Presentation on theme: "Organic chemistry The carbon compounds Prof. Paola Valentinis 2^A- 2^B Scholastic year 2006/07."— Presentation transcript:
Organic chemistry The carbon compounds Prof. Paola Valentinis 2^A- 2^B Scholastic year 2006/07
Glossary Coal Organic Combustion Rocks plants Sweeteners Laboratory Soaps Term Chemist Theory Mysterious Fibres Phenomena inorganic
Organic chemistry Organic chemistry was the term applied originally to the study of substances connected directly with animals and plants, so it is derived from the word “organism”. For this reason it received the name organic. Such substances were thought to contain a mysterius vital force wich made it impossible for man to prepare them from inorganic ingredients. But in 1828 the German chemist Friedrich Wohler attempted to prepare crystals of the inorganic salt ammonyum cyanate by evaporating its solution. Istead, he obtained crystals of urea an organic subtance already known for 50 years an the main constituent of urine. Over the following years further organic substances were prepared in the laboratory and eventually the vital force theory was abandoned. Today the study of organic chemistry is very important because it help us to understand the phenomena living in the world. Synthetic fibres, plastic, medicines, artificial sweeteners are product of industrial organic chemistry and the energy that man uses in every industrial activity derives mainly from the combustion of organic material found in coal an crude oil. Fill in the blanks using the new words
carbon The special role of carbon in the chemistry of the elements is the result of a combination of factors, including the number of valence electrons on a neutral carbon atom, the electronegativity of carbon, and the atomic radius of carbon atoms (see the table below). The Physical Properties of Carbon Electronic configuration 1s2 2s2 2p2 Electronegativity 2.55 Covalent radius nm Carbon has four valence electrons 2s2 2p2 and it must either gain four electrons or lose four electrons to reach a rare-gas configuration. The electronegativity of carbon is too small for carbon to gain electrons from most elements to form C4- ions, and too large for carbon to lose electrons to form C4+ ions. Carbon therefore forms covalent bonds with a large number of other elements, including the hydrogen, nitrogen, oxygen, phosphorus, and sulfur found in living systems. Because they are relatively small, carbon atoms can come close enough together to form strong C=C double bonds or even C C triple bonds. Carbon also forms strong double and triple bonds to nitrogen and oxygen. It can even form double bonds to elements such as phosphorus or sulfur that do not form double bonds to themselves Even though organic chemistry focuses on compounds that contain carbon and hydrogen, more than 95% of the compounds that have isolated from natural sources or synthesized in the laboratory are organic.
Carbon and life Several factors make carbon essential to life. The ease with which carbon atoms form bonds to other carbon atoms. The strength of C-C single bonds and the covalent bonds carbon forms to other non metals, such as N, O, P, and S. The ability of carbon to form multiple bonds to other non metals, including C, N, O, P, and S atoms. These factors provide an almost infinite variety of potential structures for organic compounds, such as vitamin C shown in the figure below.
hydrocarbons Compounds that contain only carbon and hydrogen are known as hydrocarbons Those that contain as many hydrogen atoms as possible are said to be saturated. The saturated hydrocarbons are also known as alkanes. Carbon not only forms the strong C C single bonds found in alkanes, it also forms strong C=C double bonds. Compounds that contain C=C double bonds were once known as olefins (literally, "to make an oil") because they were hard to crystallize. (They tend to remain oily liquids when cooled.) These compounds are now called alkenes. Alkenes are examples of unsaturated hydrocarbons because they have fewer hydrogen atoms than the corresponding alkanes Compounds that contain C C triple bonds are called alkynes. These compounds have four less hydrogen atoms than the parent alkanes
Structure and Nomenclature of Hydrocarbons The alkanes in the table above are all straight-chain hydrocarbons, in which the carbon atoms form a chain that runs from one end of the molecule to the other. The generic formula for these compounds can be understood by assuming that they contain chains of CH2 groups with an additional hydrogen atom capping either end of the chain. Thus, for every n carbon atoms there must be 2n + 2 hydrogen atoms: CnH2n+2. Because an alkene can be thought of as a derivative of an alkane from which an H2 molecule has been removed, the generic formula for an alkene with one C=C double bond is CnH2n.
pollution Hydrocarbons are a precursor to ground-level ozone, a serious air pollutant in cities across the United States. A key component of smog, ground-level ozone is formed by reactions involving hydrocarbons and nitrogen oxides in the presence of sunlight. Hydrocarbon emissions result from incomplete fuel combustion and from fuel evaporation. Today's cars are equipped with emission controls designed to reduce both exhaust and evaporative hydrocarbons.ozonepollutantsmognitrogen oxidesemissionscombustionevaporation
Try yourself: synthetizes you an organic mixture MAKING SOAP FROM OLIVE OIL INGREDIENTS 125 cm 3 of vegetable oil 100 cm 3 of water 20 g of caustic soda (sodium hydroxide) salt (if required) essential oil or perfume (optional) APPARATUS safety goggles beaker glass rod mould for setting soap METHOD Weigh out your caustic soda onto a folded piece of paper. DO NOT TOUCH IT. Pour the oil and water into a big beaker and stir with a glass rod until you make an emulsion. Carefully add the caustic soda, slowly and stirring all the time. DON'T TOUCH IT ! Keep stirring until a thick paste forms. This could take half an hour. If you still don't have a paste after half an hour, stir in 4 spatulas of salt. Add essential oil or perfume if you want. Pour into mould and leave to set for a few days. Keep your fingers crossed !
Lab- work Write a purpose for the lab in you notebook. You might also wish to think about the following questions. They will help you prepare for the lab, but you need not turn them in at the beginning of class. What reaction is described by the word saponification. What are the products from this reaction and what are the required reactants? Draw out the full structure for three of the carboxylic acids listed in books table. Identify all of the polar bonds, and find the polar and non-polar regions of the molecule. What is the most dangerous part of the lab? Why is it critical to clean up all spills immediately?