Alkenes and Addition Polymers Lecture Review

A set of vocabulary flashcards covering the structure, reactivity, isomerism, and polymerization of alkenes based on the provided lecture transcript.

Alkenes

Unsaturated hydrocarbons containing at least one carbon-carbon double bond ($C=C$) with the general formula $C_{n}H_{2n}$.

$\pi$-orbital

An orbital formed by the overlap of p-orbitals that creates a cloud of electron density above and below a single bond, resulting in restricted rotation.

Position Isomers

Monomers or compounds with the same molecular formula but where the double bond is located between different adjacent carbon atoms in the chain.

Geometrical Isomerism

A type of stereoisomerism occurring around $C=C$ bonds where the same structural formula has bonds arranged differently in space.

E-Z Isomerism

A naming system based on atomic numbers; the Z-isomer (zusammen) has high priority groups on the same side, while the E-isomer (entgegen) has them on opposite sides.

Cahn-Ingold-Prelog (CIP) Notation

The system of rules used by IUPAC to name organic compounds and distinguish between different stereoisomers using priority based on atomic number.

Electrophile

An electron pair acceptor, often a cation or a molecule with a partially positive area ($\delta+$), that is attracted to areas of high electron density.

Electrophilic Addition

A reaction mechanism typical of alkenes where an electrophile attacks the electron-rich double bond to form a saturated product.

Bond Enthalpy (C=C)

The energy required to break the carbon-carbon double bond, which in ethene is valued at $612\,kJ\,mol^{-1}$.

Carbocation

A reactive intermediate with a positively charged carbon atom, classified as primary, secondary, or tertiary based on the number of attached alkyl groups.

Positive Inductive Effect

The electron-releasing effect of alkyl groups that stabilizes the positive charge of an intermediate carbocation.

Markovnikov's Rule

A rule used to predict the major product of an addition reaction, stating that the hydrogen atom adds to the carbon with the most existing hydrogen atoms.

Bromine Water Test

A chemical test for unsaturation where an alkene decolourises a reddish-brown bromine solution through an addition reaction.

Monomer

A small molecule that can be bonded to other identical molecules to form a polymer.

Addition Polymer

A long-chain molecule formed from alkene monomers where the double bond opens to create a backbone of carbon atoms.

Plasticisers

Small molecules added to polymers to force chains apart, allowing them to slide and making the resulting plastic more flexible.

Low Density Poly(ethene) (LDPE)

A flexible polymer made at high pressure and temperature via free-radical mechanism, resulting in branched chains that do not pack together well.

High Density Poly(ethene) (HDPE)

A rigid polymer produced using a Ziegler-Natta catalyst at lower conditions, featuring minimal chain branching and high density.

Mechanical Recycling

A recycling process involving separating, washing, and grinding plastics into pellets to be melted and remoulded.

Feedstock Recycling

A recycling method where plastics are heated to break polymer bonds back into monomers for the production of new plastics.