6.1.1 Aromatic Compounds (incomplete)

What are arenes?

aromatic hydrocarbons containing one or more benzene rings

What is the relationship between aromatic and aliphatic compounds?

they are mutually exclusive

What is the molecular formula of a benzene ring?

C6H6

What is the skeletal formula of a benzene ring?

What is the displayed formula of a benzene ring?

How are benzene rings with a halogen group named?

halo-benzene

How are benzene rings with an alkyl group named?

alkyl-benzene

How are alcohols with a benzene ring named?

phenyl-alcohol

How are benzene with a ketone group named?

phenyl-ketone

What is a nitro group?

-NO2

How are arenes with a nitro group named?

nitrobenzene

How are arenes with a halogen and alkyl group named?

halo-alkyl-benzene

How is an arene with a carboxylic acid named?

benzoic acid

What is an amine group?

-NH2

How are arenes with an amine group named?

phenylamine

How are are arenes with an OH group named?

phenol

When is the phenyl-prefix used when naming arenes?

when the benzene ring is attached to a alkyl group with 7 or more carbons or that contains a functional group

When is the benzene suffix used when naming arenes?

attached to an alkyl group woth less than 7 carbons or directly attached to a group

What are the exceptions when naming arenes?

• phenol

• benzoic acid

• benzaldehyde

• phenylamine

What is the name of C6H4OHNO2?

2-nitro-phenol

Who suggested that the structure of benzene is the same as triene?

Kekule von Stradonitz

What is the Kekule structure of benzene?

triene

Give 3 pieces of evidence that suggest the Kekule structure of benzene is incorrect?

• resistance to reacting with bromine

• bond lengths

• enthalpy change of hydrogenation

Does benzene decolourise bromine at room temperature?

no

Why doesn’t benzene react with bromine?

it doesnt contain C=C bonds

How can the bond lengths of benzene be found?

xray diffraction analysis

Describe the bond lengths in benzene?

• all C-C bond lengths are the same

• the C-C bond length is between that of C-C and C=C length

What do the bond lengths of benzene suggest?

benzene does not consist of alternating, isolated C-C and C=C bonds

Compare the enthalpy change for the hydrogenation of benzene and the hydrogenation of triene?

the enthalpy change for hydrogenation of benzene is less exothermic than predicted

What does the enthalpy change for the hydrogenation of benzene suggest?

benzene does not contain 3 C=C bonds and is more stable than expected

Compare the stability of benzene and triene

benzene is more stable

What is the theoretical enthalpy change for hydrogenation of triene?

-360

What is the enthalpy change for benzene?

-208

What is the correct structure of benzene?

the delocalised structure

Describe the delocalised structure of benzene

• cyclic molecule

• shape around each C molecule is trigonal planar (120)

• sigma bonds between each carbon atom

• a pi system above and below the plane of carbon rings that consists of 6 delocalised electrons

What is the shape and around each C atom of benzene?

trigonal planar, 120

What bonds exist between the C atoms and CH atoms?

sigma bond

How are sigma bonds formed?

single overlap of orbitals directly between the nuclei of C atoms

How is rge pi system of a benzene ring formed?

formed by the sideways double overlap of p orbitals on each c atom on the carbon ring

How many delocalised electrons does the benzene pi system consist of?

6

Describe the delocalised electrons in the benzene system?

they are mobile across all 6 carbon atoms on the benzene ring

What are the similarities between the pi bond in cyclohexene and the pi system in benzene

• pi bond formed in the same way

• pi bond above and below the plane

What are the differences between the pi bond in cyclohexene and the pi system in benzene

• pi system made up of 6 delocalised electrons while pi bond made up of 2

• pi system - electrons are delocalised, pi bond- electrons are localised