Chapter 10: Unit 1. Introduction

1. Introduction:

The term organic and inorganic continue to be used in classifying compounds but the definitions of these terms no longer reflects their historical origins. Organic compounds is the study of hydrocarbons (carbons and hydrogens) and their derivatives. Almost all compounds found in living organisms are classified as Organic Compounds. Inorganic chemistry is the study of all substances other than hydrocarbons and their derivatives.  Organic chemistry is vast and complex subject. In the next view chapters we will explore the wonderful world of carbon containing compounds

Applications of Organic chemistry is worldwide and vast. Organic molecules affect almost every facet of our lives and that is why it is extremely important and useful to know about them.

                                                                        An organic molecule

Clothes, foods, medicines, gasoline, refrigerants and soaps are composed of solely organic compounds. Some like cotton, wool or silk are naturally occurring, they can be isolated directly from natural resources. Others, such as nylon and polyesters are synthetic that means they are produced by chemists in the laboratory.

Organic chemistry has given us contraceptives, plastics, antibiotics, synthetic heart valves and myriad of other materials. Our lives would be very different without these products of organic chemistry.

History of Organic Chemistry:

At one time in history, it was thought that only living things were capable of synthesizing the carbon-containing compounds present in cells. For that reason, the term organic was applied to those compounds. Eventually it was proved that carbon-containing compounds could be synthesized from inorganic substances, but the term organic has remained. Currently, organic compounds are defined as covalently bonded compounds containing carbon, excluding carbonates and oxides. By this definition, compounds such as carbon dioxide (CO ₂ ) and sodium carbonate (Na ₂ CO ₃ ) are considered to be inorganic. Organic chemistry is the study of all organic compounds.

Scientists of the 18th and early 19th centuries studied compounds obtained from plants and animals and labeled them organic because they were isolated from “organized” (living) systems. Compounds isolated from nonliving systems, such as rocks and ores, the atmosphere, and the oceans, were labeled inorganic. For many years, scientists thought organic compounds could be made by only living organisms because they possessed a vital force found only in living systems. The vital force theory began to decline in 1828, when the German chemist Friedrich Wöhler synthesized urea from inorganic starting materials. He reacted silver cyanate (AgOCN) and ammonium chloride (NH₄Cl), expecting to get ammonium cyanate (NH₄OCN). What he expected is described by the following equation.

AgOCN + NH₄Cl → AgCl + NH₄OCN

Instead, he found the product to be urea (NH₂CONH₂), a well-known organic material readily isolated from urine. This result led to a series of experiments in which a wide variety of organic compounds were made from inorganic starting materials. The vital force theory gradually went away as chemists learned that they could make many organic compounds in the laboratory.

Today organic chemistry is the study of the chemistry of the carbon compounds, and inorganic chemistry is the study of the chemistry of all other elements. It may seem strange that we divide chemistry into two branches—one that considers compounds of only one element and one that covers the 100-plus remaining elements. However, this division seems more reasonable when we consider that of tens of millions of compounds that have been characterized, the overwhelming majority are carbon compounds.

Note

The word organic has different meanings. Organic fertilizer, such as cow manure, is organic in the original sense; it is derived from living organisms. Organic foods generally are foods grown without synthetic pesticides or fertilizers. Organic chemistry is the chemistry of compounds of carbon.

Carbon is unique among the other elements in that its atoms can form stable covalent bonds with each other and with atoms of other elements in a multitude of variations. The resulting molecules can contain from one to millions of carbon atoms. In Chapter 1 “Organic Chemistry Review/Hydrocarbons” through Chapter 5 “Amines and Amides”, we survey organic chemistry by dividing its compounds into families based on functional groups. We begin with the simplest members of a family and then move on to molecules that are organic in the original sense—that is, they are made by and found in living organisms. These complex molecules (all containing carbon) determine the forms and functions of living systems and are the subject of biochemistry, a topic presented in Chapter 6 “Carbohydrates” through Chapter 11 “Metabolic Pathways and Energy Production”.

Organic compounds, like inorganic compounds, obey all the natural laws. Often there is no clear distinction in the chemical or physical properties among organic and inorganic molecules. Nevertheless, it is useful to compare typical members of each class, as in Table 1.1 “General Contrasting Properties and Examples of Organic and Inorganic Compounds”. (Keep in mind, however, that there are exceptions to every category in this table.) To further illustrate typical differences among organic and inorganic compounds, Table 1.1 also lists properties of the inorganic compound sodium chloride (common table salt, NaCl) and the organic compound hexane (C₆H₁₄), a solvent that is used to extract soybean oil from soybeans (among other uses).