Chemistry 11. Unit 10 Organic Chemistry Part I Introduction

Transcription

1 Chemistry 11 Unit 10 Organic Chemistry Part I Introduction

2 2 1. Prelude In this chapter we will be looking at organic chemistry. By definition, organic chemistry is the study of structure, properties and reactivity of organic compounds and organic materials which are made of carbon atoms. Hence, in other words, organic chemistry is simply the chemistry of carbon! But not all chemistry of carbon belongs to organic chemistry.

3 3 Depending upon the nature of the compounds, carbon chemistry is divided into two categories. (i) Inorganic carbon chemistry Element and allotropes of carbon Simple molecules of carbon such as CO, CO 2 (ii) organic chemistry Compounds with biological origins Synthetic compounds of carbon and elements such as H, N, O

4 4 Why is organic chemistry important? (1) Many of the compounds that we encounter in our daily lives are made up of organic compounds. They either occur naturally or are made artificially.

5 5 (2) Organic chemistry has a large technological and economical impact to human being. Petroleum is the largest industry that involves organic chemistry. Crude oil extracted from geological sites is processed to produce a wide variety of products such as gasoline, diesel, bitumen, plastics and pharmaceuticals.

6 6 2. A brief history of organic chemistry Organic chemistry has a very long history, dating back to the ancient time when our ancestors used plants or natural substances for curing diseases. For example, chewing willow bark can release the pain of a patient. Nowadays we know that the substance responsible for killing pain is acetylsalicylic acid.

7 7 Chinese is a tribe which has a wide knowledge of applications of medicinal plants. Ginseng (Genus Panax) is a valuable Chinese medicine which is claimed to have the following biological effects: improved memory, reduced fatigue, and reduce insulin response in people with mild diabetes. The active compounds found in ginseng and related species are ginsenoside and gintonin.

8 8 Organic chemistry formally became a branch of science since early 1800 s when J. J. Berzelius ( ) proposed to divide all substances into either inorganic, if they come from minerals or non-living things, or organic, if they come from living matter. Unfortunately, he believed in the concept of vitalism, and thought that all organic substances only arise from living organisms through some sort of vital force. That implies organic substances are by-products of life force, and people could not synthesize them.

9 9 The theory of vitalism was eventually disproved when Friedrich Wöhler ( ) performed the following chemical reaction (1828) in which urea, a typical organic substance, is made from an inorganic material. AgOCN aq + NH 4 Cl aq AgCl s + NH 4 OCN(aq) NH 4 OCN aq NH 2 2 CO(s)

10 10 Over these years organic chemistry has been evolved into one of the five major branches of modern chemistry (the others being inorganic, physical, analytical and biochemical). And the scope of organic chemistry is no longer restricted to naturally occurring substances but extended to many synthetic compounds with desirable properties.

11 11 In general, organic chemistry includes the following disciplines plus many other fields overlapping with other branches of chemistry: (1) Stereochemistry 3D structures of molecules (2) Medicinal chemistry design and synthesis of pharmaceutical drugs and natural products (3) Physical organic chemistry structure and reactivity of organic molecules (4) Polymer chemistry synthesis of organic polymers (5) Organometallic chemistry compounds between carbon and metal atoms, and catalysis

12 12 Organic chemistry is so broad a subject to study fully in chemistry 11. We will only focus on the following items: (1) Classification of different types of organic compounds based on functional groups. (2) Nomenclatures of organic molecules. (3) Characteristic physical and chemical properties of functional groups and their representative reactions.

13 13 3. Classification of organic compounds Organic compounds can be categorized based on the connectivity of atoms.

14 14 According to the composition, organic compounds can also be classified into many families of functional groups.

15 15 In this chapter, we will investigate basic organic chemistry in the following order: 1. Aliphatic compounds e.g. alkane, alkene, alkyne, alkyl halide 2. Aromatic compounds e.g. benzene, polyaromatics 3. Functional-group compounds e.g. ether, alcohol, aldehyde, ketone, acid, amine, amide, ester 4. Miscellaneous compounds