Aromatic

• Benzene


  CH, first isolated in 1825 by English chemist Michael Faraday from the oily residues after heating whale oil under pressure to produce a gas used to illuminate buildings in London
• Benzene


  • Serves as gasoline additive
  • Used in fungal infections (anti-fungal)
• Benzoic acid


  C₂H₂CO₂H, a compound obtained by chemical degradation of gum benzoin, the fragrant balsam exuded by a tree that grows on the island of Java, Indonesia
• Benzene, toluene, and related hydrocarbons, while not particularly pleasant-smelling themselves, were classified as aromatic because they were obtained from fragrant substances

  
• Aromatic compounds


  Hydrocarbons that contain a benzene ring as a structural unit

  
• Aromatic compounds


  • Benzene
  • Toluene
  • Naphthalene

  
• Benzene derivatives


  Compounds formed by replacing one of the hydrogens in benzene with a different functional group
• Benzene derivatives


  1. Alcohols yield aldehyde or ketones

  2. Aldehyde yield carboxylic acid

  3. Primary alcohol: 1 carbon attached to OH

  4. Secondary alcohol: 2 carbon attached to OH

  5. Tertiary alcohol: 3 carbon attached to OH

  
• Aromatic hydrocarbons


  • All are either liquids or solids at room temperature; none are gases
  • Insoluble in water
• Benzene was once widely used as a solvent, but evidence of its carcinogenic properties prompted its replacement by less hazardous solvents
• Electrophilic aromatic substitution reaction

  The most common reactions of aromatic compounds involve substitution of other atoms or groups for a ring hydrogen on the aromatic unit
• Bromination or chlorination of benzene

  1. Requires a Lewis acid such as ferric bromide or ferric chloride

  2. Hydrogen is substituted by halogen

  
• Iodination of benzene


  1. Electrophilic iodine (I+) is obtained by treating 12 with an oxidizing agent such as nitric acid

  2. Iodine doesn't need a catalyst, but it needs an oxidizing agent
• Nitration of benzene


  Requires nitric acid and sulfuric acid as a catalyst
• Sulfonation of benzene


  1. Fuming sulfuric acid (a solution of SO3 in sulfuric acid) or concentrated sulfuric acid is used

  2. Catalyst: heat
• Sulfonic acid


  A strong acid because of the three electron-withdrawing oxygen atoms and the stability of its conjugate base
• Friedel-Crafts acylation


  Places an acyl group on a benzene ring

  
• Friedel-Crafts alkylation


  Places an alkyl group on a benzene ring

  
• Friedel-Crafts acylation


  • Either an acyl halide or an acid anhydride can be used
  • Acyl halide limitations: can only be used to give ketones, arylamines are unreactive with acylation, amine and alcohols can give competing nitrogen, alcohol (OH) acylation

  
• Friedel-Crafts alkylation


  • Alkyl halides limitations: phenyl/aryl halides will not react, prone to carbonation rearrangement
  • Alkyl fluorides, alkyl chlorides, alkyl bromides, and alkyl iodides can all be used

  
• Aromatic hydrocarbon derivatives


  • Phenobarbital (treatment for seizures)
  • Phenytoin (excessive hair growth / jaw)
  • Phenylbutazone (NSAID)
  • Aforvastatin (for cholesterol)
  • 17α Ethinylestradiol (a contraceptive drug)
  • Warfarin (anticoagulant)
  • Amphetamine (psycho stimulant)

  
• The reaction between an aldehyde or ketone with HCN is called the Reimer-Tiemann reaction.
• The product from the Reimer-Tiemann reaction is a phenylhydrazine derivative
• Phenylhydrazines are used as antioxidants, preservatives, dyes, and pharmaceuticals.
• The reaction between an aromatic compound and NH3 is called the Gabriel synthesis
• The product from the Gabriel synthesis is an aminoalkylbenzene
• Aniline is used in the production of dyestuffs, herbicides, insecticides, fungicides, and pharmaceutical products.
• The reaction between an aromatic compound and NaNO2 followed by HCl is called the Sandmeyer reaction
• Aniline is produced by reduction of nitrobenzene using iron filings and dilute sulfuric acid.
• Aminoalkylbenzenes can be oxidised to form nitro compounds
• Benzenediazonium salts are formed when diazonium salt is treated with benzene.
• The Gabriel Synthesis produces amino alcohols which have applications such as drugs, fragrances, flavors, and pesticides.
• Nitroarenes can be reduced to aminobenzenes using hydrogen gas over a nickel catalyst (Catalytic Reduction)
• Nitroarenes can be reduced to aminobenzenes using hydrogen gas over a nickel catalyst (Catalytic Reduction)
• In the Friedel-Crafts acylation, the electrophile is an acyl cation that forms by protonating the carbonyl oxygen atom.
• In the Friedel-Crafts acylation, the electrophile is an acyl cation that forms by protonating the carbonyl oxygen atom.
• Nitro compounds can be reduced back to their parent hydrocarbon using iron filings and dilute sulfuric acid (FeSO4).
• In the Friedel-Crafts acylation, the electrophile is an acyl cation that forms by protonating the carbonyl oxygen atom.
• Nitrobenzene can be reduced to aniline with tin or zinc dust and hydrochloric acid (Zn/HCl).
• Nitro compounds can be reduced back to their parent hydrocarbon using iron filings and dilute sulfuric acid (FeSO4).