Ch.25 Flashcards
enantiomer
non-superimposable mirror image
- sp3
- tetrahedral
- 4 unique groups
chirality
a carbon is chiral when four unique groups are bounded to it
meso
has chiral centers but has a plane of symmetry making it achiral
draw an enantiomer of CH3CH(OH)CH2CH3 and determine its configuration
lec 25 slide 7
how do you determine chirality configuration
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
if you are asked to draw the enantiomer, what should you do
lec 25 slide 7
flip the original compound and switch stereochemistry
diastereomers
aren’t mirror images but are stereoisomers
with multiple chirality centers, a compound can be…
- meso
- enantiomer
- diasteriomer
draw enantiomeric relationship vs. diastereomeric relationship
lec 25 slide 8
do lec 25 slide 9
what are the reactants for a hemi acetal mechanism
ketone or aldehyde reacts with an alcohol and an acid
what is produced in a hemi-acetal mechanism
lec 25 slide 10
R2-C-OH
|
OR
what type of chemistry do sugars engage in
hemi-acetal and acetal chemistry
draw the mechanism for hemi acetal formation
lec 25 slide 11
how do acetals and hemi acetals differ
acetals occur when you do the hemi-acetal formation twice
what are the reactants for an acetal reaction
ketone or aldehyde react with alcohol (2 equivalents) and acid
what is produced in an acetal reaction
lec 25 slide 12
(RO)2-C-R2 + H2O
why is water released in the acetal reaction and why is this important
it is a condenstion reaction. this process is a major linkage in glycosidic bonds
draw the mechanism for acetal formation
lec 25 slide 13
do the examples on lec 25 slide 14
do example on lec 25 slide 15
what are the steps for drawing a fisher projection
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
what is a fisher projection
- displays a chiral molecule as a flat chain
when are fisher projections used
carbohydrate chemistry
Monosaccharide vs disaccharide
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.
D vs L configuration and what is there relationship / how are they different
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
what is an epimer
lec 25 slide 18
flipping one chirality center in a molecule with many chirality centers
how do you name an epimer
C-the number of the carbon flipped
ex.
C-3 epimer
do practice question on lec 25 slide 20
do practice question on lec 25 slide 21
what compounds do aldopentoses have
lec 25 slide 22
aldehyde and 5 carbons
practice question on lec 25 slide 23
practice question on lec 25 slide 24
an epimer is a diastereomer
describe base catalyzed epimerization
lec 25 slide 27
its an enolate based reaction at the alpha carbon
draw a base catalyzed epimerization mechanism explaining how it is at equilibrium
lec 25 slide 27-28
oxidation vs reduction of monosacharides (alcohol to aldehyde to carboxylic acid)
lec 25 slide 29
how does NaBH4 effect a monosaccharide
lec 25 slide 30
they are reduced
how can monosaccharides be oxidized
lec 25 slide 31
[O]
HNO3, H20 and heat (CH2OH to COOH)
what is a wohl degradation reaction
lec 25 slide 32
the shortening of a sugar chain
draw the mechanism (predict the products) for a wohl degradation
lec 25 slide 32
what is a kiliani-fischer synthesis
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)
draw the mechanism (predict the products) for a kiliani-fischer synthesis
lec 25 slide 33
do the practice question on lec 25 slide 33
do the practice question on lec 25 slide 304
what are the two forms a monosacharide can exist in
an open and an acyclic form
where are the electrophilic and nucleophilic centers on a monosacharide
lec 25 slide 36
E+ –> the ketone / aldehyde
Nu –> the lower OH
draw the haworth formula
lec 25 slide 36
when CH2OH of a haworth formula is UP, what configuration is it
lec 25 slide 36
its D
what does the anomeric carbon indicate
lec 25 slide 36
if the compound is alpha or beta (waht anomer it is)
when the anomeric carbon of a haworth formula is UP, what anomer is it
lec 25 slide 36
beta
draw the mechanism for the cyclization of monosacharides
lec 25 slide 38 or ALWS
what is mutarotation
see lec 25 slide 38
- how sugars transform from one anomer to the other (tautomerize)
which conformation do sugars naturally exist in
lec 25 slide 39
the D conformation
describe the formation of glycosides
lec 25 slide 40
essentially an acetal based reaction
what are the reactants for the formation of glycosides
lec 25 slide 40
CH3OH and HA
draw the mechanism for the formation of glycosides
lec 25 slide 40
describe a glycosidic bond
lec 25 slide 42
monosacharides combine to form polysaccharides
ex. sucrose
what is sucrase
lec 25 slide 43
an enzyme that hydrolyses sucrose (breaks it back into monosacharides
monosacharides vs. polysaccharides
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
why are people lactose intolerant
lec 25 slide 44
they are lacking the production of the enzyme lactase which breaks down the lactose from a polysacharde to a monosacharide
what is the anomeric effect
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.
