Chemistry 130, Midterm Exam 2

Chemistry 130, Midterm Exam 2 Instructor: Bergdahl

Spring 2019

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PartA.1‐25Questions.Eachcorrectansweris3points.(Part1max75points)1)ConstitutionalisomersareA)Moleculeswiththesamemolecularformulaandthesameconnectivitybutadifferentspatialarrangementofatomsinthree‐dimensionalspaceB)MoleculeswiththesameconnectivitybutadifferentmolecularformulaC)MoleculeswiththesamemolecularformulabutdifferentconnectivityoftheatomsD)Moleculesthathaveidenticalchemicalproperties2)WhichalkanemolecularformulahastheleastnumberofconstitutionalisomersA)C2H6B)C4H10

C)C10H22

D)C6H14

3)Whichofthefollowingcompoundsis3‐methylheptane

4)pleaseprovidetheIUPACnameofthemoleculeshownbelow

A)5‐MethylheptaneB)3‐MethyloctaneC)2‐ethylheptaneD)2‐methylhexane5)ProvidetheIUPACnameofthemoleculeshownbelow

A)2,2‐dimethyl‐5‐ethyloctaneB)3,3‐dimethyl‐6‐ethylnonaneC)6‐ethyl‐3,3‐dimethylnonaneD)2,2‐dimethyl‐5‐propylnonane

A)

B)

C)

D)

6)PleaseprovidetheIUPACnameofthemoleculeshownbelow

A)methylcyclohexaneB)methylhexaneC)methylcycloheptaneD)cyclohexylmethyl7)InthehighestenergyconformationofbutanetheC‐Cbondsareinthe_______conformation.Butane: A)StaggeredB)eclipsedC)Gauche8)Inthebelowrepresentationofbutanethe2,3C‐Cbondisinthe________conformation.

A)StaggeredB)eclipsedC)Gauche9)Themoststablecyclohexaneconformationiscalledthe________conformationA)BoatB)TwistBoatC)HalfChairDChair10)Whichofthefollowingisthelowestenergyconformationofmethylcyclohexane

H3C CH3

H HH H

CH3CH3A)

B)

C)

D)CH3

CH3

CH3

11)Whichofthefollowingstructuresistrans‐1,4dimethylcyclohexane

12)Whichofthefollowing6carbonconstitutionalisomerswillhavethelowestboilingpoint

13)AccordingtoIUPACrulesthebelowalkeneis

A)CisB)TransC)ED)ZE)Neither14)Thenameofthealkenefrom13(above)isA)E‐1‐bromo‐1‐chloro‐1‐propeneB)Z‐1‐bromo‐1‐chloro‐1‐propeneA)E‐1‐chloro‐1‐bromo‐1‐propeneD)E‐2‐chloro‐3‐butene

Me

Me

Me

Me

Me

Me

A)

B)

C)

Me

D)

Me

E) A, B&C

A) C)

B)D)

15)WhichofthefollowingmoleculesisE‐5‐ethyl‐4‐methyl‐3‐octene

16)Whichofthefollowinghydrocarbonsisleastacidic?

17)Why?A)TheconjugatebaseislessstabilizedbecausetheorbitalthathousesthelonepairhasmorePcharacter.B)TheconjugatebaseisstabilizedbecausetheorbitalthathousesthelonepairofelectronshasmoreScharacter.C)Becausetheatomwiththenegativechargeislesselectronegative18)Predicttheproductofthebelowreaction

19)Thekeyintermediateofthereactionaboveis

20)Yougetthe‘markovnikov’regiochemistry(connectivity)ofyourproductbecauseA)ThereactionproceedsviatheleaststablecarbocationB)AlkenesarebasicC)Thereactiongoesthroughviathemorestablecarbocation

21)Theleaststablecarbocationbelowis

22)ThehybridizationofcarbocationsisA)sp3A)sp2A)sp

23)Predicttheproductofthebelowreaction

24)The2ndstepofthemechanismoftheabovereactionis

25)Predicttheproductofthebelowreaction

PartB.Shortanswerquestions,26‐32,eachproblemisworth5‐12points(total61points)Problem26.(9p)

Write IUPAC names for the following hydrocarbons: (a)

(b)

(c)

Problem27.(12p) A) Following is the structure of Germacrene A, a hydrocarbon synthesized in plants

and studied for its insecticidal properties. Classify each of the sp3 hybridized carbons on Germacrene A as 1°, 2°, 3°, or 4° (9p)

B) Classify each alkene as E or Z respectively (3p)

Problem 28.Use valence-shell electron-pair repulsion (VSEPR) to predict all bond angles about each of the following highlighted carbon atoms. (8p)

(a)

(b)

(c)

(d)

Problem 29. Which alkenes can exist as pairs of E/Z isomers?

For each alkene that does, draw both isomers. (6p)

(a) CH2═CHBr (b) CH3CH═CHBr (c) (CH3)2C═CHCH3 (d) (CH3)2CHCH═CHCH3

Problem 30. In many parts of South America, extracts of the leaves and twigs of Montanoa tomentosa are used as a contraceptive, to stimulate menstruation, to facilitate labor, and as an abortifacient. The compound responsible for these effects is zoapatanol:

(a) Specify the configuration about the carbon-carbon double bond to the seven-membered ring, according to the E,Z system. (3p) (b) How many cis-trans isomers are possible for zoapatanol? Consider the possibilities for cis-trans isomerism in cyclic compounds and about carbon-carbon double bonds. (2p)

Problem31.Draw a structural formula for an alkene with the indicated molecular formula that gives the

compound shown as the major(!) product. Note that more than one alkene may give the same compound as the major product. (9p)

(a)

(b)

(c)

Problem32.Complete these equations by predicting the major product formed in each reaction. (12p)

(a)

(b)

(c)

(d)

(e)

(f)

Grading: PartA____________/75points PartB_____________/61points Total______________/136points Adjusted__________________/150points