Organic Chemistry Of Alkanoates Part 3
WAEC Chemistry
Alkanoates (Esters)
Fact 1: Alkanoates are organic compounds commonly known as esters, which are formed when an alkanol (alcohol) chemically reacts with an alkanoic acid (carboxylic acid).
Fact 2: The general molecular formula for the homologous series of open-chain, aliphatic alkanoates is represented mathematically as CnH2nO2 or RCOOR', where R can be a hydrogen atom or an alkyl group, and R' must strictly be an alkyl group.
Fact 3: The characteristic functional group of all alkanoates is the ester linkage or alkoxycarbonyl group, structurally denoted as -COO-.
Fact 4: In the International Union of Pure and Applied Chemistry (IUPAC) nomenclature, alkanoates are named as alkyl alkanoates; the alkyl part originates from the parent alcohol, while the alkanoate part originates from the parent carboxylic acid.
Fact 5: The chemical process by which alkanoates are prepared is called esterification, which involves heating a mixture of an alkanol and an alkanoic acid in the presence of a few drops of concentrated tetraoxosulphate(VI) acid (H2SO4) serving as a catalyst and dehydrating agent.
Fact 6: Esterification is a completely reversible, equilibrium reaction; to shift the equilibrium forward and maximize the yield of the alkanoate, Le Chatelier's principle is applied by continuously distilling off the ester or using excess reactants.
Fact 7: Unlike their structural isomers (alkanoic acids), lower molecular weight alkanoates are neutral, volatile liquids possessing highly characteristic, sweet, fruity odors.
Fact 8: Alkanoates exhibit lower boiling points compared to their parent alkanoic acids and alkanols of equivalent molecular mass because alkanoate molecules cannot form intermolecular hydrogen bonds with one another.
Fact 9: While lower alkanoates show slight solubility in water due to their ability to form hydrogen bonds with water molecules, their solubility rapidly decreases as the carbon chain length (hydrophobic alkyl group) increases.
Fact 10: Alkanoates can undergo acid hydrolysis when boiled with an dilute mineral acid like hydrochloric acid (HCl), yielding the parent alkanoic acid and alkanol in a reaction that is the exact reverse of esterification.
Fact 11: Alkaline hydrolysis of an alkanoate, commonly termed saponification, is an irreversible reaction with a strong base like sodium hydroxide (NaOH) or potassium hydroxide (KOH) that produces an alkanol and the alkali metal salt of the alkanoic acid (soap).
Fact 12: Natural fats and vegetable oils are complex, long-chain alkanoates structurally classified as triesters of propane-1,2,3-triol (glycerol), routinely referred to as triglycerides.
Fact 13: Saponification of natural fats and oils using concentrated sodium hydroxide yields hard soaps (sodium carboxylates), whereas using potassium hydroxide yields soft soaps or liquid shaving creams (potassium carboxylates).
Fact 14: Alkanoates undergo ammonolysis when treated with concentrated ammonia solution, breaking the ester linkage to yield an amide and an alkanol.
Fact 15: Alkanoates can be chemically reduced back to primary alkanols using powerful reducing agents such as lithium tetrahydridoaluminate(III), LiAlH4, dissolved in dry ethoxyethane.
Fact 16: Alkanoates and alkanoic acids with the same number of carbon atoms exhibit functional group isomerism; for example, ethyl methanoate (an ester) and propanoic acid (a carboxylic acid) share the identical molecular formula C3H6O2.
Fact 17: In the industrial sector, volatile lower alkanoates are widely manufactured for use as artificial flavoring agents in the food industry and sweet scents in the perfumery and cosmetics industries.
Fact 18: Due to their volatile nature and inability to form rigid hydrogen bonds, lower alkanoates like ethyl ethanoate are highly valued as industrial non-polar solvents for dissolving paints, varnishes, cellulose derivatives, and nail polishes.
Fact 19: Long-chain alkanoates containing unsaturated carbon chains (alkene groups within the fatty acid chain) form liquid oils at room temperature, which can be industrially converted into solid margarine via catalytic hydrogenation using a nickel catalyst at roughly 180°C.
Fact 20: In WAEC practical qualitative analysis, an unknown organic compound can be identified as an alkanoate if it is a colorless, neutral liquid that evolves a distinct fruity aroma when warmed with water, and fails to liberate carbon(IV) oxide gas when treated with sodium trioxocarbonate(IV) solution.
Mr Bosun
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