Qualitative tests, structure and uses of different carboxylic acids are discussed.

1. Qualitative tests, structure and
uses of different carboxylic acids
By
Dr. Nidhi Gupta
M.M. College of Pharmacy
Maharishi Markandeshwar
(Deemed to be University),
Mullana, Ambala, Haryana, India

2. The following tests can be used to identify carboxylic
acids:
1. Litmus Test
Carboxylic acid turns blue litmus red. The hydroxyl group
in carboxylic is far more acidic than that in alcohol. The
dissociation of carboxylic acid is represented as:

3. 2. Sodium Hydrogen Carbonate Test
Carboxylic acids reacts with sodium hydrogen carbonate to
produce carbon dioxide gas which can be seen in the form of
a brisk effervescence.
3. Ester Test
Carboxylic acid reacts with alcohol in presence of conc. sulphuric
acid to form ester that is identified by the presence of a fruity
smell.

4. Tests of amides:
•Reaction of NaOH:
Amides are decomposed by NaOH to evolve
ammonia. The gas can be tested by a moist red
litmus paper which is then turned blue.
•Alkaline hydrolysis of aromatic amides to
aromatic acid:
The soluble sodium salt of aromatic acid formed from
aromatic amides upon hydrolysis is regenerated as
white precipitate in acidic medium.

5. •Biuret Reaction for aliphatic diamide:
When aliphatic diamide is heated at a temperature
above its melting point, ammonia is evolved and
crystalline biuret is formed. This biuret in alkaline
medium gives a violet colour with a drop of copper
sulphate solution.

6. •Hydroxamic acid test for aromatic primary
amides:
Hydrogen peroxide reacts with aromatic primary
amides to form the hydroxamic acid, which then
reacts with ferric chloride to form ferric hydroxamate
complex having a violet colour.

7. 3. Esters
There is no simple test for an ester. Usually a colourless liquid
with a pleasant 'odour'.
Hydroxamic acid test
R-CO-OR' + H2N-OH -> R-CO-NH-OH + R'-OH
Esters react with hydroxylamine in the presence of sodium
hydroxide to form the sodium salt of the corresponding hydroxamic
acid. On acidification and addition of ferric chloride the magenta-
coloured iron (III) complex of the hydroxamic acid is formed.
It is always advisable to ensure that an unknown compound does not
give a colour with iron (III) chloride before carrying out the
hydroxamic acid test.

8. Structure of acetic acid

9. Uses of acetic acid
• The largest single use of acetic acid is in the
production of vinyl acetate monomer.
• The major esters of acetic acid are commonly
used as solvents for inks, paints and coatings.
• Glacial acetic acid is an excellent polar protic
solvent, as noted above.
• Acetic acid injection into the tumor has been
used to treat cancer

10. Structure of lactic acid

11. Uses of lactic acid
• In medicine, lactate is one of the main
components of lactated Ringer's solution
and Hartmann's solution.
• In industry, lactic acid fermentation is
performed by lactic acid bacteria, which
convert simple carbohydrates.
• Lactic acid is used as a food preservative,
curing agent, and flavoring agent.

12. Structure of tartaric acid

13. Uses of tartaric acid
• Tartaric acid is found in cream of tartar,
which is used in cooking candies and frostings
for cakes.
• Tartaric acid is also found in baking powder,
where it serves as the source of acid that
reacts with sodium bicarbonate.
• Industrial uses for tartaric acid include within
the gold and silver plating process, tanning
leather and making blue ink for blueprints.

14. Structure of citric acid

15. Uses of citric acid
• Citric acid is a weak organic acid found in citrus
fruits.
• It is a natural preservative and is also used to add an
acidic (sour) taste to foods and soft drinks.
• Citric acid’s chemical properties as a weak organic
acid make it a powerful water softener.
• Citric acid is a relatively common ingredient used in
cosmetics products to balance the pH level
according to Cosmetics Database.

16. Structure of succinic acid

17. Uses of succinic acid
• Succinic acid is a precursor to some polyesters and a
component of some alkyd resins.
• Succinic acid is used primarily as an acidity
regulator in the food and beverage industry.
• It is also available as a flavoring agent, contributing
a somewhat sour and astringent component to
umami taste.
• As an excipient in pharmaceutical products, it is
also used to control acidity or as a counter ion.

18. Structure of oxalic acid

19. Uses of oxalic acid
• Oxalic acid is rubbed onto completed marble
sculptures to seal the surface and introduce a shine.
• Oxalic acid is used as a bleach for wood, removing
black stains.
• Oxalic acid is also used for the removal of rust.
• Vaporized oxalic acid, or a 3.2% solution of oxalic
acid in sugar syrup, is used by some beekeepers as a
miticide against the parasitic varroa mite.

20. Structure of salicylic acid

21. Uses of salicylic acid
• Salicylic acid causes shedding of the outer layer of
skin.
• Salicylic acid topical is used in the treatment of
acne, dandruff, seborrhea, or psoriasis, and to
remove corns, calluses, and warts.
• Salicylic acid is used in the production of other
pharmaceuticals, including 4-aminosalicylic acid,
sandulpiride.
• Salicylic acid is used as a food preservative, a
bactericidal and an antiseptic.

22. Structure of benzoic acid

23. Uses of benzoic acid
• Benzoic acid is mainly consumed in the production
of phenol by oxidative decarboxylation.
• Benzoic acid is a constituent of Whitfield's ointment
which is used for the treatment of fungal skin
diseases such as tinea, ringworm.
• In teaching laboratories, benzoic acid is a common
standard for calibrating a bomb calorimeter.
• Benzoic acid was used as an expectorant, analgesic.

24. Structure of benzyl
benzoate

25. Uses of benzyl benzoate
• Benzyl benzoate is an effective and
inexpensive topical treatment for human
scabies.
• Benzyl benzoate is used as a repellent for
chiggers, ticks, and mosquitoes.
• It is also used as a dye carrier, solvent for
cellulose derivatives, and fixative in the
perfume industry.

26. Structure of Dimethyl
phthalate

27. Uses of dimethyl
phthalate
• Dimethyl phthalate is used as an insect repellent for
mosquitoes and flies.
• It is also an ectoparasiticide and has many other uses,
including in solid rocket propellants, and plastics.
• Industry Uses
• a) Finishing agents
• b) Intermediates
• c) Plasticizers
• d) Processing aids, specific to petroleum production

28. Structure of methyl
salicylate

29. Uses of methyl salicylate
• This product is used to treat minor aches and pains
of the muscles/joints.
• It is used in high concentrations as a rubefacient and
analgesic in deep heating liniments.
• It is used as a bait for attracting male orchid bees for
study, which apparently gather the chemical to
synthesize pheromones.
• It is used to clear plant or animal tissue samples of
color.

30. Structure of acetyl
salicylic acid

31. Uses of acetyl salicylic
acid
• Aspirin is used in the treatment of a number of
conditions, including fever, pain, rheumatic fever.
• Aspirin is used as an anti-inflammatory agent for
both acute and long-term inflammation.
• Aspirin is thought to reduce the overall risk of both
getting cancer and dying from cancer.
• Low-dose aspirin supplementation has moderate
benefits when used for prevention of pre-eclampsia.