Carbohydrates have the general formula of Cn H2n On, where the “n” is a number and subscripted. They hydrolyze to a polyhydroxy aldehyde or a polyhydroxy ketone. At the top of the Haworth projection
- Carbohydrates have the general formula of Cn H2n On, where the “n” is a number and subscripted.
- They hydrolyze to a polyhydroxy aldehyde or a polyhydroxy ketone.
- At the top of the Haworth projection, there’s either an aldehyde group for an aldose or a ketone group for an aldose.
- Monosaccharides have 3-6 carbons in the parent chain with a carbonyl group.
- If the carbonyl is at the C1 position, it’s an aldose. If the carbonyl is at the C2 position, it’s a ketose.
- In a Fischer projection, the vertical lines/backbone “recede and go away and into the page like a dashed-wedge” while the horizontal lines “come out like a wedge”.
- If there are n carbons, then look closely at the n-1 carbon position. If the H–OH with the OH on the right side, then the compound is labeled “D”. If the HO–H at the n-1 carbonposition, then the compound is designated “L”.
- A chiral carbon is one where the carbon is attached to four unique bonding groups. A carbon participating in a double or triple bond cannot be a chiral carbon.
- The human body uses “D” sugars.
- To draw the enantiomer, swap the position of “H” and “OH” down the backbone (i.e. just make them reverse of what they currently are).
Fischer to Haworth Projections (straight chain to cyclic form)
For a 6-member ring.
- Turn the Fischer diagram 90 degrees clockwise (lay it on it’s side).
- Substituents below the carbon backbone get the downward position. Substituents above the carbon backbone get the up position.
- Twist carbon-5 so that the OH group is near the carbon-1 putting carbon-6 (CH2OH) sticking up above the ring.
- The -OH group on carbon-5 reacts with the aldehyde group on carbon-1 thereby closing the ring. An oxygen takes the position between carbon-5 and carbon-1.
- The OH-H group on carbon-1 can have the OH in the “up” position (beta form, b like a bird). The OH-H group on carbon-1 can also have the OH in the “down” position (alpha form, Greek A looking like a fish in the sea).
- Carbon-1 is called the anomeric carbon where linkages are possible.
For a 5-member ring.
- A ketone at the second carbon position reacts with the OH at the n-1 carbon position to form a 5-member ring instead of a 6-member ring.
More to be continued. Work in progress.
