OrganicChemistry–1styear ChallengesinChemistry ThomasB.Poulsen

Challenges in Chemistry (CiC) Organic Chemistry Problems – 1st Year Students

a)Reactionof3,5,5-trimethyl-2-cyclohexen-1-onewithNaNH2(3equiv.)inTHFgeneratesitsenolate.Whenbromobenzeneisaddedandstirredfor4hours,theproductbelowisgeneratedin30%yield.

• Formulateareactionmechanism(whichofcourseinvolvesdrawingofthementionedenolateandtherebyalsothestructureof3,5,5-trimethyl-2-cyclohexen-1-one).

Hint:Reactioninvolvesbenzyne(read16.7inMcMurry9thedition).b)Whenthematerialontheleftisheatedinacetone/water(80/20)itisconvertedtothematerialontheright:

• Comeupwithareactionmechanismthatexplainsthisrearrangement

Hint:Reactionisrelatedtonucleophilicsubstitutionreactions.Readalso7.11inMcMurry.c)Brominationofthealkenetotheleftproducestheproducttotheright:

• Formulateareactionmechanismwhichexplainstheformationofthespecificstereoisomershown.Trytorationalizeyouranswer.

• Providesystematicnamesforbothcompounds.

Me

HOMe

Me

O

O

MeMe

O

NO2

NO2O

O

NO2

NO2O

Me Me

Me

Me

MeMe

HMe

MeMe

H

Br2

Br

Me

Br

OrganicChemistry–1styear ChallengesinChemistry ThomasB.Poulsen

d)Thecompoundtotheleftisachiralmoleculecalledcamphenilone.Whenitistreatedunderratherextremeconditionsshownbelow,themoleculebecomesdeuteratedandatthesametimetheopticalactivityislost.

• Provideanexplanationforthisobservation.Hint:H-atomscanbeacidiceveniftheyarenotlocatedatothecarbonylgroupincaseothertypesofanion-stabilizationispossible.Drawthemoleculeindifferentways,lookforsymmetry.e) Solve NMR-problems 5, 6, 10, and 11 on the following pages. Provide concisedescriptionofhowyouarrivedatyouranswers (i.e. rationalize/deduce).Forproblem10,youneedtoknowtheexperimentcalledDEPT-135.Itsuseishoweverquitesimple:InaDEPT-135spectrummethyl(CH3)andmethyne(CH)carbonsareup.Methene(CH2)carbons are down. Quaternary carbons are not visible. You may also need to findexpected 1H and 13C chemical shifts for certain functionalities. These can be easilyfoundonline.Ifyougetstuckonanyoftheproblems,thencomeanddiscussthemwithme.

Furtherhintscanbeavailable.

O

Me

MetBuOK

tBuOD, 185 oC

optically pureO

Me

Me

DD

D

racemic