Chemistry 3719 Chapter 9

  1. What is the approximate pKa of a terminal alkyne?
    Approximately 26
  2. What shape does an alkyne adopt about the triple bond?
    Linear (since, from VSEPR, only two valences repel)
  3. Which base will completely deprotonate a terminal alkyne, NaOH or NaNH2?
    NaNH2. Its conjugate acid has a pKa of 36 so NaNH2 is a very powerful base that is capable of completely deprotonating the alkyne (pKa ~26).
  4. What process is involved when an enol converts to a ketone, or vice versa?
    Keto-enol tautomerism
  5. What mechanism is involved when the sodium salt of an alkyne attacks methyl bromide to give the methylated alkyne?
    SN2 reaction
  6. Why is cyclohexyne an impossible molecule to make?
    The angles around the alkyne would deviate far too much from the ideal 180o and subsequently the cycle would be far too strained for the molecule to exist
  7. Are low molecular weight alkynes or low molecular weight alcohols typically more likely to dissolve in water? What is the reasoning behind your answer?
    Low molecular weight alcohols since they are more polar and also capable of hydrogen bonding with water
  8. What is the hybridization pattern of C atoms in triple bonds?
    sp hybridized
  9. What products are formed when acetylene is combusted in oxygen?
    CO2 and H2O
  10. Why are alkyne protons more acidic than alkane protons?
    The sp-hybridized C atoms in alkynes are more electronegative than sp3 atoms in alkynes; this stabilizes the conjugate base in the alkyne case
Card Set
Chemistry 3719 Chapter 9
YSU Organic Chemistry