Shapes of Aromatic Organic Molecules; σ & π Bonds (Cambridge (CIE) A Level Chemistry): Flashcards

A conjugated π system is a region of alternating single and double bonds in which electrons are delocalised across adjacent p orbitals, spreading electron density over the whole system.

Carbon atoms in benzene are sp² hybridised. Each carbon forms three σ bonds using its sp² orbitals and has one remaining p orbital that overlaps laterally with neighbouring p orbitals to form the delocalised π system.

True.

Because electrons are delocalised across the ring, all C–C bonds have the same length with both single and double bond character. This equal bond length is evidence for the delocalised ring structure.

Benzene is a planar molecule with bond angles of 120° due to sp² hybridisation of its carbon atoms.

An aromatic stabilisation is the extra stability gained by a molecule due to the delocalisation of π electrons over a conjugated ring system, making the compound more stable than predicted by a simple alternating double bond model.

Each sp²-hybridised carbon retains one p orbital perpendicular to the ring. These p orbitals on adjacent carbons overlap laterally around the ring, allowing electrons to spread freely across all six carbon atoms rather than being localised in fixed double bonds.

False.

In sp² hybridisation, the s orbital mixes with only two of the three p orbitals, forming three sp² hybrid orbitals. The remaining p orbital is unhybridised and participates in the π system.

Aromatic compounds often have pleasant odours. The word 'aromatic' in chemistry refers to compounds containing one or more rings with conjugated π systems.

All C–C bonds in benzene are the same length, intermediate between a C–C single bond and a C=C double bond. If benzene had alternating single and double bonds, two different bond lengths would be observed.