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Hydrocarbon Compounds 22.1 Hydrocarbons 22.2 Unsaturated Hydrocarbons 22.3 Isomerism 22.4 Hydrocarbon Rings 22.5 Hydrocarbons from Earth’s Crust Updated 5/24/2017 Created by C. Ippolito July 2007 1 Hydrocarbons 1. 2. 3. Updated 5/24/2017 Objectives Describe the relationship between the number of valence electrons and bonding in carbon Define and describe alkanes Relate the polarity of hydrocarbons to their solubility Created by C. Ippolito July 2007 2 Organic Chemistry and Hydrocarbons • Organic Chemistry – originally compounds thought to be made only in living things – now study of compounds with BOTH carbon and hydrogen • Hydrocarbons – simplest organic compounds – contain only carbon and hydrogen Updated 5/24/2017 Created by C. Ippolito July 2007 3 Alkanes • only single covalent bonds between carbons – Saturated Hydrocarbons • contain the maximum number of hydrogen atoms per carbon atom – Straight Chain Alkanes • homologous series – group of compounds that have a constant incremental change • 1 = meth• 3 = prop• 5 = pent• 7 = hept• 9 = nonUpdated 5/24/2017 • 2 = eth• 4 = but• 6 = hex• 8 = oct• 10 = dec- Created by C. Ippolito July 2007 4 Formulas • Molecular Formula – C4H10 • Structural Formula – • Condensed Structural Formulas CH3-CH2-CH2-CH3 CH3CH2CH2CH3 CH3(CH2)2CH3 • Carbon Skeleton – C-C-C-C • Line Angle Formula Updated 5/24/2017 Created by C. Ippolito July 2007 5 Branched Chains • Parent Chain – longest continuous carbon chain • Substituents – atoms or atom groups replacing a hydrogen atom • Alkyl Groups – hydrocarbon substituents » CH3― methyl group » CH3CH2― ethyl group » CH3CH2CH2― propyl group Updated 5/24/2017 Created by C. Ippolito July 2007 6 IUPAC Naming Rules for Alkanes 1. Find longest chain (parent) 2. Number carbons and use root name with –ane ending 3. Add numbers to substituent groups 4. Use prefixes for multiple appearances of same group 5. List substituents in alphabetical order 6. Use punctuation but no spaces Updated 5/24/2017 Created by C. Ippolito July 2007 7 Naming Branched Alkanes Updated 5/24/2017 Created by C. Ippolito July 2007 8 Drawing Branched-Chain Alkanes Updated 5/24/2017 Created by C. Ippolito July 2007 9 Properties of Alkanes • Hydrocarbons are NONPOLAR – weak van der Waals forces • low mass tend to be gases or liquids with low boiling points – insoluble in water Updated 5/24/2017 Created by C. Ippolito July 2007 10 Unsaturated Hydrocarbons 1. 2. Updated 5/24/2017 Objectives Describe the difference between unsaturated and saturated hydrocarbons Distinguish between the structures of alkenes and alkynes Created by C. Ippolito July 2007 11 Alkenes • contain one or more carbon-carbon double covalent bond – Unsaturated Hydrocarbon • contain less than the maximum number of hydrogen per carbon atom Updated 5/24/2017 Created by C. Ippolito July 2007 12 IUPAC Naming Rules for Alkenes 1. Find longest chain with double bond (parent) 2. Number carbons and use root name with ending –ene so that double bond has lowest number possible 3. Add numbers to substituent groups 4. Use prefixes for multiple appearances of same group 5. List substituents in alphabetical order 6. Use punctuation but no spaces Updated 5/24/2017 Created by C. Ippolito July 2007 13 Alkenes • contain one or more carbon-carbon triple covalent bond – Unsaturated Hydrocarbon • contain less than the maximum number of hydrogen per carbon atom Updated 5/24/2017 Created by C. Ippolito July 2007 14 IUPAC Naming Rules for Alkynes 1. Find longest chain with triple bond (parent) 2. Number carbons and use root name with ending –yne so that double bond has lowest number possible 3. Add numbers to substituent groups 4. Use prefixes for multiple appearances of same group 5. List substituents in alphabetical order 6. Use punctuation but no spaces Updated 5/24/2017 Created by C. Ippolito July 2007 15 Isomerism 1. 2. 3. Updated 5/24/2017 Objectives Explain why structural isomers have different properties Describe the conditions under which geometric isomers are possible Identify optical isomers Created by C. Ippolito July 2007 16 Structural Isomers • compounds with the same molecular formula but different structures – different physical and chemical properties Updated 5/24/2017 Created by C. Ippolito July 2007 17 Stereoisomers • atoms joined in same order but positions in space are different – Geometric Isomers • related to rigid double bond – Optical Isomers • asymmetrical carbon Updated 5/24/2017 Created by C. Ippolito July 2007 18 Geometric Isomers • Geometric Isomers – orientation around rigid double bond • cis configuration – groups on same side of double bond • trans configuration – groups on different sides of double bond Updated 5/24/2017 Created by C. Ippolito July 2007 19 Optical Isomers • Optical Isomers – four different groups attached to an asymmetric carbon Updated 5/24/2017 Created by C. Ippolito July 2007 20 Hydrocarbon Rings Objectives 1. Identify cyclic ring structures 2. Describe bonding in benzene Updated 5/24/2017 Created by C. Ippolito July 2007 21 Cyclic Hydrocarbons • hydrocarbon chain forms a ring – – – – cyclopropane cyclobutane cyclopentane cyclohexane Updated 5/24/2017 Created by C. Ippolito July 2007 22 Aromatic Hydrocarbons • contains a benzene ring – electrons shared evenly – “resonance” • phenyl group – benzene sub Updated 5/24/2017 Created by C. Ippolito July 2007 23 Substituted Benzene • dimethyl benzene – 3 isomers – ortho• 1,2 dimethyl benzene – o-xylene – meta• 1,3 dimethyl benzene – m-xylene – para• 1,4 dimethyl benzene – p-xylene Updated 5/24/2017 Created by C. Ippolito July 2007 24 Hydrocarbons from Earth’s Crust 1. 2. 3. Updated 5/24/2017 Objectives Identify three important fossil fuels and describe their origins. Describe the composition of natural gas, petroleum, and coal. Describe what happens when petroleum is refined Created by C. Ippolito July 2007 25 Natural Gas • source of alkanes of low molar mass – 80% methane – 10% ethane – 4% propane CH4(g) + 2O2(g) CO2(g) + 2H2O(g) + heat Updated 5/24/2017 Created by C. Ippolito July 2007 26 Petroleum • Fractional Distillation – separation by boiling points • Cracking – heat to form smaller chains from larger ones Updated 5/24/2017 Created by C. Ippolito July 2007 27 Coal • Classified by its hardness and carbon content – Peat • soft, brown, spongy, fibrous material • high water content – Lignite • harder, less fibrous, 50% carbon – Bituminous Coal • “soft” coal, 70%-80% carbon – Anthracite Coal • “hard” coal, over 80% carbon Updated 5/24/2017 Created by C. Ippolito July 2007 28