Chapter 25 Aromatic Chemistry

Question 1

what is an aromatic compound

Answer 1

an organic compound that has a benzene ring made of unsaturated bonds

Question 2

what is a benzene ring

Answer 2

a ring of delocalised electrons from the p-orbitals that fluctuate above and below

Question 3

describe the test to distinguish aromatic compounds from cycloalkenes

Answer 3

add bromine water. cycloalkene discolour the bromine water

Question 4

give a property of benzene ring molecules

Answer 4

very stable

Question 5

what type of reaction do benzene molecules undergo and why

Answer 5

electrophilic substitution because electrophiles are attracted to areas of high electron density and it doesn’t have unsaturated bonds

Question 6

what are the 3 pieces of evidence that Kekule’s model for benzene is wrong

Answer 6

> Reactivity - Benzene does not decolourise bromine water implying no C=C bond or electrophilic addition
Length of the C=C bonds - using X ray diffraction to measure bond length aromatic has bond length not equal to C-C or C=C
enthalphy change for hydrogenation - benzene releases more energy than singular cyclohexane but less than Kekule model

Question 7

what are the 4 common exceptions when naming aromatic compounds

Answer 7

phenol - OH bonded to aromatic
benzoic acid - COOH bonded to aromatic
phenylamine - NH2 bonded to aromatic
benzaldehyde - HCO bonded to aromatic

Question 8

what is an electrophile

Answer 8

an atom or group of atoms that is attracted to an electron rich and accepts pair of electrons

Question 9

what is substitution

Answer 9

when one functional group replaces another different functional group that is removed

Question 10

what are the two conditions for halogenation of an aromatic compound

Answer 10

AlBr3 or FeBr3 halogen carrier catalyst

RTP

Question 11

what is a halogen carrier

Answer 11

catalyst that can split a halogen so that they heterolytically bond fission and therefore produce positive and negative ion

Question 12

what happens during the halogenation of an aromatic

Answer 12

the halogen carrier splits the halogen into ions then which then bonds to the benzene ring then the extra H is then removed and regenerates the original catalyst

Question 13

what are the two conditions required for the nitration of aromatic compounds

Answer 13

concentrated sulfuric acid catalyst

temp below 50C

Question 14

what is an alkylation reaction

Answer 14

introduces carbon chain onto benzene ring

Question 15

what are three conditions required for an alkylation reaction

Answer 15

Room temp
halogen carrier catalyst
anhydrous

Question 16

what is an acylation reaction

Answer 16

when benzene reacts with an acyl group

Question 17

what is the condition required for acylation

Answer 17

acidic catalyst

Question 18

explain the reactivity of phenol

Answer 18

phenol is a weak acid because its OH can donate its H+ ion but can’t fully dissociate so can react with strong bases

Question 19

what governs the acidity of a compound

Answer 19

stability of the anion

Question 20

what is a directing group

Answer 20

groups that attach to benzene and have a directing effect

Question 21

which directing groups are activators and the exception

Answer 21

groups 2 and 4 and the exception is halogen

Question 22

which directing group is a deactivators

Answer 22

groups 3