Unit 2

Question 1

isomers

Answer 1

compounds which have the same molecular formula with different structures

Question 2

two types of isomers

Answer 2

• consitutional isomers
• stereoisomers

Question 3

constitutional isomers

Answer 3

chemical compounds with the same molecular formula but with a different arrangement of constituents

Question 4

stereoisomers

Answer 4

two chemical compounds with the same molecular formula and constituents, but with a different 3D arrangement

Question 5

chirality

Answer 5

an object or molecule that is not identical to its mirror image

Question 6

what is meant by the statement “chiral molecules have handedness”

Answer 6

if you superimpose the mirror image of a chiral molecule over the original, they will not match

Question 7

achiral molecule

Answer 7

a molecule that is identical to its mirror image

Question 8

what is the main distinction between achiral and chiral molecules

Answer 8

achiral molecules posses a plane of symmetry

Question 9

what does it mean to say that achiral molecules have a plane of symmetry

Answer 9

these molecules have a line that can be drawn somewhere on the molecule or in the plane of the board which will produce two equal parts

Question 10

T/F chiral and achiral molecules have a plane of symmetry

Answer 10

false

Question 11

what is a chirality center and what usually forms it

Answer 11

an atom such as carbon with four unique substiuents

a carbon with four different atoms bonded to it

Question 12

T/F any compound with one chirality center is chiral

Answer 12

true

Question 13

T/F a molecule with 2 chiraliry centers will always be achiral

Answer 13

false, if the two chirality centers are equal then there can be a plane of symmetry drawn between them

Question 14

two types of stereoisomers

Answer 14

• diastereomers
• enantiomers

Question 15

diastereomers

Answer 15

non-identical compoiunds that have the same molecular formula, all the same atom connectivity, but they are not image and mirror image

Question 16

enantiomers

Answer 16

two non-identical chiral compounds that are image and mirror image of each other

Question 17

steps to determine if a compound is a diastereomer, enantiomer, unrelated, or identical

Answer 17

1. look for different molecules
2. look for planes of symmetry
3. look for chirality centers
4. check for superimposition
5. look at the configuration of the chirality centers

Question 18

how to determine the configuration of a chirality center

Answer 18

1. rank the substituents from highest to lowest atomic number
2. if there is a tie, move to the next branch
3. draw a circle from 1-2-3
4. make sure the 4th ranked branch is going backwards
5. if the 4th ranked group is not backwards, reverse the direction of the configuration

Question 19

how does the number of chirality centers relate to the number of possible stereoisomers

Answer 19

stereoisomers = 2ⁿ, where n is the number of stereoisomers

Question 20

how many possible enantiomers can a compound have

Answer 20

only one

Question 21

what will the relationship be between two molecules that have an identical configuration at every chirality center

Answer 21

they will be identical

Question 22

what will be the relationship between two molecules that are in a different configuration at every chirality center

Answer 22

they will be enantiomers

Question 23

T/F confirmations change, configurations dont

Answer 23

true

Question 24

fischer projection

Answer 24

a simplified way of drawing tetrahedral molecules and their arrangement

Question 25

what do the direction of the lines in a fischer projection mean

Answer 25

horizontal lines are coming into the foreground

vertical lines are receding into the background

Question 26

T/F the horizontal lines of a fischer projection are in line with the page

Answer 26

false, none of the line are in plane with the page

Question 27

when assigning configuration rank, where should the lowest ranked molecule go

Answer 27

at the top or bottom

Question 28

what must be done to a molecule in a staggered arrangement before drawing it in a fischer projection

Answer 28

it must be rearranged into its eclipsed confirmation

Question 29

mesocompounds

Answer 29

achiral compounds that have chirality centers

Question 30

what are the two possible labels on a chirality center

Answer 30

R (clockwise)

S (counterclockwise)

Question 31

when there is a chirality center on a ring, how is the ring divided into branches

Answer 31

it is divided in half, if they halves are identical then the branches are identical