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a2 chem - organic > carboxylic acids and esters > Flashcards

carboxylic acids and esters Flashcards

1
Q

what is the name of the carboxylic acid functional group?

A

carboxyl group (COOH)

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2
Q

in their reactions, carboxylic acids can form…

A

metal salts (carboxylates)

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3
Q

solubility: short chain carboxylic acids are…

A

very soluble in water
- this is because the polar C=O and -OH can form H-bonds with water.

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4
Q

solubilty: as chain length increases…

A

solubility decreases (due to longer non-polar hydrocarbon chain)

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5
Q

why do carboxylic acids have a higher b.p compared to alcohols with the same Mr?

A

due to the formation of DIMERS via hydrogen bonding between two molecules (doubles the size of the molecule)

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6
Q

reactions: Carboxylic acids react with bases, alkalis and reactive metals to form…

A

salts

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7
Q

what are the observations during a reaction of carb. acids with carbonates?

A

effervescence and the solid carbonate will be used up, producing a colourless solution

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8
Q

what is the general reaction between a carb. acid and a carbonate?

A

acid + carbonate → salt + water + carbon dioxide

e.g., * ethanoic acid with sodium carbonate:
2CH3COOH + Na2CO3 → 2CH3COONa + H2O + CO2

e.g., * ethanoic acid with sodium hydrogen carbonate:
CH3COOH + NaHCO3 → CH3COONa + H2O + CO2

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9
Q

what are the observations for a reaction between carb. acids and metals?

A

effervescence and the solid metal will be used up producing a colourless solution

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10
Q

what is the general reaction between a carb. acid and a metal?

A

Acid + metal → salt + hydrogen

e.g., ethanoic acid with magnesium:
2CH3COOH + Mg → (CH3COO)2Mg + H2

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11
Q

what are the observations for the reaction between a carb. acid and a base?

A

release of heat and colourless solution remains

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12
Q

what is the general reaction between a carb. acid and a base?

A

Acid + base → salt + water

e.g., ethanoic acid with sodium hydroxide:
CH3COOH + NaOH → CH3COONa + H2O

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13
Q

what are the observations between a carb. acid and ammonia?

A

a release of heat + the colourless solution remains

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14
Q

what is the general reaction between a carb. acid and ammonia?

A

acid + ammonia → ammonium salt

e.g., ethanoic acid with ammonia:
CH3COOH + NH3 → CH3COONH4
(ammonium ethanoate formed)

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15
Q

what is the functional group for esters?

A

ester group/ester linkage (COO)

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16
Q

what is the general structure of esters?

A

R-C(=O)-O-CR’

R is from the acid
R’ is from the alcohol

17
Q

reacting: carb. acids and alcohols react in the presence of…

A

heat and a strong acid catalyst (ESTERIFICATION)

18
Q

what is the general reaction for carb. acids and alcohols?

A

carb. acid + alcohol –> ester + water

19
Q

esterification is an example of…

A

a (reversible) condensation reaction

20
Q

what are some common uses of esters?

A
  • plasticisers
  • solvents for paints, glue, printing inks and nail polish remover
  • perfumes
  • food flavourings
21
Q

what is the reverse of esterification

A

hydrolysis
- there are two types: acidic hydrolysis and alkaline hydrolysis

22
Q

what are the conditions for acid hydrolysis?

A

Catalyst: dilute hydrochloric acid

Conditions: heat under reflux

Products: carboxylic acid + alcohol
* This is a reversible reaction, giving lower yields

23
Q

what are the condition for alkaline hydrolysis?

A

Catalyst: aqueous sodium hydroxide

Conditions: heat under reflux

Products: carboxylate salt + alcohol
*This is an irreversible reaction, giving higher yields - the alkali
catalyst reacts with the carboxylic acid to form a salt.

24
Q

vegetable oils and animal fats are esters of…

A

propan-1,2,3-triol (aka glycerol) and three long chain carboxylic acids called fatty acids

25
Q

fatty acids can be…

A

saturated (no double bond) or saturated (double bond present)

26
Q

what state are fats at room temperature?

A

Fats are triglycerides that are solid at room temp. - This is because fats are mainly made of saturated fatty acids, which are straight (they can therefore fit neatly together) - This increases the van der Waals’ forces between them, leading to higher m.p

27
Q

what state are oils at room temperature?

A

Oils are triglycerides that are liquid at room temp. - This is because they mainly have unsaturated fatty acids, which are bent and have kinks that obstructs packing. - This decreases the van der Waals’ forces between them, leading to lower m.p

28
Q

what is saponification?

A

the alkaline hydrolysis of fats/oils into glycerol + the salts of the fatty acids present in the fat (AKA soaps)

29
Q

what is the general equation for saponification?

A

fat/oil + 3NaOH –> glyerol (propan-1,2,3-triol) + sodium salt (the soap)

30
Q

what is biodiesel?

A

a renewable fuel made from vegetable oils such as rapeseed oil, palm oil, and soybean oil

31
Q

use of biodiesel:

A

can be used in normal diesel engines to power cars/buses

32
Q

what is biodiesel composed of?

A

a mixture of methyl esters of long-chain carboxylic acids

33
Q

how is biodiesel made?

A

reacting vegetable oils with methanol in the presence of HEAT and A STRONG BASE CATALYST (e.g., KOH)

this process is known as trans-esterification

34
Q

what is trans-esterification?

A

reacting an ester with an alcohol to produce a different ester and alcohol

35
Q

what is the general equation for trans-esterification?

A

fat/oil + 3CH3OH –> glycerol + mixture of methyl esters (3 x methyl ester)

36
Q

what are the advantages of biodiesel?

A
  • renewable
  • carbon neutral
37
Q

what are the disadvantages of biodiesel?

A
  • need lots of farming space to make vegetable oil, crops could be
    grown for biodiesel production rather than for food leading to food
    shortages.
  • Not necessarily carbon neutral - energy is used to make the
    fertiliser to grow crops (If this energy comes from fossil fuels,
    then the process won’t be carbon neutral overall)

a2 chem - organic (6 decks)

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