Carbohydrates Flashcards
What can sugar units be drawn and labelled as?
Fischer projections
What does a Fischer projection represent?
A chiral centre as the point of intersection between two perpendicular lines
What notation is used for Fischer projections?
D and L
How are Fischer Projections set up?
The aldehyde (CHO) is always on top
The primary alcohol (CH2OH) is always on the bottom
If the tertiary OH group is on the right, it is a D structure
If the tertiary OH group is on the left, it is a L structure
How is D and L notation assigned?
Based on which direction the OH group on the bottom-most chiral centre faces.
What is the 2n rule?
How we find the number of possible configurations based on the number of chiral centres. n = the number of chiral centres, and the number of configurations is equal to 2n
What is the process for determining how a hemiacetal forms?
- Form a Fischer projection with the CHO group at the top. In the final product, this will be horizontal
- Any groups on the left face up, and any on the right face down. Exclude the last chiral OH group, this will lose its H to form an ether
Upon cyclisation, what is formed?
A new chiral centre
What are the two different forms of a cyclic sugar formed when the new chiral centre is produced?
One with the alcohol sitting on either side of the chain (above or below)
What are the two new cyclic forms of a sugar, produced upon cyclisation called?
Anomers
What are the two ways to differentiate anomers?
α - (the OH at C1 is facedown)
β - (the OH at C1 is faceup)
What are simple carbohydrates/monosaccharides?
Molecules that are single sugar units
What are the three categories of complex sugars?
Disaccharides: 2 Sugar units
Oligosaccharides: 3-10 Sugar units
Polysaccharides: 10> Sugar units
When are complex carbohydrates formed?
When multiple sugars are joined by glycosidic linkages
What are glycosidic linkages labelled in accordance to?
The positions attached at the orientation of the position
