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Organic Chemistry I > Organic Reaction Mechanisms > Flashcards

Organic Reaction Mechanisms Flashcards

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1
Q

In epoxide ring opening, which method results in the production of the more subsituted alcohol?

A

Base catalyzed ring opening

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2
Q

What does acid catalyzed epoxide ring opening result in? (3 things)

A

The attack of the solvent on the most substituted carbon of the epoxide ring.

Because the carbocation is stabilized by hyperconjugation.

The produced alcohol is on the lesser substituted carbon of the previous epoxide ring.

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3
Q

What are the 3 ways to convert an alcohol to an alkyl halide? Through which mechanism do these proceed by?

A
  1. SOCl2/pyridine
  2. PBr3
  3. H-X

All 3 can proceed through Sn2 but 3 is dependent on the substitution of the alcohol

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4
Q

What are the 6 sulfonate esters that we should know?

A

Triflate, trifyl chloride, tosylate, tosyl chloride, mesylate, mesyl chloride

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5
Q

What is the best sulfonate ester/leaving group? Why?

A

As far as we know, triflate as it is stabilized by resonance and the presence of 3 highly electronegative fluorine atoms.

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6
Q

Mechanism-wise, which mechanism is most similar to sulfonate ester formation?

A

SOCl2/pyridine mechanism

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7
Q

What conditions are needed to convert an alcohol to a sulfonate ester?

A

Sulfonate ester halide and pyridine

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8
Q

How is X2 added to an alkene?

A

Anti and thus produces a trans-dihalide

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9
Q

What reaction conditions are needed to produce halohydrins? What is the product?

A

X2 and H2O; produces a racemate of trans-halodryins

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10
Q

What do the leaving group and hydrogen need to be during elimination (dehydration) reactions?

A

Anti-periplanar on adjacent atoms

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11
Q

What reaction conditions are needed to produce epoxides?

A

mCPBA

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12
Q

What is acid activation?

A

This is the process of turning a bad leaving group (like OH-) into a good leaving group by protonating it with a strong acid

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13
Q

What reaction conditions are needed to produce an internal alkyne and what is the substrate?

A

2 eq. of NaNH2 and NH4Cl (acidic workup); alkanes

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14
Q

What reaction conditions are need to produce a terminal alkyne and what is the substrate?

A

3 eq. of NaNH2 and NH4Cl (acidic workup); alkanes

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15
Q

What reaction conditions are needed to produce an alkane from an alkyne?

A

H2 and Pd/C

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16
Q

What reaction conditions are needed to product a cis-alkene from an alkyne?

A

H2 and Lindlar’s Catalyst

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17
Q

What reaction conditions are needed to produce a trans-alkene from an alkyne? What type of reaction mechanism does this follow?

A

Li or Na, NH3; follows a dissolved metal reduction radical mechanism

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18
Q

What product is formed from the addition of H-X to an alkene?

A

Markovnikov product

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19
Q

What is a Markovnikov product?

A

This is a product where the hydrogen is added to the least substituted carbon and thus the other species is added to the most substituted carbon

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20
Q

What is a Zaitsev product?

A

This is the most substituted alkene

21
Q

What is the Hoffman product?

A

This is the least substituted alkene

22
Q

What reaction conditions can be present to result in the production of a Hoffman product?

A

High temperatures (to promote elimination) and poor base/Nu (such as tert-butoxide)

23
Q

What is one of the most important rules when it comes to dealing with an active species?

A

It must be regenerated before the end of the mechanism

24
Q

What are the 2 methods of hydration that result in a Markovnikov alcohol?

A

Acid catalyzed and oxymercuration/reduction

25
Q

What is the method of hydration that results in an Anti-Markovnikov alcohol?

A

Hydroboration/oxidation

26
Q

What are the 2 methods of hydration that result in the absence for the possibility of carbocation rearrangements?

A

Oxymercuration/reducation and Hydroboration/oxidation

27
Q

What are the reaction conditions needed to produce a Markovnikov alcohol without the possibility of carbocation rearrangements?

A
  1. Hg (OAc)2/H2O
  2. NaBH4, NaOH
28
Q

What are the reaction conditions needed to produce an Anti-Markovnikov alcohol without the possibility of carbocation rearrangements?

A
  1. BH3-THF
  2. H2O2, NaOH
29
Q

What reaction conditions are needed to produce cis-1,2-diols?

A
  1. OsO4
  2. NaHSO3
    or
  3. KMnO4, KOH, H2O, 0 degrees
30
Q

What are the names of the 2 intermediates produced during ozonlysis of an alkene?

A

Trioxalane and ozonide

31
Q

What are the reaction conditions for ozonlysis and what does it produce?

A
  1. O3
  2. (CH3)2S or DMS

Produces 1 ketone, 1 aldehyde, and 1 DMSO

32
Q

How are alkoxides formed? (2 primary methods)

A

Na or K
OR
NaH, NaNH2, n-BuLi

33
Q

What are the steps to acid catalyzed ether synthesis? Substrate?

A

2 alcohols…
1. Acid activation with H2SO4
2. Second alcohol causes protonated hydroxide to leave
3. Pushed water deprotonates protonated ether

34
Q

What is the issue with acid-catalyzed ether synthesis?

A

For the production of asymmetric ethers, a mixture of products is produced due to the possibility of alcohols to behave as electrophiles or nucleophiles

35
Q

What is Williamson Ether synthesis?

A

This is the combination of an alkoxide and alkyl halide to form an ether

36
Q

What are the reaction conditions for a Williamson Ether synthesis?

A
  1. NaH, NaNH2, or n-BuLi
  2. polar aprotic solvent
37
Q

What is an interesting thing about molecules with both alkyl halide and alcohol groups in Williamson Ether conditions?

A

It will result in the production of a cyclic ether due to an intramolecular mechanism

38
Q

What reaction conditions are needed for the other oxidative cleavage mechanism? What is its name?

A

Oxidative cleavage with KMnO4
1. KMnO4, KOH, H2O, high temperatures

39
Q

What does oxidative cleavage with KMnO4 produce?

A

1 ketone, 1 aldehyde (which can then become a carboxylic acid)

40
Q

How can the diol in oxidative cleavage with KMnO4 be isolated?

A

By using cold KMnO4 instead of warm

41
Q

What does the oxidative cleavage of alkynes produce?

A

Both ozonolysis and KMnO4 product 2 carboxylic acids

42
Q

What does the oxidative cleavage of terminal alkynes produce?

A

Both ozonolysis and KMnO4 produce 1 carboxylic acid and 1 carbon dioxide

43
Q

What reaction conditions favour Sn2 reactions?

A

Low temperatures, polar aprotic solvents, low substituted substrates (prevents steric hindrance), small/highly basic/good nucleophiles

44
Q

What reaction conditions favour Sn1 reactions?

A

Low temperatures, polar protic solvents, high substituted substrates (stabilizes carbocations), poor nucleophiles

45
Q

What reaction conditions favour E2 reactions?

A

High temperatures, polar aprotic solvents, high substituted substrates (produces Zaitsev product), good/highly basic nucleophiles

46
Q

What reaction conditions favour E1 reactions?

A

High temperatures, polar protic solvents, high substituted substrates (produces Zaitsev product), poor nucleophiles

47
Q

What is a good rule of thumb referring to basicity with nucleophilicity and strenghth of a leaving group?

A

The stronger the base, the better the nucleophile and the worse the leaving group (vice versa for weaker bases)

48
Q

What factors make a nucleophile good?

A

Unstable (no resonance), charged, decreased electronegativity, increased polarizeability, and less substituted (but good bases are better when highly substituted)

49
Q

What factors make a leaving group good?

A

Stability (if it is a stable base, it is a good leaving group), poor electronegativity, and good polarizeability

Organic Chemistry I (1 decks)

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