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CH 336 > Ch.25 > Flashcards

Ch.25 Flashcards

1
Q

enantiomer

A

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

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2
Q

chirality

A

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

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3
Q

meso

A

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

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4
Q

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

A

lec 25 slide 7

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5
Q

how do you determine chirality configuration

A

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

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6
Q

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

A

lec 25 slide 7

flip the original compound and switch stereochemistry

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7
Q

diastereomers

A

aren’t mirror images but are stereoisomers

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8
Q

with multiple chirality centers, a compound can be…

A
  • meso
  • enantiomer
  • diasteriomer
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9
Q

draw enantiomeric relationship vs. diastereomeric relationship

A

lec 25 slide 8

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10
Q

do lec 25 slide 9

A
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11
Q

what are the reactants for a hemi acetal mechanism

A

ketone or aldehyde reacts with an alcohol and an acid

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12
Q

what is produced in a hemi-acetal mechanism

A

lec 25 slide 10

R2-C-OH
|
OR

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13
Q

what type of chemistry do sugars engage in

A

hemi-acetal and acetal chemistry

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14
Q

draw the mechanism for hemi acetal formation

A

lec 25 slide 11

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15
Q

how do acetals and hemi acetals differ

A

acetals occur when you do the hemi-acetal formation twice

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16
Q

what are the reactants for an acetal reaction

A

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

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17
Q

what is produced in an acetal reaction

A

lec 25 slide 12

(RO)2-C-R2 + H2O

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18
Q

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

A

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

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19
Q

draw the mechanism for acetal formation

A

lec 25 slide 13

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20
Q

do the examples on lec 25 slide 14

A
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21
Q

do example on lec 25 slide 15

A
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22
Q

what are the steps for drawing a fisher projection

A

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

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23
Q

what is a fisher projection

A
  • displays a chiral molecule as a flat chain
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24
Q

when are fisher projections used

A

carbohydrate chemistry

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25
Q

Monosaccharide vs disaccharide

A

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.

26
Q

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

A

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

27
Q

what is an epimer

A

lec 25 slide 18

flipping one chirality center in a molecule with many chirality centers

28
Q

how do you name an epimer

A

C-the number of the carbon flipped

ex.
C-3 epimer

29
Q

do practice question on lec 25 slide 20

A
30
Q

do practice question on lec 25 slide 21

A
31
Q

what compounds do aldopentoses have

A

lec 25 slide 22

aldehyde and 5 carbons

32
Q

practice question on lec 25 slide 23

A
33
Q

practice question on lec 25 slide 24

A

an epimer is a diastereomer

34
Q

describe base catalyzed epimerization

A

lec 25 slide 27

its an enolate based reaction at the alpha carbon

35
Q

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

A

lec 25 slide 27-28

36
Q

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

A

lec 25 slide 29

37
Q

how does NaBH4 effect a monosaccharide

A

lec 25 slide 30

they are reduced

38
Q

how can monosaccharides be oxidized

A

lec 25 slide 31

[O]

HNO3, H20 and heat (CH2OH to COOH)

39
Q

what is a wohl degradation reaction

A

lec 25 slide 32

the shortening of a sugar chain

40
Q

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

A

lec 25 slide 32

41
Q

what is a kiliani-fischer synthesis

A

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)

42
Q

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

A

lec 25 slide 33

43
Q

do the practice question on lec 25 slide 33

A
44
Q

do the practice question on lec 25 slide 304

A
45
Q

what are the two forms a monosacharide can exist in

A

an open and an acyclic form

46
Q

where are the electrophilic and nucleophilic centers on a monosacharide

A

lec 25 slide 36

E+ –> the ketone / aldehyde
Nu –> the lower OH

47
Q

draw the haworth formula

A

lec 25 slide 36

48
Q

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

A

lec 25 slide 36

its D

49
Q

what does the anomeric carbon indicate

A

lec 25 slide 36

if the compound is alpha or beta (waht anomer it is)

50
Q

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

A

lec 25 slide 36

beta

51
Q

draw the mechanism for the cyclization of monosacharides

A

lec 25 slide 38 or ALWS

52
Q

what is mutarotation

A

see lec 25 slide 38

  • how sugars transform from one anomer to the other (tautomerize)
53
Q

which conformation do sugars naturally exist in

A

lec 25 slide 39

the D conformation

54
Q

describe the formation of glycosides

A

lec 25 slide 40

essentially an acetal based reaction

55
Q

what are the reactants for the formation of glycosides

A

lec 25 slide 40

CH3OH and HA

56
Q

draw the mechanism for the formation of glycosides

A

lec 25 slide 40

57
Q

describe a glycosidic bond

A

lec 25 slide 42

monosacharides combine to form polysaccharides
ex. sucrose

58
Q

what is sucrase

A

lec 25 slide 43

an enzyme that hydrolyses sucrose (breaks it back into monosacharides

58
Q

monosacharides vs. polysaccharides

A

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

59
Q

why are people lactose intolerant

A

lec 25 slide 44

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

60
Q

what is the anomeric effect

A

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.

CH 336 (6 decks)

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