EM 24, Spring 2017 Midterm #2 Ian R. Gould MPLETE TIS SETIN : Up to TW PINTS will be removed for incorrect/missing information! PRINTED FIRST 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) PRINTED LAST **YU ARE NT ALLWED T TAKE SPARE PIES F TIS EXAM FRM TE TESTING RM** PRINT YUR N EA PAGE! READ TE DIRETINS AREFULLY! USE BLANK PAGES AS SRAT PAPER work on blank pages will not be graded... WRITE LEARLY! MLEULAR MDELS ARE ALLWED D NT USE RED INK DN'T EAT, USE MMN SENSE! Li Be B N F Ne Na Mg e 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 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 N 2 R (δ, ppm) variable and condition dependent, ca. 2-6 δ R 11 220 R 10 200 9 180 8 160 7 140 Aromatic R 2 R 2 Xe 6 5 120 100 R N 2 Aromatic Ar mainly 8-6.5 2 4 80 R Interaction Energies, kcal/mol Eclipsing / ~1.0 / ~1.4 / ~2.6 Et/Et ~.1 N Infrared orrelation hart small range usually range of values strong N broad peak 1600 1660 N 00 N 2720 2820 N 000 2 peaks 100 1680 R 2200 broad with spikes ~00 175 2850 2960 1600 broad ~00 2200 broad ~000 1710 NR2 500 000 2500 2000 1650 (cm -1 ) 1500 NMR orrelation harts 2 X R 60 2 2 NR 2 NR 2 2 40 Gauche / ~0.9 Et/ ~0.95 i-pr/ ~1.1 t-bu/ ~2.7 Alkyl X Alkyl > 2 > 1 1 20 > 2 > 1 0 0
EM 24, Fall 2017 Midterm #2 Ian R. Gould YU MUST MPLETE TIS PAGE WIT YUR (EVEN TUG YU ALREADY DID TIS N TE VER PAGE) AND ALS GIVE YUR ASU R PSTING ID NUMBER WE NEED TIS NUMBER BEAUSE YU WULDN'T BELIEVE TE NUMBER F STUDENTS WSE S WE AN'T READ! PRINTED FIRST PRINTED LAST ASU ID or Posting ID Points by question 1 /11 2 /24 /24 4 /22 5 /8 6 /20 7 /14 8 /22 Points Removed for cover errors /2 Extra redit /5 Total (incl Extra) /1755 **YU ARE NT ALLWED T TAKE SPARE PIES F TIS EXAM FRM TE TESTING RM**
EMISTRY 24, Spring 2017 MIDTERM #2-2 - Question 1 (11 pts.) Give the IUPA name for the following compound. Be sure to use cis/trans, E/Z or R/S where appropriate. 1 2 4 5 (4R)-ethoxy-2-methylpent-2-ene Question 2 (24 pts) Give a curved-arrow pushing mechanism for the following reaction. Where appropriate, indicate the Lewis acid and base (LA, BA) and the onsted acid and base (BA, BB). LB conc. 2 LB LA LA 2 Extra redit (5 pts) The colors of organic molecules are determined to a large extent by the energies of electrons in? sigma-bonding orbitals anti-bonding orbitals atomic orbitals
EMISTRY 24, Spring 2017 MIDTERM #2 - - Question (24 pts) Give the major organic products of the following reactions, indicate the stereochemistry using wedged/dashed bonds as appropriate. State whether the products are achiral, a racemic mixture, meso or a single enantiomer (no explanation needed) a) Et/l (cat.) Et single enantiomer b) 1. MPBA 2. Na Et/Et Et (±) racemic mixture c) N N N (±) racemic mixture N Question 4 (22 pts) a) Give the curved arrow-pushing and the allowed product for the following electrocyclic ring closure reaction, indicate whether the product would be achiral, a meso compound or a racemic mixture (±) racemic mixture 4 b) ow many electrons are involved in the reaction? c) Does the allowed reaction proceed via a uckel or a Mobius transition state? Mobius d) Does the allowed reaction proceed via a conrotatory or disrotatory ring opening? conrotatory e) If you said that the reaction proceeds via a uckel transition state then VERY BRIEFLY explain why it doesn't go via a Mobius transition state, or if you said Mobius then why not uckel? Your explanation should include the terms "aromatic" or "anti-aromatic" as appripriate this is a 4 electron reaction, 4 electrons in a uckel transition state would be anti-aromatic
EMISTRY 24, Spring 2017 MIDTERM #2-4 - Question 5 (8 pts.) For the following reaction, give a full curved-arrow pushing mechanism for formation of BT products and indicate the Lewis acid and base at each step (LA or LB) and whether they are also onsted acids and bases (BA or BB), include all important resonance contributors for any intermediates and give the number of STEPS for each reaction. The curved arrow-pushing for the first step is provided for you. (solvent) l (cat.) A B LA BA b) Draw a reaction energy diagram for formation of BT of these products on the same diagram, you do not have to include any structures on your diagrams, but LEARLY INDIATE WI DIAGRAM REFERS T WI REATIN, and INDIATE the positions of all TRANSITIN states energy both number of steps in the mechanism for product A number of steps in the mechanism for product B thermodynamic kinetic kinetic = A thermodynamic = B reaction coordinate c) iefly explain which product is more likely to be formed under conditions of kinetic and thermodynamic control, and why kinetic = A, thermodynamic = B, B is more likely to be formed at IG temperature since higher temperature enables REVERSIBLE reactions and allows the reaction to explore the entire reaction energy surface and find the lowest energy product
EMISTRY 24, Spring 2017 MIDTERM #2-5 - Question 6 (20 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. (±) NBS, hν Ph 1. PhMg 2. Na MPBA (±) Question 7 (14 pts.) a) For the provided structure, show you you would make the bond A in a Grignard reaction, give the Grignard reagent, what it would react with and any other reagents/conditions Mg 1. 2. b) BRIEFLY explain why you can't make bond B in a Grignard reaction bond B bond A (ignore stereochemistry) that would require a Grignard to react with the most substituted side of an epoxide
EMISTRY 24, Spring 2017 MIDTERM #2-6 - Question 8 (22 pts.) a) For the cycloaddition reaction shown below... () A B a) Give the curved arrow-pushing and draw the allowed product for the reaction, be sure to include stereochemistry and indicate any racemic mixtures b) on TP of reactant A draw a pictorial representation of the M (draw it on the structure below rather than the one in the equation so that the curved arrow-pushing isn't obscured) c) on TP of reactant B draw a pictorial representation of the LUM (draw it on the structure below rather than the one in the equation so that the curved arrow-pushing isn't obscured) d) Is the allowed reaction suprafacial or antarafacial for reactant A? suprafacial e) Is the allowed reaction suprafacial or antarafacial for reactant B? suprafacial