Edited Invalid date
21 Carboxylic Acid Derivatives -- Part 6
Sugars are usually converted to silyl ethers to make them more volatile and easier to handle.
It would be more likely for glucose to char and decay inside the gas chromatograph than it would be to flow through the column with the gas phase.
The trimethylsilyl is more volatile and can survive gas chromatography and mass spectrometry at a low temperature.
Watersoluble, not volatile organic-soluble, volatile Oxidation of glucose at C6 produces glucuronic acid.
NaOH and dimethyl sulfate were used to make the glucuronide derivative a-d-glucopyranoside.
To form esters, acylate the hydroxy groups.
Sugar esters can be easily dissolved in common organic solvents.
The hemiacetal on the anomeric carbon is acetylated by this reaction.
All the hydroxy groups of a sugar are converted to acetate esters with the help of acetic anhydride and pyridine.
The stereochemistry at the anomeric carbon is usually preserved.
The product is the same as the anomer of the acetate if we start with a pure b anomer.
Predict the products formed when sugars react with acetic anhydride and pyridine.
The method for shortening the chain of an aldose was briefly mentioned in our discussion of d and l sugars.
The bromine-water oxidation of the aldose to its aldonic acid is the first step of the degradation process.
The oxidizer of the carboxyl group to CO2 is hydrogen peroxide and the oxidizer of the carbon atom is ferric sulfate.
The degradation is used for structure determination.
The structure of d-lyxose should be given.
D-threose comes from degradation of d-lyxose.
The structure of d-threose should be given.
D-allose and d-allose degradation give the same aldopentose.
The structure of d-altrose should be given.
A chain-lengthened sugar with a new carbon atom at C1 and the former aldehyde group now at C2 is the result of this process.
For determining the structure of existing sugars and for synthesizing new sugars, this synthesis is useful.
The asymmetric aldehyde carbon atom is the first step in the formation of the cyanohydrin.
D-arabinose reacts with HCN to give the following cyanohydrins.
The hydrogenation of these cyanohydrins gives two imines.
The hydrogenation is done using a poisoned catalyst of palladium on barium sulfate.
The synthesis accomplishes the opposite of the degradation.
The Kiliani-Fischer synthesis converts the shortened aldose back into a mixture of the same two C2 epimers.
Both glucose and mannose go through degradation to give arabinose.
The Kiliani-Fischer synthesis converts arabinose into a mixture of glucose and mannose.
D-erythrose comes from degradation of d-arabinose.
Give the structure of d-ribose by drawing out the reactions.
The oxime is converted to a nitrile by acetic anhydride.
The equations for the individual reactions in the degradation of d-arabinose to d-erythrose can be given using the following sequence of reagents.
There are no mechanisms required.
All degraded should be written out to (+)@glyceraldehyde.
In 1891, the structures of glucose and the seven other daldo-hexoses were determined using only simple chemical reactions and clever reasoning.
He received a prize for this work.
D-glucose is an aldohexose, and he degraded it to ( +)-glyceral dehyde.
Arabinose is the same as aldopentose after degradation.
Aldaric acid is an oxidizer of arabinose.
Arabinose gives the aldotetrose erythrose.
The hydrolyze gives the same anomer as the starting material.
The silyl ethers are hydrolyzed by floride salts.
There are three common bonding arrangements in naturally occurring disaccharides.
The oxygen atom on C4 of the second sugar is bonded to the anomeric carbon.
The prime symbol indicates that C4 is on the second sugar.
The oxygen atom on C6 of the second sugar is bonded to the anomeric carbon.
The oxygen atom bonds the anomeric carbon of the first sugar to the anomeric carbon of the second sugar.
Review flashcards and saved quizzes
Getting your flashcards
Privacy & Terms