Alkynes

Alkynes
physical properties:
-weakly or non-polar,
-no H-bonding
-relatively low mp/bp
-water insoluble
Nomenclature:
common names: “alkylacetylene”
IUPAC: parent chain = longest continuous carbon chain that contains the triple bond.
alkane drop –ane add -yne
prefix locant for the triple bond, etc.
CH3CH2C?CCH32-pentyne (ethylmethylacetylene)
“terminal” alkynes have the triple bond at the end of the chain:
CH3
CH3CH2C?CHHC?CCHCH2CH3
1-butyne3-methyl-1-pentyne
ethylacetylenesec-butylacetylene
Hydration of Alkynes
?Addition of H-OH as in alkenes
?Mercury (II) catalyzes Markovnikov oriented addition
?Hydroboration-oxidation gives the anti-Markovnikov product
Mercury(II)-Catalyzed Hydration of Alkynes
?Alkynes do not react with aqueous protic acids
?Mercuric ion (as the sulfate) is a Lewis acid catalyst that promotes addition of water with Markovnikov orientation
?The immediate product is a vinylic alcohol, or enol, which spontaneously transforms to a ketone or to an aldehyde in the event that acetylene is employed.