Two adjacent axial hydrogens in a six-membered ring have a larger coupling const
ID: 1054384 • Letter: T
Question
Two adjacent axial hydrogens in a six-membered ring have a larger coupling constant (~16Hz) than two adjacent hydrogens that have an axial-equatorial relationship (~8 Hz). Using this information identify the given H-NMR spectra of the two anomeric glucose pentaacetates. (and other ones as well, please)
No Structures have been provided with these questions
3) Two adjacent axial hydrogens in a six-membered ring have a larger coupling constant (16 Hz) than two adjacent hydrogens that have an axial-equitorial relationship (8 Hz). Using this information identify the given H NMR spectra of the two anomeric glucose pentaacetates. a. Anomer l= b. Anomer 11 = 4) Why is the peak between 5.5-6.5 ppm in each spectra so downfield? What proton does this peak represent? 5) What is the function each of the given substances in this reaction? (e.g. acid catalyst, base catalyst, electrophile, nucleophile, oxidizing agent, proton source, solvent, spectator group etc.) a. sodium acetate b. glucose c. acetic anhydride d. (1:2) methanol:water 6) What is the name of the mechanism is used in this reaction?Explanation / Answer
Glucose pentaacetate
4) The protons which are attached to the carbons having the -OH groups appears most downfield between 5.5-6.5 ppm. The electronegative oxygen attached next to hydrogen is responsible for this shift.
5) Reagents used for the reaction
a. sodium acetate : base catalyst
b. glucose : nucelophile (substrate)
c. acetic anhydride : electrophile (acetylating reagent)
d. (1:2) methanol:water : solvent
6) Mechanism for the acetylation of glucose is SN2 reaction.