Aromatic Chemistry 1

Question 1

what are the uses of aromatic compounds?

Answer 1

• medicines
• perfumes
• plastics
• dyes
• explosives
• LCDs

Question 2

how can coal be modified to make an aromatic hydrocarbon source?

Answer 2

coal —> 1000 degrees, inert Atm —> coal tar

coal tar then fractionally distillated

Question 3

how can petroleum be obtained from oil?

Answer 3

catalyst pressure + 500 degrees

Question 4

structure of benzene

Answer 4

• c6h6

- 4 degrees of unsaturation / ring systems

Question 5

what proves that benzene is not totally unreactive?

Answer 5

• metal catalyst benzene brominated
• reaction gives substitution
• further reaction gives 3 di-brominated compounds

Question 6

what did kekule suggest?

Answer 6

suggested first monocyclic hexagonal structure

problem: carbon needs 4th valence

he then suggested that benzene was cyclohexatriene

Question 7

what are the problems with benzene being cyclohexatriene?

Answer 7

• is an alkene

- we know benzene doesn’t react like alkene

Question 8

what is the single c-c bond length?

Answer 8

1.54 A

Question 9

what is the double c-c bond length?

Answer 9

1.33 A

Question 10

example of resonance hybrids

ethanoate acetate

Answer 10

• chemical resonance hybrids only available for comp with delocalised e
• allows e to move freely

Question 11

freedom of electron stability inc…

Answer 11

stability

Question 12

example of resonance hybrids

1,3 butadiene

Answer 12

• only e move, never nuclei
• only e in pi bond + lone pairs take part
• total charge + no. e must stay constant

Question 13

benzene is a …

Answer 13

resonance hybrid

Question 14

how can you remove the ring of delocalised electrons in benzene?

Answer 14

react with h2, Ni

250 degrees, 25 atm

Question 15

benzene has a lower enthalpy of hydrogenation that the alkene

therefore what is essential for aromaticity?

Answer 15

cyclic conjugated systems