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chem > topic 17c: carboxylic acids > Flashcards

topic 17c: carboxylic acids Flashcards

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?

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

A

carboxylic acid + HCl (steamy fumes)

19
Q

acyl chlrodie + alcohol

A
  • ester + HCl
  • steamy fumes
20
Q

why acyl chlrodie + alcohol favoured over carb

A
  • faster reaction
  • NOT REVERSIBILE so better yeild
21
Q

acyl chloride + ammonia

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

acyl chlroide+ primary amine

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

condesntation polymer

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

how to form polyester

A
  • dicarboxylic acid + diol
  • diacyl chloride + diol
25
Q

problem with using acyl chlrodie

A

produces HCl

26
Q

polyesters environment

A
  • can be hydrolysed so biodegradable
  • as they have polar bonds
27
Q

how to hydrolyse polyester with acid

A
  • forms dicarboxylic acid and diol
28
Q

hydrolysing polyester with alkali

A
  • diol
  • dicarboxylic acid salt
29
Q

compare acid hydrolysis of ester and alkali hydrolysis (4)

A
  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
Q

HOW TO TURN a hydroxy nitrile into a carboxylic acidl

A
  • add strong acid
  • heat under reflux
  • hydrolysis
  • also forms ammonia**
31
Q

delta g both ways

A
  • -RTlnK
  • delta h - t delta s system
32
Q

why is the single bond O in the ester link from the alcohol

A
  • 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
Q

how to form acid chloride from carboxylic acid

34
Q

why is TMS peak so strong

A
  • 12 hydrogens in the same environemtn
35
Q

what radiation is used for NMR

A

radio waves

36
Q

why is O-H peak so broad

A

due to hydrogen bpnding

37
Q

problem with acyl chloride esterification

A

-HCl gas
toxic
use fume cupboard

38
Q

do carboxylic acids react with 2,4 dnp

39
Q

what happens in NMR hwen the H absorbs radio waves

A
  • spin changes
40
Q

why is use of acyl chloride faster (3)

A
  • 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
Q

2 conditions to ensure COMPLETE oxidation

A
  • excess oxidising agent
  • heat under reflux

chem (28 decks)

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