Identification of Hydrocarbons (HCs)Physical PropertiesSlide 3Chemical ReactivityAlkenesSlide 6Slide 7AlkynesSlide 9AromaticsAddition vs. SubstitutionSlide 12UnknownsAlkene ReactionsWeak p BondsAlkene Reactions are Additions: Trading Pi for SigmaThe True Structure of BenzeneBonding in Benzene: s FrameworkBonding in Benzene: p Electrons are DelocalizedFinal InstructionsSlide 21Identification of Hydrocarbons (HCs)Using Chemical and Physical Properties to Characterize Saturated and Unsaturated CompoundsPhysical PropertiesHCs in Water and Ligroin–“Like dissolves like”Polar dissolves polar–What is polar?Nonpolar dissolves nonpolar–What is nonpolar?Physical PropertiesDensity–Hydrocarbons are less dense than waterTypically 0.7 g/mLWater is 1.0 g/mLThink of an oil spill on the oceanChemical ReactivityAlkanes–CombustReaction?Reaction done by TAsObserve flame color, quality–Not very reactive otherwiseAlkenesCombustAddition of bromine–Toxic–Corrosive–Use in hoodAlkenesAddition of sulfuric acid–Corrosive–Converts alkene to water soluble compound–NoteEvolution of heatHomogeneity of solutionAlkenesOxidation with potassium permanganate–ToxicAlkynesCombustAddition of bromine–More exothermic–SlowerAlkynesAddition of sulfuric acid–Corrosive–Alkynes only react with HgSO4 catalyst (not available)Oxidation with potassium permanganate–Same as alkenesAromaticsCombust–Sooty flameAddition of bromine–Requires iron catalyst–Purpose of pH paper?Addition vs. SubstitutionCCCCCCC CHH HHBr BrC CBrHBrH HHHHHHHH++Br BrCCCCCCHHBrHHH+H BrAromaticsAddition of sulfuric acid–Corrosive–No reactionOxidation with potassium permanganate–No reactionUnknownsIdentify functional group by comparing results with those from compounds with known functional groupAlkene ReactionsHydrocarbons have similar physical propertiesChemical properties are very different–Alkenes and alkynes are highly reactive–Alkanes and aromatics are notWhy?Weak BondsAlkene Reactions are Additions: Trading Pi for SigmaBefore Addition Reaction–One double bond C=C sigma and pi bond–One single bond Br-Br sigma bondAfter Addition Reaction–3 single bonds C-C sigma bond 2 C-Br sigma bondsThe True Structure of BenzeneC-C bond length is uniform–Shorter than single–Longer than doubleC-C bond strength is uniform–Stronger than single–Weaker than doubleCCCCCCHHHHHHCCCCCCHHHHHHCCCCCCHHHHHHCCCCCCHHHHHHBonding in Benzene: FrameworkBonding in Benzene: Electrons are DelocalizedFinal InstructionsWork with a partner (stations 1 & 2, stations 3 & 4, etc.)For solubility tests, do 1 test for the entire bench (stations 1-4, 5-8, etc.) and increase volume added by 4.–Add 20 drops (4 x 5 drops) of water to 20 drops of HC (4 x 5 drops)–Repeat with ligroin–6 tubes (3 known, 3 unknown)–Why? Larger volume makes layers easier to detectFinal InstructionsTA will do combustion demo for each benchFor H2SO4 tests, use 1 tube for the entire bench and increase volume added by 4.–Add 12 drops (4 x 3 drops) of H2SO4 to 20 drops of HC (4 x 5 drops)–6 tubes (3 known, 3 unknown)Ice machines are in yellow and red labsMay do tests in any