chapter 27- aromatic chemistry

Question 1

what are arenes

Answer 1

hydrocarbons based on benzene C6 H6

Question 2

is benzene saturated or unsaturated

Answer 2

unsaturated

Question 3

what is the structure of benzene

Answer 3

it is a flat, regular hexagon of carbon atoms each of which is bonded to a single hydrogen atom

Question 4

bonding in benzene

Answer 4

each carbon atom has 3 covalent bonds, one to a hydrogen atom and the other two to carbon atoms.
-the fourth electron of each carbon is in a p-orbital. the p-orbitals overlap to form a region of electron density above and below the ring

Question 5

why is the delocalised system of benzene important

Answer 5

because it makes benzene unusually stable, aromatic stability

Question 6

what are physical properties of arenes

Answer 6

• benzene is a colourless liquid at room temperature
• it boils at 353 K and freezes at 279 K

Question 7

why is benzenes melting point much higher than that of hexanes

Answer 7

because benzenes flat, hexagonal molecules pack together very well in the solid state. they are therefore harder to separate

Question 8

two factors that are important to the reactivity of aromatic compounds

Answer 8

• the ring is an area of high electron density and it therefore attacked by electrophiles
• the aromatic ring is very stable

Question 9

why do arenes produce noticeable smoke when burned in air

Answer 9

due to the high carbon:hydrogen ratio compared with alkanes

Question 10

what is a use of nitrated arenes

Answer 10

• to produce TNT
• to make aromatic amines which are then used to make industrial dyes