MEDCHEM7

These flashcards cover key concepts, definitions, and mechanisms related to aromatic hydrocarbons, benzene, and their reactions.

What is the molecular formula of benzene?

C6H6

What is the boiling point of benzene?

80 °C

Define 'resonance'.

Resonance is a concept in chemistry where a molecule can be represented by two or more structures that contribute to the overall hybrid structure.

What is Huckel’s rule for aromaticity?

To be aromatic, a compound should have a planar ring(s), each atom in the ring has a pz orbital, and there must be (4n + 2) p electrons (where n is an integer).

What type of reactions typically occur with aromatic compounds?

Electrophilic substitution reactions.

How does benzene's bonding differ from typical single or double bonds?

All carbon-carbon bonds in benzene are of equal length at 139 pm, showing no formal single or double bonds.

What is the aromatic stability of benzene measured by?

Heats of hydrogenation.

What does the 'aromatic sextet' refer to in benzene?

The aromatic sextet refers to the six p electrons in the p cloud of benzene.

What did Michael Faraday discover in relation to benzene?

Michael Faraday discovered benzene in 1825.

Who proposed the structure of benzene?

F. August Kekulé.

What colorless toxic liquid is classified as a hydrocarbon?

Benzene.

What are the names of the prefixes used for di-substituted benzenes?

Ortho-, meta-, and para- are used for 1,2-, 1,3-, and 1,4- positions respectively.

What is the significance of the term 'resonance hybrid'?

The resonance hybrid is the real structure of benzene, a composite of its various resonance forms.

What is the reaction mechanism of chlorination of benzene?

The mechanism involves the generation of an electrophile, followed by a reaction with the aromatic ring leading to a reaction intermediate.

What type of intermediate is formed during the electrophilic substitution in benzene?

A benzonium ion (carbocation) intermediate.

What is the effect of aromaticity on the stability of benzene?

Aromaticity imparts extra stability to benzene rings.

What are Friedel-Crafts reactions associated with?

Friedel-Crafts reactions involve carbon-carbon bond formation.

What kind of reaction do aryl halides undergo?

Aryl halides do not undergo Friedel-Crafts reactions successfully.

What type of electrophile is generated during the nitration of benzene?

Nitronium ion.

What does a curly arrow represent in reaction mechanisms?

A curly arrow represents the movement of a pair of electrons.

Where are 2pz orbitals in benzene located?

The 2pz orbitals are perpendicular to the plane of the six-membered ring.

What is the driving force for the step involving the loss of HÅ from the benzonium ion?

The regeneration of aromaticity.

What is the difference between resonance and equilibrium?

Resonance refers to various forms contributing to a single structure while equilibrium refers to the state where reactants and products are balanced.

What happens to the energy released during the hydrogenation of benzene?

The measured value is lower than expected due to extra stability from aromaticity.

What is the bond length of carbon-carbon bonds in benzene?

139 pm.

What are the names of some aromatic compounds derived from benzene?

Toluene, aniline, and phenol.

How does Friedel-Crafts alkylation differ from halogenations?

Friedel-Crafts reactions lead to the formation of carbon-carbon bonds, while halogenations involve substitution of halogens.

Who dreamt of a snake seizing its own tail to explain benzene's structure?

F. August Kekulé dreamed this, symbolizing the cyclic structure of benzene.

Why does benzene have a special stability compared to alkenes?

Benzene's aromaticity makes it more stable than alkenes.

What is considered the key electrophile in Friedel-Crafts reactions?

The carbocation generated from the alkyl halide.

What is required for a compound to be considered aromatic?

It must have a planar ring, pz orbitals on each atom in the ring, and (4n + 2) p electrons.

What is a common characteristic of the products of electrophilic substitution reactions in benzene?

They preserve the aromatic sextet.

What role does AlCl3 play in reactions involving benzene?

AlCl3 acts as a Lewis acid, helping to generate electrophiles.

What do you call compounds that contain many fused benzene rings?

Polycyclic aromatic compounds.

Which reaction mechanism uses 'curly arrows' to show bond forming and breaking?

Reaction mechanisms in organic chemistry.

What does the term 'benzenoid' refer to?

Aromatic compounds that contain a benzene ring.

What is the general outcome of Friedel-Crafts acylation?

Formation of aromatic ketones.

How do substituted benzenes differ in terms of reactivity?

Their positions and types of substituents greatly influence their reactivity in electrophilic substitutions.

What is the typical product of halogenation reactions of benzene?

Halogenated aromatic compounds.

What does it mean if a compound is non-benzenoid aromatic?

It has aromatic properties but does not contain a benzene ring.