Download 10.4 Carboxylic Acids and Esters

10.4 Carboxylic Acids and Esters
Carboxylic Acids
• These are compounds with a carboxyl group,
which consists of a carbonyl group and a
hydroxyl group (an OH group like in alcohols)
• The general structural formula is:
O
II
R - C - OH
• this can be written: R-COOH
Carboxylic Acids
• They are weak acids due to their slight
ionization in water to release a
hydrogen ion.
O
II
R - C - OH(aq)
O

II
R - C - O-(aq)
+
H+(aq)
Naming Carboxylic Acids
• In order to name these compounds:
• First, identify the longest parent chain with
the carboxyl group.
• Then drop the -e ending and add the ending oic and the word acid.
The first three Carboxylic Acids
• methanoic acid ethanoic acid
O
II
H - C - OH
O
II
CH3 - C - OH
propanoic acid
O
II
CH3 – CH2 - C - OH
Polycarboxylic Acids
• You do not have to memorize these names and
condensed formulas, all you must recognize is
that these are carboxylic acids.
Properties of Carboxylic Acids
• Like other organic derivatives many of these
compounds have common names, derived from
the origin of the acid.
• Carboxylic acids are widely distributed in
nature.
• They are present in all cells and are a
component of fats.
• Fatty acids are carboxylic acids in fact.
Properties of Carboxylic Acids
• The common name for methanoic acid is
formic acid since it is found in ants (the Latin
for ant is formica).
• For ethanoic acid the common name is acetic
acid, from acetum (Latin for sour wine, as in
vinegar).
Properties of Carboxylic Acids
• Short chain carboxylic acids are volatile
liquids with sharp, unpleasant odours such as
sweaty feet, vomit and rancid butter.
• Tracker dogs follow the trail of carboxylic
acid smell from the body odour of the
subject.
• The polar nature of the carboxyl group
allows these organic acids to be misable with
water.
• Larger chain organic acids are waxy solids
that are insoluble in water, but will dissolve
in solvents such as ethanol or propanone.
Esters
• A compound called an ester is composed
of an alcohol and a carboxylic acid.
• The process to create an ester is simply
called esterfication.
Formation of an Ester
• Since water is eliminated in the process of
this reaction, it may be called a condensation
reaction.
Naming Esters
• We name esters by identifying the
alcohol chain, dropping the -ol, and
adding –yl.
• Then we name the acid by dropping the ic acid and adding -ate.
Properties and Occurrence of Esters
• Lower molecular weight esters are colourless,
volatile liquids that are soluble in water.
• Higher molecular weight examples are
colourless, waxy solids that are insoluble in
water.
• All esters have characteristic strong “fruity”
smells and are soluble in non-polar organic
solvents.
• Esters are themselves good organic solvents.
Properties and Occurrence of Esters
• Esters break down into their respective
organic acid and alcohol from which they are
formed.
• This process is called hydrolysis.
• When sodium hydroxide is added to an ester,
for example to ethyl ethanoate, a salt, sodium
ethanoate is formed along with ethanol.
Properties and Occurrence of Esters
• The reaction is shown below:
• Hydrolysis of an ester with an alkaline
solution like sodium hydroxide is known as
saponification.
• This reaction is used in the preparation of
soaps from fats, which are esters of
glycerol and fatty acids.
Properties and Occurrence of Esters
• Esters are found widely in nature as the
flavour and odors of flowers, fruits and nuts.
• They are manufactured as artificial
perfumes or scents and artificial food
flavours that are added in many edible items
like ice creams, soft drinks, sweets, etc.
• In industry, esters are used as solvents for
making cellulose, fats, paints and varnishes
and in the pharmaceutical industries.
• Esters are also used as softeners in plastic
and molding industries.
butan-1-ol
hexan-1-ol
octan-1-ol
2-methylpropan-1-ol
butan-2-ol
Alcohol
Acid
Ester produced
Smell
Methanol
Butanoic acid
Methyl butanoate
Pineapple
Methanol
Benzoic acid
Methyl benzoate
Marzipan
Methanol
Salicylic acid
Methyl salicylate
Wintergreen
Ethanol
Methanoic acid
Ethyl methanoate
Raspberry/rum
Ethanol
Ethanoic acid
Ethyl ethanoate
Pear drops/nail-varnish remover
Ethanol
Butanoic acid
Ethyl butanoate
Pineapple
Propan-1-ol
Ethanoic acid
Propyl ethanoate
Pear
Pentan-1-ol
Ethanoic acid
Pentyl ethanoate
Banana
Pentan-1-ol
Butanoic acid
Pentyl butanoate
Apricot/pear
Pentan-1-ol
Pentanoic acid
Pentyl pentanoate
(Pine)apple
3-methylbutan-1-ol
(isoamyl alcohol)
Ethanoic acid
3-methylbutyl ethanoate
Banana/bee alarm pheromone
Octan-1-ol
Ethanoic acid
Octyl ethanoate
Orange
Phenylmethanol
(benzyl alcohol)
Ethanoic acid
Benzyl ethanoate
Peach