Alkanes: Organic Chemistry Lecture

Organic Chemistry

• Organic chemistry is the study of the structure, properties, composition, reactions, and preparation of carbon-containing compounds.
• Most organic compounds contain carbon and hydrogen, but may also include other elements such as nitrogen, oxygen, halogens, phosphorus, silicon, and sulfur.

Aliphatic Hydrocarbons

• Aliphatic hydrocarbons are compounds drawn in an open-chain format.
• They can be classified into two types: saturated and unsaturated compounds.

Saturated Compounds

• Saturated compounds are those in which two carbon atoms are linked together only via a single bond.
• Alkanes are a type of saturated compound.

Alkanes

• Alkanes are organic compounds that consist of single-bonded carbon and hydrogen atoms and lack any other functional groups.
• All alkanes have the formula CnH2n+2.
• The simplest alkane is methane.
• Alkanes with unbranched carbon chains are called normal alkanes.
• Each member of the series differs from the next higher and the next lower member by -CH2 group (methylene group).
• Sources of alkanes are natural gas and petroleum.

Nomenclature of Alkanes

• Alkanes are named according to the following rules:
  • Class suffix is ane.
  • Choose the longest chain of carbon atoms and name it.
  • Number the parent chain, starting at the end closer to the substituent.
  • Identify the substituent and its positions.
  • Attach the number and name of the substituent to the name of the parent in alphabetical order.

Physical Properties of Alkanes

• Alkanes are non-polar compounds.
• The attractive forces between molecules are weak.
• The first four members are gases at room temperature, while the C5 to C17 alkanes are liquids.
• Soluble in non-polar compounds and insoluble in water.
• Alkanes are colorless and odorless by nature.
• The intermolecular Vander Waal force attracts alkane molecules.
• Alkanes with stronger intermolecular van der Waals forces have higher boiling points.
• The melting point of alkanes follows the same trend as their boiling point, increasing with increase in molecular weight.

Importance of Alkanes in Dentistry

• Anesthetics: Some alkanes, like halothane, have been used as inhalation anesthetics in dental procedures.
• Solvents: Alkanes serve as solvents for various dental materials.
• Impression Materials: Hydrocarbon-based impression materials are widely used in dentistry.
• Waxes: Dental waxes, used for modeling and casting, often contain alkanes.
• Lubricants: Alkanes find applications as lubricants for dental instruments and equipment.

Cycloalkanes

• Cycloalkanes are alkanes in which the carbon atoms are arranged in a ring.
• General molecular formula: CnH2n.
• The simplest cycloalkane is cyclopropane.
• Nomenclature of cycloalkanes:
  • Cycloalkanes are named according to the number of carbon atoms in the ring with the prefix cyclo-added.
  • If C ring = or > C substituent, it is named as an alkyl-substituted cycloalkane.
  • If C ring < C substituent, it is named as a cycloalkyl-substituted alkane.

Uses of Cycloalkanes

• In the pharmaceutical industry, they are employed as organic solvents.
• Cancer patients are treated with carboplatin, a drug synthesized from cyclobutane.
• Used as perfumes in the perfume industry and as pigments.
• Cyclopropane is employed as an anesthetic agent in the field of medicine.
• It is also utilized in petroleum industries.