Organic Chemistry

1)Formula

• molecular formula: the number of each atom in a molecule
• structural formula: shows how many atoms are joined together in a molecule
• displayed/graphical formula:show all of the bonds and spacing of atoms in a molecule
• skeletal formula:shows the bonds but not the carbon and hydrogen atoms.

2)functional group: the functional group is an atom or group of atoms joined to a carbon atom which makes the substace have it's own characteristic set of reactions

3)homologous series: these are groups of molecules in the same functional group and shows a trend in physical properties.

first find the number of carbon atoms in the longest chain... this is the base name.

then find the position of the branches on the longest chain

then find the functional group

number of carbon longest chain branch

1 methane methyl

2 ethane ethyl

3 propane propyl

4 butane butyl

5 pentane pentyl

Isomers: compounds with the same molecular formula but the atoms are arranged in a different way

• structural isomers: same molecular formula but different structural formula, e.g Pentane and 2,2-dimethyl propane.
• stereo isomers:these are molecules with the same molecular formula but different arrangement of the atoms.e.g geometric isomers-these occur when there is a double bond which does not allow rotation i.e trans-but-2-ene and cis-but-2-ene..... and optical isomers- the central carbon should be bonded to 4 different groups. 1 arrangement is a mirror image of the other and the central carbon is the chiral centre.

• they have single bonds between carbon-hydrogen and carbon- carbon atoms.
• carbon contain the maximum number of hydrogen atoms so they are saturated
• 4-bonds radiate from the carbon atom in the tetra-hedral pattern (109.5).

General physical properties

• they are non-polar molecules
• they are unreactive
• they have weak dipole-dipole attraction(vander Waals) which increase with teh number of electrons and therefore size of the molecules.
• branched alkanes do not pack easily so they tend to have lower melting and boiling points then molecules of the same mass.