Zumdahl’s Chap. 22Chapter ContentsOrganic ChemistryModern ViewsCarbon’s FlexibilityCarbon’s ReactivityInorganic CarbonALKANESOld Possum’s NamingBranching & IsomersIsomer NamingCycloalkanes, CnH2nAlkenes, CnH2nAlkene IsomersAlkynes, CnH2n–2Unsaturated CyclesFunctional GroupsAlcohols, R–OHAldehydes, R–CHOCarboxylic Acids R–CO2HAmines, Rn–NH3–nMixed FunctionalityZumdahl’s Chap. 22Organic ChemistryChapter ContentsIntroductionAlkanes CnH2n+2–Isomers–Nomenclature–Cycloalkanes CnH2nAlkenes CnH2nAlkynes CnH2n–2AromaticsFunctional Groups–Alcohols–Aldehydes–Ketones–Carboxylic Acids–Esters–AminesOrganic ChemistryOnce upon a time …–It was believed that organic chemicals could only arise in life processes …–That they were a product of life’s vitality.In 1828, German chemist Friedrich Wöhler dispelled that myth when–(Mineral) ammonium cyanate, NH4CNO, heated gave (organic) urea, (NH2)CO(NH2). As if we needed another source.Modern ViewsWith the exception of petroleum products, geological and elemental carbon is inorganic carbon.Other carbon-containing molecules are organic by virtue of carbon’s presence.There are no end to the combinatorial possibilities since C bonds to C!Carbon’s Flexibilitysp, sp2, sp3 mean a rich geometry of 180°, 120°, and 109.43° angles in virtually endless chains and branches of organic molecules.The most potent psychotropicchemical cocktail on Earth …CHOCOLATE!Carbon’s ReactivityNOT.With the exception of unsaturated sites (multiple carbon-carbon bonds), it is at the heteroatoms (non-CH atoms, X) in an organic molecule where lies the reactive site.Common CX combinations are called functional groups and dictate reactivity.Inorganic CarbonElemental carbon–Graphite–Diamond–BuckminsterfullereneCarbon oxides and halidesCarbonates and carbidesSimple cyano- compounds like HCN.ALKANESSaturated hydrocarbons, CnH2n+2.–“Saturated” because they can’t take any more hydrogen atoms!–Straight chains are H3C–(CH2)n–2–CH3–Gaseous for n<5; solid for n>17 @ STP.–Inert (but for strong oxidizers)–Pathologically nonpolar.–Waxes, oils, & fuel gases as n decreases.Old Possum’s NamingAfter n=4, the prefixanes have Greek numbers as their prefixes.–5=pent, 6=hex, 7=hept, 8=oct, 9=non, and 10=dec, 20=eicos, 30=triacosBut n4 are named historically–CH4, Methane (“intoxicate” from the Greek)–Ethane, Propane, and Butane for 2,3,4.Branching & IsomersAfter n=3, it’s possible to let some C’s bond with more than 2 other carbons.–But fewer than 5, of course!–The # of structural isomers possible thereby grows exponentially with n.–These isomers have similar chemical and physical properties.–So they’re a bit expensive to separate, and one sees bottles labeled merely “hexanes.”Isomer NamingOlder conventions would have that as “isooctane,” but a good IUPAC name results from the following:–Name the longest C chain (pentane)–List the side groups in alphabetical order with Greek prefixes (trimethylpentane)–Supply (smallest possible) positional indices (2,2,4 trimethylpentane)–The gasoline power rating standard molecule.Cycloalkanes, CnH2nIf the two end C’s lose 1 H each, they have free valence to close a ring; voila, cyclo(whatever)ane.–Again properties similar to straight chains.–Can now have conformational isomers!–E.g., BOAT cyclohexane versus CHAIRSee the C3and S6 here?Alkenes, CnH2nCycle formation isn’t the only possible result of dehydrogenation.Adjacent C’s can double bond, C=C, making an (unsaturated) alkene.–Much more reactive (vulnerable  e– pair)–Rigid  orbitals  rigid planar partners!–E.g., trans-5-methyl-2-hexeneObligatory plane seen edge onAlkene IsomersWhile an sp3 CX2Y2 has only 1 isomer,(every X and Y is adjacent to all the others)the sp2 alkene C2X2Y2 has cis & trans isomers (where X is or isn’t on the same side of = as X).–For longer hydrocarbons, cis & trans refer to the side the chain extends:and trans for the oppositecis-2-butenetrans-2-bute necis for the same sideAlkynes, CnH2n–2sp triple bonding makes a rigid 180° segment in a hydrocarbon.It too is vulnerable to attack across the multiple bond site.–Double & triple bonds can suffer addition where an AB molecule single bonds A and B to an unsaturated site. H2, HX, and X2 (where X is halogen) are favorites.propyneUnsaturated CyclesEarlier we noted the stability lent to benzene, C6H6, by  MOs.Alternating single/double cycles occur in many organic molecules similarly.–This class is called “aromatic” (by virtue of their aroma).–The  structure is often preserved in their chemical reactions; they don’t add, they substitute instead.bromobenzeneanthracene (edge on)Functional GroupsOrganic backbones can bear hetero-atoms as reactive sites.Alkyl root symbolized as R, a generic hydrocarbon radical (methyl, ethyl, etc.)Functional groups append R, e.g.,R–OH, an alcohol, or R–CHO, aldehyde.R–CO2H, a carboxylic acid, R–NH2, amine.isobutraldehyde ormethylpropanalAlcohols, R–OH The –OH makes alcohol polar enough to hydrogen bond.  water solubleFermentation product but vulnerable to oxidation to aldehyde and acid.glucose, C6H12O6yeastethanol2CO2+ 2Aldehydes, R–CHONext C oxidation state up from alcohol.–Degradation product in your liver!If C=O isn’t a chain end substituent, it’s not an aldehyde but a ketone.Aldehydes are often flavorings, butKetones are industrial solvents. OC Hbenza ldehyde,“bitter almond”quinoneCarboxylic Acids R–CO2HUsual highest C ox. state in organics.End product of body’s alcohol degradation.Weakly acidic but important buffers.React with alcohols to make highly flavorful esters … a condensation rxn. OC O–H+  +butanoic acid“rancid yak butter”ethanol ethyl butyrat e“pineapple”waterAmines, Rn–NH3–nCome in three varieties, n = 1, 2, & 3.–“Primary” amines, n=1, are at chain end.–“Secondary” amine N bonds to 2 carbons.–“Tertiary” amines bond to 3 C.–Weak base Kb diminishes as n increases.Alcohols are also primary, secondary, and tertiary. (Primary are on end carbons.)–But this refers to the bonding of the C to which OH is attached.Coniine (2ndary) “hemlock”2-propyl-piperidineMixed FunctionalitySo H2NCH2CH2OH