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ORGO 2 > Unit 4 (Lesson 21-27) > Flashcards

Unit 4 (Lesson 21-27) Flashcards

1
Q

what facilitates nucleophilic substitution occurring on CAD

A

facilitated by the presence of a leaving group on the carbonyl carbon

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2
Q

leaving group example

A

OR, Cl, NH2, OCOR

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3
Q

not leaving group example

A

H, R, Ar

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4
Q

reactivity of carboxylic acid derivatives is based on

A
  1. leaving group ability of X
  2. Electrophilicity of carbonyl carbon
  3. Steric hindrance
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5
Q

strongest resonance contributing structure has

A

negative O and positive N

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6
Q

why are amides particularly ureactive toward nucleophilic attack

A

due to the resonance contribution from N

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7
Q

order of reactivity of carbonyl derivatives (most to least)

A

acid chloride > anhydride > ester > amide > carboxylate

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8
Q

reactivity of carboxylic acid derivative increases/decreases with decreasing basicity of leaving group

A

increases

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9
Q

why is acid chloride not found in nature

A

because it is so reactive

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10
Q

how do you make acid chloride from an acid/carboxylate

A

SOCl2, or PCl3

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11
Q

do acid halides require any acid or base to facilitate substitution

A

no - already extremely reactive

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12
Q

three different reaction perturbations with acyl halides

A

1.) negatively charged nucleophile
2.) neutral nucleophile
3.) neutral nucleophile with catalytic acid

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13
Q

reactants for hydrolysis of an acid chloride

A

H2O
* deprotonate before kicking out Cl

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14
Q

to from amide:

A
  • at least 2 equivalents of amine must be used to push the reaction to completion
  • add 1 equivalent of a primary or secondary amine AND one equivalent of a tertiary amine (pyridine)
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15
Q

what are the methods for forming an anhydride

A
  • from an acid halide
  • from a carboxylic acid
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16
Q

anhydride to ester

A

ROH(alcohol) or RO- + pyridine

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17
Q

carboxylate/acid to an ester

A

ROH (alcohol)
H+ (catalytic acid)

[strong base/CH3Br, alc/pyridine] –> will work as well

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18
Q

what controls the rate of reaction for the esterification of carboxylic acids

A

steric hinderance
- proceeds through a series of reversible steps

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19
Q

carboxylic acids only undergo nucelophilic acyl substitution when they are in their () forms

A

acidic
WHY – basic form makes it resistant to an approach from an electrophile –> carboxylate ions less reactive than amides in nucleophilic acyl substitution

20
Q

why are esters not strongly electrophilic

A

due to the strong resonance contribution from the oxygen
– reactions with esters require better nucleophiles or stronger conditions than reactions with acid chlorides and anhydrides

21
Q

three different reaction perturbations for esters

A

1.) negatively charged nucleophile
2.) neutral nucleophile (must be good nucleophile)
3.) neutral nucleophile with catalytic acid

22
Q

the strength of the () and () determines the reaction conditions and mechanisms

A

electrophile, nucleophile

23
Q

transesterification

A

one alcohol is used in excess to drive the equilibrium in the desired direction

24
Q

basic conditions

A

no (+) intermediates

25
Q

acidic conditions

A

no (-) intermediates

26
Q

true/false: esters and carboxylic acids are around the same energy/reactivity

A

true

27
Q

will an ester and H2O molecule react

A

no – needs an acid catalyst

28
Q

which of the carboxylic acid derivatives are unlikely to undergo a nucleophilic reaction with a Grignard reagent

A

amides and carboxylic acids
WHY – protic hydrogens

29
Q

true/false: addition to the ketone is faster than the addition to the ester

A

true

30
Q

true/false” addition to the aldehyde his faster than the addition to the ester

A

true

31
Q

DiBAL-H reduction of esters leads to what

A

aldehyde formation

32
Q

true/false: carboxylic acids can be reduced to primary alcohols with LiAlH4

A

true

33
Q

NaBH3CN

A
  • selective
  • only reduces imines and enamines to secondary and tertiary amines
34
Q

amide to carboxylate/acid

A

1 eq HCl, H2O, heat
or NaOH then H3O+, heat

35
Q

why are amides not very electrophulluc

A

due to the strong resonance contribution from the nitrogen
– recall 2 peaks for N-CH3’s of an amide in an H1NMR due to the barrier of rotation around the C-N bond

36
Q

are amides stable

A

yes - very - due to excellent orbital overlap and resonance contribution

37
Q

what do reactions with amides require

A

very good nucleophiles and/or strong bases

38
Q

2 different reaction perturbations for amides

A

1.) negatively charged nucleophile
2.) neutral nucleophile with catlalytic acid/base and heat

39
Q

amide hydrolysis: acidic conditons

A

no negatively charged intermediates
pattern of intermediates: (charge –> neutral –> charge)

40
Q

amide hydrolysis: basic conditions

A

no positively charged intermediates
pattern of intermediates: (charge –> neutral –> charge)

41
Q

how can nitriles be transformed in to carboxylic acid

A

through hydrolysis or an amine via reduction

42
Q

true/false

A

the sp-hydridized carbon of a nitrile is moderately electrophilic and reacts with a strong base or in the presence of a strong acid
c-c bond is made

43
Q

2 reaction perturbations for nitriles

A

1.) negatively charged nucleophile
2.) neutral nucleophile with acid (1.0 equiv) and heat

44
Q

fischer esterification only works if alcohol has less than () carbons

A

three

45
Q

electron withdraw from the carbonyl carbon increases/decreases its electrophilicity

A

increases

46
Q

true/false: the carbonyl carbon is electrophilic and is susceptible to nucleophilic attack under the right condittions

A

true

ORGO 2 (10 decks)

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