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Chapter 10 Carbon: More Than Just Another Element. Important – Read Before Using Slides in Class
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Important – Read Before Using Slides in Class Instructor: This PowerPoint presentation contains photos and figures from the text, as well as selected animations and videos. For animations and videos to run properly, we recommend that you run this PowerPoint presentation from the PowerLecture disc inserted in your computer. Also, for the mathematical symbols to display properly, you must install the supplied font called “Symb_chm,” supplied as a cross-platform TrueType font in the “Font_for_Lectures” folder in the "Media" folder on this disc. If you prefer to customize the presentation or run it without the PowerLecture disc inserted, the animations and videos will only run properly if you also copy the associated animation and video files for each chapter onto your computer. Follow these steps: 1. Go to the disc drive directory containing the PowerLecture disc, and then to the “Media” folder, and then to the “PowerPoint_Lectures” folder. 2. In the “PowerPoint_Lectures” folder, copy the entire chapter folder to your computer. Chapter folders are named “chapter1”, “chapter2”, etc. Each chapter folder contains the PowerPoint Lecture file as well as the animation and video files. For assistance with installing the fonts or copying the animations and video files, please visit our Technical Support at http://academic.cengage.com/support or call (800) 423-0563. Thank you.
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Types of Organic Compounds • Vast majority of over 20 million known compounds are based on C: organic compounds. • Generally contain C and H + other elements • Great variety of compounds
Isomerism • Isomers have identical composition but different structures • Two forms of isomerism • Constitutional (or structural) • Stereoisomerism • Constitutional • Same empirical formula but different atom-to-atom connections • Stereoisomerism • Same atom-to-atom connections but different arrangement in space.
Cis-2-butene Trans-2-butene Stereoisomers: Geometric Geometric isomers can occur when there is a C=C double bond.
Stereoisomers: Optical • Optical isomers are molecules with non-superimposable mirror images. • Such molecules are called CHIRAL • Pairs of chiral molecules are enantiomers. • Chiral molecules in solution can rotate the plane of plane polarized light.
Stereoisomers Isomers Chirality generally occurs when a C atom has 4 different groups attached. Lactic acid
Stereoisomers Isomers Lactic acid isomers are nonsuperimposable
Chirality: Handedness in Nature These molecules are non-superimposable mirror images.
Chirality: Handedness in Nature These amino acids are non-superimposable mirror images.
Right- and left-handed seashells The DNA here is right-handed Stereoisomers in Nature
Hydrocarbons • Compounds of C and H • Subgroups: • Alkanes: C-C single bonds • Alkenes: C=C double bonds • Alkynes: carbon-carbon triple bonds • Aromatic: based on benzene
Hydrocarbons • Alkanes have the general formula CnH2n+2 • CH4 = methane • C2H6 = ethane • C3H8 = propane • C4H10 = butane • C5H12 = pentane
Hydrocarbons & Structural Isomerism C5H12 has 3 structural isomers. C6H14 has 5 C7H14 has 9 Isomers of C5H12? Note names of isomers
Hydrocarbons: Alkanes Alkanes are colorless gases, liquids, and solids Generally unreactive (but undergo combustion) Not polar (or low polarity) and so are not soluble in water.
Hydrocarbons: Cycloalkanes All compounds are flexible. Cyclohexane, C6H12, has interconverting “chair” and “boat” forms.
Alkenes: Compounds with C=C Double Bonds • How many isomers are possible for a compound with the formula C4H8?
Reactions of Alkenes:ADDITION REACTIONS • Alkenes are unsaturated — more bonds can form to the C atoms • Molecules such as Br2, H2, HCl, HBr, and H2O add to the double bond
An Addition Reaction Fat placed in Br2 vapor • The fat in bacon is partially unsaturated. The fat adds Br2 to the C=C bonds. • Fats can be “hydrogenated” with H2.
An Addition Reaction Fat placed in Br2 vapor PLAY MOVIE
An Addition Reaction • Fats can be “hydrogenated” with H2. PLAY MOVIE Peanut butter has partially hydrogenated vegetable oil.
Trans Fatty Acidstend to raise total blood cholesterol CH3(CH2)7CH=CH(CH2)7CO2H
Alkynes • Alkynes have carbon-carbon triple bonds. • C2H2: common name = acetylene systematic name = ethyne Preparation: CaC2(s) + H2O(liq) --> C2H2 (g) + Ca(OH)2(s) ∆fHo(C2H2, g) = +226.7 kJ/mol ∆rH for C2H2 + O2 = –1300 kJ/mol
Aromatic Compounds • Benzene, C6H6, in the top 25 chemicals produced in the U.S. • Starting point for hundreds of other compounds.
Resonance in Benzene • C6H6 has two resonance structures with alternating double bonds. • The π electrons are delocalized over the ring.
π electrons delocalized Resonance in Benzene • CC bond order is _______________ • C–C single bond = 154 pm C=C bond = 134 pm • CC bonds in benzene = 139 pm
Other Aromatic Hydrocarbons Toluene Naphthalene
TNTtrinitrotoluene Aniline Phenol C6H5NH2 C6H5OH C6H4CH3(NO2)3 Benzene Derivatives
Naming Benzene Derivatives 1,4-dimethylbenzene Common name: Para-xylene
Reactions of Aromatics • Substitutions — not additions — are typical. AlCl3 is a catalyst. Catalysts typically used in aromatic substitutions.
Functional Groups See Chemistry Now, Chapter 10
Alcohols • Characterized by –OH group • Name: add –ol to name of hydrocarbon Methanol Butanol
Structures of Alcohols C3H5OH: how many structural isomers? Naming: Add -ol to name of 3-C hydrocarbon. Indicate position of OH with number.
Alcohol Properties • Alcohols are a derivative of water • Many alcohols dissolve in water Methanol dissolves in water. Butanol is NOT soluble in water.
“Sterno” • Alcohols burn in air • A mixture of ethanol + calcium acetate = STERNO
Ethylene glycol GLYCOLSAlcohols with Two OH Groups
Alcohol ReactionsScreen 11.6 PLAY MOVIE PLAY MOVIE Elimination—the reverse of addition Substitution
More Alcohol Reactions Ethanol is a PRIMARY ALCOHOL. It is oxidized to an ALDEHYDE and then to an ACID.
More Alcohol Reactions SECONDARY ALCOHOLS are oxidized to KETONES — and reaction stops there.