Carboxylic acid and derivatives
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- Created by: Hindleyc
- Created on: 04-12-18 16:28
Name?
Ending -oic acid no number necessary for acid group as on end of chain
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Where does numbering start from?
Carboxylic acid end
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What if carboxylic acids groups on both ends of the chain?
-dioic acid with e in name
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What is their acidity like?
Weak acids in water and only slightly dissociate
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What are they, however, strong enough to do?
Displace CO2 from carbonates
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EQN?
CH3CO2H(aq) =(reversible) CH3CO2^- (aq)+ H^+ (aq)
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Solubility?
Smaller carboxylic acids (up to C4) dissolve in water in all proportions
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What happens after this?
Solubility rapidly reduces
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Why do smaller ones dissolve?
Can hydrogen bond to water molecules (slightly negative o on C=O and +ve H on h2o)
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How are the carboxylic acid salts stabilised?
By delocalisation which therefore makes it more likely
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What does the delocalised ion have?
Equal C-O bond lengths so if it didn't occur the C=O bond would be shorter than C-O bond
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What has the Pi charge cloud done
delocalised and spread out- delocalisation makes more stable and therefore more likely to form
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What does strength of carboxylic acid depend on?
Stability of anions formed, less tech large delocalised, less stable ion, weaker acid
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Inc chain length?
Pushes e- density on the COO- ion making it more negative and less stable making acid less strong
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Propanoic vs ethanoic acidity?
ethanoic stronger
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Electronegative chlorine atom..
Withdraw electron density form COO- ion making it less negative and more stable making acid more strong
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Chloroethanoic acid vs ethanoic acid acidity>
Chloro more acidic
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What can carboxylic acids form salts with?
Metals alkalis and carbonates
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Acid + reactive metal=
Carboxylate salt and hydrogen
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Acid + alkali =
Salt and water
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Acid + metal carbonate =
salt + water + co2
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Acid + metal oxide=
Salt + water
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What can the effervescence caused by production of CO2 with carboxylic acids and solid sodium carbonate or aqueous sodium hydrogen carbonate be used for?
Functional group test for carboxylic acids
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Oxidation of methanoic acid?
Carboxylic acids cannot be oxidised by using oxidising agents but methanoic acid is an exception as its structure has effectively an aldehyde group
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What does this form +[O]
Carobnic acid that can decompose to give co2
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What is esterification
When carboxylic acids react with alcohol in the presence of a strong acid catalyst to form esters and water
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eg name of ester
Methyl propanate
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Where does -yl bit come from
alcohol that formed it and is next to single bonded oxygen (alchohol then cooh)
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Bit ending -anoate?
COOh and includes the C in the C=O bond
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What is this rxn usually
Condensation producing water but not always
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What is the rxn\?
Reversible
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What else is it?
Slow, needs heating under reflux (often for several hours or days) low yields and acid catalyst needed
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What acid catalyst?
H2SO4
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Uses as sweet smelling compounds?
Perfumes and flavourings (toxic, non soluble volatile and not react with water
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Solvents?
For polar organic substances eg glue and printing inks
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Although polar, what don't they do
Hydrogen bond as no H bonded to a highly electronegative atom- have lower bp than H bonded carboxylic acids and almost insoluble in water
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Plasticisers for polymers?
Often have limited flexibility bc can't move over each other so incorporating some plasticisers in polymer allows chain to move more easily and polymer can become more flexible
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Overall uses
Food, perfume industries, solvents and plasticisers
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how can esters be hydrolysed and split up?
by either heating with an acid or with sodium hydroxide
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Reagents with acid
Dilute HCL
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Conditions
Heat under reflux
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What is this the reverse RXN of
Ester formation
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What happens when ester hydrolysed?
Carboxylic acid and alcohol formed
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eqn
Ester+ water (reversible with H+ on top) =carboxylic acid and alcohol
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What does the carboxylic acid do?
reacts with water to reform OH- catalyst
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What is this reaction
Reversible and doesn't give a good yield of products
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Ester with Sodium hydroxide
Sodium salt and alcohol
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Reagents
Dilute sodium hydroxide
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Conditions
Heat under reflux
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What does this rxn do
Go to completion
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Ester + sodium hydroxide =
Sodium propanoate + methanol
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What is the carboxylic acid salt product?
the anion of the carboxylic acid
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What is the anion resistant to?
Attack by weak nucleophiles such as alcohol so rxn isn't reversible
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Other cards in this set
Card 2
Front
Where does numbering start from?
Back
Carboxylic acid end
Card 3
Front
What if carboxylic acids groups on both ends of the chain?
Back
Card 4
Front
What is their acidity like?
Back
Card 5
Front
What are they, however, strong enough to do?
Back
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