Addition Reactions

Question 1

The addition of water (H₂O) to an alkene in the presence of an acid catalyst, forming an alcohol

Answer 1

Acid-catalyzed hydration

Question 2

The addition of a hydrogen halide (HX, where X = Cl, Br, I) to an alkene, forming an alkyl halide.

Answer 2

Hydrohalogenation

Question 3

A two-step reaction sequence that achieves Markovnikov addition of water to an alkene without carbocation rearrangements.

Answer 3

Oxymercuration-demercuration

Question 4

A two-step reaction sequence that achieves anti-Markovnikov addition of water to an alkene.

Answer 4

Hydroboration-oxidation

Question 5

The addition of hydrogen (H₂) to an alkene in the presence of a metal catalyst (e.g., Pd, Pt, Ni), forming an alkane

Answer 5

Catalytic hydrogenation

Question 6

The addition of a halogen (Cl₂, Br₂) to an alkene, forming a vicinal dihalide (two halogens on adjacent carbons).

Answer 6

Halogenation

Question 7

The addition of a halogen and a hydroxyl group (OH) to an alkene, forming a halohydrin. This reaction occurs when the halogenation is carried out in the presence of water. The water molecule acts as a nucleophile and attacks the halonium ion, leading to the formation of a halohydrin.

Answer 7

Halohydrin formation

Question 8

Typically exothermic (ΔH < 0) due to the formation of stronger sigma bonds from weaker pi bonds.
However, they often result in decreased entropy (ΔS < 0) as two molecules combine to form one.

Answer 8

Addition reactions

Question 9

Typically endothermic (ΔH > 0) due to the breaking of strong sigma bonds to form weaker pi bonds.
However, they often result in increased entropy (ΔS > 0) as one molecule forms two.

Answer 9

Elimination reactions

Question 10

_______________ predicts the regiochemistry of addition reactions to alkenes. It states that in the addition of a protic acid (HX) to an alkene, the hydrogen atom will attach to the carbon with the greater number of hydrogen atoms already attached, while the halide (X) will attach to the more substituted carbon.

This preference is due to the stability of the intermediate carbocation formed during the reaction. The more substituted carbocation is more stable due to hyperconjugation and inductive effects, leading to the observed regioselectivity.

Answer 10

Markovnikov’s Rule

Question 11

_______________ describes the regiochemistry of addition reactions to alkenes, where the addition of a hydrogen atom (from a reagent like HBr) occurs at the more substituted carbon of the double bond, and the other atom (e.g., Br) attaches to the less substituted carbon. This is in contrast to the typical Markovnikov addition, where the hydrogen adds to the less substituted carbon.

Answer 11

anti-Markovnikov rule

Question 12

The addition of two hydroxyl groups (OH) to an alkene with anti stereochemistry, forming a diol (a compound with two alcohol groups).

Answer 12

Anti-dihydroxylation
epoxidation

Question 13

The addition of two hydroxyl groups (OH) to an alkene with syn stereochemistry, forming a diol.

Answer 13

Syn-dihydroxylation
formation of a cyclic osmate ester

Question 14

The cleavage of a carbon-carbon double bond by an oxidizing agent, forming two carbonyl compounds (aldehydes or ketones).

Answer 14

Ozonolysis
(oxidative cleavage)

Question 15

Answer 15

Hydrohalogenation

Question 16

Answer 16

Hydration acid catalyzed

Question 17

Answer 17

Oxymercuration-demercuration
- anti addition only

Question 18

Answer 18

Hydroboration-oxidation

Question 19

Answer 19

Catalytic Hydrogenation

Question 20

Answer 20

Halogenation

Question 21

Answer 21

Halohydrin Formation

Question 22

Answer 22

Syn dihydroxylation

Question 23

Answer 23

Ozonolysis

Question 24

Answer 24

Anti dihydroxylation
epoxidation
anti addition

Question 25

Markovnikov or Anti-Markovnikov?
Hydroboration

Answer 25

Anti-Markovnikov

Question 26

Markovnikov or Anti-Markovnikov?
Oxymercuration

Answer 26

Markovnikov

Question 27

Markovnikov or Anti-Markovnikov?
Hydration acid catalyzed

Answer 27

Markovnikov

Question 28

Markovnikov or Anti-Markovnikov?
Hydrohalogenation (HX)

Answer 28

Markovnikov

Question 29

Markovnikov or Anti-Markovnikov?
Halohydrin Formation

Answer 29

Markovnikov

Question 30

Syn of Anti Addition ONLY?
Hydroboration

Answer 30

Syn

Question 31

Syn of Anti Addition ONLY?
Halogenation

Answer 31

Anti
- due to bridged halonium ion mechanism and other halide backside attack

Question 32

Syn of Anti Addition ONLY?
Halohydrin Formation

Answer 32

Anti

Question 33

Syn of Anti Addition ONLY?
Dihydroxylation w OsO4 or KMnO4

Answer 33

Syn

Question 34

Syn of Anti Addition ONLY?
Dihydrozxylation via epoxidation

Answer 34

Anti

Question 35

Syn of Anti Addition ONLY?
Catalytic Hydrogenation

Answer 35

Syn

Question 36

Examples of _______________
MMPP
mCPBA
Peracetic Acid (PAA)

Answer 36

Peroxy Acids
used as epoxides

Question 37

Hydration with acid can be accompanied by rearrangements if a more stable carbocation intermediate can be formed through a hydride or alkyl shift. To avoid this, _____________ of alkenes is an alternative that does not give rearrangement.

Answer 37

oxymercuration

Question 38

Anti-Markovnikov ALCOHOLS can be obtained through ________________

Answer 38

hydroboration

Question 38

When alkenes (olefins) are treated with strong aqueous acid (H3O+) they undergo net addition of ______ across the double bond (“hydration”)

Answer 38

water

Question 39

For acid catalyzed hydration reactions:
Acids like H2SO4 are used since the conjugate base, HSO4(-), is a poor __________ and will not compete with H2O in attack on the carbocation

Answer 39

nucleophile

• if HCl is used then Cl- competes

Question 40

H2O will not add to alkenes by itself, however a __________ is required.

Answer 40

strong acid

Question 41

A ___________ reaction is one that shows a strong preference for the formation of one constitutional isomer (“regioisomer”) over another.

Answer 41

regioselective

Question 42

Useful mnemonic for Markovnikov is …….

Answer 42

“the rich (in C-H bonds) get richer (get another C-H bond)”

Question 43

Treatment of alkenes with mercury (II) salts and water leads to the addition of water and mercury across the C-C pi bond. This is called _____________

Answer 43

oxymercuration

Question 44

Oxymercuration-demercuration:
The reaction proceeds through attack of the nucleophile on a 3-membered intermediate known as an oxymercurinium ion, which resembles the halonium ion intermediate in reactions such as halogenation of alkenes. As like in halogenation, addition occurs to give the products of ___(anti or syn)___ addition

Answer 44

anti

Question 45

In the demercuration step, mercury is removed by treating the product with ____________ , giving the alcohol.

Answer 45

sodium borohydride (NaBH4)

Question 46

When an alkene is treated with a mercury(II) salt such as mercuric acetate [Hg(OAc)2] or mercuric trifluoroacetate Hg(OCOCF3)2 in the presence of H2O, addition occurs across the C-C pi bond, resulting in a new C-OH bond and a C-Hg bond. This reaction is called _____________

Answer 46

oxymercuration.

Question 47

Organomercury compounds tend to be highly _________ and it is best to avoid handling them if at all possible

Answer 47

toxic

Question 48

2 commonly used reagents used in oxymercuration
- ____________
- ____________

Answer 48

Question 49

In the demercuration step, treatment with _______________ replaces C-Hg with C-H, resulting in the alcohol and a little pool of elemental liquid mercury that accumulates at the bottom of the flask.

Answer 49

sodium borohydride (NaBH4)

Question 50

Oxymercuration is also regioselective for the “______________” alcohol products!

Answer 50

Markovnikov
- The selectivity seems to be very good – one study found only about a 1% yield of the minor anti-Markovnikov alcohol product!!!!!

Question 51

The Mechanism of Oxymercuration Goes Through A 3-Membered “________________”

Answer 51

Mercurinium Ion
- similar to bridged halonium ion of Br & Cl