Chem 2-1 Organic compounds by xiuliliaofz

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         Sc 30 Chemistry
Topic 2.1 Part 1: Organic Compounds




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Review of Science 20:

Organic chemistry is the study of compounds composed of carbon

Carbon can have single, double or triple bonds.

    Name            Example            Diagram          Formula          Saturation


Alkanes          Ethane                               CnH2n+2        Saturated




Alkenes          Ethene                               CnH2n          Unsaturated




Alkynes          Ethyne                               CnH2n-2        Unsaturated



Benzene
            Hydrocarbons can have cyclic shapes as well. A benzene ring is a
            hexagonal hydrocarbon structure that has a very high stability and is found
            within many organic compounds.

            It may also be referred to as an aromatic ring or a phenyl ring/group.

The diagram below shows why benzene is so stable. It has a unique bonding structure
called resonance. When analyzing the bonds in benzene, all of the bonds are the same
length and strength, meaning that the compound does not exist as one of the molecules
below, but instead is both configurations at the same time. The electrons are shared
with an even distribution around the ring. Because of this unique arrangement, benzene
is a planar or flat molecule with low reactivity.




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             Benzene is often shown using the diagram to the left as this represents the
             even strength of all of the carbon-carbon bonds in benzene.


Benzene issues:
Benzene is carcinogenic, however it is also a common substance within natural
resources like petroleum and coal. Gasoline contains a large amount of benzene. In
Canada there are now regulations on how much benzene gasoline can contain.

This is one of the reasons why gasoline spills can be an environmental concern.
Benzene can leak into ground water, which can then contaminate well or drinking water.
Often water tests will include tests for hydrocarbons such as benzene.

Remediation is the process of breaking down or removing hydrocarbons from soil.
Linear hydrocarbons can be broken down relatively easily. However, benzene is very
hard to break down because of its high stability. Benzene is a persistent organic
pollutant (POPs)

Polycyclic Aromatic Hydrocarbons
                  Some aromatic compounds consist of more than one ring such as
                  benzopyrene. These compounds have a very high stability and most
                  are also carcinogens. They can result from incomplete combustion of
                  oils at high temperature. This can occur in cars, furnaces, etc and are
                  particulate-matter emissions, meaning they are solid particles being
                  released.

These compounds are called PAHs

Questions:
  1) Benzene in gasoline is not broken down in car engines because the temperature
      in the engine is not high enough. Explain why benzene does not break down
      using what you know about benzene’s structure.




   2) List 2 other names for benzene




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 3) Draw three different diagrams to represent a benzene ring.




 4) Coca Cola used to have several chemicals in it (sodium benzoate and ascorbic
    acid) that can react to form benzene. Explain why this is a concern.




 5) The following substances pictured below are components of gasoline. Identify
    which appropriate descriptors apply to the following substances from the
    following list: alkane, alkene, aromatic compound, organic compound, cyclic
    hydrocarbon (every compound will have more than 1, show all that apply).

  Compound              Descriptors            Compound             Descriptors




2-methylpropane                                   1,3,5-
                                            trimethylbenzene




    butane
                                            2-methylbut-2-ene




 cyclohexane                                   napthalene


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