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organic sem 2 > 6b > Flashcards

6b Flashcards

1
Q

what does the reactivity of carboxylic acids and their derivatives depend on

A

the degree of delocalisation the substituent has

aka the e- donating power of the substituent

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2
Q

rate carboxylic acid derivatives from least delocalising to most delocalising

A
  • acyl chloride (weak - e- negative)
  • anhydride (e- negative and 2 diff resonance structures)
  • ester (some delocalisation of lone pair)
  • amide (strong delocalisation - N isnt as electronegative)
  • carboxylate ion (complete delocalisation)
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3
Q

acyl chloride to carboxylic acid

A

h20
20*C
fast reaction

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4
Q

acid anhydride to carboxylic acid

A

h20
20*C
slow

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5
Q

ester to carboxylic acid

A

h20
heat
acid / base catalyst

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6
Q

amide to carboxylic acid

A

prolonged heating
strong acid/ base catalyst

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7
Q

electrohilicilty and degree of delocalisation

A

more delocalisation = less + charge = less likely to be attacked by nucleophiles = less electrophilic.

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8
Q

carboxylic acid to acyl chloride

A

carb acid

Cl – s = o – Cl

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9
Q

what is a fischer reaction

A

carboxylic acid to ester reaction

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10
Q

what is needed in a fischer reaction

A

carboxylic acid
H2SO4 / HCl catalyst
PRIM / SEC ALCOHOL R-OH

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11
Q

describe the fischer reaction

A

carb acid to ester
=o is protonated

1-2-addition of alcohol to C+

deprotonation of alcohol

protonation of OH to form water

OH lone pair kicks off water

OH is deprotonated by water

ester is formed

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12
Q

acyl chlorides to esters

A

acyl chloride
base
alcohol

gives an ester

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13
Q

why can tertiary alcohols not react with carboxylic acids to form esters

A

too bulky

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14
Q

when is a fischer reaction used

A

when u need to make simple esters

methyl // ethyl esters

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15
Q

rds of fischer reaction

A

addition of alcohol

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16
Q

acyl chlorides to esters mechanism

A

alcohol attacks electrophilic C

alcohol is deprotonated by a base

O- kicks of Cl

ester is formed.
Cl- is formed

17
Q

when are esters made from acyl chlorides

A

when u need specific // complex esters

18
Q

why is a base used for acyl chloride mechanisms

A

u want to quench the HCl - u dont want it to form

19
Q

what base can be used for acyl chloride to ester synthesis

A

pyridine

20
Q

what esle can be used instead of cab acids and acyl chlorides to give esters

A

acid anhydrides can also be used

21
Q

what is the rds of acyl chloride to ester synthesis

A

alcohol attacking electrophilic carbon..

alcohol nucleophilic attack.

22
Q

what is a transesterification reaction

A

switching from one ester to a different ester

23
Q

what is needed in an acid catalysed transesterification reaction

A

ester
alcohol osolvent
H+ catalyst
heat and reflux

24
Q

acid catalysed transesterification reaction mechanism

A

O is protonated
alcohol attacks C
old ester group is kicked off by OH lone pair

O is deprotonated

new ester is formed.
we protonate the group we want to remove

25
Q

ester to carb acid

A

acid catalysed hydrolysis of esters

26
Q

what is needed in the acid catalysed hydrolysis of an ester to a carboxylic acid

A

ester
H3O+
H2O

27
Q

acid catalysed hydrolysis of ester to carb acid mechanism

A

o is protonated by H3O+
water attacks C
water is deprotonated
water is protonated
ester is kicked off

carboxylic acid is formed

28
Q

how else can a ester be hydrolised to give a carboxylic acid

A

base catalysed hydrolyis

29
Q

what is needed in the base catalysed hydrolysis of an ester to give a carb acid

A

ester
NaOH
H20

30
Q

why is base catalysed hydrolysis of an ester to give a carboxylic acid preferred

A

bc its irreversible

the final product is a carboxylic acid

31
Q

base catalysed hydrolysis of ester to give a carboxylic acid can also be called

A

SAPONIFICATION

32
Q

describe a saponification reaction

A

base catalysed hydrolysis from ester to carboxylic acid.

OH attacks carbon

ester is protonated

O- kicks off ester

carboxylic acid is formed

33
Q

acyl chloride to amide needs

A

acyl chloride
excess amine

gives an amide

34
Q

acyl chlorides to amides mechanism

A

amine // ammonia attacks the C

ammonia is deprotonated

O- kicks off cl

35
Q

why cant carboxylic acids react with ammonia//amines

A

carboxylic acids are acids

amines + amides are basic

they form ammonium salts

20*C.

36
Q

acid catalysed hydrolysis of amides

A

amide + H3O+ + h20 gives a carboxylic acid

O is protonated,, water attacks C,, water is deprotonated,, amine is protonated

lone pair on O kicks off amine

water neutralsises Oxygen

carboxylic acid is made

37
Q

in nature,, what turns esters into carboxylic acids

A

esterase enzymes

38
Q

in nature,, what turns amides into carboxylic acids

A

amidases

organic sem 2 (14 decks)

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