Carbon is denoted by the symbol C, is part of group 14 on the periodic table, and is the fourth most abundant element in the universe (by mass). Carbon has an electron configuration of 1s2, 2s2, 2p2. With 4 valance shell electrons it is expected to form 4 bonds, this means carbon is tetravalent. However the s orbitals do not form the same type of bond (with other atoms) as the p orbitals, this is because their shapes are different. For example CH4 would have the following bonds: C(s)-H(s), C(s)-H(s), C(p)-H(s), C(p)-H(s).
This would also mean that CH4 would have a mixture of ? onds and ? bonds. However in reality this is not the case, all the bonds of CH4 are identical. This is due to hybridization, this is where the 2s orbital and the three 2p orbitals hybridize to form sp3, a hybrid orbital. sp3 hybrid orbitals have a tetrahedral shape because each orbital positions itself at angles of 109. 5° (around CH4) maximising the distance between the repelling electrons. Carbon is therefore tetravalent which means it can form four covalent chemical bonds. Another important property of carbon is its catenation (the ability to form long chains with itself).
Silicon (Si), is another element in group 14 of the periodic table, also has four valence electrons and can make large molecules called silicones, but its atoms are too large to fit together into as great a variety of molecules as carbon atoms can. Carbon also has the ability to bond with other carbon atoms in complex branches (not just straight chains), this means they can form rings such as benzene. Carbon atoms can not only a single electron with another atom to form a single bond, but it can also share two or three electrons, forming a double or triple bond. All of these qualities show how carbon is fundamentally important.
This due to its ability to form a large variety of organic compounds with a wide variety of different chemical properties. Organic compounds contain both carbon and hydrogen by definition, but will commonly contain other elements, oxygen and nitrogen for example. Hydrocarbons are the simplest organic compounds and only contain hydrogen and oxygen. Crude oil is a mixture of hydrocarbons, it is separated by the process of fractional distillation. IUPAC is the International Union of Pure and Applied Chemistry, they set the rules for the generation of systematic names for chemical compounds.
The advantage of an international organisation dictating the rules of nomenclature (name of naming system) is that it is the most frequently used system worldwide. There are different types of nomenclature used for naming a variety of sub types i. e. organic, inorganic, compositional, substitutive and additive. In organic chemistry organic compounds can be categorised into alkanes and alkenes, functional groups are specific groups of atoms or bonds within molecules which are responsible for the characteristic reactions of the molecules.
To identify an organic molecules correct name a number of steps need to be taken. The first step is to recognise the longest chain of carbon atoms, this will give the root name of the compound (take figure 1 for example). In figure 1 there are several different “paths” which can be taken through the molecule, it is important to differentiate the main chain from the different side chains. In figure 1 the longest chain of carbon atoms is seven, therefore the name it is given is heptane. There are two side chains present, both of them are methyl groups.
The second step of the naming process is to label the carbon atoms so the atoms bonded on the side chains have the lowest number possible (see figure 2). In this case if the carbon atoms had been labelled from the other direction the methyl group on carbon 4 could continue to be labelled as carbon 4, however the second methyl group on carbon 3 would be labelled as carbon 5. Therefore the numeration is chosen where the methyl groups are attached to 3rd and 4th carbon atoms. The third step of the naming process is combine the names of the longest chain, side chains and the numbered carbon atoms.
The name of the side chains are prefixes and are placed in front of the root name (alkane- heptane). The quantity of side chains with the same number of carbon atoms is counted, if there is a number larger than one, a prefix is placed in front of the side chain name (in this case there are two methyl groups so methyl, becomes dimethyl). The number to which each side chain is located based on the numbered carbon atoms is placed before the prefix methyl (the methyl groups are attached to the 3rd and 4th carbons). Therefore figure 1 (and 2) is called 3, 4 -dimethylheptane according to the IUPAC nomenclature of organic chemistry.
In figure 3 the molecule but-1-ene can be seen, because it has a double bond the second name “ene” is added, butane would only have single bonds and therefore retains its last name “ane. ” The digit one is added to show where in the molecule the double bond lies. When a molecule has a functional group attached to it its characteristics change, in figure 4 the functional group shown is a hydroxyl group. Hydroxyl groups are polar, this allows the molecules to mix with water. The carbon chain in figure 4 is 4 which means the molecules root name is butane. However because of the functional group (an alcohol) the ending “e” is replaced by “ol”.
Similar to the example given in figure 3 a digit is given to show which carbon atom in the chain is attached to the functional group. The name of figure 4 is therefore named butan- 2-ol, this is an example of a secondary alcohol as the functional group attached to a carbon atom that has two other carbon atoms attached to it. Isomers are molecules with the same chemical formula (same number of atoms of each element) but have different chemical structures (different arrangement of atoms in space). Isomers can have very different properties and there are many different classes of isomers.
