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# Carbon Compounds

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 Sub Topics Carbon has far the greatest number of compounds of any element. The thousands of combinations of carbon with other elements give it the diversity of compounds that makes it basis of life. Carbon has a reacting power of 4 as it has four electrons in its outermost shell and is placed in group 4 of the periodic table. It's chemical bonds are all covalent. There are over half a million compounds of carbon and hydrogen alone and some are very useful, including the hydrocarbons in petrol. Carbon has four valence electrons and ordinarily forms four covalent bonds involving four bond orbitals containing two electrons each. Carbon is a constituent of all organic cell material and therefore represents nearly 50 percent of the cell dry weight. Organic carbon compounds not only provide the carbon for synthesis but also meet the energy requirement by entering into energy yielding metabolic pathways and are eventually oxidized to CO2.

## Naming Carbon Compounds

A set of rules was developed to name organic compounds by the International Union of Pure and Applied Chemistry (IUPAC). The IUPAC nomenclature allows chemists to write a name for any compound based on its structure or to identify the formula and structure of a compound from its name.
• The names of alkanes end in "ane". When naming specific alkane, the root of the name identifies the longest carbon chain in a compound. Specific substituent groups attached to this carbon chain are identified by name and position.
• Alkenes have names ending in "-ene". The name of an alkene must specify the length of the carbon chain and the position of the double bond. As with alkanes both identity and position of substituent groups must be given. The carbon chain is numbered from the end that gives the double bond the lowest number.
• The naming of alkynes is similar to the naming of alkynes, except that cis-trans isomerism. The ending "-yne" on a name identifies a compound as an alkyne.
• For benzene derivatives the carbon atoms in the six-member ring are numbered 1 through 6, and the name and position of substituent groups should be given.

## Examples of Carbon Compounds

Lavoisier was the first to establish that the compounds derived from animal and vegetable sources have an almost similar composition of elements. Nearly all of them were composed of carbon, hydrogen and oxygen elements. In view of the similarity of composition the compounds obtained from living organisms that is animals and plants were collectively called organic compounds.

The list of organic compounds along with their sources are given below.
1. Plants - sugars, starch, cellulose, dyes, drugs, acetic acid, oxalic acid, methyl alcohol etc.
2. Animals - proteins, fat, vitamins, urea, enzymes etc.
3. Coal tar - benzene, toluene, xylenes, napthalene, phenol, pyridine, dyes, drugs, perfumes etc.
4. Petroleum - Petrol, kerosene oil, lubricating oil, vaseline, paraffin wax etc.
5. Synthetic methods - In addition to the above sources, a very large number of organic compounds have been obtained by laboratory synthesis and fermentation methods.

## List of Carbon Compounds

Some elements exist in various forms. These forms have different physical properties but have the same chemical properties. They are called allotropes of the element. Carbon, phosphorous and sulphur have allotropes. Diamond and graphite are allotropes of carbon. The differences in the physical properties of diamond and graphite are because of the manner in which the carbon atoms are arranged. Their chemical properties however are the same. They both burn in air to form carbon dioxide.

"Diamond the hardest natural substance known."

1. Diamond
• is one of the purest forms of carbon.
• is represented by the same symbol of carbon C.
• occurs in all shapes and sizes.
• is found in igneous rocks.
Diamonds are formed under intense pressure and heat. It is found in the igneous rock and gravel, but is unevenly distributed.

2. Graphite

Graphite the black slippery solid that is a major component of pencil "lead" is also pure carbon. Pencil lead or graphite has been used for writing since the sixteenth century.

Graphite is used
• as a lubricant - graphite grease.
• as a crucible to melt metals (because of its high melting point 3500oC).
• in electric motors (carbon brushes).

## Chemical Properties of Carbon Compounds

As our chemical knowledge increased, it was realized that most carbon compounds were associated with living organisms, so the study of carbon compounds became known as organic chemistry. By comparison the study of all other compounds is called inorganic chemistry. True organic compounds are widespread and include.
• fossil fuels
• fats, cooking oils, coconut oil
• turpentine, kerosene, petrol, diesel and tar
As the number and range of organic substances is so large they are classified by the atoms present and their structure. A systematic naming system has been developed to easily identify the number and arrangements of the carbon atoms, as well as identifying any functional groups attached to the carbon chain that give the substances special properties.

## Combustion

2H2 + O2 $\rightarrow$ 2H2O