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๐Ÿ“ Alkanes

๐ŸŽง๏ธ Listen to the recording and mind pronunciation of words.#


The physical and chemical properties of organic compounds depend on the number, arrangement of carbon atoms in the molecule and the functional groups in the molecule.
All the carbon atoms are arranged in a straight chain. Often there are shorter chains of carbon atoms branching off a longer chain. These are known as branched molecules. Carbon atoms can be arranged to form rings. These are known as cyclic molecules. These are some of the most important functional groups found in organic molecules: alkane with single bonds only (no functional group), alkene with double bond, halogenoalkane with Cl, Br or I atom attached to a carbon atom, and alcohol with O atom in between a C atom and an H atom.
Organic compounds can be represented in a number of ways: displayed formula (showing all covalent bonds), structural formula (not showing covalent bonds), skeletal formula (not showing carbon atoms), molecular formula showing the number of each atom in one molecule of the compound. Organic compounds with the same functional group, but a different number of carbon atoms, are said to belong to the same homologous series. Isomers are molecules which have the same molecular formula but different structures. Structural isomers are molecules which have the same molecular formula but a different arrangement of covalent bonds.
The different arrangement of covalent bonds can result from:

  • positional isomers are molecules with the same molecular formula but have the functional group on different positions in the molecule;
  • chain isomers are molecules with the same molecular formula but a different arrangement of carbon atoms; and
  • functional group isomers are molecules with the same molecular formula but different functional groups.

Stereoisomers are molecules with the same structural formula but a different spatial arrangement of atoms. Cisโ€“trans isomers arise because of the restricted rotation around a C=C double bond. Optical isomers contain a chiral centre (a carbon atom bonded to four different atoms or groups of atoms), resulting in mirror images of the molecule that cannot be superimposed.