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chem > topic 17c: carboxylic acids > Flashcards

topic 17c: carboxylic acids Flashcards

(41 cards)

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1
Q

functional group

A

-cooh

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2
Q

which carboxylic acids are solublce

A
  • up to c4
  • can form h bonds with water
  • but after this proption that can do this is lower
  • so insoluble
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3
Q

H bonding in ethanoic acid

A

forms a DIMER!!!!!!!!

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4
Q

Why are they so stable

A
  • pi electron cloud delocalises in c=o and spreads out
  • makes ion more stable, and very likely to form
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5
Q

which carboxylic acids are stronger and why (consider chain length)

A

-SHORTER ONES
- long alkyl groups = positive inductive effect, pushes e- density onto the coo-, making it less stable so WEAKER ACID

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6
Q

adding a chlorine onto the alkyl group effecton strength of acid

A
  • v electronegative so withdraws electron density from coo- ion
  • more stable, stronger acid
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7
Q

how to make from aldehyde (or alcohol)

A
  • oxidation
  • acidified potassium dichromate
  • heat under reflux
  • orange cr2o7 2- to green cr 2+
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8
Q

another method to preapre carboxylic acid

A
  • hydrolysis of nitrile
  • dilute HCl (include water in reaction)
  • heat under reflux
  • forms carb and ammonium salt

IF UNDER ACID CONDITIONS
- forms carboxylic SALT eg ch3coona and ammonia GAS

include the acid/alkali and the water in the reactions!!!!!!

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9
Q

reduction of carboxylic acid

A
  • LiAlH4 in dry ether
  • to primary alcohol
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10
Q

what is the only carboxylic acid that can be oxidised and to what

A
  • METHANOIC ACID (effectively an aldehyde)
  • forms carbonic acid
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11
Q

carboxylic acid + Pcl5

A
  • STEAMY HCl FUMES
  • acid chloride + POCl3 + HCl
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12
Q

carboxylic acid + alcohol

A
  • sulfuric acid catalyst
  • refluc
  • forms an ester
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13
Q

problem with acid and alcohol method

A
  • reversible
  • so smaller yeild
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14
Q

esters

A
  • sweet smelling liquids
  • used in perfumes and flavourings
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15
Q

how to hydrolyse ester, ACIDIC conditions

A
  1. dilute acid and heat under refluc
  2. forms carboxylic acid and alcohol
  3. reversible so bad yeild
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16
Q

how to hydrolyse ester ALKALI conditions

A
  1. add dilute sodium hydroxide
  2. heat under refluc
  3. forms alcohol and SODIUM CARBOXYLATE SALT. add a strong acid to protonate
  4. NOT REVERSIBLE
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17
Q

why is an acyl chloride much more reactive?

Study These Flashcards
A
  • Cl- a better leaving group than OH-
  • Cl- more electronegative so withdraws charge from c=o, so delta + on c stronger
18
Q

acyl chloride + water

Study These Flashcards
A

carboxylic acid + HCl (steamy fumes)

19
Q

acyl chlrodie + alcohol

Study These Flashcards
A
  • ester + HCl
  • steamy fumes
20
Q

why acyl chlrodie + alcohol favoured over carb

Study These Flashcards
A
  • faster reaction
  • NOT REVERSIBILE so better yeild
21
Q

acyl chloride + ammonia

Study These Flashcards
A
  • amide (add an NH2)
  • ammonium chloride (white smoke)
22
Q

acyl chlroide+ primary amine

Study These Flashcards
A
  • secondary amine (add nh)
  • Rnh3+ cl-
23
Q

condesntation polymer

Study These Flashcards
A
  • 2 monomers join together
  • small molecule given off, usually water
24
Q

how to form polyester

Study These Flashcards
A
  • dicarboxylic acid + diol
  • diacyl chloride + diol
25
problem with using acyl chlrodie
produces HCl
26
polyesters environment
- can be hydrolysed so biodegradable - as they have polar bonds
27
how to hydrolyse polyester with acid
- forms dicarboxylic acid and diol
28
hydrolysing polyester with alkali
- diol - dicarboxylic acid salt
29
compare acid hydrolysis of ester and alkali hydrolysis (4)
1. both make alcohol 2. acid reversible, alkali irreversible 3. acid gives carboxylic acid, alkali gives carboxylate salt 4. ACID A CATALYST, ALKALI REACTANT
30
HOW TO TURN a hydroxy nitrile into a carboxylic acidl
- add strong acid - heat under reflux - hydrolysis - also forms ammonia****
31
delta g both ways
- -RTlnK - delta h - t delta s system
32
why is the single bond O in the ester link from the alcohol
- it is the oxygen in the ethanol that acts as the nucleophile - the single bond c-o in the carboxylic acid is the one that breaks
33
how to form acid chloride from carboxylic acid
add PCl5
34
why is TMS peak so strong
- 12 hydrogens in the same environemtn
35
what radiation is used for NMR
radio waves
36
why is O-H peak so broad
due to hydrogen bpnding
37
problem with acyl chloride esterification
-HCl gas toxic use fume cupboard
38
do carboxylic acids react with 2,4 dnp
no
39
what happens in NMR hwen the H absorbs radio waves
- spin changes
40
why is use of acyl chloride faster (3)
- C-Cl weaker than C-O - Cl- a better leaving group than OH- - Cl more electronegative so withdraws charge from c=o, so c more positive, more susceptible to nucleophile attack
41
2 conditions to ensure COMPLETE oxidation
- excess oxidising agent - heat under reflux

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