chem_264_exam1_020311

8/3/2019 CHEM_264_Exam1_020311

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CIIEM 264

Ksam #1

Spring 2010

ENolen NAME

737~'.vunz ~.ontuins ~lgt ' .swith I 0 p r o h l ~ ~ n . ~ , f i ) r/o/u107'180po i t l / . ~

Pleasre bt, rrn7indt'd uf th e C'olgule Honor (I'ode.

1. [ I 4ptl For tl ie two general react ions shown in the boxes, co~ np letehe en ergy profi lesidiagrams

and for each case label both products on the diagram. Assume these are one step react ions.

I major

Rxn A

2. 1 I-lpll !Imall pol-lion of'the ' H - N M R spectrum for the tw o c o ~ n p o u i ~ t l ss 5110~vn bclo\?;. I 11tlabclcd metl~ylene C H L ) isplays :i dif-ferent paltern in t he se tw o c o n r p o ~ ~ n d s .hy?

NMR+-

Ha, HbH CH, 1 1 1 1 \*<. : cntC

a2<oyy~~3 -- - -- . -. -.

i-'. 1. . -+ ?o wL.~,, jbu., (ji,ak,,cc k?c

4 .5 pprn .qb @~& ,L - , U+ ?

?

I I -NMR

4.5 pprn C.q*-,,&c:z-p- e+.\ fu-

8/3/2019 CHEM_264_Exam1_020311


3. [24pt] The following result w as observed for an asymm etric hydroboration s sing (Ipc*)-13t17.

(Ipc*)-BH2 initial pr od uc ts

a ) Wha t is the percent enan tiorneric exc ess (% ee ) for this initial reaction prod uct mixture'?

b) 1 he initial product mixture is usually recrystallized. After isolation of the n eu crystals. uh at

would you expect the %e e to be? (pick one choice below)

-no way to tell

I: ) A t j ~ical rocedure on the recrystallized product mixture is to react the boraiie with basic

I I ! ~ I - o ; : ~ I ~ peroxide ( N a O H . H?O,) to give the alcohol products, outlined bc l ow . . I'hc cl ~~c stion

i s . . ca n J~OI; I-evtrsc hc order ant1 get tlie sam e results? As sho wn a long the left side. can you lirjt

c o n \ c ~ . to ! I I C alcohols. and then do tlie recrystallization to get the same results? For f i l l 1 credit.

.!;.;I\\ l ? c b i!j;:ollols ::~ndclescribe thc results.

TYPICAL PR OTOCO L- --.- - - - -- -- -.- -

9 1recrystallize NaOH. H 2 0 2

~ n ~ t ~ a lroduct mixture-

_recrystall~zed

product mrxture-

lcohols

I1 NaOH, H2 02IC

alcohols

I! recrystallize

8/3/2019 CHEM_264_Exam1_020311


4. [48pt] Page O'Reactions. Provide the product(s) of the following transformations. A s s u me a n

appropriate workup was eniployed in each case. There is no need to draw sp ecific

stzreochemistr-y- use the blank on the far right to indicate stereochemical conc erns: i f the reaction

favors a single enantiomer (*), a racem ic mixture(*), or if chirality is of no concern (no* ).

RhCI(PPh3)3,Hz,EtOH-

8/3/2019 CHEM_264_Exam1_020311


5. [ 1 Opt] Provide an arro ism for the following tra~lsforliiation.

6. (14p tJ Part of the mech anism for a Wilkinson hydrogentation is shown below.

:rj I;or tilc r ! iod i i~n~n each compound, t ab i ~ l geile coord ination ni111iber ncl thc.~?i\:daiio~

1111!Lb.~!. ./

. ._ ---- _-I T--- 1

bpLloordination # I Oxidation # I

b) Considering the results of your table, below label the two reactions as oxidative addition,

reductive elin~ination.migratory insertion, or other.

8/3/2019 CHEM_264_Exam1_020311


7. 124pt] Co mp lete the follo wi ng exercise wit11 reference to (S)-BIN AP. sho wn here

a) There are no tetrahedral carb ons in (S)-BIN AP, yet it is optically activc. What is thc source of

chirality? Briefly.TI.% W T X N ~ PW - - r ~ ~ f f e b w j ~

h) Llraw (I<)-BINAP n the space above. ag ~~;m- %=

c F LA%-2c) I he resolut~on l ' the (K) - and (S)-enantiomers fbr the RINAP reagents was acco mp l~sh cd n

t l le b~napl~tl iols,ih ic h re have somewhat ac ld ~c rotons. Describe In words how ~ O L I ould

car rj out the resolution s sing any o f the following:

good separation skills. a base, an acid, a chiral base, a chiral acid, luck

8/3/2019 CHEM_264_Exam1_020311


8. [32pt] Synthesis. Prepare a single enantiomer of compou nd 1 using bromoben zene, lithium

di~nelhylcuprate. nd cyclohexan one as your source of carbons. A t remendous amount of partial

c ~ e d i ts possible here. Table 16.2. is attached below .

chem_264_exam1_020311

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