Alkanes are a type of organic compounds composed of carbon and hydrogen atoms, and they form a family of saturated hydrocarbons with single covalent bonds.
Alkanes belong to a homologous series, which is a group of organic compounds having the same functional group (in this case, single carbon-carbon bonds) but differing by a CH2 unit in molecular formula from one member to the next.
Organic compounds are present in natural gas, a fossil fuel composed mainly of methane (CH4) and other hydrocarbons, formed from the decomposition of organic matter in ancient deposits of plants and microorganisms.
All compounds in the series have the same functional group.
Each successive member has an additional CH2 unit in the molecular formula compared to the previous one.
Members of the series exhibit analogous chemical behavior.
There is a gradual change in physical properties, such as boiling points and melting points.
The series can be represented by a general formula to express the relationship between members.
Alkyl radicals form when alkanes undergo homolytic bond cleavage, breaking the carbon-carbon single bond equally, resulting in the formation of two highly reactive species called radicals (a species with an unpaired electron).
Initiated by the absorption of energy, usually in the form of heat or light, which breaks the weak carbon-hydrogen (C-H) bond in an alkane to create two alkyl radicals.
The alkyl radicals formed in the initiation step react with other molecules, often alkanes, producing new radicals and generating a chain reaction.
The alkyl radicals formed in the initiation step react with other molecules, often alkanes, producing new radicals and generating a chain reaction.
Eventually, the radicals combine with each other or react with other molecules to form stable products, terminating the chain reaction.
Alkanes | Molecular Formula | Alkyl Radical | Name of Alkyl Radical |
Methane | CH₄ | CH₃- | Methyl |
Ethane | C₂H₆ | C₂H₅- | Ethyl |
Propane | C₃H₈ | C₃H₇- | Propyl |
Butane | C₄H₁₀ | C₄H₉- | Butyl |
Pentane | C₅H₁₂ | C₅H₁₁- | Pentyl |
Hexane | C₆H₁₄ | C₆H₁₃- | Hexyl |
Heptane | C₇H₁₆ | C₇H₁₅- | Heptyl |
Octane | C₈H₁₈ | C₈H₁₇- | Octyl |
Nonane | C₉H₂₀ | C₉H₁₉- | Nonyl |
Decane | C₁₀H₂₂ | C₁₀H₂₁- | Decyl |
The alkyl radicals formed in the initiation step react with other molecules, often alkanes, producing new radicals and generating a chain reaction.
Saturated Hydrocarbons | Unsaturated Hydrocarbons |
Contains only single bonds between carbon atoms. | Contain at least one double or triple bond between carbon atoms. |
Have the maximum possible number of hydrogen atoms. | Have fewer hydrogen atoms due to double or triple bonds. |
Less reactive compared to unsaturated hydrocarbons. | More reactive due to the presence of multiple bonds. |
Generally, have higher boiling points. | Tend to have lower boiling points than saturated hydrocarbons. |
Examples include alkanes (e.g., methane, ethane). | Examples include alkenes (e.g., ethene, propene) and alkynes (e.g., ethyne, propyne). |
Are relatively stable and less likely to undergo chemical reactions. | Can undergo addition reactions due to the presence of multiple bonds. |
CnH2n+2 is the general formula. | CnH2n is the general formula for alkenes, and CnH2n-2 for alkynes. |
Each carbon atom forms four single covalent bonds. | Carbon atoms form one or more double or triple covalent bonds with each other. |