sugars Flashcards
how do you know if a sugar molecule is D or L configuration?
D configuation is when the highest number chiral carbon on the fischer projection has the OH on the RIGHT side and is L if highest chiral carbon has OH on left hand side
what is another name for glucose that shows its configuation?
D-aldohexose - has an aldehyde functional group and highest chiral carbon has OH on right hand side hex meaning 6 carbon chain molecule with OSE meaning a sugar
what is alpha and beta forms of aldohexose?
alpha form is when the OH on the carbon that is attacked is on the bottom, which appears on the equitorial position within the chair conformer. beta is when OH of the carbon attacked it in the up position which will appear in the axial position in the chair conformer
is the alpha or beta form of the aldohexose more stable? draw pyrose (aldohexose) and explain
beta form predominates where 2/3 of the enantomer ratio is in this form. This is because the OH on the attacked carbon is in the equitorial position. atoms in this position are positited away from the rest of the molecule which decreases steric hinderance (decrease electric repulation between other atoms of the molecule). OH in the alpha position is in the axial position which is positioned within the plane of the molecule - where the aotms will interact with the rest of the molecule - casuing i,3-diaxial interactions, and thus only 1/3 of this enatiomer is present in the product mixture.
what are some 5 membered sugar moelcules biologically important to us?
fructose and ribose and are aldopentoses (5 membered rings with an aldehyde funcitonal group.
what form of the frutose and ribose predominated in the product mixture? what is their conformer? is it different to the shape of 6 membered rings?
5 membered rings - frutose and ribose - predominate in evelope form where one of the carbon is puckered. C2 endo is when carbon 2 is the puckered carbon and C3 endo is when carbon 3 is puckered. puckered position is the “tip evelope” position
