 29

IF a lone pair is on a N, it is _______ @ room temp because of rapid inversion

Answer 29

achiral