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ORGANIC CHEMISTRY
Organic chemistry is the study of carbon containing compounds and their properties. This includes the great majority of chemical compounds on the planet, but some substances such as carbonates and oxides of carbon are considered to be inorganic substances even though they contain carbon.
Organic chemicals are continually released into the environment in large quantities. There is a need to understand how these organic molecules will interact with the environment in order to minimise their impact. To achieve this the type of reactions that organic molecules undergo needs to be understood.
Comparison of the properties of organic and inorganic compounds
Organic Compounds |
Inorganic Compounds |
Use mostly covalent bonding Are gases, liquids or solids with low melting points Mostly insoluble in water Many are soluble in organic solvents such as petroleum, benzene and hexane Solution in water generally do not conduct electricity Almost all burn Slow to react with other chemicals |
Mostly ionic bonding Are generally solids with high melting points Many are water soluble Most are not soluble in organic solvents When dissolved in water conducts electrical current Most not combustible Often undergo fast chemical reactions |
The vast majority of organic compounds are typically chains or rings of carbon atoms that contain other elements such as O, N, P, S, Cl, Br and I. There are over five million of these compounds known today and an almost infinite number of new compounds could possibly be synthesized. This can be compared to the total number of inorganic compounds, which is approximately half a million.
Why does carbon form so many compounds?
Carbon has the ability to bond with itself to form long chains and ring structures; hence it can form molecules that contain from one to an infinite number of C atoms.
Additionally C atoms may:
- be bonded by multiple bonds (i.e. double and triple) as well as single
- contain branches of other carbon chains
- need additional atoms attached to them to make them stable. The most common of these is H, but, N, O, X, P and S also commonly occurs attached to C and may even be attached in several different ways.
Functional Groups
The behavior of any molecule in a particular chemical environment is determined by the stability or reactivity of its bonds. Each different type of bond shows different levels of reactivity.
Generally in a molecule there is a group of bonds that are more reactive than all the others and this group tends to determine how the whole molecule behaves in a particular chemical environment regardless of the structure of the rest of the molecule.
Chemists call these dominant groups of atoms and bonds functional groups and these are used to classify organic compounds into families.
Understanding the types of reactions that functional groups undergo will enable an understanding of how an organic molecule interacts with the environment.
A carbon-carbon double bond is an example of a functional group. Organic compounds that contain a carbon-carbon double bond and no other functional group are called alkenes (a family name used to classify these compounds). All alkenes react with bromine to yield dibromoalkanes
Hence if you know a functional group reacts in one molecule you can predict how it will react in almost all other molecules.
It is possible to get more than one functional group in a single molecule, but the generalisation stated above still applies.