An organic compound contains carbon and in almost all cases also hydrogen.

A homologous series is a family of organic compounds.

Features:
1. Successive members of a homologous series differ by a -CH2 group.
2. Members of a homologous series can be represented by the same general formula (for example C_nH_2n+2)
3. Members of a homologous series show a gradiation in physical properties (such as boiling point, density and viscosity).
4. Members of a homologous series have similar chemical properties (such as chemical reactivity).

The length of the carbon chain determines the boiling point with compounds with more carbon atoms having higher boiling points. As the molecules get larger and larger, the van der Waals forces between them increases and this makes the boiling point go up.

The longest chain of carbon atoms in the molecule gives the stem of the name.

Rule to remember: ME EAT PROPER BUTTER called PENT-HEX

1 carbon atom in longest chain is meth-
2 carbon atom in longest chain is eth-
3 carbon atom in longest chain is prop-
4 carbon atom in longest chain is but-
5 carbon atom in longest chain is pent-
6 carbon atom in longest chain is hex-

Identify the functional group because that gives the ending (or suffix) to the name. If for example there is a -OH group in the molecule then it is an alcohol and the name ends with -anol.

Identify the side chains of substituent groups and see what the number is of the carbon atom in the main chain that it is attached to. The name of these side chains will give the first part of the name (the prefix).

-CH₃ is called methyl-
-C₂H₅ is called ethyl-
-C₃H₇ is called propyl-
-NH₂ is called amino-
-F is called fluoro-
-Cl is called chloro-
-Br is called bromo-
-I is called iodo-

The two things that have to be considered when predicting physical properties are:

1. The length of the CH_n chain (the hydrocarbon skeleton).
2. The functional group.

Volatility is how easy a compound goes from liquid to gas.

High volatility = Low boiling point.

High volatility = weak intermolecular forces.

Hydrocarbon skeleton

1. Larger molecules have stronger van der Waals forces between them = Higher boiling point

2. Straight chained molecules without branches have stronger van der Waals forces between them = Higher boiling point

Functional group

3. Functional groups that are polar will develop dipole-dipole interaction = Higher boiling point



Note: Halogenoalkanes are alkanes with side chains containing Cl-,Br-, F- or I- atoms.

The solubility is determined by the extent to which molecules can form hydrogen bonds with water.

Hydrocarbon skeleton

1. Smaller molecules = Higher solubility

Functional group

2. Functional groups that enables hydrogen bonds = Higher solubility

10.2 - Alkanes

Hydrocarbon = compound that contains only hydrogen and carbon.

Saturated = compound with only single carbon-carbon bonds.

Alkanes have a low chemical reactivity because:

1. The C-C and C-H bonds are strong and therefore a strong source of energy is needed to break these bonds.

2. The C-C and C-H bonds are non-polar and therefore do not react with most reactants.

Free radical: contains unpaired electrons and is therefore very reactiv. Example: Cl^* contains 7 electrons in the outer shell.

Ion: has lost or picked up electrons and is therefore charged. Example: Cl^- contains 8 electrons in the outer shell because it has picked one up.

Homolytic fission: When a bond breaks by splitting the shared electrons so that two free radicals are produced (each with unpaired electrons).

Example Cl₂:

Since alkanes are saturated hydrocarbons they undergo substitution reactions in which one of the hydrogen atoms in the alkane is swapped for another atom. An example is halogenation in which the news atom is a halogen such as Cl, BR, I or F.

10.3 - Alkenes

Hydrocarbon = compound that contains only hydrogen and carbon.

Unsaturated = compound with at least one double carbon-carbon bond.

Since alkanes are unsaturated hydrocarbons they undergo addition reactions in which the double bond is broken so that new bonding positions are created and the compound becomes saturated (only single bonds).

1.Alkenes undergoes addition reactions easily but not alkanes. If one put alkanes and alkenes in red bromide water it will become clear for alkenes because of reactions with the bromide but not with alkanes.

2. If one burn alkanes and alkenes, the alkenes have a dirtier, smokier flame because they have a higher ratio of carbon to hydrogen atoms. Compounds with benzene rings are very unsaturated (have many double bonds) and have even dirtier flames because of even higher carbon to hydrogen ratios.

The process of making long chains of thousands of atoms (polymers) from alkenes by breaking their double bonds are called polymerization. Plastics are typical polymers.

The alkene used is called the monomer and determines the chemical properties of the polymer.

10.4 - Alcohols

Alkanes: C_nH_2n+2

Alkenes: C_nH_2n

Alcohols: C_nH_2n+1OH

Halogenoalkanes: C_nH_2n+1X where X = halogen = F, Cl, BR, I

The -OH group is polar and increases therefore volatility and water solubility compared to alkanes.

Burning of methanol:

2CH₃OH(l) + 3O₂(g)   →   2CO₂(g) + 4H₂O(g)

Longer alcohol molecules will release more energy per mole due to the increasing number of CO₂ molecules that are produced in the reaction.

10.5 - Halogenoalkanes