Principles and Techniques

Principles and Techniques After studying this unit, you will be able to u n d e r s t a n d r e a s o n s f o r tetravalence of carbon and shapes of organic molecules; write structures of organic molecules in various ways; classify the organic compounds; name the compounds according to IUPAC system of nomenclature and also derive their structures from the given names; understand the concept of organic reaction mechanism; explain the influence of electronic displacements on structure and reactivity of organic compounds; recognise the types of organic reactions; lear n the techniques of p u r i f i c a t i o n o f o r g a n i c compounds; write the chemical reactions involved in the qualitative analysis of organic compounds; understand the principles involved in quantitative analysis of organic compounds. I n the previous unit you have learnt that the element carbon has the unique property called catenation due to which it forms covalent bonds with other carbon atoms. It also forms covalent bonds with atoms of other elements like hydrogen, oxygen, nitrogen, sulphur, phosphorus and halogens. The resulting compounds are studied under a separate branch of chemistry called organic chemistry . This unit incorporates some basic principles and techniques of analysis required for understanding the formation and properties of organic compounds. . General Introduction Organic compounds are vital for sustaining life on earth and include complex molecules like genetic information bearing deoxyribonucleic acid (DNA) and proteins that constitute essential compounds of our blood, muscles and skin. Organic compounds appear in materials like clothing, fuels, polymers, dyes and medicines. These are some of the important areas of application of these compounds. Science of organic chemistry is about two hundred years old. Around the year , chemists began to distinguish between organic compounds obtained from plants and animals and inorganic compounds prepared from mineral sources. Berzilius, a Swedish chemist proposed that a ‘vital force’ was responsible for the formation of organic compounds. However, this notion was rejected in when F. Wohler synthesised an organic compound, urea from an inorganic compound, ammonium cyanate. NH CNO NH CONH Ammonium cyanate Urea The pioneering synthesis of acetic acid by Kolbe ( ) and that of methane by Berthelot ( ) showed conclusively that organic compounds could be synthesised from inorganic sources in a laboratory.