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ACS Organic Chemistry Exam.
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ACS Organic Chemistry Exam.
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ACS Organic Chemistry ExamWhat is the general formula for a carbohydrate? - (CORRECT ANSWER)-Cx(H2O)y
v v v v v v v v v v
How do you determine the number of stereoisomers for a given carbohydrate? -
v v v v v v v v v v v v
(CORRECT ANSWER)-2^n where n= number of stereocenters
v v v v v v v
Distinguish between the D and L designations for carbohydrates. - (CORRECT ANSWER)-In
v v v v v v v v v v v
the L form the hydroxy group is on the bottom left closest to the CH2OH group in the
v v v v v v v v v v v v v v v v v v
frame of a Fischer projection
v v v v v
In the D form the OH is on the bottom right
v v v v v v v v v v
What are anomers? - (CORRECT ANSWER)-Diastereomers formed by the cyclization of
v v v v v v v v v v
carbohydrates (*note they have different configurations at the new stereocenter-this is
v v v v v v v v v v v
what makes them diastereomers)
v v v v
Distinguish between alpha and beta anomers. - (CORRECT ANSWER)-beta anomers have
v v v v v v v v v v
the OH belonging to the hemiacetal carbon equatorial
v v v v v v v v
alpha anomers have the OH belonging to the hemiacetal carbon axial
v v v v v v v v v v
What is the definition of mutarotation? - (CORRECT ANSWER)-the process for which alpha
v v v v v v v v v v v v
and beta anomers come to equilibrium (aqueous) in a specific ratio. It is the same ratio is
v v v v v v v v v v v v v v v v v
observed when you start with the alpha anomer in water versus the beta anomer in water
v v v v v v v v v v v v v v v v
What agent is most often used for complete oxidation of a carbohydrate? - (CORRECT
v v v v v v v v v v v v v
ANSWER)-HNO3
v
, What kind of agents are used for selective or partial oxidation of carbohydrates? -
v v v v v v v v v v v v v
(CORRECT ANSWER)-most commonly Br or some other MILD oxidative agent
v v v v v v v v v v
What are reducing sugars? - (CORRECT ANSWER)-Carbohydrates that yield positive
v v v v v v v v v
results of the oxidative tests, because in being oxidized they reduce the metal ion (or
v v v v v v v v v v v v v v v
other reducing agent)
v v v
Carbohydrates undergo reactions similar to which functional group? - (CORRECT
v v v v v v v v v
ANSWER)-OH (hemiacetals and acetals)
v v v v
How does the Tollen's test work? - (CORRECT ANSWER)-Carbohydrate is oxidized by Ag+
v v v v v v v v v v v v
and positive result shows a silvery mirror as Ag+ is reduced to metallic (elemental) silver
v v v v v v v v v v v v v v v
How do the Benedict's and Fehling's tests work? - (CORRECT ANSWER)-Both employ a
v v v v v v v v v v v v
solution of aqueous Cu2+ in base. When reduced it forms Cu2O which is a red ppt.
v v v v v v v v v v v v v v v v
What is a glycoside? - (CORRECT ANSWER)-a sugar bonded to another oxygen containing
v v v v v v v v v v v v
functional group to make the carbohydrate a full acetal rather than a hemiacetal
v v v v v v v v v v v v v
What does a glycosidic bond consist of? - (CORRECT ANSWER)-A glycosidic bond is
v v v v v v v v v v v v
between C4 (the acetal carbon) and another oxygen atom
v v v v v v v v v
What is the difference between an alpha and a beta glycosidic bond? - (CORRECT
v v v v v v v v v v v v v
ANSWER)-the alpha bond is axial
v v v v v
the equatorial bond is equatorial
v v v v
What is a nucleophile? - (CORRECT ANSWER)-An electron rich species than seeks an
v v v v v v v v v v v v
electron poor site
v v v
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