Aromatic Organic Chemistry Quiz

Aromatic Organic Chemistry

• Aromatic compounds, also known as "mono- and polycyclic aromatic hydrocarbons," are organic compounds containing one or more aromatic rings.
• The word "aromatic" originally referred to the odor of the molecules, but the current definition is unrelated to odor.
• Aromatic compounds are closely related to heterocycles, which have at least one carbon atom in the CH group replaced by another heteroatom (oxygen, nitrogen, or sulfur).
• Examples of non-benzene aromatic compounds include furan and pyridine.
• Aliphatic hydrocarbons lack aromatic rings.
• Aromatic compounds play crucial roles in biochemistry, serving as building blocks of proteins (e.g., histidine, phenylalanine, tryptophan, and tyrosine).
• Important aromatic hydrocarbons like benzene, toluene, ortho-xylene, and para-xylene are major industrial chemicals, with worldwide production exceeding 35 million tonnes annually. They are extracted from petroleum and coal tar, and used to create various chemicals and polymers (e.g., styrene, phenol, aniline, polyester, and nylon).
• Benzene has the molecular formula C6H6. Its structure consists of a hexagonal ring of carbon atoms, each bonded to one hydrogen atom.
• Benzene is a colorless, highly flammable liquid with a sweet odor and is a crucial precursor for complex chemicals like ethylbenzene and cumene.
• Benzene is classified as an aromatic hydrocarbon due to its cyclic continuous pi bonds.

Benzene Derivatives

• Many benzene derivatives have specific names.
  • Examples include toluene, styrene, cumene, benzaldehyde, phenol, benzoic acid, acetophenone, aniline, benzenesulfonic acid, and anisole.
• Nomenclature of benzene derivatives:
  • For simple mono-substituted benzene, the substituent prefix is combined with the word "benzene" (e.g., aminobenzene, nitrobenzene).
  • Di-substituted benzene derivatives use prefixes (ortho, meta, para) to specify the positions of substituents.
  • More complex substitution patterns use numerical prefixes.

Aromatic compounds. General properties

• Aromatic compounds are ring-shaped and have carbon atoms in the same plane.
• They are characterized by conjugated double bonds.
• Hybridization of the atoms is SP2
• Huckel's rule applies.
  • The number of pi electrons equals 4n + 2, where n = 0, 1, 2 ...

Benzene isomers:

• Different structures of benzene rings have similar names

Preparation of Benzene

• Benzene can be prepared through various reactions.
  • Reaction of phenol with zinc dust.
  • Reaction of benzoic acid and its salts with sodalime.
  • Passing acetylene through a hot red tube.
  • Boiling benzene sulfonic acid in HCl/H₂O

Chemical Reactions of Benzene and its Derivatives

• Electrophilic substitution reactions (e.g., nitration, sulfonation, halogenation, Friedel-Crafts alkylation, and Friedel-Crafts acylation) are common for benzene derivatives.
• Addition reactions (e.g., addition of hydrogen or halogens) are also possible for benzene, but less common than substitution.

Mechanisms of electrophilic substitution reactions.

• The mechanism involves electrophilic attack on the benzene ring, followed by proton transfer to restore aromaticity.

Nomenclature of Benzene

• Different groups of benzene have similar names
• The position of substituent is indicated with O,M, or P

Isomerism

• different structures can have same names

Reactions of Aromatic Aldehydes and Ketones

• Aromatic aldehydes and ketones undergo various reactions.
  • Oxidation (e.g., using KMnO₄, MnO₂/H₂SO₄).
  • Reduction (various methods).
  • Formation of hydrazones, phenylhydrazones, oximes, and semicarbazones (various methods).
  • Cycloaddition reactions

Synthesis of Aromatic Ketones

Reactions of Aromatic Compounds

• Various reactions to prepare aromatic ketones and aldehydes.

Aromatic Carboxylic Acids

• A wide range of carboxylic acids with aromatic rings exist
• Methods of Synthesis from toluene
• Reactions of Carboxylic Acids
  • Reaction with sodium hydroxide
  • Reaction with sodium carbonate
  • Reaction with ammonia hydroxide
  • Reaction with LiAlH₄
  • Esterification reaction.

Phenols

• Phenols are organic compounds with a hydroxyl group directly attached to an aromatic ring
• Phenols have different types (e.g., catechol, resorcinol, quinol)

Synthesis of Phenols

• Preparation methods for phenols
  • From salicylic acid -From benzene -From aniline

Reactions of Phenols

• Ester Formation
• Reactions with Phosphorous Pentachloride
• Reactions with Bromine
• Alkylation reactions
• Nitration
• Reduction reactions.