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chemistry > Carboxylic acids and Esters > Flashcards

Carboxylic acids and Esters Flashcards

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1
Q

What is the carboxylic acid funtional group?

A
  • It is COOH
  • The group can only be at end of a carbon chain
    *
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2
Q

How do you name carboxylic acids?

A
  • The suffix -oic acid is used
  • The C of the functional group is counted as part of the overall chain
  • When there’s side chains/substituents they are numbered from the C of functional group
  • When functional group attached to benzene the suffix -carboxlic acid used and C of functional group not counted as part of overall chain
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3
Q

Name the following compound:

A

Methanoic acid

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4
Q

Name the following:

A

3-methyl butanoic acid

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5
Q

Name the following compound:

A

Benzenecarboxylic acid

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6
Q

What are the properties of carboxylic acids?

A
  • OH group in carboxylic acids is much more acidic then OH in alcohols
  • Carboxylic acid group can form hydrogen bonds with water molecules so up to butanoic acid they are completely soluble in water
  • Acids can form hydrogen bonds with each other in solid state so have higher Mpts than alkanes of similar relative molecualr mass
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7
Q

What is the formula of an ester?

A
  • It is RCOOR
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8
Q

How do you name esters?

A
  • Alcohol is named first with suffix -yl
  • Acid is named second with suffix -oate
  • COO part is alcohol and other part is acid
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9
Q

Name the following compound:

A

Methyl ethanaote

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10
Q

Describe the reactvity of carboxylic acids:

A
  • The carboxylic acid group is polarised
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11
Q

What are the 3 usual acid reactions that take place?

A
  1. acid + metal → salt + hydrogen
  2. acid + alkali → salt + water
  3. acid + carbonate → salt + water + carbon dioxide
  • The suffix -oates are used to name salts
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12
Q

How are esters formed from carboxylic acids?

A
  • Carboxylic acids react with alcohols to form esters and water. The reaction speeded up by strong acid catalyst and called Esterfication.It is also reevrsible.
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13
Q

What 2 ways are esters hydrolysed?

A
  1. acid catalysed hydrolysis - heat under reflux with dilute HCL/H2SO4 .Doesn’t go to completion and produces equilbrium misture of ester,water,acid and alcohol.
  2. base catalysed hydrolysis - heat under reflux with dilute NaOH (aq). This way salt of acid produced rather than acid itself.Acid is removed from reaction mixture so equilibrium not established and reaction goes to completion.
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14
Q

What 2 ways can carboxylic acids be made?

A
  1. Oxidation of primary alcohols or alcohols using acidified potassium dichromate (Kr2Cr2O7/H+)
  • Primary alcohol → aldehyde → carboxylic acid
  • e.g. CH3CH2OH + 2[O] → CH3COOH + H20
  1. Hydrolysis of nitrile or esters - nitriel refluxed with water and HCL so that carboxylic acid can be distilled from reaction mixture.
    * CH3CN + 2H20 + HCL → CH3COOH + NH4CL
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15
Q

What are the uses of esters?

A
  • short chain esters fairly volatile and usually have fruity smells so are used in artificial flavourings and perfumes
  • solvent - used in nail varnish remover
  • plasticisers - makes PVC more flexible by acting as a lubricant between chains
  • Fats and oils
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16
Q

What are fats and oils?

A
  • esters of alcohol propane - 1,2,3-triol (glycerol). Also known as triesters/triglycerides as 3 long carboxylic acids (fatty acids) undergo esterification with the 3 OH groups in glycerol.
17
Q

What is the hydrolysis of fats and oils?

A
  • Fats and oils can be hydrolysed in acidic conditions to give a mixture of glycerol and fatty acids. They can also be hydrolysed by boiling with alkaline NaOH to give glycerol and sodium salts of long chain acids. This is called Saponification.
  • These salts are soaps and can be a mixture of different sodium salts. The salts are ionic so disociate to form Na+ and RCOOF-. The COO is the polar/ionic hydrophobic head mixing with water and the non-polar hydrocarbon mixes with grease.
18
Q

What is glycerol?

A
  • colourless viscious liquid with a sweet taste that is very soluble in water
19
Q

What are the uses of glycerol?

A
  • cosmetics - as it attracts water things won’t dry out
  • solvent - in medicines, toothpaste,food colouring
  • plasticisers - making PVC more flexible and adding to polymers
20
Q

What are lipids?

A
  • naturally occuring esters known as fats and oils
21
Q

How is biodiesel made?

A
  • Produced by reacting lipids with methanol and KOH as catalyst. A reaction called base-catalysed transesterification occurs.
22
Q

What is biodiesel?

A
  • It is a mixture of methyl esters of fatty acids
23
Q

What is an acyl group and acylation?

A
  • acylation - process where acyl group introduced into another molecule
  • acyl group = RCO
24
Q

What are acid derivatives and their general formula?

A
  • acid derivatives - all have acyl group as part of their structure
  • general formula = RCOZ
25
Q

What are 2 important acid derivatives and their formulas?

A
  1. acyl chlorides - contain Cl atom attached to acyl group so RCOCl. Named using -oyl chloride depending on no. of carbons.
  2. acid anyhydrides - 2 carboxylic acid molecules react resulting in elimiantion of H20 so RCOOCOR. Named using -oic anhydride depending on no. of carbons.
26
Q

What are nucleophiles?

A
  • nucleophiles - species which have lone pairs of electrons and that attack delta+ C
27
Q

What nucleophiles in order of reactivity react with acyl chlorides and acid anhydrides?

A
  1. ammonia = :NH3
  2. primary amine = :NH2R
  3. alchols = :OHR
  4. water = H2O:
28
Q

What products form when acid anhydrides and acyl chlorides react with the 4 nucleophiles?

A
  1. water = carboxylic acids / RCOOH
  2. alcohols = esters / RCOOR
  3. ammonia = amides / RCONH2
  4. primary amines = N-substituted amides / RCONHR
29
Q

What type of reactions occur when acid anhydrides and acyl chlorides react with the 4 nucleophiles?

A
  • The reactions are called Nucleophilic addition-elimination reactions where all nucleophiles lose a H+ during the reaction and is replaced by an acyl group.
30
Q

Why are acid derivatives important acylating agents?

A
  • It’s due to their polarised carbonyl group Delta+ C bonded to Delta- O which is attacked by nucleophiles at the C repalcing Z.
31
Q

What does the speed of acylation depend on?

A
  1. reactivity of nucleophile according to its ability to donate its lone pair to e- deficient C.
  2. electron releasing or attracting power of Z which affects magnitude of +charge on C.
  3. how easily Z is lost.
32
Q

What is the reactivity of acyl chlorides and acid anyhdrides?

A
  • Both acyl chlorides and acid anhydrides are good acylating agents with acyl chlorides being more reactive.
33
Q

What are the uses of acylation reactions?

A

Ethanoic anhydride has advantages over ethanoyl chloride as an acyalting agent because:

  • it’s cheaper
  • it’s less corrosive
  • it doesn’t react with water as readily
  • safer as by-product is ethanoic acid rather than hydrogen chloride
  • its important in production of aspirin
34
Q

What is the mechanism for acyl chloride with water?

A
35
Q

What is the mechanism of an acyl chloride with an alcohol?

A
36
Q

What is the mechanism of an acyl chloride with an amine?

A
37
Q

What is the mechanism of an acyl chloride with ammonia?

A

chemistry (3 decks)

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