Study Set Content:
Alkynes undergo hydration readily in the presence of mercury (II) sulfate as a
Lewis acid catalyst
Enol intermediate rearranges into a ketone through the process of
keto-enol tautomerism
rearrange to the isomeric ketone by the rapid transfer of a proton from the hydroxyl to the alkene carbon
Enols
Isomeric compounds that can rapidly interconvert by the movement of a proton are called
Tautomers
Hydration of an unsymmetrically substituted internal alkyne (RC≡CR') results in a mixture of both
possible ketones
Hydroboration-Oxidation of Alkynes
- Borane adds to alkynes to give a vinylic borane
- Oxidation with H2O2 produces an enol that converts to the ketone or aldehyde by tautomerization
Reduction of Alkynes
- Accomplished by addition of
- of H2 over a metal catalyst is a two-step reaction using an alkene intermediate
Addition of H2 using deactivated (blank) on carbon as a catalyst (the Lindlar catalyst) produces a cis alkene
Palladium
Lindlar catalyst
Palladium on carbon
Alkynes can also be converted to alkenes using (blank) as the reducing agent in liquid ammonia as the solvent.
sodium or lithium metal
Alkynes can also be converted to alkenes using sodium or lithium metal as the reducing agent in liquid ammonia as the solvent. This method produces
trans alkenes
Strong oxidizing reagents (O3 or KMnO4) cleave
internal alkynes
Strong oxidizing reagents (O3 or KMnO4) cleave internal alkynes, producing
2 carboxylic acids
are formed from the cleavage of an internal alkyne
carboxylic acids
is one of the products formed by cleavage of a terminal alkyne
CO2
Saturated cyclic hydrocarbons
Cycloalkanes or Alicyclic Compounds:
Cycloalkanes or Alicyclic Compounds:
General formula (CnH2n)
Cycloalkanes are less flexible than
open-chain alkanes
- Significantly lesser conformational freedom in cycloalkanes
cycloalkanes
(cyclopropane, cyclobutane)
Small rings
