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Chemistry > Carboxylic Acids, Esters and Fatty Acids > Flashcards

Carboxylic Acids, Esters and Fatty Acids Flashcards

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1
Q

What is the structure of a carboxylic acid?

A
  • contains carboxyl functional group COOH
  • includes a carbonyl (C=O) group and a hydroxyl (O-H) group
  • the bonds are in a planar arrangement
  • are isomeric with esters: -‘RCOOR’
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2
Q

What is the nomenclature of a carboxylic acid?

A

Remove -e from alkane and replace with -OIC ACID.

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3
Q

Describe the solubility of carboxylic acids.

A
  • acids are very soluble in organic solvents
  • soluble in water due to hydrogen bonding
  • small one dissolve readily in water
  • as mass increases, solubility decreases
  • benzoic acid is fairly insoluble in cold water but soluble in hot
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4
Q

Describe the boiling point properties etc. of carboxylic acids.

A
  • increases as size increases (incr. van der Waals forces)
  • they have high boiling points for their relative masses, arises from inter-molecular hydrogen boding due to the polar O-H group
  • additional intermolecular attractions = more energy to separate molecules
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5
Q

Describe the acidic behaviour of COOH (carboxylic acids).

A
  • the polar carbonyl group enables the hydroxyl group to ionise partly in water
  • this ionisation is due to delocalisation of the negative charge over the carbon and two oxygen atoms spreading the negative charge and increasing the stability of the anion
  • COOH are weak acids as they partially disassociate into carboxylate ions and hydrogen ions
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6
Q

What are the products of carboxylic acid’s reactions with metal, metal oxide, metal hydroxide and metal carbonate?

A

CA + metal -> salt + hydrogen
CA + metal oxide -> salt + water
CA + metal hydroxide -> salt + water
CA + metal carbonate -> salt + water + carbon dioxide

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7
Q

What is the nomenclature of salts made from carboxylic acids?

A
  • oate
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8
Q

What is the analytical use of carboxylic acids?

A

Carboxylic acids are strong enough acids to liberate CO2 from carbonates. Phenols are also acidic but are not strong enough to liberate CO2.

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9
Q

Preparation of carboxylic acids:

What are the oxidation/hydrolysis equations of aldehydes, primary alcohols and esters?

A
  • Ox. of aldehydes: RCHO + [O] -> RCOOH
  • Ox. of primary alcohols: RCHOH + 2[O] -> RCOOH + H2O
  • Hydr. of esters: RCOOR + H2O -> RCOOH + ROH
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10
Q

What is the structure of an ester and its nomenclature?

A

STRUCTURE: Sub. an organic group for the H in acids.
NOMENCLATURE: First part from the alcohol, second part from the acid. Extension is -oate.

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11
Q

What are esters made from?

A

Carboxylic acid + Alcohol -> Ester + Water.

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12
Q

What are esters used for?

A
  • to flavour food
  • to make sweet smelling perfumes, toiletries etc.
  • as solvents
  • as plasticisers to make polymers soft and flexible
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13
Q

What are the reagent, conditions and equation for esterification? Use ethanoic acid and methanol as an example.

How can products be seperated?

A

REAGENTS: alcohol and acid catalyst (e.g. conc. H2SO4)
CONDITIONS: Reflux
EQUATION: CH3COOH + CH3OH -> CH3COOCH3 + H2O
Separated via fractional distillation! ~

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14
Q

Draw an ester linkage.

A

O
||
R - C - O - R’

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15
Q

PREPARATION OF ESTER FROM AN ACID ANHYDRIDE:

1) What are anhydrides made of?
2) Reagents, conditions, general equation and notes?

A

REAGENTS: alcohol and acid anhydride
CONDITIONS: reflux under dry conditions
GENERAL EQ.: alcohol + acid anhydride -> ester + carb. acid
NOTES: reaction is irreversible and no catalyst is needed also, products can be separated via fractional distillation

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16
Q

What is hydrolysis the opposite of?

A

Esterification: ester + water carboxylic acid + alcohol

e.g. ethyl methanoate -> HCOOH methanoic acid + C5H6OH ethanol

17
Q

What are the reagents and the conditions of the hydrolysis of an ester?

A

REAGENTS: aqueous acid or alkali
CONDITIONS: reflux

18
Q

What are the products of the hydrolysis of an ester (both alkali and acidic)?

A

acidic: carboxylic acid + alcohol
alkali: water soluable ionic salt (e.g. CH3COO-Na+) + alcohol
- the carboxylic acid can be made by treating salt with HCl
CH3COO-Na+ +HCl -> CH3COOH + NaCl

19
Q

What are the physical and chemical properties of an ester?

A
  • no hydrogen bonding
  • insoluble in water
  • fairly unreactive
  • hydrolysed to acids
20
Q

What are the features of saturated and unsaturated fatty acids?

A
  • saturated: no double bonds

- unsaturated: contains double bonds

21
Q

In which type of fatty acids do cis-trans isomers occur?

A

unsaturated

22
Q

Describe cis and trans in fatty acids.

A
  • cis: 2 Hs on same side of double bond
    molecule bent at the double bond
    all natural fatty acids cis
  • trans: 2 Hs on opposite sode of double bond
    molecule is straight, man-made fatty acid
23
Q

What are trigycerides?

A
  • triesters of the alcohol glycerol (propane-1,2,3-ol) & fatty acids
  • can be saturated (animal fats like butter & lard, solid at RT)
  • can be unsaturated (veg oil like sunflower, liquid at RT)
24
Q

How do you make a triglyceride?

A

glycerol + 3x fatty acids -(esti…/conden…)-> triglyceride + 3x H2O

  • the triglyceride contains 3 ester functional groups
25
Q

What is cholesterol?

A

It is a soft, waxy material found in cell membranes and transported in your bloodstream.
It is partly produced by your body and partly absorbed from animal products you eat e.g. eggs, meat and dairy products.

26
Q

What are the 2 types of cholesterol?

A
  • ‘bad’: low density lipoprotein (LDL) cholesterol

- ‘good’: high density lipoprotein (HDL) cholesterol

27
Q

What does bad cholesterol do?

A
  • can clog blood vessels
  • increases risk of high blood
  • increases risk of CHD (coronary heart disease)
  • increases risk of strokes
28
Q

What does good cholesterol do?

A
  • removes bad cholesterol, taking it to the liver to be destroyed
  • high levels can give protection from heart disease
29
Q

What are trans fats and what do they do?

A
  • triglycerides made of trans fatty acids, almost all man made
  • are in foods like biscuits, crisps, chips and cakes
  • incr. amount of bad cholesterol but red. good cholesterol
30
Q

How can bad cholesterol be increased?

A
  • by eating food with trans fats and saturated fats
31
Q

What type of unsaturated fats are there?

A
  • polyunsaturated: several double bonds (shown to reduce bad
    cholesterol)
  • monounsaturated: one double bond per chain
32
Q

Where can unsaturated fats be found?

A

plant oils such olive and sunflower

33
Q

How are plant oils made ‘spreadable’ margarines?

A

By treating oils with hydrogen to saturate some of the double bonds (hydrogenation) in their triglycerides molecules, straightening out their chains.
It also converts cis isomers into trans isomers, thus increasing their melting points.

34
Q

What is biodiesel?

A
  • a renewable fuel made from vegetable oil or animal fat that can
    be used in diesel engines
  • it is carbon neutral
  • it is a mixture of methyl and ethyl esters of fatty acids
35
Q

How do you make biodiesel?

A
  • by reacting triglycerides (oil or fats) with methanol or ethanol
  • methanol or ethanol are used as they are cheap, renewable and
    burn more efficiently
36
Q

Where can the materials needed to make biodiesel be obtained from?

A
  • veg oil: can be new, low grade oil or waste oil from fish & shops
    and restaurants
  • animal fat: chicken fat, waste fish oil and lard from meat
    processing
37
Q

What are the benefits of biodiesel?

A
  • biodegradable and non-toxic
  • fuel and exhaust emissions are less pleasant
  • high flashpoint
38
Q

Draw a simple acid anhydride.

A

O O O
| | | | e.g. //
C C CH3 - C
/ \ / \ > O
R O R’ CH3 - C

O

Chemistry (5 decks)

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