Carbon has a special place amongst all the elements. It is king of covalent compounds and a separate branch of chemistry called organic chemistry is devoted to the carbon compounds. These organic compounds are formed by the bonds formed between carbon and carbon or carbon and hydrogen or oxygen atoms. Carbon can form 4 covalent bonds and hence there are endless possibilities of compounds. Organic compounds are major constituents of our bodies and food.
Carbon has atomic number of six. This means that it has 4 electrons in the outer L shell and thus is tetravalent and combines with 4 atoms. The arrangement of atoms about carbon is tetrahedral in nature. Ranging from the hydrocarbons which are the constituents of the petroleum to carbohydrates there is a plethora of carbon based compounds.
Elemental carbon in itself is very interesting element. Till recently, it was supposed to be existing in two allotropic forms which were called graphite and diamonds. Allotrope differ in their physical properties like melting point, hardness and electrical conductivity but chemical properties are almost same though the rates of reaction shall differ due to the different energy requirements to break the structures. Graphite has two dimensional layers consisting of repeating hexagons like a honeycomb. These layers exist parallel to one another. Due to this, they can slip over under stress. This property makes it an lubricant. In between the layers are clouds of electrons which make the graphite a good conductor of electricity.
Diamond,on the other hand, is known to be the hardest elements due to its compact structure formed by joining the tetrahedrons. They are as everyone knows are the most sought after items of jewelry. Many of them had been the cause of wars between kingdoms and bad luck for their possessors. They are the bad conductors of electricity.
So this was the status till recently. But there was one addition to the two allotropes. This new allotrope is called as Fullrenes and was found by Robert Curl, Harold Kroto and Richard Smalley on analyzing the products formed when carbon is evaporated in the vacuum in the inert atmosphere. The structures contain up to 60 to 70 carbons. The special one which has 60 carbon atoms resembles a football and has been named “Buckyball” after the architect Buckminster Fuller who had designed the Geodesic Globe. The balls surface contains pentagons and hexagons juxtaposed.
Why were these not recognised for so many years? Why did they eluded the scientists for so long? . One reason is the miniscule amount of these which exists only in the stars. With the advent of latest instruments like Mass spectrometers and ingenuity of the some brilliant human beings, these have been synthesised in micro scale in the laboratory. Experiments are on to develop the affordable commerical methods for their productions.
Fullrenes and buckyballs belong to class of nanomolecules. They have certain properties which will revolutionize the future science. Some of the applications include the synthesis of special molecules inside them becuase they act like a cage and trap molecules of many types. Fullrenes are cylindrical tubes which are the lightest but very strong. There are vast possibilities for their use. Beginning from construction of efficient air planes and energy efficient machines and in the construction of super conducting materials.
Incidentally, there is another class of carbon compounds called diamondoids. These are compounds like the Bucky balls but having few hydrogen atoms in the place of carbon atoms. These compounds have been found in the petroleum. These are also detected by mass spectrometry and NMR. They also belong to the category of nano-molecules and hold promise for many new applications in the metallurgy, super conducting materials and shed the light on the formation, generation and migration of petroleum.