18 - CARBOHYDRATES Flashcards
why is the beta anomer of glucose favored?
why is the equilibrium percentage concentration of the beta anomer (64%) lower than expected?
there is a tendency for an electronegative atom at the C1 anomeric position to occupy the less favored axial orientation
this tendency is called the anomeric effect
what are epimers and some examples?
either of two stereoisomers that differ in the arrangement of groups on a single chiral carbon atom
epimers are a special class of diastereomers
anomers are a special class of epimers (differ on C1)
how is the fischer projection converted to a Haworth projection?
what is the anomeric effect
the anomeric effect stabilises the alpha anomer, where steric effects destabilise it
BUT, for glucose, sterics»anomeric effect and the beta anomer predominates
what are two ways to explain the anomeric effect?
how does the solvent play a role in anomeric stabilisation
anomeric effect and orbital energies
pyranose vs furanose of glucose and which is more stable
what is an example of a sugar where both the furanose and pyranose forms are observed
what method is used to distinguish between the alpha and beta anomers of glucopyranose?
can be done by HNMR
J is the coupling constant
when trans, J is greater than when cis
what is the karplus equation
what is Tollen’s test for the identification of aldehydes
what does the oxidation of glucose give
gluconic acid
glucose is also a reducing sugar, it reduces silver
why do ketones not react to the Tollen’s test, and an exception?
what is the mechanism of reaction of aldehydes and Tollen’s test?
why can fructose act as a reducing sugar even though it does not have an aldehyde group?
what is the mechanism for the epimerization reaction of fructose into mannose and glucose?
Benedict’s test
how is glucose detected in the blood and in the urine?
diagnosis and management of diabetes
