ORGANIC - KLEIN 3E CH.9 -...
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ORGANIC - KLEIN 3E
CH.9 - ALKYNES
CONCEPT: DEHYDROHALOGENATION
□ The name given to an E2 reaction of an alkyl halide. The major product will depend upon the type of base used.
Mechanism:
EXAMPLE: Supply the mechanism and major/minor products for the following dehydrohalogenation reaction:
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CONCEPT: DOUBLE DEHYDROHALOGENATION (ALKYNE SYNTHESIS)
□ When two equivalents of halide are present, bases can eliminate twice, creating alkynes as products
VICINAL: Adjacent to each other (aka “Vicinity”) GEMINAL: On the same carbon (aka “Gemini – Twins”)
EXAMPLE: Supply the mechanism and major/minor products for the following dehydrohalogenation reactions:
a.
b.
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CONCEPT: ALKYNIDE SYNTHESIS
□ Recall that terminal alkynes are uniquely acidic due to the hybridization effect:
● Terminal alkynes can be deprotonated with a strong base
(usually _________ or ___________) to create a strong nucleophiles called
__________________________.
EXAMPLE: Predict the product of the following reaction sequences:
a.
b.
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CONCEPT: HYDROGENATION OF ALKYNES
There are three methods commonly used to saturate double and triple bonds. They differ in the degree of saturation they
provide and in the stereochemistry of their reactions.
Catalytic Hydrogenation or Wilkinson’s Catalyst: Full Saturation
Stereochemistry: Syn Addition
Dissolving Metal Reduction: Partial Saturation
Stereochemistry: Anti Addition
Lindlar’s Catalyst: Partial Saturation
Stereochemistry: Syn Addition
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PRACTICE: Predict the product of the following multi-step synthesis:
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CONCEPT: ALKYNE HYDROHALOGENATION
□ Alkynes react with some addition reagents in excess to produce double addition products.
● Keep in mind that _____________ carbocations CANNOT easily rearrange.
Hydrohalogenation of Alkynes
□ Product: __________________________
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CONCEPT: ALKYNE HALOGENATION
Halogenation
□ Product: __________________________
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CONCEPT: ALKYNE HYDRATION
□ Vinyl alcohols are uniquely reactive due to a phenomenon called tautomerization.
● They reversibly swap the positions of a ___________ and a _____ bond.
Oxymercuration of Alkynes
□ Product: __________________________
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Hydroboration of Alkynes
□ Product: __________________________
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CONCEPT: OXIDATIVE CLEAVAGE
Cleavage of Alkynes: Carboxylic Acid + Carbon Dioxide
EXAMPLE: Predict the product of the following reaction.
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CONCEPT: MULTISTEP SYNTHESIS
Predict the MAJOR products of the following multistep transformations.
a.
b.
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CONCEPT: RETROSYNTHESIS
Provide the reagents to best perform the following transformations.
a.
b.
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