Applications of Functional Groups: Polymers, Soaps, and Lipids

Comprehensive vocabulary flashcards covering synthetic polymers, addition and condensation polymerisation, soaps, detergents, and major lipid classes from Module 08.

Polymer

A long-chain molecule made by chemically linking repeating monomer units, typically characterized by a molecular weight ranging from $10{,}000$ to $1{,}000{,}000\,\text{g/mol}$.

Thermoplastics

Polymers that can be melted, become fluid enough to be poured into moulds, and can be repeatedly reheated and reshaped (recyclable).

Thermosetting Plastics

Polymers that can be moulded when first synthesized, but once cooled, harden irreversibly and cannot be remelted or reshaped (not recyclable).

Repeating Unit

The smallest molecular fragment that contains all the non-repeating structural features of a polymer chain.

Degree of Polymerisation

The numerical subscript ($n$) positioned outside the brackets enclosing a polymer's repeating unit, denoting how many times that unit repeats within the chain.

Condensation Polymerisation

A polymer formation process requiring di-functional monomers, in which two functional groups join with the elimination of a small molecule such as water ($\text{H}_2\text{O}$).

Addition Polymerisation

A polymer formation process in which alkene monomers join end-to-end via a radical mechanism to yield polyalkanes without the loss of atoms or production of by-products.

Nylon 66

A synthetic polyamide formed via condensation polymerisation from hexanedioic acid (adipic acid) and 1,6-hexanediamine (hexamethylenediamine).

Kevlar

A polyaromatic amide synthesized by condensation polymerisation, known for being lightweight and exceptionally strong.

Dacron (Mylar)

A polyester polymer formed via condensation that gains high structural strength from its aromatic ring content.

Initiation (Polymerisation)

The first phase of addition polymerisation, wherein a catalyst or initiator decomposes to generate a highly reactive radical species containing an unpaired electron.

Propagation (Polymerisation)

The chain-lengthening stage of addition polymerisation in which a radical reacts with an alkene monomer, extending the chain and transferring the unpaired radical electron to the chain end.

Termination (Polymerisation)

The final stage of addition polymerisation in which reactive radical intermediates are consumed or destroyed, stopping chain propagation.

Poly(methyl methacrylate) (PMMA)

An addition polymer commercially known as Plexiglass, formed from the monomer methyl 2-methylprop-2-enoate.

Saponification

The base-promoted hydrolysis of ester bonds in a triglyceride using concentrated $\text{NaOH}$ or $\text{KOH}$ solution to produce glycerol and fatty acid salts (soaps).

Soap Molecule Structure

An amphipathic structure possessing an ionic, water-soluble hydrophilic head ($\text{RCOO}^-$) and an insoluble, non-polar hydrophobic hydrocarbon tail.

Hard Water

Water characterized by high concentrations of dissolved metal cations such as $\text{Ca}^{2+}$, $\text{Mg}^{2+}$, or $\text{Fe}^{3+}$, which precipitate soaps into an insoluble scum.

Synthetic Detergents

Synthetic cleaning agents composed of a non-polar hydrocarbon tail and a polar sulfonate head group (such as benzene sulfonate) that remain soluble and functional in hard water.

Sodium Dodecyl Sulfate (SDS)

A synthetic detergent and surfactant (also known as lauryl sulfate) containing a 12-carbon aliphatic chain and an anionic sulfate ester group, commonly used in shampoos.

Micelle

A spherical colloidal assembly of surfactant molecules in aqueous solution, where hydrophobic tails cluster inward to encapsulate non-polar grease and hydrophilic heads face outward toward water.

Lipids

A chemically diverse category of biological compounds defined by shared solubility: they are insoluble in water but soluble in non-polar organic solvents.

Saponifiable Lipids

Lipids containing ester functional groups that can undergo basic hydrolysis into smaller components, such as waxes, triglycerides, and phospholipids.

Non-Saponifiable Lipids

Lipids lacking ester functional groups that cannot be broken down by base hydrolysis, including steroids and prostaglandins.

Fatty Acids

Unbranched, long-chain carboxylic acids usually containing an even number of carbons ($10$ to $22$ carbons), which can be saturated or unsaturated (predominantly occurring as the cis isomer).

Essential Fatty Acids

Polyunsaturated fatty acids—specifically linoleic acid and linolenic acid—that human cells cannot synthesize internally and therefore must obtain through nutrition.

Linoleic Acid

An essential omega-6 polyunsaturated fatty acid with an $18:2$ profile ($18$ carbon atoms and $2$ double bonds) used to synthesize arachidonic acid and inflammatory regulators.

Linolenic Acid

An essential omega-3 polyunsaturated fatty acid with an $18:3$ profile ($18$ carbon atoms and $3$ double bonds).

Triglycerides

Triesters of glycerol formed by esterifying three fatty acid chains to a single glycerol molecule; also referred to as triacylglycerols, fats, or oils.

Hydrogenation (Hardening)

The catalytic addition of hydrogen ($\text{H}_2$) across carbon-carbon double bonds in unsaturated vegetable oils to produce saturated chains with higher melting points and firmer consistencies.

Bile Salts

Steroid-derived amphipathic compounds (such as salts of cholic acid and lithocholic acid) that emulsify dietary fats into smaller droplets in the digestive tract.

Waxes

High molecular weight saponifiable esters formed from the esterification of a long-chain fatty acid with a long-chain alcohol, lacking a glycerol backbone.

Phospholipids

Complex saponifiable membrane lipids consisting of a glycerol backbone linked to two fatty acids and one phosphate group bonded to an aminoalcohol.

Lecithin

A common phospholipid (phosphatidylcholine) containing a choline aminoalcohol unit, frequently used as an emulsifying agent to blend oil and water in margarine and chocolate.

Lipid Bilayer

A double-layered sheet of phospholipids that forms cell membranes, stabilized by hydrophobic interactions between inward-facing non-polar tails while polar heads face the aqueous surroundings.

Ergosterol

A steroid constituent in fungal cell membranes that regulates membrane fluidity and rigidity, analogous to cholesterol in human cells.

Amphotericin B

An antifungal medication derived from Streptomyces nodosus that selectively binds to fungal ergosterol to disrupt cell membrane function.

Sphingolipids

Complex lipids built upon a sphingosine aminoalcohol backbone rather than glycerol, typically linked to a fatty acid and a phosphate or carbohydrate group.

Steroids

Non-saponifiable lipids possessing a fused four-ring carbon skeleton (three six-membered rings and one five-membered ring), serving as hormones and membrane stabilizers.

Cholesterol

The most abundant steroid in the human body, providing membrane structural rigidity and serving as a precursor for bile salts, steroid hormones, and vitamin D.

Lipoproteins

Biochemical transport assemblies of lipids and proteins that package non-polar lipids for transport through the aqueous bloodstream.

Low Density Lipoproteins (LDLs)

Lipoprotein complexes responsible for transporting fats and cholesterol away from the liver and around the body through the bloodstream.

High Density Lipoproteins (HDLs)

Lipoprotein complexes that collect excess cholesterol and fats from peripheral body cells and tissues and return them to the liver.

Prostaglandins

Non-saponifiable, locally acting autocrine/paracrine messengers with a 20-carbon skeleton that includes a cyclopentane ring, biosynthesized in vivo from arachidonic acid.