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 200oC, 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
Define Addition polymerization
This is the combination of monomer molecules containing carbon-carbon double bonds (C=C) to form a large complex molecule
OR: addition polymerization is the combination of many monomer units to form a large molecule of higher molecular mass but having the same empirical formula as the monomer units.
State characteristics of addition polymerization
- The monomer is an unsaturated molecule having a C=C bond
- The double bond is lost as the saturated polymer forms
- The empirical formula of the polymer is the same as that of the monomer.
State examples of addition polymers
Polyethene
How is Polyethene formed?
When ethene is heated to about 200oC at a pressure of 2000 atmospheres in the presence of traces of oxygen acting as a catalyst.
What is the monomer of Polyvinyl chloride (PVC)?
Vinyl chloride or chloroethene
State uses of PVC
- To make gas pipes
- water drain pipes
- gutters
- fascial boards
- window frames
- floor coverings
- insulation material for electrical wiring and plugs.
What is the monomer of Polypropene?
Propene
What are the uses of polypropene?
It is used to make
- ropes
- carpets
- milk crates
- plastic furniture
- thermal underwear
- pipes and containers which can withstand boiling water.
What is the monomer of Polyphenylethene or Polystyrene?
Phenylethene or styrene
What are the uses of polystyrene?
- It is used to make disposable cups for hot drinks like tea, coffee and soup.
- Polystyrene foam (or expanded polystyrene) is used for thermal insulation and packaging breakable objects and valuable items like computers since it is light and the trapped gas bubbles in it give the material excellent heat insulation properties.
What is the monomer of Polytetrafluoroethene (PTFE)?
Tetrafluoroethene
What is the use of terafluoroethene?
- Used to make car engine seals and gaskets
- oven floors and
- coating for non-stick cookware such as non-stick frying pans.
What is the monomer of Polypropenenitrile?
Propenenitrile
What is Polypropenenitrile used for?
- Production of nitrile rubber, cylinder head gasket,
- petrol lines
- seat belts
- conveyor belts
What is the monomer of Polymethyl-2-methylpropenoate (Perspex)?
Methyl-2-methylpropenoate
What is Perspex used for?
- Making rulers
- windscreens
- lenses
- aeroplane windows
What is the monomer of natural rubber?
Isoprene (2-methyl-1,3-butadiene).
Since isoprene has two double bonds, it still retains one of them after the polymerization reaction.
Describe Vulcanization of natural rubber
- Natural rubber is converted into tough, rigid and strong usable rubber by a process called Vulcanization.
- During vulcanization, rubber is heated with sulphur under high pressure in the presence of accelerators and activators at 140oC to 160oC.
- This introduces cross links of sulphur atoms between the long hydrocarbon chains of natural rubber, making it stronger, tougher, harder, more durable, more rigid, more elastic, non-sticky, more weather resistant and less sensitive to temperature changes.
Give the differences between raw rubber and vulcanized rubber
Raw rubber:
- Soft and sticky
- Soluble in organic solvents
- Easily melts when heated
Vulcanized rubber:
- Hard, tough and rigid
- Insoluble in organic solvents
- Does not melt when heated (thermoset)
What is the monomer of synthetic rubber?
Neoprene (2-chloro-1,3-butadiene)
Synthetic rubber is used to make gloves, conveyor belts, hoses and as insulation material for electric wires and cables.
What are the characteristics of condensation polymerization?
- The monomer units combine by means of a condensation rection during which a small molecule is eliminated to give a product of higher molecular mass.
- The empirical formula of the polymer is different from that of the monomers.
- Monomers of condensation polymerization normally contain 2 functional groups per molecule.
What are the monomers of Nylon-6,6?
- Hexanedioic acid or hexanedioyl chloride
- 1,6-diaminohexane
What are the monomers of Terylene (polyester)?
- Ethane-1,2-diol
- Either benzene-1,4-dicarboxylic acid or a dimethyl ester of benzene-1,4-dicarboxylic acid.
What is the monomer of Proteins (polyamides)?
Proteins are formed by condensation polymerization between amino acid molecules.
What are the monomers of Bakelite?
- Phenol
- formaldehyde (methanal)
When phenol is heated with methanal under alkaline conditions to form an addition product (trimethylol phenol) which undergoes subsequent polymerization to form Bakelite.
State naturally occurring condensation polymers
State naturally occurring condensation polymers?
- Starch
- Cellulose
- Proteins
Give advantages of nylon-6,6 as a fiber
- It is cheap
- It is durable
- It is soft
- Easy to clean
Give disadvantages of nylon-6,6 as a fiber
- Can easily melt
- Can easily catch fire
What are natural polymers?
These polymers that exist naturally on earth.
Examples; proteins, starch, rubber, cellulose, silk, wool etc.
What are artificial or synthetic polymers?
These are man-made polymers
Examples: polyethene, polystyrene, polyester, polypropene, PVC, nylon-6,6 etc.
Give advantages of synthetic polymers over natural polymers
- Synthetic polymers are relatively cheaper than natural polymers
- Synthetic polymers are easier to process than natural polymers
- Synthetic polymers are usually stronger and more durable than natural materials
Give disadvantages of synthetic polymers
- They are non-biodegradable, therefore accumulate in the environment in the environment causing adverse effects to man and the environment.
- They give off poisonous fumes to man and the environment during their manufacture or when burnt.
- They are prone to fire accidents since they easily catch fire.
What are thermosoftening plastics (or thermoplastics)?
These are plastics which become soft and mouldable on heating without undergoing any significant chemical change and harden on cooling.
They can be moulded, softened and remoulded into new shapes repeatedly without affecting the properties of the plastic.
They have linear structures and on heating them, the distance between polymer chains increases making them more flexible.
Give examples of thermosoftening plastics
Polyethene, polystyrene, polypropene, PVC, Perspex etc.
What are thermosetting plastics or thermosets?
These are plastics which cannot be softened by heating but instead decompose and therefore cannot be remoulded into new shapes after their manufacture.
They are only moulded during the polymerization stage of their manufacture and cannot be melted or remoulded once they have solidified.
State examples of thermosetting plastics
Bakelite, melamine and Formica.
State the general uses of plastics
- Used to make packaging material, carrier bags, toys, water bottles, tumblers, pens, rulers, markers and a number of household items.
- Used as insulators of electric cables, switches, sockets, bulb holder, plugs etc.
- Making construction and plumbing materials e.g., pipes, sinks, toilet seats, fascial boards, roofing material etc.
- Used for making plastic water tanks.
- Making and fitting of artificial human body parts (prosthetics).
- Materials for manufacturing clothes, bags, caps, footwear, fishing nets etc.
- Plastic are used for road and parking yard surfacing.
What are the disadvantages of plastics?
Plastics are non-biodegradable, can cause pollution, can be harmful to health.
What is condensation polymerization?
This is the repeated joining together of two bifunctional monomers/ two types of molecules having two functional groups on each molecule to form one large molecule with the loss of a small molecule
