Let’s Recall
Homologous Functional General Formula
Formula Suffix Example
Series Group (m≥0, n≥1)
Alkane Alkyl RH CnH2n+2 -ane Ethane
Alkene Alkenyl R2C=CR2 CnH2n -ene Ethene
Alcohol Hydroxyl ROH CnH2n+1OH -ol Methanol
Belongto a homologous series of organic
compounds similar to alkanes, alkenes and
alcohols
Thehydrocarbon chains contain the
functional group -COOH (carbonyl group)
Structural Formula Chemical Formula
CH3COOH
= or
CH3CO2H
Methanoic acid Ethanoic acid Propanoic acid
Total of one Total of two Total of three
carbon atom carbons atoms carbon atoms
(meth-) (eth-) (propan-)
C0H1COOH C1H3COOH C2H5COOH
*Take note of the functional group’s location, highlighted by the
dotted box
Replace the ‘e’ with ‘oic acid’ at the end of
the name of the hydrocarbon
Example:
H H H O
H C C H H C C O H
H H H
ethane ethanoic acid
Similar to its alcohol:
Colourless liquid at room temperature & relatively
low boiling point of 118oC
Completely miscible (able to dissolve) in water
Has a characteristic ‘sour-ish’ smell
Is a weak acid of pH 3
Are carboxylic acids the same as the acids we
have learnt about in the chapter on acids and
bases?
Watch and observe!!
Ascarboxylic acid is weak, its reactions
produce the same outcomes as those learnt
from the chapter of Acids, Bases and Salts
But, the reactions are less vigorous
Weak acids (pH ≈ 3).
Most of the acid molecules are unionised in water.
For example: 1.0 mol/dm3 solution of ethanoic acid
CH3COOH(aq) CH3COO (aq) + H+(aq)
Pure acid 1000 0 0
Acid in water 996 4 4
Reaction with bases
to form a salt and water
For example:
CH3COOH + NaOH CH3COONa + H2O
Reaction with reactive metals
to form a salt and hydrogen
For example:
2CH3COOH + Mg (CH3COO)2Mg + H2
Reaction with carbonates
to form a salt, carbon dioxide and water
For example:
2CH3COOH + Na2CO3 2CH3COONa + CO2 + H2O
Ethanoic acid is the most important organic
acid
It is used in vinegar as preservative and
flavourings.
Organic acid Where it is found
Lactic acid Sour milk
Oxalic acid Rhubarb plant
Citric acid Limes, lemons
Formic acid Insect bites
Tartaric acid Grape juice
Acetic acid Vinegar
Malic acid Apples and pears
Making of drugs, dyes, paints, insecticides,
plastics.
Making of esters.
Carboxylic acids reacts with alcohols
to form esters
in the presence of a few drops of concentrated
sulphuric acid as catalyst
General equation:
acid + alcohol ester + water
Have the general formula RCOOR’
R C O R'
Functional group of
ester
Alcohol + Carboxylic acid Ester + Water
Alkanol + Alkanoic acid Alkyl alkanoate + Water
R’OH + RCOOH RCOOR’ + H2O
H H O H
H C C O H + H O C C H
H H H
+ O
H H
H O H H O H
H C O C C H O
H C OH + H O C C H
+ H H
H H H H
methanol + ethanoic acid methyl ethanoate + water
CH3OH + CH3COOH CH3COOCH3 + H 2O
Chemical Molecular Structural Alcohol Organic
name formula formula used acid used
methyl ethanoic
HCOOH H3C C methanol
ethanoate O CH3 acid
ethyl H2 ethanoic
CH3COOH C C ethanol
ethanoate H3C O CH3 acid
Are esters
acidic, neutral
or basic?
Esters are neutral compounds with a sweet smell
Colourless and insoluble in water
Fruity flavours for perfumes, sweets, drinks and
cakes
◦ Artificial pineapple flavour is an ester made from
ethanol and butanoic acid, called ethyl butanoate.
Solvents for organic compounds, such as glues,
varnishes and paints.
Summary
Homologous Functional General Formula
Formula Suffix Example
Series Group (m≥0, n≥1)
Alkane Alkyl RH CnH2n+2 -ane Ethane
Alkene Alkenyl R2C=CR2 CnH2n -ene Ethene
Alcohol Hydroxyl ROH CnH2n+1OH -ol Methanol
Carboxylic acid Carboxyl RCOOH CmH2m+1COOH -oic acid Ethanoic acid
Alkyl Ethyl
Ester Ester RCOOR’ CmH2m+1COOCnH2n+1
alkanoate butanoate
How it all ties up
