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Reactions of Amino Acids: Hydrogenolysis quiz

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  • What is hydrogenolysis in the context of amino acid reactions?
    Hydrogenolysis is the cleavage of a bond through catalytic hydrogenation, typically using H2 and a metal catalyst, to break down benzyl esters and N-Cbz derivatives.
  • Which bond is cleaved during hydrogenolysis of benzyl esters?
    The carbon-oxygen (C–O) bond is cleaved during hydrogenolysis of benzyl esters.
  • What are the typical products of hydrogenolysis of benzyl esters?
    The products are an amino acid and toluene.
  • Which metal catalysts are commonly used in hydrogenolysis reactions?
    Palladium, nickel, and platinum are commonly used, with palladium being the most frequent choice.
  • What happens to the CH2 group in benzyl esters during hydrogenolysis?
    The CH2 group gains a hydrogen to become CH3, forming toluene.
  • How does hydrogenolysis differ from typical catalytic hydrogenation of alkenes?
    Hydrogenolysis cleaves C–O bonds and adds hydrogens to oxygen and carbon, rather than just adding hydrogens to pi bonds.
  • What is the abbreviation for N-benzyl oxycarbonyl derivatives?
    N-benzyl oxycarbonyl derivatives are abbreviated as N-Cbz.
  • What intermediate is formed during hydrogenolysis of N-Cbz derivatives?
    An unstable carbamic acid intermediate is formed.
  • What happens to carbamic acid after it is formed in N-Cbz hydrogenolysis?
    Carbamic acid immediately undergoes decarboxylation, releasing CO2 and producing the free amino acid.
  • What is released during the decarboxylation of carbamic acid?
    CO2 (carbon dioxide) is released.
  • What is the final product after hydrogenolysis and decarboxylation of N-Cbz derivatives?
    The final product is a free amino acid.
  • What role does hydrogenolysis play in amino acid synthesis?
    Hydrogenolysis is crucial for selective bond cleavage and reduction, aiding in amino acid synthesis and protecting group removal.
  • What is toluene and how is it formed in these reactions?
    Toluene is benzene with a methyl group, formed when the CH2 group gains a hydrogen during hydrogenolysis.
  • Why is carbamic acid considered unstable in these reactions?
    Carbamic acid is unstable because it rapidly decarboxylates, losing CO2 to form the amino acid.
  • What is the significance of catalytic hydrogenation in hydrogenolysis beyond alkene reactions?
    Catalytic hydrogenation in hydrogenolysis demonstrates selective bond cleavage and reduction, not just syn addition to pi bonds.