Chapter 11: Addition Reactions

Question 1

What is the outcome of this reaction?

Answer 1

Question 2

What is the regiochemistry of this molecule?

Answer 2

Markovnikov product/addition

Question 3

What is the regiochemistry of this molecule?

Answer 3

Anti-markovnikov product/addition

Question 4

What is the stereochemistry of this molecule?

Answer 4

Syn

Question 5

What is the stereochemistry of this molecule?

Answer 5

Anti

Question 6

What are the products of this reaction if they are Markovnikov and syn

Answer 6

Question 7

What are the products of this reaction if they are anti-markovnikov and syn?

Answer 7

Question 8

What are the products of this reaction if they are anti-markovnikov and anti?

Answer 8

Question 9

What is the regiochemistry and stereochemistry of a H2 (H-H) addition reaction?

Answer 9

Question 10

What is the outcome of this reaction?

Answer 10

Meso because there is a plane of symmetry

Question 11

What is the outcome of this reaction?

Answer 11

Have to show D atoms

Question 12

What is the outcome of this reaction?

Answer 12

results in enantiomers

Question 13

What is the regiochemistry and stereochemistry of H-Halogen addition reactions?

Answer 13

Question 14

What is the mechanism of H-Halogen addition reactions?

Answer 14

Carbocation forms on the more substituted carbon because it is more stable. The halogen then acts as a nucleophile to attack the carbocation forming a Markovnikov addition.

Question 15

What is the mechanism of this H-Br addition reaction?

Answer 15

There is a carbocation rearrangement to stabilize the secondary carbocation, creating a tertiary carbocation. Br then acts as a nucleophile and attacks the tertiary carbocation, forming a markovnikov addition.

Question 16

What is the mechanism of this H-Br addition reaction?

Answer 16

Alkyl migration occurs to make the secondary carbocation a tertiary carbocation so it is more stable.

Question 17

What will cause a H-Halogen addition reaction to be anti-Markovnikov?

Answer 17

Adding peroxide (ROOR) as a reagent in the reaction

Question 18

What is the mechanism when H-Halogen, ROOR are used in an addition reaction?

Answer 18

RO OR are broken homolytically (each oxygen keeps their shared electron) in the presence of light or heat. The radical RO obstructs H, H-Br bond breaks, forming radical Br which attacks the less substituted carbon so the radical can be transferred to the tertiary carbon (more stable). The radical tertiary carbon is then abstracts a H from H-Br to from an anti-markovnikov addition with 2 enantiomers.

Question 19

What is the regiochemistry and stereochemistry of H and OH addition reactions?

Answer 19

Question 20

Why is a different arrow used for radical reactions?

Answer 20

Represents the movement of 1 electron

Question 21

What is the mechanism of this reaction?

Answer 21

Pi bond extracts H from H3O+ and the H-OH bond is broken to from a tertiary carbocation (more stable) plus water. H2O then acts as a nucleophile and attacks the tertiary carbocation. The new molecule formed has a + charge on H2O, so another H2O extracts an H forming an OH markovnikov addition.

Question 22

Why are two arrows used in this reaction?

Answer 22

The reverse of the reaction is an E1 elimination reaction (H2O in the presence of acid creates a good LG)

Question 23

What are the reagents used to make a H and OH addition reaction anti-markovnikov and syn?

Answer 23

Question 24

What is the mechanism used to make a H and OH addition reaction anti-markovnikov and syn?

Answer 24

Borane (BH3) does not have an octet (empty p orbital but no positive charge) making it very reactive. The solvent THF can donate electron density into the empty p orbital of borane to help stabilize it. However, borane still looks for areas of electron density (in this case the Pi bond which attacks the empty p orbital of borane and triggers a hydride shift). Borane ends up on the less substituted carbon because it is bulkier and is sterically hindered. An oxidation reaction with H2O2 and NaOH then occurs that replaces the borane with OH (see page 196 in textbook)

Question 25

What is the regiochemistry and stereochemistry of a Br2 (Br-Br) addition reaction?

Answer 25

Question 26

What is the mechanism of this reaction?

Answer 26

A bromonium ion is formed and then attacked from behind by Br-, creating anti stereochemistry

Question 27

How does a Bromonium ion form?

Answer 27

The Pi bond has an area of high electron density and when Br2 approaches it, the Pi bond repels the electron density of Br2 creating a temporary dipole. The electron dense Pi bond then attacks the electron poor bromine

Question 28

What is the regiochemistry and stereochemistry of a Br and OH addition reaction?

Answer 28

Don't use markovnikov/anti-markovnikov here because there is no H atom

Question 29

What is the mechanism of this reaction?

Answer 29

Bromonium ion formed in the first step. H2O acts as the nucleophile and attacks the more substituted carbon because it acts as a carbocation and is more stable. The oxonium ion (H2O+) is then deprotonated by another water molecule to from OH.

Question 30

What reagents are used to form an anti OH and OH addition reaction?

Answer 30

Peroxyacids (example: meta-chloroperbenzoic acid (MCPBA)) reacts with alkene to form an epoxide. H3O+ (water under conditions of acid-catalysis) protonates the epoxide to form a + charged intermediate that is attacked by water from the back side (why it is anti). Water then acts as a base and removes a proton from the H2O+ to form anti OH and OH enantiomers. (see page 210)

Question 31

Name the molecule

Answer 31

peroxyacid

Question 32

Name the molecule

Answer 32

meta-choloroperbenzoic acid (MCPBA)

Question 33

Name the molecule

Answer 33

peroxide

Question 34

What reagents are used to form an syn OH and OH addition reaction?

Answer 34

Reaction is called syn dihydroxylation H2O2 Osmium tetroxide (OsO4) adds across the alkene in a concerted process (both oxygen atoms attach to the alkene at the same time). This is why it results in syn stereochemistry. The same process can occur with cold KMnO4 and hydroxide

Question 35

What is this reaction?

Answer 35

ozonolysis (adding across alkene and completely cleaving the Pi bond)

Question 36

What is the mechanism of ozonolysis

Answer 36

Question 37

How to draw an ozonolysis reaction

Answer 37