Addition reactions of alkenes Flashcards

1
Q

Addition reactions

A

Reactions with alkenes where the double bond is broken & forms 2 new sigma bonds (Addition of 2 groups)

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2
Q

Addition reactions are the reverse reactions of an ____________ reaction

A

Elimination reaction

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3
Q

Addition reaction is favored at ____________

A

Low Temp.

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4
Q

Elimination reaction are favored at ___________

A

High temp

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5
Q

Are addition reaction usually exothermic or endothermic?

A

Exothermic

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6
Q

Hydrohalogenation

A

An addition reaction that involves hydrogen & a halogen (HX, X= cl, br, or I)

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7
Q

In a hydrohalogenation reaction the H is placed on a position that already has alot of hydrogens & the halogen is placed on the more ______________

A

Substituted position

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8
Q

Markovnikov addition

A

When the H is placed on a position that has alot of hydrogens & when the halogen is placed on the more substituted position

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9
Q

Anti-Markovnikov reaction

A

The halogen is placed on the less substituted position & the H is placed on the side that doesnt have much hydrogens

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10
Q

When _______ reagents are used then the reaction will occur as markovnikov addition

A

Pure

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11
Q

When _______ reagent are used such as peroxides (ROOR) then it will occur as an anti- Markovnikov addition

A

Impure

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12
Q

What is the mechanism for hydrohalogenation?

A
  1. Proton Transfer
  2. Nucleophilic Attack
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13
Q

The regioselectivity for hydrohalogenation is what?

A

Markovnikov Addition

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14
Q

Hydrohalogenation products will have __________ centers where a pair of enantiomers will be observed

A

Chirality Center

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15
Q

Hydration

A

Addition of water (H & OH) across a double bond

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16
Q

Acid- Catalyzed Hydration

A

Addition of water across a double bond in the presence of an acid

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17
Q

The regiochemsitry of an Acid Catalyzed Hydration is what?

A

Markovnikov addition

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18
Q

What is the mechanism for an Acid - Catalyzed Hydration?

A
  1. Proton Transfer
  2. Nucleophilic Attack
  3. Proton Transfer
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19
Q

In an Acid - Catalyzed Hydration how do you control the position equilibrium?

A

Can control the position of equilibrium by controlling the amount of water present (Using either concerated or dilute acid)

20
Q

What is the stereochemistry of Acid-Catalyzed Hydration?

A

The intermediate carbocation can be attack from either side so it forms a new chirality center & a racemic mixture of enantiomers

21
Q

Oxymercuration - Demercuration

A

Addition of water (H & OH) across a double

22
Q

Mercuric Acetate

A

Hg(OAc)2

23
Q

When the double bond (π bond) is protonated in an oxymercuration - demercuration reaction what happens?

A

A carbocation intermediateis formed

24
Q

When the double bond (π bond) is attacked by a mercuric cation what happens?

A

An Mercurinium ion is formed

25
Q

The regiochemistry of an oxymercuration-demecuration is what?

A

A Markonvikov addition

26
Q

Demercuration

A

Removal of mercury occurs by a radial reaction & results in the addition of H & a nucleophile (which is usually water

(H2O)

27
Q

Hydroboration - Oxidation

A

Places the OH group on the less substituted position

28
Q

What is the regiochemistry of an Hydroboration - Oxidation Reaction?

A

Anti- Markovnikov addition

29
Q

What is the stereochemistry of a Hydroboration - oxidation reaction ?

A

Syn Addition (The prodcuts chirality centers have the H & OH on the same plane (Cis conformation))

30
Q

If there is no chirality center formed in an hydroboration-oxidation reaction then what are the outcome of the products?

A

There will only be one product formed

31
Q

When only one chirality center present in the products of an hydroboration - oxidation reaction then what is the outcome of the products?

A

Both enantiomers are observed

32
Q

When there is two chirality center present in the products of an hydroboration reaction then what is the outcome of the products?

A

The chirality center are formed by a syn addition (So they are on the same plane) & a pair of enantiomer is observed

33
Q

Catalytic Hydrogenation

A

Involves the addition of molecular hydrogen (H2) across a double in the presence of a metal catalyst

34
Q

What is the stereochemistry of catalytic hydrogenation ?

A

When two new chirality center are formed then a pair of enantiomers are formed by a syn addition

35
Q

What are the common heterogenous Catalyst in a catalytic hydrogenation reaction?

A

Pt, Pd, & Ni (They dont dissolve in a reaction)

36
Q

What is the common homogeneous catalyst in a catalytic hydrogenation?

A

Wilkinson’s Catalyst (Rh(PPh3)3Cl)

37
Q

Halogenation

A

Involves the addition of X2 (Either Br2 or Cl2) across an alkene

38
Q

What is the regiochemistry of halogenation reaction?

A

Anti-Markonvikov addition

39
Q

What is the stereochemistry of an halogenation reaction?

A

Anti Addition where the products will have the halogens on the opposite planes

40
Q

In an Halohydrin reaction the OH is placed on what?

A

the more substituted position

41
Q

What is the indications of a halohydrin reaction?

A

When you have a halogenation (either Br2 or Cl2) as a reagent & water as the solvent (Adds a halogen & OH across a double bond & the OH is placed on the more substituted position )

42
Q

Dihydroxylation

A

Adding two OH

43
Q

Halohyrin can make an epoxide through an ________ reaction

A

SN2

44
Q

Ozonolysis Reaction

A

A reaction that cleaves the double bond ( The common reagents are DMS & ZN/H2O)

45
Q

What do have consider when predicting the products of an addition reaction?

A
  1. What groups are being added across a double bond
  2. What is the expected regiochemistry (markovnikov addition or anti- markovnikov addition)
  3. What is the expected stereochemistry (Syn or Anti addition)
46
Q

How do you change the position of a leaving group?

A
  1. Elimination reaction
  2. Addition reaction
47
Q

How do you change the position of a double bond (π bond)?

A
  1. Addition reaction

2 Elimination reaction