Carbohydrates Flashcards
What is the general formula for carbohydrates
C(H2O)n
Define a tautomer
Molecules that differ in their connectivity with H bonds and double bonds
Define a constitutional isomer
Same molecular formula but different connectivity
What are stereoisomers?
Atoms that are different in spatially but not in their connectivity
Molecules that differ at their chiral centres
What are enantiomers?
Non superimposable images of each other
Differ in configuration at 1 carbon
How do you assign D or L to a molecules
- Identify the chiral centres
- find furthest away from carbonyl group
- if functional group on left, L on right, D
How do you figure out how many stereoisomers a molecule has?
- find the amount of chiral centres (n)
- 2^ n
How are hemiacetal/ hemiketal groups formed ?
- alcohol and aldehyde react to form hemiacetal
- alcohol attacks aldehyde, double bond on O then forms a OH group on acetal
What’s the different between a hemiacetal group and an acetal group
Acetal has has 2 OR’ group and R’ and an H
Hemiacetal has an OH, OR’, R’ and H group
Which hemiacetal/hemiketal structures can form rings
- Aldotetraoses or higher
- ketotetraose can not
In the formation of hemiacetal, an anomeric carbon is formed, why
The carbonyl group goes from achiral the chiral
Draw the formation of glucose to glucopyranose
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What’s the different between a hemiketal group and an ketal group
Ketal - 2 OR’
Hemiketal -OR’ , 2 R groups, and OH group
Difference between furan and pyran
Pyran has 5 carbons and 1 oxygen
Furan has 4 carbons and 1 oxygen
What are the rules for drawing Fischer projections
- C1 is always on the right
- Last carbon will ALWAYS be part of a CH2OH group (Not CHIRAL)
- Numbering of the carbons is clockwise
- Groups on the right are written below the plane of the ring
- β anomer has the –CH2OH group at C5 and the –OH at C1/C2 on the same side of the ring
- a anomer has the –CH2OH at C5 and the –OH at C1/C2 on opposite sides of the ring
