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14 Cards in this Set
- Front
- Back
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2 ways to synthesize alkynes?
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1. Nucleophilic attack on either electrophile - a) primary alkyl halide (Sn2) or b) carbonyl cpd (addition --> alcohol)
2. double dehydrohalogenation of a dihalide |
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How to make an acetylide ion?
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React terminal alkyne w/ strong base NaNH2
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Acetylenic hydrogen?
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A hydrogen on a terminal alkyne (if internal alkyne, no acetylenic hydrogen)
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How to make a longer alkyne
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acetylide ion (terminal alkyne + NaNH2) + primary alkyl halide
OR addition rxn --> alcohol of carbonyl cpid |
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Carbonyl cpd --> alcohol?
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1. nuc attack (can be by acetylide ion)
2. protonation (w/ water or dilute acid) |
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Terminal alkyne --> alcohol?
(reagents) |
1. NaNH2
2. H2C--O (carbonyl cpd) 3. H30+ or H20 |
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aldehyde + acetylide ion? (+ protonation)
--> |
2* alcohol: two R groups = original R on aldehyde, R on acetylide
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ketone + acetylide ion? (+ protonation)
--> |
3* alcohol: 3 R groups = 2 originals on ketone + 1 on acetylide
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elimination --> alkyne?
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dehydrohalogentation - remove 2 molecules of HX from a dihalide
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Conditions to get:
dihalide --> alkyne? |
strongly basic (ex. molton or alcholic KOH + heat, or NaNH2 in water)
(dehydrohalogenation --> vinyl halide, if very basic conditions can occur again --> alkyn) |
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Dihalide --> vinyl halide?
(reagents) |
base, -HX
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Vinyl halide --> alkyne?
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base, -HX
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Rate limiting step of dihalide --> alkyne?
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2nd (vinyl halide --> alkyne)
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dihalide --> alkyne?
(reagents) |
KOH (fused/alcholic) @ 200*C
OR NaNH2 @ 150*C, H2O |
