Ch.25

Question 1

enantiomer

Answer 1

non-superimposable mirror image
- sp3
- tetrahedral
- 4 unique groups

Question 2

chirality

Answer 2

a carbon is chiral when four unique groups are bounded to it

Question 3

meso

Answer 3

has chiral centers but has a plane of symmetry making it achiral

Question 4

draw an enantiomer of CH3CH(OH)CH2CH3 and determine its configuration

Answer 4

lec 25 slide 7

Question 5

how do you determine chirality configuration

Answer 5

lec 25 slide 7

order the groups from highest priority (greatest EN or largest) and make sure H is pointing back

clockwise –> R config
counter clockwise –> S config

Question 6

if you are asked to draw the enantiomer, what should you do

Answer 6

lec 25 slide 7

flip the original compound and switch stereochemistry

Question 7

diastereomers

Answer 7

aren’t mirror images but are stereoisomers

Question 8

with multiple chirality centers, a compound can be…

Answer 8

• meso
• enantiomer
• diasteriomer

Question 9

draw enantiomeric relationship vs. diastereomeric relationship

Answer 9

lec 25 slide 8

Question 10

do lec 25 slide 9

Question 11

what are the reactants for a hemi acetal mechanism

Answer 11

ketone or aldehyde reacts with an alcohol and an acid

Question 12

what is produced in a hemi-acetal mechanism

Answer 12

lec 25 slide 10

R2-C-OH
|
OR

Question 13

what type of chemistry do sugars engage in

Answer 13

hemi-acetal and acetal chemistry

Question 14

draw the mechanism for hemi acetal formation

Answer 14

lec 25 slide 11

Question 15

how do acetals and hemi acetals differ

Answer 15

acetals occur when you do the hemi-acetal formation twice

Question 16

what are the reactants for an acetal reaction

Answer 16

ketone or aldehyde react with alcohol (2 equivalents) and acid

Question 17

what is produced in an acetal reaction

Answer 17

lec 25 slide 12

(RO)2-C-R2 + H2O

Question 18

why is water released in the acetal reaction and why is this important

Answer 18

it is a condenstion reaction. this process is a major linkage in glycosidic bonds

Question 19

draw the mechanism for acetal formation

Answer 19

lec 25 slide 13

Question 20

do the examples on lec 25 slide 14

Question 21

do example on lec 25 slide 15

Question 22

what are the steps for drawing a fisher projection

Answer 22

lec 25 slide 16

the vertical end “points down” while the horizontal end “points up”
1. take edge points and point them down
2. take the groups and flip them up
3. if the groups are pointed away they go on the left

Question 23

what is a fisher projection

Answer 23

• displays a chiral molecule as a flat chain

Question 24

when are fisher projections used

Answer 24

carbohydrate chemistry

Question 25

Monosaccharide vs disaccharide

Answer 25

Monosaccharides are comprised of a single simple sugar unit, glucose, fructose, or galactose, and they cannot be broken down into simple sugar units. These three monosaccharides are combined in various ways to make more complex carbohydrates. Disaccharides are comprised of two monosaccharides bonded together.

Question 26

D vs L configuration and what is there relationship / how are they different

Answer 26

lec 25 slide 18 D: -OH to the right L: -OH on the left D and L are enantiomers D-glucose gives us energy; L-glucose doesnot

Question 27

what is an epimer

Answer 27

lec 25 slide 18 flipping one chirality center in a molecule with many chirality centers

Question 28

how do you name an epimer

Answer 28

C-the number of the carbon flipped ex. C-3 epimer

Question 29

do practice question on lec 25 slide 20

Question 30

do practice question on lec 25 slide 21

Question 31

what compounds do aldopentoses have

Answer 31

lec 25 slide 22 aldehyde and 5 carbons

Question 32

practice question on lec 25 slide 23

Question 33

practice question on lec 25 slide 24

Answer 33

an epimer is a diastereomer

Question 34

describe base catalyzed epimerization

Answer 34

lec 25 slide 27 its an enolate based reaction at the alpha carbon

Question 35

draw a base catalyzed epimerization mechanism explaining how it is at equilibrium

Answer 35

lec 25 slide 27-28

Question 36

oxidation vs reduction of monosacharides (alcohol to aldehyde to carboxylic acid)

Answer 36

lec 25 slide 29

Question 37

how does NaBH4 effect a monosaccharide

Answer 37

lec 25 slide 30 they are reduced

Question 38

how can monosaccharides be oxidized

Answer 38

lec 25 slide 31 [O] HNO3, H20 and heat (CH2OH to COOH)

Question 39

what is a wohl degradation reaction

Answer 39

lec 25 slide 32 the shortening of a sugar chain

Question 40

draw the mechanism (predict the products) for a wohl degradation

Answer 40

lec 25 slide 32

Question 41

what is a kiliani-fischer synthesis

Answer 41

lec 25 slide 33 the lengthening of a sugar chain - stereochemistry is important because the CN can come in from either the front or the back (which gives a 50:50 mixture)

Question 42

draw the mechanism (predict the products) for a kiliani-fischer synthesis

Answer 42

lec 25 slide 33

Question 43

do the practice question on lec 25 slide 33

Question 44

do the practice question on lec 25 slide 304

Question 45

what are the two forms a monosacharide can exist in

Answer 45

an open and an acyclic form

Question 46

where are the electrophilic and nucleophilic centers on a monosacharide

Answer 46

lec 25 slide 36 E+ --> the ketone / aldehyde Nu --> the lower OH

Question 47

draw the haworth formula

Answer 47

lec 25 slide 36

Question 48

when CH2OH of a haworth formula is UP, what configuration is it

Answer 48

lec 25 slide 36 its D

Question 49

what does the anomeric carbon indicate

Answer 49

lec 25 slide 36 if the compound is alpha or beta (waht anomer it is)

Question 50

when the anomeric carbon of a haworth formula is UP, what anomer is it

Answer 50

lec 25 slide 36 beta

Question 51

draw the mechanism for the cyclization of monosacharides

Answer 51

lec 25 slide 38 or ALWS

Question 52

what is mutarotation

Answer 52

see lec 25 slide 38 - how sugars transform from one anomer to the other (tautomerize)

Question 53

which conformation do sugars naturally exist in

Answer 53

lec 25 slide 39 the D conformation

Question 54

describe the formation of glycosides

Answer 54

lec 25 slide 40 essentially an acetal based reaction

Question 55

what are the reactants for the formation of glycosides

Answer 55

lec 25 slide 40 CH3OH and HA

Question 56

draw the mechanism for the formation of glycosides

Answer 56

lec 25 slide 40

Question 57

describe a glycosidic bond

Answer 57

lec 25 slide 42 monosacharides combine to form polysaccharides ex. sucrose

Question 58

what is sucrase

Answer 58

lec 25 slide 43 an enzyme that hydrolyses sucrose (breaks it back into monosacharides

Question 58

monosacharides vs. polysaccharides

Answer 58

lec 25 slide 43 monosacharides are the only energetically useful form of a sugar polysacharides are used for energy storage --> they are usually hydrolyzed into monosachardes using sucrase

Question 59

why are people lactose intolerant

Answer 59

lec 25 slide 44 they are lacking the production of the enzyme lactase which breaks down the lactose from a polysacharde to a monosacharide

Question 60

what is the anomeric effect

Answer 60

heteroatomic substituents (such as an OH group) adjacent to a heteroatom within a cyclohexane ring to prefer the axial orientation instead of the less hindered equatorial orientation that would be expected from steric considerations alone.