UNIVERSITY OF CALGARY FACULTY OF SCIENCE MIDTERM EXAMINATION CHEMISTRY 353

Transcription

1 UNIVERSITY F ALGARY FAULTY F SIENE MIDTERM EXAMINATIN EMISTRY 353 WEDNESDAY MAR 9th, 2011 Time: 2 ours PLEASE WRITE YUR NAME AND FULL STUDENT I.D. NUMBER N BT YUR MPUTER ANSWER SEET and on the ANSWER BKLET provided. READ ALL TE INSTRUTINS AREFULLY The exam consists of Parts 1-7, each of which should be attempted. Note that some Parts provide you with a choice of questions, e.g. answer any 5 out of 6. These will be graded in numerical order until the required number have been completed, regardless of whether they are right or wrong. Parts 1-4 will be computer graded, and Parts 5, 6 and 7 are to be answered IN TE BKLET PRVIDED. A periodic table with atomic numbers and atomic weights and spectroscopic data tables are included with this examination paper. Parts 1-4 consist of a series of multiple choice questions numbered 1-34 which are to be answered on the computer answer sheet. Indicate your answer by blackening out the appropriate space, A, B,, D or E on the answer sheet. Use a soft pencil only and not ink. In some cases it is required that you indicate multiple items for a complete and/or correct answer by blackening out more than one space. In some other cases more than five options are available and some of these also require more than one space to be blackened out. For an example, an option specified as AB requires that you blacken out both space A and space B. Part marks may be awarded in some of the questions. Incorrect answers must be erased cleanly. Molecular models are permitted during the exam; calculators are also permitted, but NT programmable calculators. Absolutely no other electronic devices are allowed.

2 hem 353 MT W of 18 PART 1: RELATIVE PRPERTIES 16% ANSWER ANY EIGT (8) F QUESTINS Arrange the items in each of the questions in this section in DEREASING RDER (i.e. greatest first) with respect to the indicated property. Use the following code to indicate your answers. A. i > ii > iii D. ii > iii > i B. i > iii > ii E. iii > i > ii. ii > i > iii AB. iii > ii > i 1. The relative stability of each of the following: + + i ii iii + 2. The relative strengths of the bonds at the positions indicated in each of the following: i ii iii 3. The relative reactivity of each of the following towards l: i ii iii NTINUED -->

3 hem 353 MT W of 18 Use the following code to indicate your answers. A. i > ii > iii D. ii > iii > i B. i > iii > ii E. iii > i > ii. ii > i > iii AB. iii > ii > i 4. The relative rate of reaction of each of the following towards / dark / N 2 : i ii iii 5. The relative stability of the following: i ii iii 6. The optical purity of the following samples of tartaric acid given that (R,R)-tartaric acid [α] D = : i a mixture composed of : g 0.75g ii a sample whose observed rotation = o when 2.00g of a mixture was dissolved in 10mL and measured in a standard 10cm polarimeter cell iii a racemic mixture NTINUED -->

4 hem 353 MT W of 18 Use the following code to indicate your answers. A. i > ii > iii D. ii > iii > i B. i > iii > ii E. iii > i > ii. ii > i > iii AB. iii > ii > i 7. The relative yields of the following products from the reaction of 2-methylpent-2-ene with / peroxides : i ii iii 8. The % yield of the product alcohol from each of the following reactions of propene with B 3 followed by work up with excess alkali 2 2 : i. 4.2g propene with 0.10 mol B 3 giving 3.0g 1-propanol ii. iii. 4.2g propene with 0.02 mol B 3 giving 3.0g 1-propanol 0.3 mol propene with 0.1 mol B 3 giving 6.0g 1-propanol 9. The relative reactivity of each of the following towards cyclopentadiene: 2 3 i ii iii 10. The relative oxidation states of the atoms indicated in each of the following: 2 2 i ii iii NTINUED -->

5 hem 353 MT W of 18 PART 2: STARTING MATERIALS, REAGENTS AND PRDUTS 14% ANSWER ANY SEVEN (7) F QUESTINS For each of questions select the MISSING component (the starting material, the product or the reagents) required in order to BEST complete each of the reaction schemes NaN gs 4, 3 + A B D E 12. A 1. 2 / Pd B 1. Na / N / Lindlar's catalyst / Zn u / Zn u / Zn u D 1. Na / N / K( 3 ) 3 E 1. 2 / Lindlar's catalyst 2. 3 / K( 3 ) heat / pressure A B D E NTINUED -->

6 hem 353 MT W of / Lindlar's catalyst , dark, N 2 A B D E K / heat Zn / 3 + A B D E 16. ( 3 ) 3 -= 2 aq. 2 S 4 A B D E B 3 / TF ( 3 ) 3 -= 2 2. aq. Na / 2 2 A B D E 18. ( 3 ) 3 -= 2 conc. 2 S 4 heat A B D E NTINUED -->

7 hem 353 MT W of 18 PART 3: REGIEMISTRY and STEREEMISTRY F REATINS 18% ANSWER ANY SIX (6) F QUESTINS For each of the questions 19-25, select the structure required to BEST complete the reaction shown Na, N 3 2. g(ac) 2, 2 3. NaB 4, K A B D E l 2, 2 2. K 3. 2 S 4, Me Me Me l l A B D E B 3, TF , Na 3. Na, TF A B D E NTINUED -->

8 hem 353 MT W of cat. s 4, t-butylperoxide, t-butanol 2. 2 S 4, heat 3. Me 2 2 Me, heat 2 Me 2 Me A B D E , Lindlar's cat Et Et Me Et Me Me Me Et Me Et A B D E , Lindlar's catalyst 2. l, heat 3. Potassium t-butoxide, heat l l A B D E NBS, l , excess KN, DMS 4. water workup Ph N N Ph N N Ph N N N Ph N N A B D E N Ph N NTINUED -->

9 hem 353 MT W of 18 PART 4: PI SYSTEMS 16% ANSWER ANY EIGT (8) of the questions For each of the questions select the appropriate answer from the answers provided. In some cases more than one selection may be required for full credit. 26. Which of the following molecules are NT conjugated systems (select all that apply) A B D E 27. Which of the following systems are resonance contributors of the carbocation shown below (select all that apply) A B D E 28. Which of the following isomers is the most stable as drawn A B D E NTINUED -->

10 hem 353 MT W of Which of the following isomers is the most stable A B D E 30. Which of the following systems has the most vinylic carbons A B D E 31. Which of the following molecules contain sp-hybridised atoms (select all that apply) 3 N N A B D E 32. Which of the following systems would be the most reactive towards aq. 2 S A B D E NTINUED -->

11 hem 353 MT W of Which of the bonds indicated below is the shortest 3 D B 2 2 A E 34. Which of the following compounds used in the hem 353 laboratory experiments will show 13 -NMR resonances between ppm (select all that apply) A. glycerol (also known as 1,2,3-propane-triol) B. biodiesel. terephthalic acid (the monomer recovered from PETE depolymerisation) D. benzophenone E. benzaldehyde NTINUED -->

12 hem 353 MT W of 18 PART 5: MEANISMS 10% ANSWER TW (2) QUESTINS, NE FRM PART A and NE FRM PART B WRITE YUR ANSWER IN TE BKLET PRVIDED Draw curly arrow mechanisms to explain the following reactions / observations. No other reagents are required. A. Show the mechanism for one of the following reactions: aq. 2 S 4 R 2 R R 3 K R' R' 3 + R" 2 R" 3 (you only need to show the reaction of one of the chains) 2 B. Use your knowledge of the reaction of alkenes with and peroxides (or uv light) and of alkynes with (dark / N 2 atmosphere) to predict based on a 2 mechasism the outcome of the following reaction: excess 3 3 uv light R Use your knowledge of the reactions of alkenes and dienes with halogens at high temperature to predict the outcome of the following reaction: l NTINUED -->

13 hem 353 MT W of 18 PART 6: SYNTESIS 15% ANSWER ANY TREE (3) F QUESTINS WRITE YUR ANSWERS IN TE BKLET PRVIDED. Design an efficient synthesis for any TREE (3) of the following target molecules SW YUR ANSWER AS A STEPWISE REATIN SEME SWING TE PRDUT F EA STEP D NT SW MEANISMS (i.e. curly arrows are NT required) Allowed starting materials and reagents: any compounds with 3 or less atoms In addition, you may use any solvents or reagents that do not contribute carbon atoms to the final structure. 1,2-dimethylbenzene 3 3 NTINUED -->

14 hem 353 MT W of 18 PART 7: STRUTURE DETERMINATIN 11% WRITE YUR ANSWER IN TE BKLET PRVIDED Use the information in the following paragraph to answer the questions below. ompound A ( 6 12 ), a cis alkene, was reacted with P 3 / Et 3 N in TF to give B ( 6 11 ). A was also reacted with 2 S 4 and heat to give ( 6 10 ). ydrocarbon quickly reacted with 2 at high temperatures to give D ( ) as a racemic mixture. The enantiomers of D were separated and one enantiomer of D was treated with potassium permanganate, in the presence of K at 0 to give (2S,3S,4R)-1,4- dibromo-3-methylpentane-2,3-diol and (2R,3R,4R)-1,4-dibromo-3-methylpentane-2,3- diol in equal amounts. Molecules B and were heated in a sealed tube to give E ( ), which was further reacted with aqueous acid to give F ( ). F was dissolved in TF and sodium metal was added, which resulted in the formation of the molecule shown below. Draw the structures of A to F. Which isomer of D was used in the reaction ow many configurational isomers of D are theoretically possible TS / IR / W11 *** TE END ***

15 hem 353 MT W of 18 SPETRSPI TABLES 1 NMR - -N R ppm R --X Ar- = Ar --N --S --= --= NMR ARATERISTI EMIAL SIFTS / ppm methyl methylene methyne other R R R N Ar R N R-Ar R R l R R R

16 hem 353 MT W of NMR = - = X Ar aldehydes ketones carboxylic acid derivs. ppm 13 NMR ARATERISTI EMIAL SIFTS / ppm l

17 hem 353 MT W of 18 INFRA-RED GRUP ABSRPTIN FREQUENIES TYPE F VIBRATIN FREQUENY (cm -1 ) WAVELENGT (µ) INTENSITY (1) Alkanes (stretch) s 3 (bend) 1450 and and 7.27 m 2 (bend) m Alkenes (stretch) m (bend) s Aromatics (stretch) s (out-of-plane bend) s Alkyne (stretch) ca ca.3.03 s Aldehyde w w Alkane not usually useful = Alkene m-w Aromatic m-w Alkyne m-w = Aldehyde s Ketone s arboxylic acid s Ester s Amide s Anhydride ca ca s ca ca s Acyl chloride s Alcohols, Ethers, Esters, arboxylic acids s Alcohols, Phenols Free m -Bonded m arboxylic acids (2) m N Primary and secondary amines ca ca m N Nitriles m N= Nitro (R N 2 ) s s X Fluoride s hloride s omide, Iodide <600 >16.7 s (1) s = strong, m = medium and w = weak (2) note that the - absorption of solid carboxylic acids which run as a nujol mull can be difficult to see as they maybe very broad.

18 hem 353 MT W of 18 PERIDI TABLE 1 1A 18 8A A 13 3A 14 4A 15 5A 16 6A 17 7A 2 e Li Be B N F Ne Na Mg Al Si P S l Ar K a Sc Ti V r Mn Fe o Ni u Zn Ga Ge As Se Kr Rb Sr Y Zr Nb Mo Tc (98) 44 Ru Rh Pd Ag d In Sn Sb Te I Xe s Ba * La f Ta W Re s Ir Pt Au g Tl Pb Bi Po (209) 85 At (210) 86 Rn (222) 87 Fr (223) 88 Ra ** Ac (227) 104 Rf (261) 105 a (262) 106 Sg (263) 107 Ns (262) 108 s (265) 109 Mt (266) 110 Uun (269) 111 Uuu (272) Lanthanides * 58 e Pr Nd Pm (145) 62 Sm Eu Gd Tb Dy o Er Tm Yb Lu Actinides ** 90 Th Pa U Np Pu (244) 95 Am (243) 96 m (247) 97 Bk (247) 98 f (251) 99 Es (252) 100 Fm (257) 101 Md (258) 102 No (259) 103 Lr (260)