Practice Exam-III ' Name Key - {a5iaYlO - Organic Ich235.yolasite.com/resources/Velu Exam III- Key.pdf ·  · 2011-11-14Practice Exam-III ' Name Key - {a5iaYlO ... multiple choice

Practice Exam-III '

Name Key - {a5iaYlO(Last) (First)

BOO# _

This exam is divided up into two parts, multiple choice and short answer questions. All workmust be shown in order to receive full credit. Please turn off all electronic communicationdevices.

Multiple choice questions. Choose the correct answer and record it on the scantron provided(2 points each).

1. Which of the following compounds gives a carbonyl bond absorption at the highestfrequency?

o

(d)

2. Which of the following is the best set of conditions for the preparation of tert-butyl methylether?

~

a) tert-butyl fluoride and NaOCH3 in CH30H(b) methang] and sodium tert-butoxide in tert-butanolc) ~methane and sodium tert-butoxide in tert-butanol@ tert-butyl bromide and CH30H f(J(' 5N)...

~3. The reaction of methyl iodide with sodium azide, NaN3, proceeds by an SN2 mechanism·I'Clfc= /{!Jab,,][tl1Jt7

What is the effect of doubling the concentration of Nabl, on the rate of the reaction? f.e- r. ] :J(a) the rate remains the same (b) the rate decreases by a factor of2 ('(); - K L1. J).,](§) the rate increases by a factor of 2 (d) the rate increases by a factor of 4 !'ale ~ .1K

4. What is the equation for the rate of formation of tert-butyl alcohol from the reaction of tert-butyl bromide (t-BuBr) with water by an SN1 mechanism?@Rate = k [t-BuBr] (b) Rate = k [t-BuBr]DH20](c) Rate = k [H20] (d) Rate = k [t-BuBr]~

5. Which of the following is not a characteristic of SN2 reactions?(a) the electrophilic carbon undergoes inversion of stereochemistry V(b) the rate is proportional to the concentration of substrate v rate ~ )) .,K'r,;: , ·.I[ ](c) the rate is proportional to the concentration of nucleophile Y L?N7 - L5uPfimft.J J nu ~@ the rate is independent of the solvent

1

. carj;()-CIt/tfJll6. Which of the following is most likely to undergo rearrangement during reaction with

methanol?

7.J:m:~~~~~:~~J:dX:lo;;:n~B'N6,,- tfiJl.t"/{;{lAI/(,y- (a) Br (b) @ Br (d)

8. What is the ~dij&tftr~duct formed upon treatment of (R) 2-bromohexane with sodiumcyanide by SN2 mechanism?W (R) 2-cyanohexane l'd~1II-Iw?~ (5) 2-cyanohexane/'nveI"$NI"/(b).1-hexene ejlmln,.H~ ~ 2-hexene e/l',n-Jrz4~ . 8Vv

a/9. In which of the following solvents would the reaction of l-bromobutane with sodium azide,

NaN3, proceed the fastest?(a) CH3COOH (b)CH3CH20H (c) H20

I;t(}Hc t""He. rITe10. Which of the following is the most nucleophilic?

(§) sodiu~, ethoxide C/wy-c (b) acetic €¥V (c) methanol

~f -',O(H1CH3 eN [of) i1I6f JI1fIr/ C#} OH•. J '()H I'lu:

11. Which of the following energy diagrams represents the course of an exothermic El reaction?

t;) ,/ ~ &? \ f~ .>k//uJ _ .~rB r.g rft, rF(d) water

I~~

reactioncoordinate

reactioncoordinate

reactioncoordinate

reactioncoordinate

12. Which of the following processes takes place upon absorption of infrared radiation?@ bond vibration (b) electron excitation (c) nuclear spin flip (d) electron spin flip

13. Which of the following bonds gives rise to a strong, broad, absorbance at approximately3200-3650 cm-1 in the infrared spectrum?

)a(C=O @O-H ~C=C ;arC-H-1715 /\. / fr!O A/t?f- }~

14. Which of the following compounds gives an infrared spectrum with peaks at 3300 cm-1

(sharp peak) and 2150 cm-1 (sharp peak)? ~p l. fC£C H Hc=cH

//C'-..., ~CH2 I I ~/1la( H-C SfH2C"")Cl ~ v: H2C~r2

Alb ~f-H yd~ftfJ 2 I

f5YJ1lrtJeft','C4{ trtrre ~PndfVllft(Jlecu/evfl/l rcqd,'t1j at' J.J5"()cm'" (

CH3CH2C==CH@!7rr~'II4(

>,P - Hr"t''!~t1

15. Which of the following compounds gives an infrared spectrum with peaks at 3000-3500 em-Iand ~1720 em-I?

Jbr17/~

Short answer questions.

1. Propose a mechanism for the formation of these products in the solvolysis of thisbromoalkane (12 points).

+ + HBr

H~ .. .0 ,-t- ·PT.

3

2. l-Chloro-2-butene undergoes hydrolysis in warm water to give a mixture of these allylicalcohols. Propose a mechanism for their formation (12 points).

2-butene-l-ol

OH

Nr~Cl

l-Chloro-2-butene

.f~IH20 .-

fDIM- I'fYJh'c~OH

+

3-butene- 2-01

[H3

I ~ /J/f//l-.qH ~ H-LZ/CH:J

4

4. How would you use IR spectroscopy to determine if this reaction went to completion (10points)?

d~HA stroll! ,br'Uad C4V5(JrpHOf} frf)q1 'J5rY()- 3Jf)Ocl11-r ~kld inti/calc the

,rc~c.e ~f aYJ a/{'tJh~/. Thl.r Wtmfd /1j,f W fC~/J I~ fhe de~/~c/!fOdtuf: A re~d/Ilf f/lfhrl), abfJve 5(JiJtJCM-t w~uld Ilut/cafe C{J1

5pl [-H pfltIj ,11 fhltnduc~ and a rwtdfIJ aTfJUtld "-/flte", ~I wouLdl~d,'Clttc lit (-c. ~ph ~.f f-he5e rY;ltdfrtf~ wbttld bR SUn ,'f f-he «Ciellenw~n+- +0 Q;m~leHorl.

5. Show the stereochemistry (R and S) of the two stereoisomeric products formed in thefollowing SN 1reaction. Indicate which the major product is and explain why that is the case?(12 points).

6. MATCH a structure from the list below to the following IR spectra. Place the letter of thestructure in the blank to the left of the spectrum (12 points).

~ C() ~0 0

I II III

HOxy ()OH H

00

IV V VI

LOO

50 /' P\2?~P . I~OVI . '.~B'SO>p"'t'r ~K> c'Z.csp! C··-H-(lUt! fo C-H. rthJ

. in '" dt 11,;)(L S'r}C-q t-rn9P!/l'tlvr h1 (fMICI

0/7:J.b .

~uoo 3000 2000 ". 1000 '"0HAVENunB EflI-11

LOO

T·•..

50

MAl'ENUMD EFi!I-11

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100

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