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Chapter 4 Carbon and the Molecular Diversity of Life Ch 4 Carbon and the Molecular Diversity of Life 1. What is organic chemistry? - Branch of chemistry that studies carbon compounds Ch 4 Carbon and the Molecular Diversity of Life 1. 2. What is organic chemistry? What do you know about carbon? • • • • • • Atomic # = 6 Forms covalent bonds Tetravalent – 4 valence electrons – forms 4 bonds Tetravalence makes large, complex molecules possible. Determines 3D shape of molecules Compatible with other abundant elements Hydrogen Oxygen Nitrogen Carbon (valence = 1) (valence = 2) (valence = 3) (valence = 4) H O N C Ch 4 Carbon and the Molecular Diversity of Life 1. 2. 3. What is organic chemistry? What do you know about carbon? How does carbon contribute to molecular diversity? • Carbon skeletons – covalent bonds that link C atoms together & form the skeletal framework of organic molecules Figure 4.5 Variations in carbon skeletons H H H H H H C C H H H H C C C H H H H Ethane Propane H H H H H H C H H H H C C C C H H H H H H C C C H H H H (a) Length (b) Branching Butane (c) Double bonds 2-methylpropane (commonly called isobutane) H H H H H H H H H C C C C H H H H C C C C H H H 1-Butene (d) Rings H H H H H H H C C C H C C H H C H H Cyclohexane 2-Butene H H C H C C H CC C H H Benzene Ch 4 Carbon and the Molecular Diversity of Life 1. 2. 3. 4. What is organic chemistry? What do you know about carbon? How does carbon contribute to molecular diversity? What are hydrocarbons? – – – – Molecules consisting of only hydrogen & carbon Fossil fuels Some are biologically important (fats) Hydrophobic (non-polar) – oil & water don’t mix Ch 4 Carbon and the Molecular Diversity of Life 1. 2. 3. 4. 5. What is organic chemistry? What do you know about carbon? How does carbon contribute to molecular diversity? What are hydrocarbons? What are isomers? - cmpds w/ the same molecular formula but w/ different structures & therefore, different properties Figure 4.7 Three types of isomers H H C H H H H (a) Structural isomers H C C C C C H H H C C C H H H H H H H X (b) Geometric isomers X H C C X C C X H H (c) Enantiomers H C H H H H H H CO2H CO2H C C H H NH2 NH2 CH3 L isomer CH3 D isomer H Ch 4 Carbon and the Molecular Diversity of Life 1. 2. 3. 4. 5. 6. What is organic chemistry? What do you know about carbon? How does carbon contribute to molecular diversity? What are hydrocarbons? What are isomers? What are functional groups? • Parts of molecules involved in chemical rxns FUNCTIONAL GROUP HYDROXYL CARBONYL CARBOXYL O OH (may be written HO OH ) OH), a hydrogen atom is bonded to an oxygen atom, which in turn is bonded to the carbon skeleton of the organic molecule. (Do not confuse this functional group with the hydroxide ion, OH–.) drawing electrons toward itself. Attracts water molecules, helping dissolve organic compounds such as sugars (see Figure 5.3). C C STRUCTURE In a hydroxyl group (— FUNCTIONAL Is polar as a result of the PROPERTIES electronegative oxygen atom O The carbonyl group ( CO) consists of a carbon atom joined to an oxygen atom by a double bond. When an oxygen atom is doublebonded to a carbon atom that is also bonded to a hydroxyl group, the entire assembly of atoms is called a carboxyl group (— COOH). A ketone and an aldehyde may be structural isomers with different properties, as is the case for acetone and propanal. Has acidic properties because it is a source of hydrogen ions. The covalent bond between oxygen and hydrogen is so polar that hydrogen ions (H+) tend to dissociate reversibly; for example, H H C H Figure 4.10 Exploring some important functional groups of organic compounds H O H C OH Acetic acid C H O + H+ C O Acetate ion AMINO SULFHYDRYL H O SH N (may be written HS ) H FUNCTIONAL GROUP PHOSPHATE O P O OH The amino group (—NH2) consists of a nitrogen atom bonded to two hydrogen atoms and to the carbon skeleton. The sulfhydryl group consists of a sulfur atom bonded to an atom of hydrogen; resembles a hydroxyl group in shape. In a phosphate group, a phosphorus atom is bonded to four oxygen atoms; one oxygen is bonded to the carbon skeleton; two oxygens carry negative charges; abbreviated P . The phosphate group (—OPO32–) is an ionized form of a phosphoric acid group (—OPO3H2; note the two hydrogens). Acts as a base; can pick Two sulfhydryl groups Makes the molecule of which up a proton from the surrounding solution: can interact to help stabilize protein structure (see Figure 5.20). it is a part an anion (negatively charged ion). Can transfer energy between organic molecules. H N H +N H (nonionized) H H (ionized) Ionized, with a charge of 1+, under cellular conditions. STRUCTURE FUNCTIONAL PROPERTIES