C7__Organic

Definition

A Hydrocarbon is a molecule is ONLY hydrogen and carbon. This means that they are Simple Covalent molecules


Name Scheme

Hydrocarbons are named based on the number of carbon atoms they have and then the type of molecule they are.

Number of C atomsPrefix
1Meth-
2Eth-
3But-
4Prop-
5Pent
6Hex-
7Hept-
8Oct-

Types of Hydrocarbons

Alkanes

Name Scheme - Prefix + -ane They have general formula . They are Saturated. Meaning they contain the maximum number of hydrogen atoms allowed by the bond capacity of the carbon atoms, There are no double bonds and each carbon is only bonded to one other carbon.

Alkenes

Name Scheme - Prefix + -ene They have general formula . They contain 1 double carbon bond which is electron dense making them HIGHLY REACTIVE. Alkenes can react with elements and the double carbon bond opens up and becomes single bonds. They are a Homologous series meaning they all have the same general formula.

Alcohols

Name Scheme - Prefix + -anol They have general formula with Functional Groups (Hence why it is written at the end and why hydrogen appears twice instead f it being 2n+2) They can produce a solution in water however this becomes harder the longer the chain.

Carboxylic Acid

Name Scheme - Prefix + -anoic + Acid They have general formula Functional Groups. Since the functional group contains a carbon atom n starts at so methanoic acid is They are a Homologous series meaning they all have the same general formula. They are Weak Acids


Short vs Long Chain Hydrocarbons

Short Chain Hydrocarbons have WEAKER intermolecular forces as there is less atoms - this is the reason for many of the differences so if you remember this you can figure out the rest with common sense

PropertyShort-Chain HydrocarbonsLong-Chain Hydrocarbons
Number of Carbon AtomsFew (e.g., C1-C4)Many (e.g., C15+)
Boiling PointLowHigh
Viscosity (thickness)Low (runny)High (thick)
FlammabilityHigh (burns easily)Low (hard to ignite)
Volatility (how easily it evaporates)HighLow
Smokiness of FlameClean flameSmoky flame
UsesFuels (e.g., LPG, petrol)Lubricants, bitumen (road surfacing)
Fractional Distillation LocationCollected at the top (cooler)Collected at the bottom (hotter)
Cracking Needed?NoYes (to make useful short-chain hydrocarbons)

Key Points:

  • Short-chain hydrocarbons are more useful as fuels because they ignite easily and burn with a clean flame.
  • Long-chain hydrocarbons are broken down by cracking to produce more useful, smaller molecules.
  • Fractional distillation is used to separate different hydrocarbons based on their boiling points.

Uses of Hydrocarbons

Combustion Of Hydrocarbons

Complete

Fuel + Oxygen Carbon Dioxide + Water

Incomplete

Fuel + Oxygen (Not Enough) Carbon Monoxide + Water


Esters

An ester is an organic compound formed by a Carboxylic Acid and Alcohol. It has general formula where is the hydrocarbon group from the carboxylic acid and is the hydrocarbon group from the alcohol. It has Functional Groups which is the link between the carboxylic acid and alcohol. The carboxylic acid is bonded to the carbon and the alcohol is bonded to the single bond oxygen.


Reactions

Alkenes

Hydrogenation

The double carbon bond opens up to form 2 single bonds for hydrogen

Alkene + Bromine Water

The bromine goes from orange to colourless. This means it is a good test for Alkene presence

Alkene + Halogen

It is an Addition Reaction as the double bond opens up forming 2 single bonds for the Halogen so only one molecule is produce. Effectively the halogen is just added on hence the name. Similar to Alkene + Hydrogen

Example

Hydration of Alkene

Requires temperature of 360, pressure of 70 and a phosphoric catalyst. It is high yield but requires lots of energy.

Alcohols

Oxidation

Alcohol + Oxidation Agent Carboxylic Acid + Water

Combustion

Fermentation of Sugar

Requires temperatures of 30 and yeast and to take place in anaerobic conditions. The ethanol must then be purified by distillation requiring lots of energy.

Carboxylic Acid

How to name salt Metal + alkane name + -oate

Carboxylic Acid + Metal

Carboxylic Acid + Metal Salt + Hydrogen

Example

Carboxylic Acid + Carbonate

Carboxylic Acid + Carbonate Salt + Water + Carbon Dioxide

Example

Carboxylic Acid + Alkali

Carboxylic Acid + Alkali Salt + Water This is a Neutralisation Reaction

Example

Making Esters

Carboxylic Acid + Alcohol Ester + Water This is a Condensation Reaction

Example