Organic chemistry is that branch of chemistry which deals with carbon and hydrogen and their mutual bonds. In addition to this basic discipline of chemistry, with the passage of time and with the development of the chemical science there were additional non-conventional areas of chemistry that has organic chemistry as a subdiscipline such as organometallic and chemistry of heterocyclic compounds in addition to green chemistry which deals with environmentally benign organic as well as inorganic compounds.
Organic compounds have widespread prevalence and uses. As an example to their significance it suffices here to mention that our body including the basic units the cells all are composed of hydrogen and carbon compounds such as DNA and RNA molecules with the addition of several heteroatoms such as nitrogen and oxygen.
Organic compounds find uses in industry as well as in the chemical laboratory. Petroleum is an example of a mixture of organic compounds which are found in large quantities under the earth surface. Organic compounds are usually combustible. Burning the carbon hydrogen bonds by its oxidation with oxygen to form CO2 and H2O. Thus releasing large quantities of energy.
For this reason petroleum derivatives are used to generate energy that is used in various areas of life such as in heating. Besides its ability to burn generating energy the carbon-hydrogen bond is usually inert for chemical reactions. This is so due to the comparable electronegativities of these two atoms.
The bond between carbon and hydrogen is usually covalent in nature. Sometimes it can be polarized forming a separation of positive and a negative charges under certain conditions such as the attachment of electron withdrawing group to the carbon. Thus increasing the acidity of the C-H bond.
For example the compound nitromethane which is a fuel for rockets can be easily deprotonated due to the stabilizing effect of the nitro group on the adjacent negative charge on the carbon atom bearing the nitro group. O-H bond is more polarized than that between C-H due to the greater electronegativity of oxygen compared to that of carbon.
The typical organic compound is methane or CH4. This is an inert compound except of its ability to combust and its ability to react via radical reactions. It can react with halogens under UV light to generate CH3Cl for example. CH3Cl is a more reactive compound in comparison with CH4 itself due to the plarizing effect of the C-Cl bond which imparts reactivity to it.
For example, putting a solution of CH3Cl in KOH will lead to the substitution of the chlorine atom by OH ion. On the other hand, passing a stream of CH4 gas into a solution of KOH will not yield any reaction. The other typical organic compound is ethane or CH3CH3. This compound is similar to CH4 in reactivity.
Namely, it is not reactive under normal conditions except for its ability to combust and release energy and to react with UV light and a halogen. Ethane reacts with UV light and a halogen to form ethylchloride for example. This compound is more reactive that ethane by several orders and its chemistry is widespread. It is analogous to CH3Cl in reactivity. Passing a stream of CH3CH2Cl into a solution of KOH will give ethanol. On the other hand, passing a stream of CH3CH3 into a solution of KOH will give no reaction.