Synthesis pathways: benzene & phenol

benzene → nitrobenzene

conc HNO3

conc H2SO4

reflux 50°C

mechanism for formation of electrophile in nitration of benzene

HNO₃ + H₂SO₄ ⇌ H₂NO₃⁺ + HSO₄^-

H₂NO^₃+ → H₂O + ⁺NO₂

nitrobenzene → phenylamine

Sn(s)

conc HCl

heat under reflux

nitrobenzene → phenylamine equation

phenylamine → 2,4,6 tribromo aniline

Br2

benzene → methylbenzene

CH3Cl

AlCl3

mechanism for benzene → methylbenzene

methylbenzene → 1-methyl-2-nitrobenzene/1-methyl-4-nitrobenzene

monosubstitution:

conc H2SO4

conc HNO3

room temp

methylbenzene → 1-methyl-2,4,6-nitrobenzene

conc H2SO4

conc HNO3

reflux

benzene → bromo-benzene

FeBr3 (halogen carrier e.g. Fe, AlCl3)

Br2

mechanism for benzene → bromobenzene

benzene → phenylethanone

AlCl3

ethanoyl chloride

phenylethanone → phenylethanol

NaBH4

phenol → 2,4,6-tribromo phenol

Br2

(white ppt) + 3HBr

orange decolourises

mechanism for phenol + Br2 (1 substitution)

phenol → sodium phenoxide

+ Na/NaOH

phenol → 2-nitrophenol/4-nitrophenol

HNO3(aq)

room temp

(product is also + H2O)

phenol → 2,4,6-nitrophenol

3HNO3(aq)

conc H2SO4(aq)

room temp

(product is also + 3H2O)

acid strength vs reactivity w Na compounds table

what substituents are 3 directing

• RCOR

• -COOR

• -SO3H

• -CHO

• -COOH

• -CN

• -NO2

• -NR₃⁺

(all are sightly e- withdrawing)

what substituents are 2,4 directing

• -NH2 or -NHR

• -OH

• -OR

• -R or -C6H5

• -F, -Cl, -Br, -I

(all are slightly e- donating)