Chemistry Notes on Hydrocarbons and Functional Groups

Introduction to Hydrocarbons

  • Hydrocarbons are organic compounds composed only of carbon and hydrogen.
  • They are classified into four types:
    • Alkanes (saturated): single C-C bonds.
    • Alkenes (unsaturated): contain double bonds (C=C).
    • Alkynes (unsaturated): contain triple bonds (C≡C).
    • Aromatic hydrocarbons: cyclic structures with delocalized π electrons.

Importance of Carbon

  • Carbon forms extensive compounds, over 10 million known carbon compounds.
  • The study of carbon is organic chemistry; relevant to biochemistry, which involves the chemistry of living organisms.

Properties of Hydrocarbons

  • Hydrocarbons are generally nonpolar and insoluble in water but dissolve in nonpolar solvents.
  • Their boiling and melting points increase with molar mass due to London dispersion forces.

Structural Types of Alkanes

  • Alkanes have a general formula of CnH(2n+2).
  • Each carbon forms four bonds (single bonds).
  • Structural isomers, differing in bond arrangement, exist for alkanes with 4 or more carbon atoms.

Nomenclature of Alkanes

  • Named using IUPAC system: longest chain of carbons as the base name; substituents are numbered to minimize numbers assigned to them.
  • Example: 3-ethyl-2,4,5-trimethylheptane.

Reactions of Alkanes

  • Relatively unreactive; primary reaction is combustion.
  • Standard combustion reaction of alkanes generally involves complete oxidation to produce CO₂ and H₂O.

Unsaturated Hydrocarbons

  • Alkenes and alkynes undergo characteristic addition reactions.
  • Alkenes: contain at least one C=C bond; e.g., ethylene (C₂H₄).
  • Alkynes: contain at least one C≡C bond; e.g., acetylene (C₂H₂).

Aromatic Hydrocarbons

  • Aromatic compounds, like benzene, undergo substitution reactions instead of addition.
  • Stable due to delocalized π electrons.
  • Examples of reactions: nitration and Friedel-Crafts alkylation.

Functional Groups

  • Alcohols (R-OH): contain hydroxyl group (-OH); suffix -ol.
  • Ethers: contain an oxygen atom between two alkyl or aryl groups; suffix ether.
  • Important reactions of functional groups vary based on the group present, influencing the compound's reactivity.