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Unit 3 Organic Chemistry Chemistry 2202 CHAPTERS 9-11 (PARTIAL) Introduction Organic Chemistry is the study of the molecular compounds of carbon. eg. CH4 CH3OH CH3NH2 Organic compounds exclude oxides of carbon and ions containing carbon. ie. CO, CO2, KCN, CaCO3 are NOT organic compounds!! History of Organic Chemistry Can be traced back to ancient times when medicine men extracted chemicals from plants and animals to treat members of their tribes First defined as a branch of modern science in the early 1800's by Jon Jacob Berzelius Berzelius believed in Vitalism - organic compounds could only originate from living organisms through the action of some vital force organic compounds originate in living or once-living matter inorganic compounds come from "mineral" or non-living matter In 1828, Friedrich Wöhler discovered that urea - an organic compound - could be made by heating ammonium cyanate (an inorganic compound). NH4OCN(aq) (NH2)2CO(s) inorganic organic organic chemistry branched into disciplines such as polymer chemistry, pharmacology, bioengineering and petro-chemistry 98% of all known compounds are organic The huge number of organic compounds is due mainly to the ability of carbon atoms to form stable chains, branched chains, rings, branched rings, multiple rings, and multiple bonds (double and triple bonds) to itself and to many other non-metal atoms. Sources of Organic Compounds 1. Carbonized Organic Matter 2. fossil fuels such as coal, oil, and natural gas basis for the petrochemical industry Living Organisms penicillin from mold ASA from the bark of a willow tree Sources of Organic Compounds 3. Invention antibiotics, aspirin, vanilla flavoring, and heart drugs are manufactured from organic starting materials plastics Structural Isomers Structures that have the same molecular formula but different structural formulas are called structural isomers eg. C4H10 Structural Isomers Draw all structural isomers of C5H12 and C6H14 Structural Isomers Have the same chemical formula but have different chemical and physical properties. Handout Organic #1 Classifying Organic Compounds Organic Compounds Hydrocarbons Hydrocarbon Derivatives Classifying Organic Compounds hydrocarbons consist of carbon and hydrogen atoms only Methane - CH4 hydrocarbon derivatives have one or more hydrogen atoms replaced by another nonmetallic atom bromomethane - CH3Br methanol - CH3OH Hydrocarbons Aliphatic Hydrocarbons Aromatic Hydrocarbons (benzene based) AlkAnes AlkEnes AlkYnes Hydrocarbons aliphatic hydrocarbons have carbon atoms bonded in chains or rings with only single, double, or triple bonds aromatic hydrocarbons contain at least one 6 carbon benzene ring Aliphatic Hydrocarbons 1. Alkanes hydrocarbons that have only single bonds between carbon atoms general formula CnH2n+2 eg. C3H8 C6H14 IUPAC prefixes Prefix meth eth prop but pent hex hept oct non dec # of carbon atoms 1 2 3 4 5 6 7 8 9 10 Complete this methane ethane table for the first 10 alkanes propane CH4 A series of compounds which differ by the same structural unit is called a homologous series eg. each successive member of the alkanes increases by CH2 Representing Alkanes (4 ways) 1. Structural formulas eg. propane H H H H–C–C–C–H H H H Representing Alkanes (4 ways) Hydrogen atoms may be omitted from structural formulas eg. propane –C–C–C– Representing Alkanes (4 ways) 2. Condensed Structural Formula eg. Propane CH3-CH2-CH3 Representing Alkanes (4 ways) 3. Line Structural Diagrams eg: propane (the endpoint of each segment is a carbon atom) Representing Alkanes (4 ways) 4. Expanded Molecular Formulas eg. Propane CH3CH2CH3 Alkyl Groups An alkyl group has one less hydrogen than an alkane. General Formula: CnH2n + 1 To name an alkyl group, use the prefix to indicate the # of carbon atoms followed by the suffix –yl eg. -C7H15 heptyl Alkyl Groups methyl -CH3 ethyl -C2H5 or -CH2CH3 propyl -C3H7 or -CH2CH2CH3 Alkyl Groups Branched alkanes are alkanes that contain one or more alkyl groups eg. Naming Branched Alkanes 1. Find the longest continuous chain of carbons and name it using the alkane name. This is the parent chain. 1. Number the carbons in the parent chain starting from the end closest to branching. These numbers will indicate the location of alkyl groups. Naming Branched Alkanes 3. List the alkyl groups in alphabetical order. Use Latin prefixes if an alkyl group occurs more than once. (di = 2, tri = 3, tetra = 4, etc.) 4. Use a number to show the location of each alkyl group on the parent. Naming Branched Alkanes 5. Use commas to separate numbers, and hyphens to separate numbers and letters. Naming Branched Alkanes eg. ethyl 7 6 5 4 3 2 1 methyl 4-ethyl-3-methylheptane Naming Branched Alkanes Pages 336 - 339 #’s 5 – 11 Handout Organic #2 Alkenes and Alkynes saturated compounds contain only single bonds between carbon atoms eg. alkanes saturated compounds have the maximum number of hydrogen atoms bonded to carbon atoms Alkenes and Alkynes unsaturated compounds contain double or triple bonds between carbon atoms eg. alkenes and alkynes General Formulas: Alkenes Alkynes CnH2n CnH2n - 2 Naming Alkenes and Alkynes 1. Name the longest continuous chain that contains the double/triple bond. Use the smallest possible number to indicate the position of the double or triple bond. Naming Alkenes and Alkynes 2. Branches are named using the same rules for alkanes. Number the branches starting at the same end used to number the multiple bond. Naming Alkenes and Alkynes Page 347 #’s 17 - 19 Page 354 #’s 28 & 29 Handout Organic #3 Cyclic hydro carbons Carbon chain is joined together to form a circle Lose two Hs Naming cyclic hydrocarbons 1. 2. 3. 4. Use the general formula (prefix + root + suffix) All carbons are equal start at 1 anywhere Two or more branches, CW or CCW Double bonds must be 1 and 2 3-ethyl-1-methylcyclopentane cyclopentane 2 1 ethyl 3 methyl 1-ethyl-3-methylcyclopentane methyl 1,2,3,4-tetramethylcyclohexane Cyclic Hydrocarbons Pages 356 – 358 questions 30 & 31 Handout Organic #4 Aromatic Compounds Aromatic hydrocarbons contain at least one benzene ring. The chemical formula for benzene, C6H6 , was determined by Michael Faraday in 1825. Structural formula was determined by August Kekulé in 1865. Aromatic Compounds benzene ring consists of six carbon atoms, each of which is bonded to a hydrogen atom (Try to draw this!!) C6H6 can be drawn with alternating single and double bonds. Aromatic Compounds While C=C double bonds are shorter than CC single carbon bonds, x-ray crystallography shows that all six C-C bonds in benzene are the same length. Benzene molecules behave like alkanes in chemical reactions, not like the alkenes Aromatic Compounds Kekulé thought benzene could exist in two forms and used the idea of resonance to explain its structure. The resonance structure is an average of the electron distributions. Aromatic Compounds or Aromatic Compounds bonding electrons that were thought to be in the double bonds are delocalized and shared equally over the 6 carbon atoms the bonds in benzene are like “1 ½” bonds – somewhere between single and double. Naming Aromatic Compounds an alkyl benzene has one or more H atoms replaced by an alkyl group. name the alkyl groups, using numbers where necessary, followed by the word benzene. Aromatic Compounds methylbenzene ethylbenzene propylbenzene Aromatic Compounds 1,3-dimethylbenzene 1,4-dimethylbenzene 1,2-dimethylbenzene Aromatic Compounds ortho- means positions 1 and 2 and is represented by an italicized "o" meta- means positions 1 and 3 and is represented by an italicized "m" para- means positions 1 and 4 and is represented by an italicized "p" Aromatic Compounds m-dimethylbenzene p-dimethylbenzene o-dimethylbenzene Aromatic Compounds Benzene is treated as a branch if it is not attached to the terminal carbon of an alkyl group Benzene as a branch is called phenyl Aromatic Compounds CH3 CH2 CH2 propylbenzene 2-phenylpropane CH3 CH CH3 Aromatic Compounds CH3 CH2 CH2 CH CH CH3 CH2 CH3 Aromatic Compounds CH3 CH2 CH2 CH3 CH3 CH2 CH2 CH CH2 CH CH CH3 Aromatic Compounds Page 361 #’s 32 – 35 Pages 363, 364 #’s 4 – 9 Handout organic #5 Hydrocarbon Derivatives Hydrocarbon Derivatives have one or more H atoms replaced by another nonmetallic atom Types of derivatives: alcohols ethers aldehydes Ketones carboxylic acids organic halides esters Hydrocarbon Derivatives A functional group is the reactive group of atoms that gives a family of derivatives its distinct properties. The general formula for a derivative is R - functional group where R stands for any alkyl group. Bonded to Hydrocarbon Derivatives eg. ALCOHOLS ethanol propanol hydroxyl group R-OH C2H5OH carboxyl C3H7OH group CARBOXYLIC ACIDS R-COOH ethanoic acid CH3COOH propanoic acid C2H5COOH Hydrocarbon Derivatives Types of derivatives (See p. 378) Alcohols – pp. 386 - 388 Ethers – pp. 394 – 396 Aldehydes & Ketones – pp. 402,403 Carboxylic Acids – pp.405, 406 Alkyl Halides – pp. 390, 391 Esters – pp. 410, 411 Structure and naming Handout organic #6 Handout organic #7 Aldehydes and ketones Handout organic #8 Alcohols and esthers Caboxylic acids and alkyl halides Handout organic #9 Esters Reactions in hydrocarbons 1. Combustion Uses O2 to produce CO2 and H2O Reactions in hydrocarbons 2. Cracking and reforming Cracking: Large hydrocarbon is broken in smaller pieces Requires H2 Reforming: Small hydrocarbons combine Releases H2 Reactions in hydrocarbons 3. Substitution In alkanes and aromatics In the presence of light H is replaced by and halogen Reactions in hydrocarbons 4. Addition In alkene and alkynes Molecules added across a double/triple bond Reactions in hydrocarbons 5. Esterification Between an alcohol and a carboxylic acid Acid catalyst (H2SO4 or H+) and heat (Δ) is necessary Reactions in hydrocarbons 6. Elimination a) In alcohol Water is removed Acid catalyst (H2SO4 or H+) and heat (Δ) is necessary Reactions in hydrocarbons 6. Elimination b) In alkyl halide Halogen atom is removed Metal hydroxyde (eg. NaOH) is required Handout organic #10