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OChem 1 > Quiz 6 > Flashcards

Quiz 6 Flashcards

1
Q

Tertiary sulfonates will undergo — in strongly basic reagants and — — in polar protic solvents

A

E2 and unimolecular reactions

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2
Q

when forming a sulfonate is there inversion of the carbon attatched to the oxygen?

A

no, there is no inversion of the carbon because the sulfonate group is “strapped” to the oxygen not the carbon

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2
Q

What is the beginning step in any conversion of OH into a better leaving group?

A

a proton transfer so the OH can be converted into H2O which is a good leaving group

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2
Q

When converting alcohols into better leaving groups what kind of reagant will produce a substitution reaction?

A

An HX regant

X= a halogen

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2
Q

What kind of alcohols will undergo an E1 reaction

A

tertiary alchols treated with Heat and H2SO4

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3
Q

what kind of alcohols will undergo an SN1 reaction?

A

primary or secondary alcohols

dont forget about carbocation rearrangements

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3
Q

What are the three steps to retrosynthesis?

A
  1. identify a bond that can be broken or formed
  2. select suitable reagants and substrated to break or make that identifed bond
  3. draw the forward reaction

dont forget to count your carbons

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4
Q

Addition Reactions

A

Two things are added to either side of a pi bond and pi bond is protonted to form a singma bond

can be seen as a reverse elimination reaction (X added, pi bond broken)

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5
Q

Addition reactions are made possible because?

A

pi bonds can act as weak bases or weak nucleophiles

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6
Q

True or false?

addition and elimination reactions are favored at low temperatures?

A

False, addition is favored at low temperatures and elimination is favored at high temperatures

bc/ G needs to be negative for a spontaneous process

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7
Q

Hydrohalogenation

A

addition of a halide and proton to an alkene

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8
Q

does hydrohalogenation follow markovnikovs rule?

A

yes

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9
Q

what are the mechanistic steps of hydrohalogenation?

A
  1. pi bond is protonated to form a carbocation intermediate
  2. nucleophilic attack by halide
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10
Q

What is the rate determining step for hydrohalogenation?

A

the formation of the carbocation intermediate

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11
Q

True or false?

Hydrohalogentation is unlike SN1 if a re-arrangment is possible there will be no mixture formed

A

false, if a rearrangment is possible for a hydrohalogenation reaction then the products will be a mixture of with and without the rearrangement

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12
Q

Markovnikovs rule

A

the proton will be placed on the less substitued end of the alkene (place with more H already present)

X will go on more substituted end (or whatever other group it is)

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13
Q

Explain the stereochem of hydrohalogenation

A

if the addition of a group produces a chiral center a racemic mixture of both R and S is formed

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14
Q

Acid catalyzed hydration

one of three possible hydration reactions

A

the addition of OH and H across an alkene in the presence of an acid

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15
Q

the rate of a acid catalyzed hydration reaction depends on —–

A

the substitution of the alkene, the more substitued the better

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16
Q

What are the mechanistic steps of Acid catalyzed hydration?

A
  1. protonation of the pi bond by the acid
  2. addition of H2O
  3. Proton transfer to get rid of any charges
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17
Q

— acid will favor products in an acid catalyzed hydration

A

dilute acid

18
Q

— acid will favor reactants in acid catalyzed hydration

A

concentrated acid

19
Q

Stereochem of Acid cataylzed Hydration

A

similar to hydrohalogenation, if a chiral center is formed by the addition of a group then a racemic mixture will be formed

20
Q

Hydroboration Oxidation

third of three hydration reactions

A
  • anti markovnikov addition of water using BH3 to stabilize any charges that would form

OH is added to less substituted side and H on more substitued side

21
Q
A
22
Q

What are the two mechanistic steps to hydroboration oxidation?

A
  1. hydroboration attatches to less substitued side of alkene, triggering simultaneous hydride shift
  2. Boron group is replaced with oxygen group
23
Q

explain the eletronic and steric reasons why anti markovinikov addition is seen in hydroboration oxidation

A
  1. electronic reasons: positive charges form on more substitued positions so as a partial charge is forming BH3 must attatch to the less substitued positon
  2. Steric reasons: BH3 is larger than just H so it attaches to the less substitued positon to reduce steric interactions
24
Q

Explain the stereochem of hydroboration oxidation

A
  • syn addition: OH and H groups are added on same side as each other
  • anti markovnikov
25
Q

If one chiral center is formed for hydroboration oxidation?

A

an enantiomer is observed

26
Q

If two chiral centers are formed in hydroboration oxidation?

A

syn addition is a requriement and they are added on the same side (only the both wedged and both dashed stereoisomers are seen)

27
Q

Oxymercuration Demercuration

two of three hydration reactions

A

markovnikov addition of water across an alkene using a mercurium atom to stabilize charges

28
Q

What are the mechanistic steps of oxymercuration demercuration

A
  1. mercuric acetate dissociates in mercurium cation and attatches to the less substitued side of alkene to form cylic intermediate
  2. nucleophilic attack on more substitued side of alkene
  3. dermercuration: mercurium cation is removed and replaced with H
29
Q

sterochem of oxymercuration demercuration

A
  • anti addition: H and O group added to opposite sides of each other
  • if a chiral center is formed racemic mixtures are observed

racemic mixtures are also seen in acid catalysed and hydrohalogenation

30
Q

catalytic hydrogenation

A

addition of two H with the use of a metal catalyst

31
Q

What is the stereochem of catalytic hydrogenation

A

syn addition is observed when two chiral centers are formed

look out for meso compounds

32
Q

— alkenes will produce meso compounds

A

symmetrical

33
Q

what does the metal cataylst do to aid in the addition of hydrogens across the alkene?

A

it coordinates the molecule and adsorbds the hydrogens

34
Q

Halogenation

A

addition of two halogens across an alkene

only addition of Cl or Br

35
Q

stereochem of halogenation

A

anti addition bc of cylic intermediate

36
Q

how does the cylic intermediate create anti addition in halogenation

A

it triangle ring occupies either the top or the bottom of the molecule so the nucleophile in the second step must attack opposite to the triangle ring

37
Q

mechanistic steps of halogenation

A
  1. pi bond attacks Cl2 or Br2 (nucleophilic attack + llg)
  2. solo halogen created in step one attacks molecule from opposite side
38
Q

Halohydrination

A

X + OR group added across an alkene

39
Q

mechanistic steps of halodhydrin

A
  1. pi bond attacks Cl2 or Br2 + llg
  2. OR group attakcs opposite side of molecule
  3. proton transfer to create neutral product
40
Q

stereochem of halohydrin

A

anti bc of cylic intermediate

41
Q

regiochem of halohydrin

A

OR group attacks more substitued carbon where an electrophilic carbocation would have been likely to form

42
Q

Dihydroxylation

A

addition of two OH groups across an alkene

43
Q

syn dihydroxylation

A

OH groups are added to the same side

concerted rxn

44
Q

anti dihydroxylation

A

OH groups are added to the opposite sides bc of cylic intermediate

45
Q

What reagant promotes anti dihydroxylation?

A

peroxy acids, MCPBA

46
Q

what reagant promotes syn dihydroxylation?

A

cold potassium permanganate or a osmate esther group

47
Q

ozonolysis

A

C=C bond is split by O3 (ozone) to form C=O bonds

48
Q

what is the only reaction we know to make ketones and aldehydes?

A

ozonolysis

OChem 1 (8 decks)

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