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1、AlkanesandCycloalkanesChapter 2Chapter 2第1页/共70页Structure Hydrocarbon:Hydrocarbon:acompoundcomposedonlyofcarbonandhydrogen Saturatedhydrocarbon:Saturatedhydrocarbon:ahydrocarboncontainingonlysinglebonds Alkane:Alkane:asaturatedhydrocarbonwhosecarbonsarearrangedinanopenchain Aliphatichydrocarbon:Alip
2、hatichydrocarbon:anothernameforanalkane第2页/共70页Hydrocarbons第3页/共70页StructureShapetetrahedralaboutcarbonallbondanglesareapproximately109.5第4页/共70页Drawing AlkanesLine-angleformulasanabbreviatedwaytodrawstructuralformulaseachvertexandlineendingrepresentsacarbon第5页/共70页Constitutional Isomerism Constitut
3、ionalisomers:Constitutionalisomers:compoundswiththesamemolecularformulabutadifferentconnectivityoftheiratomsexample:C4H10第6页/共70页Constitutional Isomerismdotheseformulasrepresentconstitutionalisomers?findthelongestcarbonchainnumbereachchainfromtheendnearestthefirstbranchcomparechainlengthsaswelltheid
4、entityandlocationofbranches第7页/共70页Constitutional IsomerismWorld populationWorld populationis aboutis about6,000,000,0006,000,000,000第8页/共70页Nomenclature-IUPACSuffix-aneanespecifiesanalkaneanePrefixtellsthenumberofcarbonatoms第9页/共70页Nomenclature-IUPAC Parentname:Parentname:thelongestcarbonchain Subs
5、tituent:Substituent:agroupbondedtotheparentchain alkylgroupalkylgroup:asubstituentderivedbyremovalofahydrogenfromanalkane;giventhesymbolR-第10页/共70页Nomenclature-IUPAC1.Thenameofasaturatedhydrocarbonwithanunbranchedchainconsistsofaprefixandsuffix2.Theparentchainisthelongestchainofcarbonatoms3.Eachsubs
6、tituentisgivenanameandanumber4.Ifthereisonesubstituent,numberthechainfromtheendthatgivesitthelowernumber第11页/共70页Nomenclature-IUPAC5.Iftherearetwoormoreidenticalsubstituents,numberthechainfromtheendthatgivesthelowernumbertothesubstituentencounteredfirstindicatethenumberoftimesthesubstituentappearsby
7、aprefixdi-,tri-,tetra-,etc.usecommastoseparatepositionnumbers第12页/共70页Nomenclature-IUPAC6.Iftherearetwoormoredifferentsubstituents,listtheminalphabeticalordernumberfromtheendofthechainthatgivesthesubstituentencounteredfirstthelowernumber第13页/共70页Nomenclature-IUPAC7.Theprefixesdi-,tri-,tetra-,etc.are
8、notincludedinalphabetizationalphabetizethenamesofsubstituentsfirstandtheninserttheseprefixes第14页/共70页Nomenclature-IUPACAlkylgroups第15页/共70页Nomenclature-CommonThenumberofcarbonsinthealkanedeterminesthenameallalkaneswithfourcarbonsarebutanes,thosewithfivecarbonsarepentanes,etc.iso-indicatesthechainter
9、minatesin-CH(CH3)2;neo-thatitterminatesin-C(CH3)3第16页/共70页Classification of C&H Primary(1)C:Primary(1)C:acarbonbondedtooneothercarbon1H:ahydrogenbondedtoa1carbon Secondary(2)C:Secondary(2)C:acarbonbondedtotwoothercarbons2H:ahydrogenbondedtoa2carbon Tertiary(3)C:Tertiary(3)C:acarbonbondedtothreeother
10、carbons3H:ahydrogenbondedtoa3carbon Quaternary(4)CQuaternary(4)C:acarbonbondedtofourothercarbons第17页/共70页CycloalkanesGeneralformulaC Cn nHH2n2nfive-andsix-memberedringsarethemostcommonStructureandnomenclaturetoname,prefixthenameofthecorrespondingopen-chainalkanewith cyclo-cyclo-,andnameeachsubstitue
11、ntontheringifonlyonesubstituent,noneedtogiveitanumberiftwosubstituents,numberfromthesubstituentofloweralphabeticalorderifthreeormoresubstituents,numbertogivethemthelowestsetofnumbersandthenlistsubstituentsinalphabeticalorder第18页/共70页CycloalkanesLine-angledrawingseachlinerepresentsaC-Cbondeachvertexa
12、ndlineendingrepresentsaC第19页/共70页Cycloalkanes Example:Example:namethesecycloalkanes第20页/共70页Bicycloalkanes Bicycloalkane:Bicycloalkane:analkanethatcontainstworingsthatsharetwocarbonsBicyclo4.4.0decane(Decalin)Bicyclo4.3.0nonane(Hydrindane)Bicyclo2.2.1heptane(Norbornane)第21页/共70页BicycloalkanesNomencl
13、atureparentisthealkaneofthesamenumberofcarbonsasareintheringsnumberfromabridgehead,alonglongestbridgebacktothebridgehead,thenalongthenextlongestbridge,etc.showthelengthsofbridgesinbrackets,fromlongesttoshortest第22页/共70页IUPAC-Generalprefix-infix-suffix prefixprefixtellsthenumberofcarbonatomsinthepare
14、nt infixinfixtellsthenatureofthecarbon-carbonbonds suffixsuffixtellstheclassofcompoundone or more triple bondsone or more double bonds all single bonds-yn-en-an-Nature of Carbon-Carbon Bonds in the Parent ChainInfixSuffix Class-e-ol-al-one-oic acidhydrocarbonalcoholaldehydeketonecarboxylic acid-amin
15、eamine第23页/共70页IUPAC-Generalprop-enen-e=propeneeth-anan-ol=ethanolbut-anan-one=butanonebut-anan-al=butanalpent-anan-oicacid=pentanoicacidcyclohex-anan-ol=cyclohexanoleth-ynyn-e=ethyneeth-anan-amine=ethanamine第24页/共70页Conformations Conformation:Conformation:anythree-dimensionalarrangementofatomsinamo
16、leculethatresultsfromrotationaboutasinglebond Newmanprojection:Newmanprojection:awaytoviewamoleculebylookingalongacarbon-carbonsinglebond第25页/共70页Conformations Staggeredconformation:Staggeredconformation:aconformationaboutacarbon-carbonsinglebondinwhichtheatomsorgroupsononecarbonareasfarapartaspossi
17、blefromtheatomsorgroupsonanadjacentcarbon第26页/共70页Conformations Eclipsedconformation:Eclipsedconformation:aconformationaboutacarbon-carbonsinglebondinwhichtheatomsorgroupsofatomsononecarbonareascloseaspossibletotheatomsorgroupsofatomsonanadjacentcarbon第27页/共70页Conformations TorsionalstrainTorsionals
18、trainalsocalledeclipsedinteractionstraineclipsedinteractionstrainstrainthatariseswhennonbondedatomsseparatedbythreebondsareforcedfromastaggeredconformationtoaneclipsedconformationthetorsionalstrainbetweeneclipsedandstaggeredethaneisapproximately12.6kJ(3.0kcal)/mol第28页/共70页Conformations Dihedralangle
19、Dihedralangle(Q)(Q):theanglecreatedbytwointersectingplanes第29页/共70页ConformationsEthaneasafunctionofdihedralangle第30页/共70页ConformationsTheoriginoftorsionalstraininethaneoriginallythoughttobecausedbyrepulsionbetweeneclipsedhydrogennucleialternatively,causedbyrepulsionbetweenelectroncloudsofeclipsedC-H
20、bondstheoreticalmolecularorbitalcalculationssuggestthattheenergydifferenceisnotcausedbydestabilizationoftheeclipsedconformationbutratherbystabilizationofthestaggeredconformationthisstabilizationarisesfromthesmalldonor-acceptorinteractionbetweenaC-HbondingMOofonecarbonandtheC-HantibondingMOonanadjace
21、ntcarbon;thisstabilizationislostwhenastaggeredconformationisconvertedtoaneclipsedconformation第31页/共70页Conformations anticonformationanticonformationaconformationaboutasinglebondinwhichthegroupslieatadihedralangleof180第32页/共70页Conformations StericstrainStericstrain(nonbondedinteractionstrain)nonbonde
22、dinteractionstrain):thestrainthatariseswhenatomsseparatedbyfourormorebondsareforcedclosertoeachotherthantheiratomic(contact)radiiwillallow Anglestrain:Anglestrain:strainthatariseswhenabondangleiseithercompressedorexpandedcomparedtoitsoptimalvalueThetotalofalltypesofstraincanbecalculatedbymolecularme
23、chanicsprogramssuchcalculationscandeterminethelowestenergyarrangementofatomsinagivenconformation,aprocesscalledenergyminimizationenergyminimization第33页/共70页Conformationsconformationsofbutaneasafunctionofdihedralangle第34页/共70页Anti ButaneEnergy-minimizedanticonformationtheC-C-Cbondangleis111.9andallH-
24、C-Hbondanglesarebetween107.4and107.9thecalculatedstrainis9.2kJ(2.2kcal)/mol第35页/共70页Eclipsed Butanecalculatedenergydifferencebetween(a)thenon-energy-minimizedand(b)theenergy-minimizedeclipsedconformationsis5.6kJ(0.86kcal)/mol第36页/共70页Cyclopropane anglestrain:anglestrain:theC-C-Cbondanglesarecompress
25、edfrom109.5to60 torsionalstrain:torsionalstrain:thereare6setsofeclipsedhydrogeninteractionsstrainenergyisabout116kJ(27.7kcal)/mol第37页/共70页Cyclobutanepuckeringfromplanarcyclobutanereducestorsionalstrainbutincreasesanglestraintheconformationofminimumenergyisapuckered“butterfly”conformationstrainenergy
26、isabout110kJ(26.3kcal)/mol第38页/共70页Cyclopentanepuckeringfromplanarcyclopentanereducestorsionalstrain,butincreasesanglestaintheconformationofminimumenergyisapuckered“envelope”conformationstrainenergyisabout42kJ(6.5kcal)/mol第39页/共70页Cyclohexane Chairconformation:Chairconformation:themoststablepuckered
27、conformationofacyclohexaneringallbondC-C-Cbondanglesare110.9allbondsonadjacentcarbonsarestaggered第40页/共70页CyclohexaneInachairconformation,sixHareequatorialandsixareaxial第41页/共70页CyclohexaneForcyclohexane,therearetwoequivalentchairconformationsallC-Hbondsequatorialinonechairareaxialinthealternativech
28、air,andviceversa第42页/共70页Cyclohexane Boatconformation:Boatconformation:apuckeredconformationofacyclohexaneringinwhichcarbons1and4arebenttowardeachothertherearefoursetsofeclipsedC-Hinteractionsandoneflagpoleinteractionaboatconformationislessstablethanachairconformationby27kJ(6.5kcal)/mol第43页/共70页Cycl
29、ohexane Twist-boatconformationTwist-boatconformationapproximately41.8kJ(5.5kcal)/mollessstablethanachairconformationapproximately6.3kJ(1.5kcal)/molmorestablethanaboatconformation第44页/共70页Cyclohexane第45页/共70页EquatorialandaxialmethylconformationsMethylcyclohexane第46页/共70页 G0 axial-equatorialgiventhedi
30、fferenceinstrainenergybetweenaxialandequatorialconformations,itispossibletocalculatetheratioofconformationsusingthefollowingrelationship第47页/共70页Cis,Trans Isomerism Stereoisomers:Stereoisomers:compoundsthathavethesamemolecularformulathesameconnectivityadifferentorientationoftheiratomsinspace Cis,tra
31、nsCis,transisomersisomersstereoisomersthataretheresultofthepresenceofeitheraring(thischapter)oracarbon-carbondoublebond(Chapter5)第48页/共70页Isomersrelationshipsamongisomers第49页/共70页Cis,Trans Isomers1,2-Dimethylcyclopentane第50页/共70页Cis,Trans Isomerism1,4-Dimethylcyclohexane第51页/共70页Cis,Trans Isomerismt
32、rans-1,4-Dimethylcyclohexanethediequatorial-methylchairconformationismorestablebyapproximately2x(7.28)=14.56kJ/mol第52页/共70页Cis,Trans Isomerismcis-1,4-Dimethylcyclohexane第53页/共70页Cis,Trans IsomerismThedecalins第54页/共70页SteroidsThesteroidnucleusCholestanol第55页/共70页BicycloalkanesNorbornanedrawnfromthree
33、differentperspectives第56页/共70页BicycloalkanesAdamantane第57页/共70页Physical PropertiesIntermolecularforcesofattraction(example)ion-ion(Na+andCl-inNaCl)ion-dipole(Na+andCl-solvatedinaqueoussolution)dipole-dipoleandhydrogenbondingdispersionforces(veryweakelectrostaticattractionbetweentemporarydipoles)第58页
34、/共70页Physical PropertiesLow-molecular-weightalkanes(methane.butane)aregasesatroomtemperatureHighermolecular-weightalkanes(pentane,decane,gasoline,kerosene)areliquidsatroomtemperatureHigh-molecular-weightalkanes(paraffinwax)aresemisolidsorsolidsatroomtemperature第59页/共70页Physical PropertiesConstitutio
35、nalisomershavedifferentphysicalproperties第60页/共70页Oxidation of AlkanesOxidationisthebasisfortheiruseasenergysourcesforheatandpower heatofcombustion:heatofcombustion:heatreleasedwhenonemoleofasubstanceinitsstandardstateisoxidizedtocarbondioxideandwater第61页/共70页Heat of CombustionHeatofcombustionforcon
36、stitutionalisomers第62页/共70页Heats of CombustionForconstitutionalisomerskJ(kcal)/mol-5470.6(-1307.5)-5465.6(-1306.3)-5458.4(1304.6)-5451.8(1303.0)8CO2+9H2O第63页/共70页Heat of Combustionstrainincycloalkaneringsasdeterminedbyheatsofcombustion第64页/共70页Sources of AlkanesNaturalgas90-95%methanePetroleumgases(
37、bpbelow20C)naphthas,includinggasoline(bp20-200C)kerosene(bp175-275C)fueloil(bp250-400C)lubricatingoils(bpabove350C)asphalt(residueafterdistillation)Coal第65页/共70页Gasoline Octanerating:Octanerating:thepercent2,2,4-trimethylpentane(isooctane)inamixtureofisooctaneandheptanethathasequivalentantiknockprop
38、erties第66页/共70页Synthesis GasAmixtureofcarbonmonoxideandhydrogeninvaryingproportionswhichdependonthemeansbywhichitisproduced第67页/共70页Synthesis GasSynthesisgasisafeedstockfortheindustrialproductionofmethanolandaceticaciditislikelythatindustrialroutestootherorganicchemicalsfromcoalviamethanolwillalsobedeveloped第68页/共70页Alkanes andCycloalkanesEnd Chapter 2End Chapter 2第69页/共70页感谢您的观看。第70页/共70页