3351 midterm 2 - Chemistry 3351—100 Organic Chemistry Dr...

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Unformatted text preview: Chemistry 3351—100 Organic Chemistry / Dr. Barney Ellison Thursday: Oct. 25th @ 7:00pm -’r 9:00 / 211d Exam/_I—Ie11ems 252 Name: h § (please print) 1. (20 pts) For each of the following compounds, assign R or S the each stereocenter. ca ® g/ C a) an”!!! ems :4/ b) 2. (20 pts) Write structures f0 each of the folIOwing compounds a) (1R, 3R)-1,3—dichlorocyclohexane b) (35, 4R)—3~eh10ro—4-methylhexane c) the mesa isomer of 1,3-dimethy1cyclopentane i _. H H F d) an optically active isomer of 1,2-dimethy1cyclobutane 3. (10 pts) In the formation of Grignard reagents from Mg and alkyl halides, the most frequent side reactions are dimerization and disproportionation, as in the following example. Propose a mechanism for these side reactions. Cf Mng Ms ‘—"'"" + + ether solvent LC: 0.417 \/ -'—-""“' fl“ N37777:.“ FL)_ ////%7 4. (10 pts) Explain the following observations. a) (S)~3-br0m0~3-methylhexane reacts in aqueous acetone to give racemic 3-methyI-3-hexan01. Br CH3 HZO/ acetone HO CH3 (5) -—-—+ (i) AX/ 1,. w 4-0? c1“; p\ ,. 055014 4' ¥ 0 y): 4r /\./\. / fl; AX/ w \ps’fim 30 a?” 5:000 b) *7. (R)-2-bromo-2,4-dimethylhexane reacts in aqueous acetone to give optically active 2,4-dimethyl—2—hexanol. g at, L 3 L QH ’5 \%f A SN): (33 kg“; . U _# I m / I}? H2L\ L“ / Q‘wc n: 7 4\ LR; Wyc’fiz L Qw’uz‘ ~ J W V 0} 9“ ’2‘“ LHL/' \ Gym [\ C H; 5. (10 pts) When a solution of cis—l-t-butyl-4-chlorocyclohexane in ethanol is refluxed for several hours, the major product is found to be trans-Li- butyl—4«ethoxycyclohexane. However if the solution is made 2.0 M in sodium ethoxide, the major product is found to be 4—t—butylcyclohexene. Explain. C\E‘321Q\ MM -——-’7 w} H "" a SN 3 UR l A 0:23p \ 1* V 8614 _ xx 00%“; OKLRLCHB gfilp‘flfll W A“; + (A; as“; /,___._._.i Wishf- & ‘ (W) “M MD "m w \L flAMmi %‘ %‘STD MU: ,L\ “j \PW-‘L {gafg‘m J9 firtho \Wcfifl- 6. (10 pts) Optically active 3-br0m0-2—butan01 is treated with KOH in CH3OI-I to obtain an optically inactive product having the formula C4HSO. What is the structure for this material? W3 {Br CPA—CH / \CH Civil 3 QM \09-3 H: R0 f‘ (n 50 E H W t H at :4 3 o “f Ar l m” QM 89V C“: by. \L a}? \\J a... r“ (H; 0:1. Qfih b\ LBAH |\ r" \ \§ :‘ M\ 9.1g Kj%( 3;, \\, O O ILLE/ \m l DH: (list?y "s 4 g M _, mi Rig 0 Wm CANVJL mix~ “Ce’w‘fi -10- 7. (20 pts) In each of the following pairs of reactions, predict which one is faster and explain why. a) (CH3)2CHCH2C€ + N3“(EtOH solvent) —> (CH3)2CHCH2N3 + CE— FC \M (CH3)2CHCHZI + N; (EtOH solvent) —> (CH3)2CHCH2N3 +1— 04-: T“ 4.9 a. \m‘hm haw: 3W6 JAM C" sp—F" b) (CH3)3CBr + H20 +A —) (CH3)3COH+HBr 6-- Cam (CH3)2CHBr + H20 + A —> (CH3)2CHOH + HBr H1 Cfikmgfi ,4; MM pkg“ \WM“ 3 \LRB m > W; + OH { 0 CH5 ' Z d) CH3CHzBr + CN_ [CH30H solvent] —2* CHSCHZCN + Br— CHSCHZBrJr CN—-[(CH3)2NCHO solvent] —> CHSCHZCN + Br— _11_ ...
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