Quiz 3

Question 1

What are the two positions found on a chair conformation?

Answer 1

axial and equitorial

Question 2

How will you know if an equitorial substituent is up or down?

Answer 2

look at the axial position, if the axial is up the equitorial will be down and vice versa

Question 3

If a substituent is in an axial down position what position will it be in after a ring flip?

Answer 3

equitorial down

Question 4

1,3 diaxial interaction

Answer 4

a kind of steric/ gauche interaction that occurs when substituents that are not hydrogens are in axial positions at the same time

Question 5

True or false?

the larger the substituent the more likely it will be best placed in an axial position?

Answer 5

false, the larger the substiuent the more likely it will want to be placed in an equitorial position

Question 6

stereoisomerism

Answer 6

molecules that differ in spatial arrangment of groups, not connectivity of atoms

ex: cis/trans isomers

Question 7

cis isomer

Answer 7

groups exist on the same side

Question 8

trans isomer

Answer 8

groups exist on opposite sides

Question 9

constiutional isomer

Answer 9

same formula different connectivity

Question 10

True or false?

two atoms that are stereoisomers of each other will have the same effects

Answer 10

false, they could have very different effects

Question 11

what does it mean to be a chiral object?

Answer 11

that you cannot superimpose the mirror image of that object onto the object

ex: hands

Question 12

Achiral

Answer 12

an object has a plane of symmetry, identical to mirror image and cannot rotate plane of polarized light bc of identical mirror image

Question 13

chiral center

Answer 13

atom with four different groups attatched

also a stereo center

Question 14

stereo center

Answer 14

an atom where two of its groups can be swapped and a stereosiomer is formed

Question 15

How can you identify a stero center that is not also a chiral center?

Answer 15

stereo centers that are not chiral centers will usually be attatched to a double bond

Question 16

enantiomer

Answer 16

the mirror image of a molecule

Question 17

A compound can have — enantiomer/s

Answer 17

one

never more and never less

Question 18

What are the steps for designating R or S configurations?

Answer 18

1. find the chiral center
2. determine priority of the four groups by numbering 1-4
3. rotate the molecule so the lowest priority is going into the plane (dashed)
4. Determine after rotation if the groups count counter clockwise (S) or clockwise (R)

Question 19

How do you determine priority of groups for conformations R and S?

Answer 19

By atomic number
high # = higher priority
low # = lower priority

Question 20

How do you determine priority if two groups are the same?

Answer 20

look at what they are connected to, first point of priority difference wins

Question 21

True or false?

A triple bond is only counted once

Answer 21

False, a triple bond will be counted as three single bonds to the atom it is attatched to

Question 22

Where is the R/S conformation placed when naming the molecule?

Answer 22

at the beginning of the name in parentheses, if there is more than one chiral center the locant comes before the R/S

Question 23

What does it mean for a molecule to be optically active?

Answer 23

it can rotate a plane of polarized light

Question 24

True or false?

A chiral molecule is optically active

Answer 24

True, chiral molecules will rotate polarized light

Question 25

You — use R/S to determine the rotation of a molecule

Answer 25

can not

Question 26

What are the steps to labeling a diastereomer

E/Z

Answer 26

1. assign a priority group on each side of the double bond
2. both priority groups on same side = Z
3. priority groups on different sides = E
4. to be neither E or Z there must be same group on same side of the double bond

Question 27

Any compound with a — will be achiral

Answer 27

plane of symmetry

Question 28

what do you do to your total number of predicated stereoisomers if you have a plane of symmetry?

Answer 28

subtract one to account for identical mirror image

Question 29

If you encoutner two stereocenters on either side of the pi bond how many times should they be counted?

Answer 29

once, becauce you cannot have one without the other

Question 30

how do you calcualte total number of predicted stereoisomers?

Answer 30

2^n

n = number of chiral centers

Question 31

Meso compound

Answer 31

achiral compound with two or more chiral centers and a plane of symmetry