1 LIU Chem. 121, Sect 012, Exam III Fall, 2012, 100 points ... - myweb

Chem. 121, Sect 012, Exam IIIL. I. U.Fall, 2012, 100 points1. Draw all of the stereoisomers of 3-bromo-2-pentanol and assign the absolute configuration (R or S)to each chirality center. (13 pts).A HB HC H2D H2HO C CH 223CH 3 C OHHO C CH 3CH 3 C OHBr C CH 2 CH3 3 CH 3 CH 2 C Br3CH 3 CH 2 C BrBr C CH32 CH33HHHH2S, 3R 2R, 3S2S, 3S2R, 3R2. Give the relationship between the following molecules. They may be the same molecule, differentmolecules, constitutional isomers, enantiomers, or diastereomers. Show your work for partial credit.(a)ACH 3AClClClCH 3BThese molecules are mirror images and there is no plane ofsymmetry. Therefore, they are each chiral and they are notsuperimposable. Therefore, they are enantiomers.(b)CHCH 3CO 2 HHClBrCH 3HCO 2 HCH 3BrHClCO 2 HHHC ClC BrCH 3DClHCH 3HBrCO 2 HClHCH 3C HC BrCO 2 H(12 pts)These are constitutional isomers. The Cl and Br are attachedto different carbons.1CO 2 HBrHCCrotate 180° in theplaneCO 2 H3. Give the product(s) of the following reactions, giving the full reaction mechanism in each case andshowing the correction stereochemistry where applicable. If there is more than one product expected,indicate the major and minor product. For (c) indicate whether or not the product is optically active.(40 pts)(a)H(no mech. for step one)OHClOSOCH 3FCH 3OCOHHOHCl O -SHO CH 3CH 3HCCCH 3OCBrClO -HCl -CH 3HOHClOHSSOO CH 3OO CH 3E

(b)CH 3HBrHS - Na +S N 2 with inversionCH 3HGHS(c)CH 2 CH 3HOCH 2 CH 3CH 3 CBr CH CH 3CH 3optically activeThe reaction mixture is not opticallyacitive since it consists of more or lessequal mixtures of both enantiomers.CH 3 CH 2 OHH CH 2 CH 3CH 3 H CH O3 HOCH 2 CH 3 CH 3CC H CH 3CCH 3 CH 2 CH 3CH 3 CH 2 CH 3HOCH 2 CH 3(-H + )CHCH CH 33 HCCH 3 CH 2OCH2 CHCH 3 3O CH 2CH 3CH 3CH CH 3C HCH 3 CH 2 CH 3CH 3 Br(d) CH 3 C CCH 3 HHOCH 2 CH 3CH 2NaOCH 2 CH 3HCH 3CH 3C CCH 3 HCH 2IE2 is the major product.4. Which reaction would proceed faster? Explain, paying careful attention to all reasons, including thesubstrate structure, the nature of the nucleophile, the leaving group and the effect of the solvent. Givethe product of each reaction and indicate the reaction mechanism. (15 pts)I - DMSOF - CH 3CH 3K CH 3 CH 2 CH 2 Br CH 3 CH 2 CH 2 IHOCHCH 3 C CH 2 Cl3CH 3 C CH 2JCH 3 CH 3FReaction K is faster. the Br is a better leaving group than Cl; the substrate is less hindered to backside attack,I - is a better nucleophile than F - and finally, DMSO is a polar aprotic solvent, very good in S N 2 reactions since itis good at solvating the cation, K + , but not the anion.5. Synthesize TWO of the following molecules from starting materials given on the left as shown. Doall three for extra credit. (20 pts)(a) H C C HNaNH 2C C: - HCH 3 CH 2 BrHC C CH 2 CH 3NaNH 2 - :C C CH 2 CH 3CH 2 BrCH 2Na, NH 3CH 2C C CH 2 CH 3(b)CH 3HHOHCH 3 CH 2O+ Cl S CH 3OCH 3HHONaBrOSO CH 3CH 3HBrH(c)H Br Br KCNCN2