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Organic Chemistry Introduction


Carbon is the basis of life. Because of its central role in biology, and the very large number and variety of compounds and processes involving carbon, it has its own subject within chemistry. organic chemistry.

Carbon is a non-metal element, and is found in the second row of the periodic table, with valency 4. The first electron energy shell has two electrons and is therefore full. The second shell needs 8 electrons, and neutral carbon has only 4. When it bonds with other atoms, often hydrogen, oxygen, and nitrogen, it forms very strong bonds.

The bond enthalpy C-C is 348 kJ mol$^{-1}$. C-H (412), O=O (496), C=O (743), O-H (463)

Methyl group

The history of chemistry is a fascinating journey. Modern chemistry evolved out of fields like alchemy, which combined superstition, material greed and nutty religion with practical experimentation.

The struggle to understand the difference between elements and compounds lasted two hundred years, from Boyle in the mid-1600s to the creation of the Periodic Table by Mendeleev in 1860.

Abandoned Concepts

4-Element System

The ancient Greeks figured that all the matter of the world could be reduced to just four elements: earth, water, air, and fire.

This concept prevailed until the early 1800s, by which time scientists like Priestly, Lavoisier, and Davey had shown that substances could be broken down to many more distinct elements, and that fire was not an 'element', but energy.

Potassium oxidising in water, and igniting hydrogen

A vital discovery by Humphrey Davy in 1807 was electrolysis, which allowed him to isolate potassium from the compound potash, and sodium from salt. These discoveries, and that of oxygen and hydrogen recombining to form water, paved the way to the distinction of elements and compounds.

Today, the Periodic Table describes the properties of all 92 naturally occurring elements. Since there are no gaps, it is assumed there are no more. Larger elements can be created artifically in the laboratory, but they are unstable and short-lived.

Phlogiston Theory

The phlogiston theory was first proposed by Johann Becher in 1667, and strongly championed by Joseph Priestley till put to rest by Antoine Lavoisier in the 1780s.

The word derives from the Ancient Greek [φλογιστόν phlogistón] for combustion, or burning up. The theory proposed that combustion was due to an element called phlogiston. All combustible substances supposedly contained this element, and it was released during combustion.

Although precursing the understanding of oxidation, its influential adherents obstructed scientific progress in the field.

Content © Andrew Bone. All rights reserved. Created : May 7, 2015 Last updated :May 7, 2016

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