EM 233, Fall 2017 Midterm #2 Ian R. Gould MPLETE TIS SETIN : Up to TW PINTS will be removed for incorrect/missing information! PRINTED FIRST PRINTED LAST 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) **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 Br 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 Interaction Energies, kcal/mol Eclipsing / ~1.0 / ~1.4 Et/ ~1.8 / ~2.6 Et/ ~2.8 Et/Et ~3.1 N Infrared orrelation hart small range usually range of values strong N broad peak 1600 1660 N 3300 N 2720 2820 N 3000 2 peaks 3100 1680 R 2200 broad with spikes ~3300 1735 2850 2960 1600 broad ~3300 2200 broad ~3000 1710 NR2 3500 3000 2500 2000 1650 (cm -1 ) 1500 NMR orrelation harts 2 Aromatic Ar mainly 8-6.5 2 4 80 R 2 X R 3 60 2 3 2 NR 2 NR 2 Gauche / ~0.9 Et/ ~0.95 i-pr/ ~1.1 t-bu/ ~2.7 2 40 Alkyl X Alkyl 3 > 2 > 1 1 20 3 > 2 > 1 0 0
EM 233, 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 /12 2 /25 3 /24 4 /25 5 /25 6 /26 7 /38 Points Removed for cover errors /2 Extra redit /5 Total (incl Extra) /175+5 **YU ARE NT ALLWED T TAKE SPARE PIES F TIS EXAM FRM TE TESTING RM**
EMISTRY 233, Fall 2017, MIDTERM 2-2 - Question 1 (12 pts) Give the IUPA name for the following structure Question 2 (25 pts) For the following structure a) Draw both chair conformations b) Determine the energy difference between the two chair conformations using the tables on the front page of this test, be sure to clearly show each energy contribution that you take into account when answering this question c) Indicate the lower energy chair EXTRA REDIT (5 pts) Which of these techniques forms the basis for the device that is used to detect traces explosives and/or narcotics at airport security checkpoints? mass infrared proton nmr carbon nmr spectrometry spectroscopy spectroscopy spectroscopy
EMISTRY 233, FALL 2017 MIDTERM #2-3 - Question 3 (24 pts.) In this question, non-bonding electrons are omitted for clarity. a) onvert the following Newman projection into a 3-D/sawhorse structure. You MUST draw your sawhorse as if you are looking at the structure from the direction indicated by the arrow. Br Pr Et b) Draw BT chair conformations for the following cyclohexane. You MUST draw your chairs as if you are looking at the structure from the direction indicated by the arrow. You do NT NEED to indicate which chair would be lower in energy. Br l Question 4 (25 pts.) For 3-methylhexane a) Draw a line-angle structure b) Draw Newman projections (only, no 3-D/sawhorse structures) corresponding to the lowest AND highest energy conformations for rotation around the 3-4 bond, draw the Newmans looking FRM TE 4 ARBN T TE 3 ARBN (i.e. with the 4 carbon in "front") c) Determine the energy difference between these conformations (use the data in the tables on the front page of this test), be sure to clearly show each energy contribution that you take into account when answering this question
EMISTRY 233, Fall 2017, MIDTERM 2-4 - Question 5 (25 pts.) Assign the BT IR spectra to NE of the TREE provided structures A -. NE of the structures does not have a provided spectrum. n each spectrum, identify the peaks that are associated with a specific functional group or type of - bond by drawing the functional group or bond and drawing an arrow from the specific bond in the functional group that vibrates to the absorption peak, as appropriate, include all - bond types. A B the spectrum below corresponds to structure 3502 3401 3101 2301 1943 1883 945 3085 2715 1051 2802 1413 1601 1456 1406 1191 1683 1291 the spectrum below corresponds to structure 1851 761 1051 3005 2725 2899 1443 1321 1207 998 904 2989 1702
EMISTRY 233, Fall 2017, MIDTERM 2-5 - Question 6 (26 pts.) This anion is inadequately represented by the provided Lewis structure. a) Draw additional resonance contributors that show how the negative charge is delocalized, include curved arrow-pushing and resonance arrows/brackets. b) Indicate the major contributor or contributors and give a BRIEF justification for your choice that includes the phrase "energy of the electrons". c) Draw an "actual" or resonance hybrid anion and on this structure AND, clearly indicate the atom or atoms where the greatest partial negative charge would be found (you should use the δ notation to indicate partial charges). d) The hybridization of the NITRGEN ATM is N make SURE you answer ALL PARTS of this question!
- 6 - EMISTRY 233, Fall 2017 MIDTERM #2 Question 7 (38 pts.) The purpose of this question is to decided which of the bonds -a and -b, has the higher and which the lower bond dissociation energy. a) Give the products of homolytic cleavage of both of the - bonds as indicated below, and include ALL REASNABLE resonance contributors for the radical products. It is not necessary to show the curved arrow pushing for either the bond cleavages or to show how the resonance contributors are interrelated, but if it helps you, you can include these. But you MUST include all resonance arrows and resonance brackets. a homolysis of bond -a b a homolysis of bond -b b b) Indicate which of -a and -b has the larger and which the smaller bond dissociation energy and give a BRIEF explanation for your choice. Your explanation must include the term "energy of the electrons", or something close or equivalent. c) Axes for an energy diagram are provided below. 1) n these axes, draw the energy diagram for homolytic bond dissocation for BT of the bonds -a and -b N TE SAME DIAGRAM. Because both are in the same molecule, your diagrams should both start at the same energy in the bonds. 2) Indicate the bond dissociation energies for BT BNDS on the diagram. 3) LABEL BT AXES.