Chapter 8 - Mechanisms Flashcards

1
Q

What is the reaction for Hydrohalogenation?

A

R−CH=CH2 + HBr → R−CHBr−CH3

This represents Markovnikov addition.

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2
Q

What is the first step in the Hydrohalogenation mechanism?

A

Protonation of the Alkene

The π-bond of the alkene acts as a nucleophile and attacks the proton (H+) from HBr.

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3
Q

What occurs during the Nucleophilic Attack in Hydrohalogenation?

A

The bromide ion (Br−) attacks the carbocation, forming the final product.

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4
Q

How does the presence of peroxides affect Hydrohalogenation?

A

A radical mechanism occurs where Br adds to the less substituted carbon (Anti-Markovnikov).

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5
Q

What is the reaction for Acid-Catalyzed Hydration?

A

R−CH=CH2 + H2O/H2SO4 → R−CHOH−CH3

This represents Markovnikov addition.

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6
Q

What is the initial step in the Acid-Catalyzed Hydration mechanism?

A

Protonation of the Alkene.

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7
Q

What does water do during the Nucleophilic Attack in Acid-Catalyzed Hydration?

A

Water (H2O) attacks the carbocation, forming an oxonium ion (R−CHOH2+).

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8
Q

What happens during the Deprotonation step in Acid-Catalyzed Hydration?

A

Another water molecule deprotonates the oxonium ion to form the alcohol.

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9
Q

What is a key note regarding carbocation in Acid-Catalyzed Hydration?

A

Carbocation rearrangements are possible if a more stable carbocation can form.

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10
Q

What is the reaction for Oxymercuration-Demercuration?

A

R−CH=CH2 + Hg(OAc)2, H2O/NaBH4 → R−CHOH−CH3

This represents Markovnikov addition without rearrangements.

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11
Q

What is formed in the first step of the Oxymercuration mechanism?

A

Formation of the Mercurinium Ion.

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12
Q

What occurs during the Nucleophilic Attack in Oxymercuration?

A

Water attacks the more substituted carbon, breaking the three-membered ring.

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13
Q

What is the final step in the Oxymercuration-Demercuration mechanism?

A

Sodium borohydride (NaBH4) replaces the mercury with a hydrogen atom.

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14
Q

What is the reaction for Hydroboration-Oxidation?

A

R−CH=CH2 + BH3⋅THF/H2O2, NaOH → R−CH2−CH2OH

This represents Anti-Markovnikov, syn addition.

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15
Q

What happens during Hydroboration?

A

Borane (BH3) adds across the double bond with boron attaching to the less substituted carbon.

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16
Q

What replaces boron during the Oxidation step of Hydroboration-Oxidation?

A

Hydroxyl group (−OH) replaces boron.

17
Q

What type of addition occurs in Hydroboration-Oxidation?

A

Syn addition.

18
Q

What is the reaction for Halogenation?

A

R−CH=CH2 + Br2 → R−CHBr−CH2Br

This represents Anti addition.

19
Q

What is formed during the Formation of the Bromonium Ion in Halogenation?

A

A three-membered bromonium ion.

20
Q

What occurs during the Nucleophilic Attack in Halogenation?

A

The second bromine ion (Br−) attacks the more substituted carbon, breaking the bromonium ion.

21
Q

What is the reaction for Halohydrin Formation?

A

R−CH=CH2 + Br2/H2O → R−CHBr−CH2OH.

22
Q

What is the first step in the Halohydrin Formation mechanism?

A

Formation of the Bromonium Ion.

23
Q

What is formed during the Nucleophilic Attack in Halohydrin Formation?

A

An oxonium ion.

24
Q

What happens during the Deprotonation step in Halohydrin Formation?

A

A water molecule deprotonates the oxonium ion to form the halohydrin.

25
Q

What is the reaction for Syn Dihydroxylation?

A

R−CH=CH2 + OsO4/NaHSO3 → R−CH(OH)−CH2(OH)

This represents Syn addition.

26
Q

What is formed during the Cyclic Osmate Ester Formation in Syn Dihydroxylation?

A

A cyclic osmate ester.

27
Q

What cleaves the ester in Syn Dihydroxylation?

A

Sodium bisulfite (NaHSO3).

28
Q

What is the reaction for Oxidative Cleavage?

A

R−CH=CH−R′ + O3/DMS → R−CHO + R′−CHO.

29
Q

What is formed during the Ozonide Formation in Oxidative Cleavage?

A

A molozonide, which rearranges to an ozonide.

30
Q

What reduces the ozonide in Oxidative Cleavage?

A

Dimethyl sulfide (DMS).

31
Q

What can KMnO4 (hot) further oxidize during Oxidative Cleavage?

A

Aldehydes to carboxylic acids.