Chapter 9' Alkynes

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Chapter 9. Alkynes
CH
A. Uses HC
Acetylene - welders gas
norethynodrel Enovid
Look at the structure of ethynyl estradiol in the
book -very similiar
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B. Nomenclature - just like the alkenes - use
alkane name, drop the ane and add yne. There
are a couple of common names
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C. Acidity of alkynes 1. reaction with bases
Carbon AOs
2p
2s
PE
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2. Synthetic uses- making more complicated
alkynes a. general reaction
b. example
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3. addition to carbonyl compounds a. backround
information
(N- nucleophile)
(carbonyl functionality)
(alkoxide -strong base)
b.examples
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D. Formation of acetylenes - elimination reactions
E. Reactions of alkynes - essentially identical
to that for alkenes (with a few exceptions)!
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1. hydrogenation
But we can stop this at the cis alkene by
using Lindlars catalyst
We can also use ammonia/metal reductions
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2. addition of HX a. overall reaction
b. mechanism and orientation
And now
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And why
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3. oxymercuration a. general reaction
b. mechanism
And now
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4. hydroboration/oxidation
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Synthetic tools!
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5. permanganate oxidations
6. ozonolysis
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F. Summary 1. Acidity - formation uses of
acetylides a. reaction with carbonyls b.
nucleophilic substitutions 2. Formation of
alkynes - elimination from dihalides 3.
Reactions of acetylenes a. hydrogenation i.
H2/metal ii. Lindlars catalyst -
sterochem. iii. metal/ammonia - stereochem.
b. addition of HX - mech. orientation c.
oxymercuration - mech. d. hydroboration e.
oxidation i. permanganate ii. ozonolysis