2125_02_29 Petroleum Technology, Volume 1-2

Petroleum Technology, Volume 1-2

Vol.2CYCLOPENTADIENEANDDICYCLOPENTADIENE

991

21.InternationalAgencyforResearchonCancer,IARCMonographsontheEvaluation

ofCarcinogenicRisktoHumans,Vol.77,2000,p.227.

22.ACGIH(ed.):DocumentationoftheBiologicalExposureIndices,7thed.,Cincinatti

2001.

VINCENTA.WELCH

KEVINJ.FALLON

WashingtonGroupIntl.,Inc.

(formerlyTheBadgerCompany)

Cambridge,Massachusetts,UnitedStates

HEINZ-PETERGELBKE

BASFAktiengesellschaft,Ludwigshafen

FederalRepublicofGermany

CYCLOPENTADIENEAND

DICYCLOPENTADIENE

1.Introduction

Cyclopentadiene[542-92-7](CPD),C5H6,(1)anditsmorestabledimer,dicyclo-pentadiene[77-73-6](DCPD),C10H12(2)arearethemajorconstituentsofhydro-carbonresins,cyclicole npolymers,andahostofspecialtychemicals.

5

43

(1)125643a3877a1

(2)2

Theycanbetransformedintomanychemicalintermediatesusedinthepro-ductionofpharmaceuticals,pesticides,perfumes, ameretardants,andantioxi-dants.Becauseoftheirwideindustrialuses,theirchemistryhasbeenextensivelyinvestigatedanddocumented.Numerousreviews(1–12)havebeenpublishedonthesubject.TheproductionprocessesandindustrialusesofCPDandDCPDaresummarizedinRef.13.Inadditionaltotheclassicalorganicreactions,CPDformsorganicmetalliccomplexes,ferrocene,withtransitionmetals(14).Someofthesecomplexeshavebeenestablishedasexcellentole npolymerizationcatalysts.Severalreviewshavebeenpublishedonthisrapidgrowing eld(15–19).

2.PhysicalProperties

ThephysicalpropertiesofCPDandDCPDaregiveninTable1.DCPD,3a,4,7,7a-tetrahydo-4,7-methano-1H-indene,canexistintwostereoisomers,theendoandKirk-OthmerEncyclopediaofChemicalTechnology.CopyrightJohnWiley&Sons,Inc.Allrightsreserved.10.1002/0471238961.0325031211050514.a01.pub2

Petroleum Technology, Volume 1-2

992CYCLOPENTADIENEANDDICYCLOPENTADIENEVol.2Table1.PhysicalPropertiesofCyclopentadieneandDicyclopentadiene

Physicalproperties

molecularweight

bp,101.3kPa,a8C

mp,8C

physicalform

odor

d204

d354

n20

D

n35

Dheatofcombustion,kJ/molb

heatofvaporization,kJ/mold

heatoffusion,kJ/molb

speci cheat,kJ/(kgK)b

heatofcracking,kJ/molb

spontaneousignitiontemp,8C

inoxygen

inair

dielectricconstantat408C

ionizationenergy,eV

a

bCyclopentadiene66.140.0À97:2colorlessliquidsweetterpenic0.80211.4440292928.98.01.75106408.5Dicyclopentadiene132.217032colorlesssolidcamphoraceous0.93021.51051.5050576738.52.11.7102.95102.432.438.8ToconvertkPatommHg,multiplyby7.5.ToconvertkJtokcal,pideby4.184.

exoforms.BecausecommerciallyavailableDCPDismostlytheendoisomer,theproperties

in

(endo DCPD)(exo DCPD)

Table1arepertinenttothoseoftheendoisomer.SpectroscopicalinformationonCPDandDCPDcanbefoundinthefollowingreferences:Massspectrum,ref.20;nmrspectrum,ref.21;infrared,ultravioletandRamanspectraref.2.

DCPDdecomposesrapidlyatitsnormalboilingpointtotwomoleculesofcyclopentadiene.Puri cationofDCPDbydistillationmustbeconductedundervacuumconditions.Figure1depictstheloweringoftheboilingpointasafunc-tionofpressure.ThedimeristheforminwhichCPDissoldcommercially.

3.ChemicalReactions

Cyclopentadieneisveryreactive.InadditiontothevastnumberofreactionsoneexpectsfromaconjugateddoublebondstructureswhichincludeDiels–Alderaddition,hydrogenation,halogenaddition,etc,thehighlyacidicmethylenegrouppromotesanumberofcondensationreactions.Ontheotherhand,DCPDbehaveslikenon-conjugateddienes,withtheexceptionthatthedoublebondin

Petroleum Technology, Volume 1-2

Vol.2CYCLOPENTADIENEANDDICYCLOPENTADIENE

Boiling point, CPressure in mm Hg993

Fig.1.Boilingpointofdicyclopentadieneasafunctionofpressure.

thebicyclohepteneringismorereactivethanthatinthe ve-memberringbecauseofthebondanglestraininthebicycloheptenering.

3.1.Diels–AlderAddition.InDiels–Alderaddition,theconjugateddoublebondsofCPDreactwiththepbondofadienophile,acompoundcontain-ingethylenicoracetylenicunsaturation.Theethylenicoracetylenicgroupisaddedacrossthe1,4positionofthe

CPD,

R1

+

R3

(1)R44R212resultinginabicyclo[2.2.1]heptenederivative,acyclohexenederivativewithabridgedmethylenegroup.BecauseofDiels–Alderreactions,manymulticycliccompoundscanbesynthesizedwithCPDasthebuildingblocks.Examplesofthesereactions,whicharehighlyexothermic(71–75kJ/mol),areshowninTable2.

BothCPDandDCPDcanbeusedinthereactions.Howeverforthelatter,thereactionneedstobecarriedoutattemperaturesabove1758CinorderfortheDCPDtodissociaterapidlytotheCPDmonomer.Therateofthereactionisstronglyaffectedbyothersubstituentsofthedienophile.Forinstance,thereac-tionbetweenCPDandmaleicanhydrideoccursspontaneouslywhereasthatbetweenCPDandethylenerequireselevatedtemperaturesandveryhighpressure.Along oppychainonthedienophileisalsoastronginhibitorofthereaction(22).

Diels–Alderadditionisstereochemicallyspeci c(22).Thereisastrongten-dencyofmostsubstituentsofthedienophiletoorientintheendocon gurationin

Petroleum Technology, Volume 1-2

994CYCLOPENTADIENEANDDICYCLOPENTADIENEVol.2Table2.Diels–AlderAdductsfromCyclopentadiene

Dienophile

Dibasicacidsandderivatives

maleicanhydride,R¼H

chloromaleicanhydride,R¼ClStructureofadductHORO

Monobasicacids

crotonicacid,R1¼H;R2¼CH3methacrylicacid,R1¼CH3;R2¼HR1COOH

R2

Aldehydes

acrolein,R¼H

crotonaldehyde,R¼CH3HCHOR

H

Ketones

methylpropenylketone(3-penten-2-one),R1¼CH3;R2¼CH3methylvinylketone(3-buten-2-one),R1¼H;R2¼CH3

Vinylcompounds

ethylene,R¼H

styrene,R¼C6H5vinylacetate,R¼CH3COOHCOR2R1HR

H

Acetylenes

acetylene,R¼H

acetylenedicarbonitrile,R¼

CN

OQuinones

p-benzoquinone

O

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