**YOU ARE NOT ALLOWED TO TAKE SPARE COPIES OF THIS EXAM FROM THE TESTING ROOM**

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1 EM 234, Spring 2018 Final Exam Ian R. Gould MPLETE TIS SETI : Up to TW PITS will be removed for incorrect/missing information! PRITED FIRST AME Answer Key Person on your LEFT (or Empty or Aisle) Person on your RIGT (or Empty or Aisle) lass you are REGISTERED FR (onground or hybrid) The room where most students will take the test for your class, i.e. LS A-191 for onground and PS -152 for hybrid) PRITED LAST AME **YU ARE T ALLWED T TAKE SPARE PIES F TIS EXAM FRM TE TESTIG RM** PRIT YUR AME EA PAGE! READ TE DIRETIS AREFULLY! USE BLAK PAGES AS SRAT PAPER work on blank pages will not be graded... WRITE LEARLY! MLEULAR MDELS ARE ALLWED D T USE RED IK D'T EAT, USE MM SESE! Li Be B F e a Mg e Al Si P S l Ar K a Sc Ti V r Mn Fe o i u Zn Ga Ge As Se Br Kr Rb Sr Y Zr b Mo Tc Ru Rh Pd Ag d In Sn Sb Te I s Ba Lu f Ta W Re s Ir Pt Au g Tl Pb Bi Po At Rn R 2 R (δ, ppm) variable and condition dependent, ca. 2-6 δ R R Aromatic R 2 R 2 Xe R 2 Aromatic Ar mainly R Interaction Energies, kcal/mol Eclipsing / ~1.0 /Me ~1.4 Me/Me ~2.6 Et/Et ~3.1 Infrared orrelation hart small range usually range of values strong broad peak peaks R 2200 broad with spikes ~ broad ~ broad ~ R (cm -1 ) 1500 MR orrelation harts 2 X R R 2 R Gauche Me/Me ~0.9 Et/Me ~0.95 i-pr/me ~1.1 t-bu/me ~2.7 Alkyl X Alkyl 3 > 2 > > 2 > 1 0 0

2 M 234, Spring 2018, FIAL EXAM AME Question 1 (13 pts.) Provide a IUPA name for the following structure, do not forget to use E/Z and R/S as appropriate bromo-8-phenyloct-(6Z)-en-2-one Br Question 2 (24 pts.) n each side of the following equilibrium: a) IDETIFY TE IRLED FUTIAL GRUPS b) add the curved arrow pushing in both directions c) identify the stronger and weaker acid and base on each side d) indicte which acid would have the LWER pka e) indicate which side the equilibrium would lie f) Give a brief explanation for your choices of strong and weak acids and bases amide ester weaker base weaker acid larger pka stronger acid smaller pka stronger base equilibrium on TIS side The second pair of nonbonding electrons on the deprotonated amide are stabilized by conjugation into the = bond, lowering their energy and stabilizing the anion. This ion is thus the weaker base, corresponding to the stronger acid. the stronger base is stronger because of the presence of the nitrogen that acts as a strnger donating group to destabilize the enolate anion, compared to the weaker oxygen donating group in the ester Question 3 (12 pts.) Rank the following three structures in order of increasing Bronsted acidity. Give a BRIEF explanation. A F least acidic B F < B < A most acidic F the carboxylate is stabilized by the fluorines via the inductive effect, the further the F from the anion, the weaker the inductive effect

3 M 234, Spring 2018 FIAL EXAM -3 - AME Question 4 (16 pts.) Rank in order of increasing rate of reaction with a Grignard reagent, give a BRIEF explanation that includes the terms Lewis acid/electrophile and Lewis base/nucleophile A l B Me Me slowest B < < A fastest The Grignard is a nucleophile/lewis base, the carbonyls are the electrophiles/lewis acids, the electrophilic atom is the of the =, in A the electrophilic l activates this carbon towards nucleophilic attach and in B the -Me is resonance electron donating and deactivates this carbon towards nucleophilic attack Question 5 (12 pts.) Rank the following in order of increasing basicity, give a BRIEF explanation. sp 2 sp sp3 A B least basic < A < B most basic non-bonding electrons are lower in energy the more s-character the A.., lower in energy means less reactive, less basic

4 M 234, Spring 2018, FIAL EXAM AME Question 6 (26 pts) Give a curved arrow pushing mechanism for the following reaction For each ITERMLEULAR step, indicate the Lewis acid and base (LA or LB) and whether they are also Bronsted acids and bases (BA or BB) as appropriate You MUST show where every proton comes from and goes to, no abbreviated /- notation you do T need to show resonance contributor for the intermediates in this case! l l LA l -l (cat.)/heat 2 LB l E2 is also acceptable here 2 l l the order of these 2 steps can be reversed

5 M 234, Spring 2018, FIAL EXAM AME Question 7 (48 pts) Provide the missing major organic products or reagents/conditions for the following reactions. Do not forget to include stereochemistry as appropriate and IDIATE AY RAEMI MIXTURES. a) 2 F 3 F 3 heat 2 F3 F 3 (±) b) 1 Equiv. l Br 2 c) 1. a 3 2. LiAl d) MgBr (±) e) Br 1. a LiAl f) 1 Equiv. l l don't panic, this is a simple Brønsted acid/base reaction, all it is asking is where the proton would go IGRE STEREEMISTRY/Racemic mixtures for this problem

6 M 234, Spring 2018 FIAL EXAM AME Question 8 (16 pts.) Provide the missing major organic products for the following reactions. Do not forget to include stereochemistry as appropriate and IDIATE AY RAEMI MIXTURES. These two reactions are either Aldol or laisen reactions. a) Ts (cat.) heat or the Z- stereoisomer do an Aldol or laisen reaction, as appropriate b) Me Me 1. a - Me 2. 3 Me (±) Question 9 (16 pts) a) Give the reactants AD reagents/conditions that would allow you to synthesize the provided structure in a laisen reaction Et Et excess Et 1. a - Et 2. 3 Et Et b) Give the reactants AD reagents/conditions that would allow you to synthesize the following structure in an Aldol condensation. or Base excess heat

7 EMISTRY 234, Spring 2018 FIAL EXAM AME Question 10 (36 pts.) Give a curved arrow-pushing mechanism for the following two reactions SW WERE EVERY PRT MES FRM AD GES T Indicate the Lewis acid and base (LA or LB) at each ITERMLEULAR step and whether they are also Brønsted acids and bases ( or BA/BB) a) LA K / 2 K LB b) Me a Me/Me Me Me Me

8 EMISTRY 234, Spring 2018 FIAL EXAM AME Question 11 ( 28 pts.) Give a curved arrow-pushing mechanism for the following reaction SW WERE EVERY PRT MES FRM AD GES T (no or - ) DRAW ALL RESAE TRIBUTRS for the intermediates Add bonds as necessary At each ITERMLEULAR step, IDIATE TE Lewis acid and base (LA or LB) and whether they are also Bronsted acids and bases (BA or BB) as appropriate l 2 2 LA LB 2 2 Extra redit Question (5 pts). Which functional group formed the basis of the "two-electron sensitizer" molecule that enhances the speed of motion picture film? amine ester amide aldehyde

9 M 234, Spring 2018, Final Exam AME Question 12 (50 pts.) Show how you would make the target componds on the right from the starting compounds on the left. Show reagents and conditions where appropriate, and the structures of important intermediate compounds. Do not show any (arrow pushing) mechanisms. For question a) you must indicate steps that require separation of isomers. a) 2 l All 3 l 3 / 2 S 4 l 2 /All 3 Zn/g/l/ 2 l l TE EXT TW SYTESIS PRBLEMS, b) and c), USE MAILY REATIS FRM TE "MIIMAL SET F REATIS" PRVIDED REETLY TE LASS WEB PAGE! b) 1. B 3.TF 2. - / 2 2 P 1. 3 MgBr c) Br Br 2 / FeBr 3 1. Mg.TF a 2 r 2 7 / 2 S 4 / 2 2.

10 M 234, Spring 2018 FIAL EXAM AME Question 13 (40 pts.) Synthesize the (target) molecule on the right from the starting molecule the left. this can not be done in one reaction. Give reagents and conditions and the intermediate molecules at each step. Do not show any mechanisms or transient intermediates. a) BS/hν 1. KMn 4 / - / Br a P direct reductive amination is also K here 1. / (cat.) 2. 2 /Pd/ 1. LiAl Sl 2 l b) Br 2, hν Br Mg. TF MgBr Sl 2 l 2. 3

11 M 234, Spring 2018 FIAL EXAM AME Question 14 (14 pts.) a) Is imidazole (shown below) aromatic, non-aromatic or antiaromatic? aromatic b) Give the product of the reaction of imidazole with l, i.w., where will the proton go? l l imidazole Question 15 (24 pts.) There are several kinds of ylids in organic chemistry, we only looked at one in our course, i.e. the phosphonium ylid. When I did postdoctoral work at olumbia, I studied the reactions of nitrile ylids, such as the one shown below. 3 ylid F 3 heat F 3 a) Draw the curved arrows that describe the bond making and making in this reaction. 3 F 3 F 3 b) ow many electrons are involved in the transition state of this reaction? c) For an allowed reaction, should this number of electrons be in a ückel or a Möbius transition state? ückel d) Draw the M of the ylid and the LUM of the alkene on TP of the structures that are re-drawn for you below. 6 3 F 3 F 3 e) Does the reaction shown above proceed via a ückel or a Möbius transition state? ückel f) Is the reaction shown above allowed or forbidden? Allowed