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Ochem 2 > Quiz 6 > Flashcards

Quiz 6 Flashcards

1
Q

Four ways to prepare Esters

A
  1. via Sn2
  2. fischer esterification
  3. Bayer village reaction
  4. alcoholysis of acid halides
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2
Q

What are the reagents to prepare an ester via Sn2

A

carb acid and strong base + alkyl halide

alkyl halide must be primary

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3
Q

What are the reagents to create an ester via fischer esterificaiton?

A

carb acid + alcohol group and acid catalyst

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4
Q

Mechansim of Fischer esterifiaction

A

1.pt to create better e-
2. nuc attack by alcohol group
3. pt to create neutral intermediate
4. pt to create better LG
5. LLG
6. pt to create neutral product

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5
Q

Saphonification/base catalysed hydrolysis of esters

A

ester + NaOH and an acid = carb acid

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6
Q

Why does base catalyzed hydrolysis of ester require an acid

A

bc the carb acid gets deprotonated by the -OR group and the acid re protonates the carb acid

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7
Q

Acid catalyzed hydrolysis of esters

A

ester +H3O+ = carb acid

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8
Q

mechanism for acid catalyzed hydrolysis of esters

A
  1. pt to create better e-
  2. nuc attack by water
  3. pt to create neutral intermediate
  4. pt to create better LG
  5. LLG
  6. pt to create neutral product
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9
Q

Three ways to reduce esters
(One New Way)

A
  1. LAH + ester = 1 alcohol
  2. ester + xs grignard = 3 alcohol
  3. DIBAH + ester = aldehhyde (New way)
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10
Q

Is DIBAH stronger or weaker than LAH

A

weaker/milder, it stops the reaction at the aldehyde

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11
Q

What is the most efficent way to prepare amides?

A

via a acid halide + amine

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12
Q

Acid catalyzed hydration of amides

same as acid catalyzed hydration of esters

A

amide + H3O+ = carb acid
1. pt to create better electrophile
2. nuc attack
3. pt for neutral intermediate
4. pt for better LG
5. LLG
6. pt for neutral product

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13
Q

Base catalyzed hydration of amides

A

amide + NaOH and H3O+
1. nuc attack
2. LLG
3. pt from carb acid to N- LG
4. 2nd pt to restore carb acid by H3O+

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14
Q

Reduction of amides

A

amides + xs LAH and H2O = amine
1. nuc attack by LAH
2. LLG
3. 2nd nuc attack by LAH

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15
Q

what is the intermediate for reduction of an amide?

A

imine intermediate

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16
Q

What are the two ways to prepare nitriles?

A
  1. alkyl halide + NaCN = R-CN
  2. amide + SOCl2 = R-CN
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17
Q

Acid hydrolysis of nitriles

A

R-CN + H3O+ and heat = carb acid

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18
Q

what is the intermediate for acid hydrolysis of nitriles?

A

amide

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19
Q

Basic hydrolysis of nitriles

A

NaOH and H3O+ + heat = carb acid

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20
Q

What is the intermediate for basic hydrolysis of nitriles?

A

amide

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21
Q

Nitriles and grignard reagents

A

R-CN + grignard reagent and H3O+ = ketone

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22
Q

What is the intermediate for nitrile + grignard reagent reaction?

A

imine intermediate

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23
Q

Reduction of nitriles

A

R-CN + xs LAH and H2O= amine

24
Q

What reaction is similar to the reduction of nitriles (aka has the same product)

A

reduction of amides using xs LAH

25
Q

True or false?

The alpha position for a carbonyl containing molecule is the C conneced to the carbonyl bond

A

false, it is the adjacent carbons with the highly acidic protons

26
Q

Enol

A

an overall neutral molecule that is a tautomer of a ketone

27
Q

What factors may lead to the enol being favored over the ketone?

A
  1. if the enol is conjugated
  2. if the enol is aromatic
  3. if the enol can form intermolecular hydrogen bonds with others
28
Q

Tautomers

A

two rapidly interconverting constiutional isomers that differ in double bond and proton placement

29
Q

Acid Catalyzed tautomerization

A
  1. pt to create resonance stabilized cation
  2. pt to create adjacent double bond
30
Q

Base catalyzed tautomerization

A
  1. pt to create resonance stabilized anion
  2. pt to create OH of enol
31
Q

enolates

A

over all negativley charged and act as nucleophiles

32
Q

What are the two kinds of attacks enolates can perform? And which is favored?

A

C attack and O attack
- C attack is favored

33
Q

What kinds of bases do you choose for reversible enolate formation?

A

mildly strong bases where the ketone can also exist with the enolate

34
Q

What kind of bases do you chose for non reversible enolate formation?

A

very strong bases like LDA and NaH

35
Q

why are the protons of a di ketone so acidic?

A

because they have three resonance structures compared to the one resonance structure of a standard ketone

36
Q

Alpha halogenation of ketones in acidic condtions

A

Ketone +H3O+ and Br2 = bromine at the most substituted position

37
Q

mechanism of alpha halogenation of ketones in acidic conditions

A

pt 1: forming the enol
- pt to create resonance stabilized cation
- pt to create most stable enol
pt 2: forming product
- nuc attack by enol on Br2
- pt to create neutral product

38
Q

Alpha halogenation in basic conditions

A

ketone + NaOH and Br2 and an acid = bromination at the less substituted alpha carbon or a carboxylic acid

39
Q

True or false? Monobromination is not possible for basic halogenation at the alpha position?

A

True, bromines will be added until there are no alpha protons left, this often results in a LG

39
Q

How is the alpha halogenation under basic conditions similar to the reaction of an ester to a carboxylic acid under basic conditions?

A

This reaction also requires an acid to protonate at the end bc the LG steals the proton

39
Q

Hell-volhard- Zelinsky reaction

A

carb acid + PBr3 and Br2 = bromine at the alpha position of the carb acid

40
Q

Aldols

A

molecules with an aldehyde and a alcohol

41
Q

mechanism for aldol formation

A
  1. pt to create enolate
  2. nuc attack by enolate on aldehyde
  3. pt to create alcohol group
42
Q

Crossed aldol reactions

A

reactions between two aldehydes or a ketone that are not the same

43
Q

What are the two ways you can prevent all the messy products from crossed aldol reactions?

A
  1. by using one reagent that has no alpha carbons or alpha protons and is unhindered
  2. treat one reagent with a strong base like LDA for irreversible enolate formation and then add in second aldehyde/ketone
44
Q

Retro aldol reaction

A

if a ketone was one of the reagents in the aldol formation the ketone will be favored
- the part of the molecule with the C=O is the original enolate, start there

45
Q

mechanism for retro aldol formation

A
  1. pt to create alkoxide
  2. LLG by resonance
  3. pt to create final ketone
46
Q

Aldol condensation reaction

A

aldol product is treated with a base and heat to lose the OH group and form a pi bond

47
Q

mechansim for aldol condensation

A

pt 1: aldol formation
1. pt to create enolate
2. nuc attack by enolate
3. pt to create alcohol
pt 2: condensation
4. pt to create alkoxide
5. LLG to form new pi bond

48
Q

What is the driving force behind aldol condensation reactions?

A

to form a conjugated system

49
Q

True or false?

The aldol condensation reaction is favored at all temperatures

A

False, at extremely cold temperatures it can be less favored and even the addition product can be favored

50
Q

In both claisen condensation and aldol intramolecular reactions what kind of rings are most favored to form?

A

5 or 6 membered rings bc they contain the least amount of ring strain

51
Q

Claisen condensation

A

aldol condensation reactions but with esters
- ester + Na Matching O- base and H3O+ = claisen product

52
Q

Mechanism for claisen condensation

A
  1. pt to create enolate
  2. nuc attack by enolate
  3. LLG
  4. pt
  5. pt to restore neutrality
53
Q

What is necessary to proceed with the claisen reaction?

three things

A
  1. at least two alpha protons on the ester
  2. NO NaOH
  3. O- base must match the R group on the ether part of the ester
54
Q

Diekmann cyclization

A

the intramolecular claisen condensation

-same as aldol intramolecular just a diff name

Ochem 2 (7 decks)

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