Organic Chemistry – Fuels & Heats of Reaction

Organic Chemistry – Fuels & Heats of Reaction

Organic chemistry is the chemistry of carbon containing compounds.

hydrocarbon is a substance that contains only carbon and hydrogen.

There are three main hydrocarbons on the course – alkanesalkenes and alkynes.

homologous series is a series of compounds:

  • of similar chemical type.
  • that show gradual change in their physical properties.
  • all are prepared in a similar way.
  • have a common general formula (C_{n} H_{2n + 2}).
  • differ one from the next by a (CH_{2}) group.

The Alkanes

The first homologous series we deal with is calles the alkanes (The ending tells us the chemical family).

  1. Methane – CH_{4}
  2. Ethane – C_{2}H_{6}
  3. Propane – C_{3}H_{8}
  4. Butane – C_{4}H_{10}
  5. Pentane – C_{5}H_{12}
  6. Hexane – C_{6}H_{14}
  7. Heptane – C_{7}H_{16}
  8. Octane – C_{8}H_{18}
  9. Nonane – C_{9}H_{20}
  10. Decane – C_{10}H_{22}

Structural Isomers

Structural isomers are compounds with the same molecular formula but different structural formulas.

butane-structural-representation

The isomers are named systematically by IUPAC (International UNion of Pure and Applied Chemistry). The above C_{4}H_{10} is names as 2, methy propane.

How to give systematic names to Isomers

  1. Identify the longest straight chain. (eg. propane).
  2. Identify any groups hanging off the chain. (eg.  CH_{3} – methyl).
  3. Number the carbons to identify (bu the lowest number) which carbon the methyl group is hanging off – (In this case 2).

The name of the compound: 2, methyl propane.

Representing Structures of Organic Molecules

The Alkenes

The alkenes are the second homologous series of hydrocarbons in the course.

  • Alkenes contain a carbon-carbon double bond _{H}^{H}>\textrm{C} = \textrm{C} < _{H}^{H}
  • Alkenes are said to be unsaturated.
  • General formula: C_{n} H_{2n}
  • In the lab ethene is made by dehydrating ethanol using the dehydrating agent aluminium oxide.

The Alkynes

Alkynes are hydrocarbons characterised by a carbon-carbon triple bond.

  • Alkynes contain a carbon-carbon triple bond H -\textrm{C} \equiv \textrm{C} - H
  • They are highly unsaturated.
  • General formula: C_{n} H_{2n-2}
  • To prepare ethyne, we drop water onto calcium dicarbide or calcium carbide.

Configurations of carbons

When a carbon is surrounded by four single bonds, it is said to be in tetrahedral configuration.

When a carbon is joined to another atom with a double or triple bond, it is said to be in a planar configuration.

Aromatic Hydrocarbons

Aromatic compounds are compounds that contain a benzene ring structure in their molecules.

500px-Benzene-2D-full-264x300

An aliphatic compound is an organic compound that consists of open chains of carbon atoms and closed chain compounds (rings) that resemble then in chemical properties.

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