Organic compounds are often written as structural formulae, with lines representing bonds.

Structural formulae may be expanded, condensed, or skeletal:

• Expanded form has each hydrogen atom drawn individually coming off the carbons.
• Condensed form has the hydrogens for each carbon written directly next to it.
• Skeletal form means not writing the letters for carbon or hydrogen at all - the chains are drawn as straight lines with corners, where each corner represents a carbon and all its necessary hydrogens.

The number of bonds on each element follows specific rules:

• Carbon atoms must have exactly 4 bonds each
• Hydrogen atoms must have exactly 1 bond each
• Neutral oxygen atoms must have exactly 2 bonds each, and oxygen atoms with a 1- charge must have exactly 1 bond each
• Neutral nitrogen atoms must have exactly 3 bonds each, and nitrogen atoms with a 1+ charge must have exactly 4 bonds each

Number of carbons in main chains or side chains is determined by these prefixes:

• meth = 1 carbon
• eth = 2 carbons
• prop = 3 carbons
• but = 4 carbons
• pent = 5 carbons
• hex = 6 carbons
• hept = 7 carbons
• oct = 8 carbons

Functional group positions are indicated by numbers, with each number representing a carbon along the main chain (or a bond on the main chain, for alkene and alkyne groups.

A table of functional group formulae and names is attached.

If there are multiple of the same functional group in the compound, this will be indicated by a prefix:

• di = 2 of the same group
• tri = 3 of the same group
• tetra = 4 of the same group

Organic practice programs: naming | drawing

The melting and boiling point of a compound depends on the strength of secondary forces:

• The strength of dispersion forces (longer chains lead to higher melting/boiling points)
• The presence of polar groups (more polar groups leads to higher melting/boiling points)

The solubility of a compound in another depends on how similar their secondary forces are. Compounds with a shorter nonpolar hydrocarbon chain and more polar groups will tend to dissolve better in water, because it is highly polar.

Some of the common reactions between organic compounds include:

• combustion (burning in the presence of oxygen gas) to produce carbon dioxide and water
• addition (combining a small molecule onto a larger molecule) for example addition of bromine to an unsaturated compound
• elimination (producing a small molecule from a larger molecule) for example condensation of water in esterification
• oxidation, for example of a primary alcohol to an aldehyde, of a secondary alcohol to a ketone, or of an aldehyde to a carboxylic acid
• reaction of an aldehyde with Tollen's reagent to produce a silver mirror
• hydrolysis (reaction with water)

Some organic compounds are quite unreactive, for example:

• Tertiary alcohols are not oxidised
• Benzene is a reasonably unreactive group

Organic practice programs: reactions | products | polymers/monomers

Isomers are compounds that have the same molecular formula (number of each element) but different shape. Homologous series include compounds with the same general formula (the molecular formula follows a certain pattern).