NATURE OF ORGANIC COMPOUNDS
Organic chemistry can be defined as the chemistry of carbon compounds. Carbon compounds have been studied from separately from compounds of all other hundred odd elements of the periodic table because there are numerous compounds of carbon and their molecules can in fact be very large and complex.
These organic compounds have been divided into families which generally have no counterparts among the inorganic compounds. Member of each family usually will have similar chemical behaviors and often a gradation in their physical properties.
Organic molecules containing thousands of atoms are known to be in existence and the arrangement of atoms in even relatively small molecules can be very complicated. One of the many problems in organic chemistry is to determine the structure of the compounds, that is to find out how the atoms are arranged in molecules.
There are many ways in which organic molecules can break apart or arrange themselves to form new molecules or how new atoms substitute for old ones. Much of organic chemistry is dedicated to finding out what these processes(reactions) are, how they take place, and how they can be used to synthesize compounds we need.
1.1 DISTINCTIVE FEATURES OF ORGANIC COMPOUNDS:
1.Profusion of organic compounds(organic compounds are numerous).
2. Isomerism: Organic compounds exhibit the phenomenon of isomerism (structural and stereo-isomerism). This is discussed later in this section.
3.Rates of reaction: Organic reactions are generally slow compared to the inorganic reactions which are generally fast.
The following reasons can be offered for the above distinctive features of organic compounds.
1.Carbon atoms can cremate (ie form series as links of carbon in carbon chain).
2. Carbon atoms can be involved in different types of bonding viz
a) ionic bonding(mostly when organic compounds react with metals).
b) covalent bonding as in single, double and triple bonding and
1.2 Sources of Organic Compounds: Organic compounds can be obtained from any of the following.
1.Coal the chief source of aromatic hydrocarbons. Aliphatic hydrocarbons are however also obtained from coal
2. Petrol (crude oil) – the chief source of aliphatic hydrocarbons. However aromatic compounds are also obtained from petroleum.
3. Biological materials – organic compounds can be obtained from plants or animals. Compounds of this origin are generally referred to as natural products. Many biologically active compounds (chemotherapeutic agents) come from this source.
4. Synthesis – new organic compounds can be prepared by the modification or reaction of compounds obtained from any of the above sources.
Methods of production of organic Compounds:
from coal (a) Coal carbonization: This can be regarded as destructive distillation of coal (in the absence of air) to give pure carbon (coke) as well as gaseous (coal gas) and liquid by products. The coke produced in this process is a major raw material in iron and steel (metallurgical) industries. Coal tar which is a product of the carbonization process is a rich mixture of the aromatic compounds, the main constituents are naphthalene, fluorene, anthracene, phenanthracene, fluoranthene, phenol and pyridine.
Brazil which is also another product of the process is a mixture of predominantly aromatic hydrocarbons and to a lesser extent. Olefins (cyclopentadiene) and aliphatics. It’s main constituent is benzene which is present in about 60 – 70 percent. Other components of Brazil include toluene, ethylbenzene, xylenes and higher benzene’s.
b) Coal gasification: This is a process for the production of synthesis gas (a mixture of water gas and hydrogen) which aims at producing aliphatic chemicals and ammonia.
2) From petroleum: By the process of fractional distillation crude oil is separated into the various fractions which contain mainly aliphatic hydrocarbons. This is basically the process that is in operation in the various petroleum refineries.
3. From Biological Materials : eg plants – usually the materials (the leaves, stem or root) are extracted by the use of suitable solvents or other processes to give organic compounds, which can be further separated and purified.
4. From synthesis: This involves the reaction of one, two or more compounds to produce other compounds of interest. The products so obtained from organic synthesis can be separated or purified.
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