Reactions of Alkenes and Alkynes

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18 Terms

1
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Hydrohalogenation of alkenes

- The addition of H and a halogen (Br)

- Markovnikov

- Forms a stable carbocation

<p>- The addition of H and a halogen (Br)</p><p>- Markovnikov</p><p>- Forms a stable carbocation</p>
2
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Hydrohalogenation with peroxide in alkenes

- The addition of a halogen (Br) and H with the use of a free-radical mechanism

- The use of free-radicals makes this anti-markovnikov

- No carbocation, but instead forms a stable free radical

<p>- The addition of a halogen (Br) and H with the use of a free-radical mechanism</p><p>- The use of free-radicals makes this anti-markovnikov</p><p>- No carbocation, but instead forms a stable free radical</p>
3
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Acid-catalysed hydration of alkenes

- Addition of H and OH

- Markovnikov, forms a stable carbocation

- Needs an acid catalyst to happen

- Acid catalysts include H+, H2SO4, or just H3O+

<p>- Addition of H and OH</p><p>- Markovnikov, forms a stable carbocation</p><p>- Needs an acid catalyst to happen</p><p>- Acid catalysts include H+, H2SO4, or just H3O+</p>
4
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Acid-catalysed ether formation of alkenes

- Addition of H and OCH3

- This is a hydration reaction, but instead of H2O, we use CH3OH

- Markovnikov, forms a stable carbocation

<p>- Addition of H and OCH3</p><p>- This is a hydration reaction, but instead of H2O, we use CH3OH</p><p>- Markovnikov, forms a stable carbocation</p>
5
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Hydrogenation of alkenes

- Addition of two H molecules

- Syn-addition

- Uses a metal catalyst (Pt)

<p>- Addition of two H molecules</p><p>- Syn-addition</p><p>- Uses a metal catalyst (Pt)</p>
6
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Halogenation of alkenes

- Addition of two halogens (Br)

- Anti-addition, no carbocation (due to cyclic bromonium formation)

- Uses a solvent like Ch2Cl2

<p>- Addition of two halogens (Br)</p><p>- Anti-addition, no carbocation (due to cyclic bromonium formation)</p><p>- Uses a solvent like Ch2Cl2</p>
7
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Halohydrin formation

- Addition of a halogen (Br) and OH

- Anti-addition, no carbocation (due to cyclic bromonium formation)

- The same thing as halogenation, but uses H2O as solvent instead of Ch2Cl2

- The H2O competes with Br to bind to C, and it wins because it is high in abundance

- The H2O attaches to the C with least H (Markovnikov)

- Can also be done with CH3OH or NaCl, where OH or Cl would add instead of Br

<p>- Addition of a halogen (Br) and OH</p><p>- Anti-addition, no carbocation (due to cyclic bromonium formation)</p><p>- The same thing as halogenation, but uses H2O as solvent instead of Ch2Cl2</p><p>- The H2O competes with Br to bind to C, and it wins because it is high in abundance</p><p>- The H2O attaches to the C with least H (Markovnikov)</p><p>- Can also be done with CH3OH or NaCl, where OH or Cl would add instead of Br</p>
8
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Oxymercuration-Reduction

- Addition of H and OH

- Markovnikov, no carbocation (no shift)

- Makes and alcohol like hydration and hydroboration-oxidation, but this may be done if no carbocations/shifts are wanted with markovnikov

- Step 1 Oxymercuration [ Hg(OAc)2 / H2O) ]: Hg-OAc bonds to C with least H and then H2O attacks the C with least H as a nucleophile; the left over OAc- takes an H off of the H2O, leaving it as OH- on the C

- Step 2 Reduction [ (NaBH4) / (NaOH) ]: The C-Hg bond is replaced with a C-H bond with the H coming from BH4

<p>- Addition of H and OH</p><p>- Markovnikov, no carbocation (no shift)</p><p>- Makes and alcohol like hydration and hydroboration-oxidation, but this may be done if no carbocations/shifts are wanted with markovnikov</p><p>- Step 1 Oxymercuration [ Hg(OAc)2 / H2O) ]: Hg-OAc bonds to C with least H and then H2O attacks the C with least H as a nucleophile; the left over OAc- takes an H off of the H2O, leaving it as OH- on the C</p><p>- Step 2 Reduction [ (NaBH4) / (NaOH) ]: The C-Hg bond is replaced with a C-H bond with the H coming from BH4</p>
9
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Hydroboration-Oxidation of alkenes

- Addition of OH and H

- Anti-Markovnikov, no carbocation (no shift)

- Same thing as hydration and oxymercuration-reduction, but this may be done if no carbocations wanted with anti-markovnikov

- Step 1 Hydroboration (BH4): An H in BH4 attacks the C with least H as a nucleophile, while BH3 attaches to the other C

- Step 2 Oxidation (OH-, H2O2, H2O): H2O2, OH-, and H2O are used in sequence to replace the BH3 on the C with OH

<p>- Addition of OH and H</p><p>- Anti-Markovnikov, no carbocation (no shift)</p><p>- Same thing as hydration and oxymercuration-reduction, but this may be done if no carbocations wanted with anti-markovnikov</p><p>- Step 1 Hydroboration (BH4): An H in BH4 attacks the C with least H as a nucleophile, while BH3 attaches to the other C</p><p>- Step 2 Oxidation (OH-, H2O2, H2O): H2O2, OH-, and H2O are used in sequence to replace the BH3 on the C with OH</p>
10
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Ozonolysis

- Breaking of a double bond and forming ketones or aldehydes

- The usual solvent is (CH3)2S, but if done in H2O2, any resulting aldehydes would be oxidized with carboxylic acid groups

<p>- Breaking of a double bond and forming ketones or aldehydes</p><p>- The usual solvent is (CH3)2S, but if done in H2O2, any resulting aldehydes would be oxidized with carboxylic acid groups</p>
11
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Hydrohalogenation of Alkynes

- Addition of H and Br

- Markovnikov, no carbocation rearrangement

- If there is excess HBr, one more Br can be added to the C with least H

<p>- Addition of H and Br</p><p>- Markovnikov, no carbocation rearrangement</p><p>- If there is excess HBr, one more Br can be added to the C with least H</p>
12
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Hydrohalogenation with peroxide in alkynes

- Addition of Br and H with the use of free radicals

- Anti-markovnikov, no carbocation

<p>- Addition of Br and H with the use of free radicals</p><p>- Anti-markovnikov, no carbocation</p>
13
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Hydration of alkynes

- Addition of an H and OH to make an alcohol, which then gets tautomerized into a ketone

- Markovnikov, no carbocation

<p>- Addition of an H and OH to make an alcohol, which then gets tautomerized into a ketone</p><p>- Markovnikov, no carbocation</p>
14
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Hydroboration of alkynes

- The addition of an H and OH to make an alcohol, which gets tautomerized into a ketone

- Anti-markovnikov, no carbocation

<p>- The addition of an H and OH to make an alcohol, which gets tautomerized into a ketone</p><p>- Anti-markovnikov, no carbocation</p>
15
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Halogenation of alkynes

- The addition of two halogens (Br) to an alkyne

- Anti-addition, no carbocation due to cyclic bromonium ion

- Uses a solvent like Ch2Cl2

- If excess Br2, two more will be added to the structure

<p>- The addition of two halogens (Br) to an alkyne</p><p>- Anti-addition, no carbocation due to cyclic bromonium ion</p><p>- Uses a solvent like Ch2Cl2</p><p>- If excess Br2, two more will be added to the structure</p>
16
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Hydrogenation of alkynes (Pt catalyst)

- The addition of H molecules

- Syn-addition

- Makes an alkane, no in between

<p>- The addition of H molecules</p><p>- Syn-addition</p><p>- Makes an alkane, no in between</p>
17
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Hydrogenation of alkynes (Lindlar's catalyst)

- The addition of H molecules

- Syn-addition

- Makes a cis alkene

<p>- The addition of H molecules</p><p>- Syn-addition</p><p>- Makes a cis alkene</p>
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Hydrogenation of alkynes (Na/NH3 (l))

- The addition of H molecules

- Syn-addition

- Makes a trans alkene

<p>- The addition of H molecules</p><p>- Syn-addition</p><p>- Makes a trans alkene</p>