EM 233, Spring 2016 Midterm #1 MPLETE TIS SETI : Up to TW PITS will be removed for incorrect/missing information! SWER KEY PRITED FIRST ME PRITED LST ME Ian R. Gould Person on your LEFT (or Empty or isle) Person on your RIGT (or Empty or isle) SU or Posting ID lass you are REGISTERED FR (onground or hybrid) The room where most students will take the test for your class, i.e. LS -191 for onground and PS -152 for hybrid) **YU RE T LLWED T TKE SPRE PIES F TIS EXM FRM TE TESTIG RM** PRIT YUR ME E PGE! RED TE DIRETIS REFULLY! USE BLK PGES S SRT PPER work on blank pages will not be graded... WRITE LERLY! MLEULR MDELS RE LLWED D T USE RED IK D'T ET, USE MM SESE! 1 /12 2 /22 3 /24 4 /40 5 /30 6 /16 7 /31 Points Removed (cover errors) /2 Extra redit /5 Total (incl Extra) /1755 Li Be B F e a Mg e l Si P S l r K a Sc Ti V r Mn Fe o i u Zn Ga Ge s Se Br Kr Rb Sr Y Zr b Mo Tc Ru Rh Pd g d In Sn Sb Te I s Ba Lu f Ta W Re s Ir Pt u g Tl Pb Bi Po t Rn R 2 R (δ, ppm) variable and condition dependent, ca. 2-6 δ R 11 220 R 10 200 9 180 8 160 7 140 romatic R 2 R 2 Xe 6 5 120 100 R 2 romatic r mainly 8-6.5 2 4 80 R Interaction Energies, kcal/mol Eclipsing / ~1.0 /Me ~1.4 Me/Me ~2.6 Me/Et ~2.9 Infrared orrelation hart small range usually range of values strong broad peak 1600 1660 3300 2720 2820 3000 2 peaks 3100 1680 R 2200 broad with spikes ~3300 1735 2850 2960 1600 broad ~3300 2200 broad ~3000 1710 R2 3500 3000 2500 2000 1650 (cm -1 ) 1500 MR orrelation harts 2 X R 3 60 2 3 2 R 2 R 2 2 40 Gauche Me/Me ~0.9 Et/Me ~0.95 i-pr/me ~1.1 t-bu/me ~2.7 lkyl X lkyl 3 > 2 > 1 1 20 3 > 2 > 1 0 0
EMISTRY 233, Fall 2016, MIDTERM #1 F ketone - 2 - ME Question 1 (12 pts.) ircle and identify all functional groups in the following structure, ignore alkyl groups. Indicate any amines, amides or alcohols as primary, secondary or tertiary, as appropriate. 2 amine 3 amine halide aromatic 3 amine carboxylic acid iprofloxacin, the only drug specifically approved by the FD for treatment of inhalation anthrax exposure Question 2 (22 pts.) Rank the pairs of electrons indicated,, B, and D in order of increasing energy. Give an explanation for your choice, most of the points are for the explanation, not the order. B (σ-bonding) (non-bonding) B < D < < (non-bonding) P D (π-bonding) lowest energy highest energy non-bonding electrons are higher in energy than bonding electrons, therefore and are highest in energy, phosphorus is larger and less electronegative than oxygen, are thus highest π-bonding electrons are higher in energy than σ-bonding electrons, thus D is next highest and B is lowest Question 3 (24 pts.) For the structures and B below: a) Indicate (in words, do not draw on the structures) the largest BD DIPLE moment(s) in each the largest bond dipole moment in is that associated with the - triple bonds the largest dipole moment in B is that associated with the -F bond b) Between these two largest bond dipole moments (the one from and the one from B), which would be larger? Give a brief explanation. has a larger MLEULR dipole moment because it has two larger bond dipole moments that add in (roughly) the same direction as the two smaller bond dipole moments in B c) Draw the MLEULR DIPLE MMETS TP F TE STRUTURES. Your drawings do not need to illustrate the size of the dipole, only the direction. If there is no molecular dipole, indicate so. BRIEFLY explain which structure would have the larger MLEULR dipole moment. B Br F the - triple bond dipole moment is larger because even though F is more electronegative than, the electrons in the pi-bonds in the triple bond are highly polarizable
EMISTRY 233, Fall 2016, MIDTERM #1-3 - ME Question 4 (40 pts.) For the molecular formula 4 8 a) Give the degrees of unsaturation 1 degree of unsaturation b) Draw SEVE structural isomers that obey the normal rules of valence for each atom. Include all non-bonding electrons. You can draw Lewis structures or line-angle structures (your choice). If you draw line-angle structures, don't forget to include the atoms that are normally included as part of the functional groups. here are a few... c) Draw TW PIRS of stereoisomers that obey the normal rules of valence for each atom. Include all non-bonding electrons. If you draw line-angle structures, don't forget to include the atoms that are normally included as part of the functional groups. D T ILUDE Y STRUTURES in part c) TT WERE DRW S PRT F YUR SWER T PRT b) F TIS QUESTI here are four pairs Extra redit (5 pts.) BRIEFLY give E way in which anti-bonding orbitals are used by organic molecules they accept electrons in chemical reactions D they are where the electrons "go to" upon photochemical excitation
EMISTRY 233, Fall 2016, MIDTERM #1-4 - ME Question 5 (30 pts.) The structure shown is a protonated aldehyde, we will discuss the chemistry of these next semester. ll non-bonding electrons and formal charges are shown. a) What is the hybridization of the oxygen atom? the oxygen is sp2 hybridized b) This next question asks if you know what hybridization really means. Give a list of LL of the atomic orbitals that the oxygen uses in this molecule according ot the hybridization model, D, state exactly how the oxygen uses each one, e.g. the oxygen uses an sp3 orbital to make a π-bond to sulfur, it uses a p orbital to hold a non-bonding pair of electrons, it uses an sp orbital to make a σ-bond to nitrogen, etc. (I know that these examples are nonsense, they are just to illustrate the FRMT you should use to answer the question) 3 the oxygen uses an sp2 hybridized atomic orbital to make a sigma-bond to carbon the oxygen uses an sp2 hybridized atomic orbital to make a sigma-bond to hydrogen the oxygen uses an sp2 hybridized atomic orbital to hold the non-bonding pair of electrons the oxygen uses a p atomic orbital to make a pi-bond to carbon c) Directly TP of the protonated aldehydes that are redrawn for you below, draw a picture of the Ψ R Ψ 2 as requested, for the indicated orbitals, D, in each case write down the atomic orbital or orbitals that you used, as appropriate sp3.. on carbon 3 sp2.. on carbon Ψ for the - σ M.. (ignore any influence of hybridization on electronegativity) sp2.. on carbon 3 Ψ 2 for the - σ* M.. 1s.. on hydrogen Question 6 (16 pts). Give line-angle structures for both stereoisomers of the following condensed formula. Do not forget to add all non-bonding electrons. Label each stereosiomer as either cis- or trans-. 3 2 3 cis- trans-
EMISTRY 233, Fall 2016, MIDTERM #1 Question 7 (31 pts.) - 5 - ME a) Rank the bonds indicated, B and in terms of increasing bond dissociation energy, give a brief explanation. B < B < smallest largest BDE BDE P bond is from to the most electronegative and smallest element, thus has the largest BDE bond is to the largest and least electronegative element, it thus has the smallest BDE b) Draw an energy versus bond separation distance (r Z- ) diagram for homolysis of the three bonds, B and above, all on the same diagram provided below. learly indicate which diagram refers to which bond cleavage and clearly indicate the three bond dissociation energies. Energy BDE BDE B BDE r Z c) Treat homolytic bond dissociation as a simple chemical reaction. For BD below, add the curved arrows to the structure that illustrate bond-breaking and show the products of homolytic bond breaking (i.e. what you get after breaking the bond) on the "product side" of the reaction arrow below.