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  1. Hydrocarbons Section 21.1Introduction to Hydrocarbons Section 21.2Alkanes Section 21.3Alkenes and Alkynes Section 21.4Hydrocarbon Isomers Section 21.5 Aromatic Hydrocarbons Click a hyperlink or folder tab to view the corresponding slides. Exit Chapter Menu

  2. Section 21.1 Introduction to Hydrocarbons • Explain the terms organic compound and organic chemistry. • Identify hydrocarbons and the models used to represent them. • Distinguish between saturated and unsaturated hydrocarbons. • Describe where hydrocarbons are obtained and how they are separated. microorganism:a tiny organism, such as a bacterium or a protozoan, that cannot be seen without a microscope Section 21-1

  3. Section 21.1 Introduction to Hydrocarbons (cont.) organic compound hydrocarbon saturated hydrocarbon unsaturated hydrocarbon fractional distillation cracking Hydrocarbons are carbon-containing organic compounds that provide a source of energy and raw materials. Section 21-1

  4. Organic Compounds • Chemists in the early 19th century knew living things produced a variety of carbon compounds, called “organic” compounds. • They were not able to synthesize them in the lab and labeled them as mysterious. • Wöhler was the first to produce an organic compound in the lab. Section 21-1

  5. Organic Compounds (cont.) • Organic compound is applied to all carbon-containing compounds with the primary exceptions of carbon oxides, carbides, and carbonates, which are considered inorganic. • In organic compounds, carbon nearly always shares its electrons and forms four covalent bonds. Section 21-1

  6. Organic Compounds (cont.) • Carbon atoms are bonded to hydrogen atoms or other elements near carbon on the periodic table. • Carbon atoms also bond to other carbon atoms and form long chains. Section 21-1

  7. Hydrocarbons • The simplest organic compounds are hydrocarbons, which consist of only the elements carbon and hydrogen. • There are thousands of hydrocarbons. Section 21-1

  8. Hydrocarbons (cont.) • Carbon atoms bond to each other by single, double, and triple bonds. • Saturated hydrocarbons contain only single bonds. • Unsaturated hydrocarbonscontain at least one double or triple bond. Section 21-1

  9. Refining Hydrocarbons • Many hydrocarbons are obtained from the fossil fuel petroleum. • Fractional distillationinvolves boiling petroleum and collecting each group of components as they condense at different temperatures. Section 21-1

  10. Refining Hydrocarbons (cont.) Section 21-1

  11. Refining Hydrocarbons (cont.) • Fractional distillation towers do not yield fractions in proportion to demand. • Heavier fractions are converted to gasoline or other lighter fractions by a process called cracking. Section 21-1

  12. Refining Hydrocarbons (cont.) • Gasoline is not a pure substance. • Most molecules have 5 to 12 carbons. • Gasoline is modified by adjusting its composition to improve performance, resulting in the octane rating system. Section 21-1

  13. A B C D Section 21.1 Assessment Petroleum is separated into usable parts by boiling and condensing each component in a process called ____. A.cracking B.fractional distillation C.saturation D.bonding Section 21-1

  14. A B C D Section 21.1 Assessment What is a hydrocarbon that contains only single bonds called? A.unsaturated C.saturated D.fully bonded Section 21-1

  15. End of Section 21-1

  16. Section 21.2 Alkanes • Name alkanes by examining their structures. • Draw the structure of an alkane when given its name. • Describe the properties of alkanes. IUPAC (International Union of Pure and Applied Chemistry): an international group that aids communication between chemists by setting rules and standards in areas such as chemical nomenclature, terminology, and standardized methods Section 21-2

  17. Section 21.2 Alkanes (cont.) alkane homologous series parent chain substituent group cyclic hydrocarbon cycloalkane Alkanes are hydrocarbons that contain only single bonds. Section 21-2

  18. Straight-Chain Alkanes • Alkanes are hydrocarbons that have only single bonds between atoms. Section 21-2

  19. Straight-Chain Alkanes (cont.) • The names of alkanes end in –ane. • Prefixes are derived from Greek numbers. • A series of compounds that differ from one another by a repeating unit is called a homologous series. Section 21-2

  20. Straight-Chain Alkanes (cont.) Section 21-2

  21. Branched-Chain Alkanes • Carbon atoms can bond to one, two, three, or four other carbon atoms making a variety of chains possible. Section 21-2

  22. Branched-Chain Alkanes (cont.) • Straight chains and branched chains can have the same molecular formula. • Order and arrangement of atoms in organic compounds determine their identities. • When naming branched chain alkanes, the longest continuous chain of carbon atoms is called the parent chain. • All the side branches are known as substituent groups. Section 21-2

  23. Branched-Chain Alkanes (cont.) Section 21-2

  24. Branched-Chain Alkanes (cont.) • Naming branched-chain alkanes • Count the number of carbon atoms in the longest continuous chain. • Number each carbon in the parent chain. • Name each alkyl group substituent. • If the same alkyl group appears more than once as a branch on the parent structure, use a prefix to indicate how many times it appears. • When different alkyl groups are attached to the same parent chain, place their names in alphabetical order. Section 21-2

  25. Branched-Chain Alkanes (cont.) • Naming branched-chain alkanes • Write the entire name, using hyphens to separate numbers from words and commas to separate numbers. Section 21-2

  26. Cycloalkanes • An organic compound that contains a hydrocarbon ring is called a cyclic hydrocarbon. • Cyclic hydrocarbons with only single bonds are called cycloalkanes. Section 21-2

  27. Cycloalkanes (cont.) • Naming substituted cycloalkanes is the same as straight-chains but with a few exceptions. • The ring is always considered the parent chain. • Numbering starts on the carbon that is bonded to the substituent. • When more than one carbon has a substituent, number in the direction that gives the lowest possible numbers for the substituents. Section 21-2

  28. Properties of Alkanes • Structure affects molecular properties. • Alkanes are not polar and are good solvents for other nonpolar molecules. Section 21-2

  29. Properties of Alkanes (cont.) • Physical properties of alkanes • Compared to water, methane boils and melts and lower temperatures. • Methane molecules have little intermolecular attraction compared to water. Section 21-2

  30. Properties of Alkanes (cont.) • Chemical properties of alkanes • Alkanes have low reactivity because they are nonpolar and have no charge, and because they have strong single bonds between carbon atoms. Section 21-2

  31. A B C D Section 21.2 Assessment What is a cyclic alkane with no substituents groups and 6 carbon atoms? A.heptane B.cycloheptane C.cyclohexane D.cyclobutane Section 21-2

  32. A B C D Section 21.2 Assessment Alkanes contain how many double bonds? A.greater than 2 B.2 C.1 D.0 Section 21-2

  33. End of Section 21-2

  34. Section 21.3 Alkenes and Alkynes • Compare the properties of alkenes and alkynes with those of alkanes. • Describe the molecular structures of alkenes and alkynes. • Name an alkene or alkyne by examining its structure. • Draw the structure of an alkene or alkyne by analyzing its name. hormone: chemical produced in one part of an organism and transported to another part, where it causes a physiological change Section 21-3

  35. Section 21.3 Alkenes and Alkynes (cont.) alkene alkyne Alkenes are hydrocarbons that contain at least one double bond, and alkynes are hydrocarbons that contain at least one triple bond. Section 21-3

  36. Alkenes • Unsaturated hydrocarbons that contain at least one or more double covalent bonds between carbon atoms are called alkenes. Section 21-3

  37. Alkenes (cont.) • Alkenes are named in much the same way as alkanes. • Alkenes end in –ene. • When four or more carbon atoms are present, specify the location of the double bond. Section 21-3

  38. Alkenes (cont.) • When naming branched-chain alkenes, follow the same rules as for alkanes, with two exceptions. • The parent chain is always the longest chain that contains double bond, whether it is the longest chain or not. • The position of the double bond, not the branches, determine the numbering. • Use a prefix to designate the number of double bonds. Section 21-3

  39. Alkenes (cont.) • Alkenes are nonpolar and have low solubility in water. • Alkenes are more reactive than alkanes because the double bond increases electron density between the two carbon atoms, providing a good site for chemical reactivity. Section 21-3

  40. Alkynes • Unsaturated hydrocarbons that contain one or more triple bonds between carbon atoms are called alkynes. Section 21-3

  41. Alkynes (cont.) • Straight-chain and branched-chain alkynes are named in the same way as alkenes, except the ending is –yne. Section 21-3

  42. Alkynes (cont.) • Alkynes have physical and chemical properties similar to alkenes but are generally more reactive because the triple bonds cause even larger electron densities than double bonds. Section 21-3

  43. A B C D Section 21.3 Assessment Which of the following is generally the most reactive? A.cycloalkanes B.alkanes C.alkenes D.alkynes Section 21-3

  44. A B C D Section 21.3 Assessment What is the name of a straight-chain hydrocarbon with six carbon atoms and a triple bond between the second and third carbon atoms? A.2-hexene B.3-hexene C.2-hexyne D.3-hexyne Section 21-3

  45. End of Section 21-3

  46. Section 21.4 Hydrocarbon Isomers • Distinguish between the two main categories of isomers—structural isomers and stereoisomers. • Differentiate between geometric isomers with cis- and transprefixes. • Describe the structural variation in molecules that results in optical isomers. electromagnetic radiation: transverse waves that carry energy through empty space Section 21-4

  47. Section 21.4 Hydrocarbon Isomers (cont.) isomer structural isomer stereoisomer geometric isomer chirality asymmetric carbon optical isomer optical rotation Some hydrocarbons have the same molecular formula but have different molecular structures. Section 21-4

  48. Structural Isomers • Isomersare two or more compounds that have the same molecular formula but different molecular structures. • Structural isomers have the same chemical formula but their atoms are bonded in different arrangements. Section 21-4

  49. Structural Isomers (cont.) • There are two main classes of isomers: structural isomers and stereoisomers. • Structural isomers have different physical and chemical properties. • The structure of a substance determines properties. Section 21-4