Applied Organic Chemistry Flashcards
What are Fats and oils?
Naturally occurring esters derived from long-chain carboxylic acids (fatty acids) and propan-1,2,3-triol (glycerol).
What is the equation for the formation of fats and oils from glycerol and carboxylic acids?
Glycerol + Carboxylic acid → Ester + water
What is the difference between fats and oils?
Fats are solids at room temperature and contain a high proportion of long-chain saturated carboxylic acids
while
oils are liquids at room temperature and contain a high proportion of unsaturated carboxylic acids.
How are oils converted to fats?
By heating them with hydrogen gas in the presence of Nickel catalyst at 150oC, a process called hydrogenation.
Name plant oil sources
Groundnuts, sim-sim, palm, castor oil etc.
Name animal oil sources
Whale, cod, liver, fish etc.
Name plant fat sources
Cocoa butter, palm
Name animal fat sources
Mutton, lard (fat from a pig), butter, tallow, chicken fat, milk.
How is vegetable oil extracted from plant seeds?
- The seeds are cleaned, dried, crushed and pressed so as to get oil out of them, leaving behind a solid cake.
- The solid cake may be heated and pressed further to extract more oil and the remaining solid product can be used to make animal feeds.
What is soap?
Soap is a sodium or potassium salt of a long chain carboxylic acid such as stearic acid.
Therefore, the chemical name for such soap is Sodium stearate or potassium stearate.
What materials are required for the manufacture of soap (Saponification)?
- Fat or oil
- Concentrated alkali (Sodium hydroxide or potassium hydroxide)
- Concentrated sodium chloride solution
Describe the process of saponification
- The fat or oil is boiled with a concentrated alkali (sodium or potassium hydroxide) for some time until frothing stops.
- Soap is formed in solution.
- Concentrated sodium chloride solution is added so as precipitate out soap by lowering its solubility in the mixture (due to the common ion effect).
- This is called “salting out” of soap.
- The precipitated soap floats on top of the liquid mixture.
RCOONa (aq) RCOO─(aq) + Na+(aq)
NaCl(aq) Na+(aq) + Cl─(aq) - The precipitated soap is filtered off.
- This may be purified, deodorized, perfumed, medicated, processed into bars or tablets and branded.
Describe the cleansing action of soap
- A soap molecule is made-up of 2 parts i.e. the ionic or polar part (─COO ̄Na+) which is water-soluble (hydrophilic) and the non-polar hydrocarbon part (─R) which is fat-soluble (hydrophobic)
- During washing, soap dissolves in water; soap molecules are dispersed in solution with the polar ends getting attracted to water molecules while the non-polar hydrocarbon part dissolves the dirt or stains.
- This results into the reduction of the surface tension of water.
- Subsequently, soap molecules form congregates around the dirt particles (micelles)
- Repulsion between the polar ionic heads and attraction by the positive partial charges of the polar water molecules helps to lift the dirt particles off the fabric with the help of agitation or scrubbing.
What is the result of using soap with hard water?
- When soap is used with hard water (contains Ca2+ or Mg2+), an insoluble curd (precipitate) of calcium stearate or magnesium stearate commonly called scum is formed.
2Na-St (aq) Sodium stearate (soap)
+
CaSO4 (aq) Calcium sulphate
(in hard water)
→ CaSt2 (s) + Na2SO4 (aq) calcium stearate sodium sulphate
(scum)
How does using hard water lead to wastage of soap?
The lather can only form after all the Ca2+ or Mg2+ ions present are turned into scum.
What are Detergents (Soapless soaps)?
Detergents are sodium salts of sulphonic acids.
They are cleaning agents which do not form scum with hard water.
How can the performance of a detergent can be improved?
By adding:
i) Inorganic phosphates that remove soluble calcium and magnesium ions present in water
as complexes.
ii) Sodium peroxoborate which is a bleaching agent. in water it releases hydrogen peroxide
which bleaches the stains in the garment and makes it look brighter.
iii) Sodium sulphate which increases the bulk of the detergent.
What are the advantages of detergents over soap?
- Detergents are more soluble in water than soap
- Detergents do not form scum with hard water unlike soap
What are the disadvantages of detergents?
- Detergents contain inorganic phosphates that cause eutrophication (enrichment of water bodies with nutrients) which promotes rapid growth of algae (algal blooms). This affects a number of aquatic flora and fauna.
- Some detergents contain highly branched hydrocarbon groups which are non- biodegradable and cause pollution
What are the advantages of soap over detergents?
- Soap is cheaper than detergents
- Soap is environmentally friendly since it is biodegradable while detergents are non- biodegradable and cause pollution
What is a polymer?
This is a chemical substance consisting of large molecules made from many smaller and simpler molecules.
What is a monomer?
This is a molecule that can be bonded to other identical molecules to form a polymer.
What is a homopolymer?
A polymer having identical molecules e.g., polyethene
What is a co-polymer?
A polymer having different units e.g., nylon-6,6, terylene etc.
What is polymerization?
Polymerization is chemical reaction in which many small molecules combine to form a single large molecule of higher molecular mass
