INTRODUCTION TO ORGANIC CHEMISTRY

The life of human beings, animals and plants depends upon a large number of molecules from

the simplest like󠀥 H₂O, O₂ to the complex macromolecules like hormones, proteins, amino acids

etc through chemical interactions.

The common factor for each of these compounds is the carbon backbone upon which these

molecules are built. All organic compounds contain carbon but not all carbon containing

molecules are organic!

Even though some compounds like Na₂CO₃, CO, CO₂ contain carbon they are not considered to be organic, for a compound to be organic must fulfill the following requirements:

• Organic compounds are covalently bonded
•  They are mainly not soluble in water and are poor electrolytes
•  They have low fusion point and boiling points, many of them are liquids at room temperature
•  They possess the density close to unity
•  They are easily decomposed by heat tᵒ > 500ᵒC
• They are almost all combustible

Organic chemistry is a part of chemistry that studies compounds of carbon since organic compounds are mainly made of Carbon. In addition other elements include Hydrogen, Oxygen, Nitrogen, Sulfur, Halogens etc.

Till 19th century Chemists believed that only living matter, animals and plants, can only produce

organic compounds, the so called ―vitalism theory

But the production of Urea 

by heating ammonium cyanate in the

laboratory by WÖller changed the atmosphere since then many organic chemicals started to be

also synthesized in the laboratory. This was the death of Vitalism theory.

OCCURENCE OF CARBON
Carbon is found in the environment both as an element and in its combined form. Although carbon ranks about 17th in abundance by mass among the elements in the earth’s crust. It is exceedingly important because it is found in all living matter. Carbon is present in the body tissues and fluids and in the food we eat. It is also found in common fuels such as coal, petroleum, natural gas and wood.
Depending upon the internal arrangement of atoms in pure carbon we can distinguish two forms of carbon:

• Amorphous carbon: charcoals, peat
• Crystalline carbon: diamond, graphitE

STRUCTURE AND UNIQUE PROPERTIES OF CARBON

Carbon is the first member of group 14, and has mostly non-metallic properties. In its ground state carbon has an electronic configuration of 1s², 2s², 2p².

It has four electrons more than Helium and four electrons fewer than Neon; this means that the formation of carbon ions is energetically impossible under normal conditions. Its electronegativity and position in the periodic table indicates that carbon shares electrons to attain a filled outer shell, and that it bonds covalently in almost all its elemental forms and compounds.

It is seen from the above configuration that carbon can only form two covalent bonds like in CO C=O but in its many compounds, carbon is tetravalent like in methane CH₄.

How to explain such behavior?

Because 2s and 2p orbitals are approximately of the same energy level, one electron move from

2s to 2p and 227 Kjmol-1 of energy is sufficient to promote 1electron from 2s orbital to 2p

orbital.

BOND ENERGY, CATENATION AND MOLECULAR SHAPE

The number and strength of carbon atoms bonds leads to its outstanding ability to catenate which

allows it to form a multitude of chemically and thermally stable chain, ring, and branched

compounds.

ALLOTROPES OF CARBON

Carbon occurs in several solid allotropic forms that have dramatically different properties.

• Diamond: this is a colorless, crystalline solid form of carbon. It is the hardest material

known; it is the densest form of carbon, about 3.5 times more dense than water. It also

has an extremely high boiling point (greater than 3500ᵒC).

• Graphite: It is a soft, black, crystalline form of carbon that is a fair conductor of electricity.
•  Fullelenes: They are dark colored solids made of spherically net worked carbon atoms cages. It is a C60 compound resemble to a soccer ball. The uses of which are not well known.