Exam 1 Key-Fall 2006 - UT EID Page 2 Page 3 I Page 4 Page 5...

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Unformatted text preview: UT EID Page 2 Page 3 I Page 4 Page 5 Page 6 Page 7 Page 8 Total First two letters of LAST NAME Organic Chemistry CH318M Test One Wednesday, September 27, 2006 Dr. J. L. Sessler / 20pts / 40pts / 20pts / 40pts / l8pts / 26pts / 20pts /184 pts T-Score KEY 1. Nomenclature — 5 pts each. No partial credit will be given. (3) Convert the following names into the corresponding molecular structures. After doing so, check to see if the name of each molecule as given here is in accord with the IUPAC system of nomenclature. It not, name the molecule correctly. (i) 5-(1,1-dimethylpropyl)nonane Nmme. '6 correct 05 WY‘W' (ii) 2,3,4-trimethyl-4-butylheptane 32 ‘3)4- 'fimcM\’ 4’ ‘Pr°?‘3\_owc (b) Name the following molecules according to the IUPAC system of nomenclature. (i) 4 - isoproptjl-Z ,5- dime/M hqfiMG 0% C .15 dime/MA ‘(VMM "* “ 3m“ E (ii) 2. Acids and Bases. 10 pts. each. (a) Circle the molecule that is the stranger acid and explain your choice based on the factors discussed in class. Again, you need an explanation of why your choice is the stronger acid, in addition to listing the pKa'values. (i) vs. CH3CH20H eh ~\€‘\"l ,. 1 \r1 eflcer CA W afiwmm W“ OB (iv) vs. /\N/\ H 25+. 9K4 <35 «lot "35 ficMA'as - 3. (20 points) Pyrroloquinoline quinone (structure shown below) is used by a certain alcohol dehydrogenase enzyme to catalyze the oxidation of alcohols (remember the hang- over lecture?). (a) Draw one plausible minor resonance structure to the right of the above compound, showing the flow of electrons using curved arrows. Remember to include lone pairs and formal charges. Does your structure highlight any points. of potential reactivity? If so, circle the site(s) and briefly explain why. Wspcu-w MC \“Wl’u‘ mm .Auwhvg Er «Ma/MU MCAWPWV‘ Mh'pu Wm WM- (b) Circle and clearly label three functional groups in the given structure. Muwpu Agwp’mbu Awswcxs (c) Determine the hybridization of the atoms indicated by the arrows above. Write your answers in the appropriate spaces below. (1) sl’3 C" 59‘ 0"5‘WM) (2) 59‘ 1. (3) 5? 2. (4) SF 4. (40 points) READ ALL INSTRUCTIONS CAREFULLY. Shown below are two of the six Newman projections that correspond to idealized energy conformations of the C1- C2 bond of 2-methylpropanol. Fill in the remaining four and label all eclipsed and gauche interactions usin arrows labeled E or G, respectively. Q 0H / C" OH 1 C1 ‘ 5/ 0H ' H3C CH3 H “*3 ll, 1+ H H H. H H H H w Ho\/I\ ‘ E a a E; “'5 Hsc OH OH . Ha OH CH3 “9 H; HQ; K H H W H H R r H E E E er'er‘e ‘ Ef’ugc b). Next, use these structures to complete the energy diagram shown below. While you should pay attention to the relative levels between the difi‘erent maxima and minima, you do not need to estimate activation energies. (Hint: Identifying the number of high energy interactions such as eclipsed and gauche will help you determine the relative energies of each conformation.) BE NEAT! ch 0H Torsional angle 5. (44 points) The following molecule (1) is called an enolate anion. It is formed from the corresponding aldehyde by treatment with a strong base and is commonly seen in reactions to make carbon-carbon bonds. 0. / It-l a. Draw the dominant resonance forms for enolate anion ;: 26:9 10‘ 2 a p; a) b. Sketch the bonding sigma molecular orbital for enolate anion ;: :6.- @cha c. For 1, how many electrons are present in the following: iii.) n—bonds: 4‘ Canon e‘pax'l’fU'PW in w bananas“ , > we, saw: in «my MOM i.) obonds: ‘0 ii.) lone pairs: 4' d. Draw the three 1: molecular orbitals of enolate anion ; in the order of increasing energy with the lowest energy orbitals at the bottom. Fill in the appropriate orbitals with the available Jt-electrons using lines or arrows, and label as B, NB, or AB. Bonding (B). Non- bonding(NB), or Anti-bonding (AB) u-electrons Lem _ Eew 4L 4% 4;— e. What is the bond order between: i.) Carbon-Carbon Carbon-Oxygen — 6. (20 points) The following molecule is called cyclobutadiene, a conjugated, yet highly unstable system. a Shown below are the four 1: molecular orbitals for cyclobutadiene. Use these to generate an “energy ladder” for the 1r system. Fill in the appropriate number of n- electrons and label the orbitals as B, NB, or AB. ' Evror lay—£3 w 5: —-_ ——> Bonding (B), . Non- bonding(NB), or JI-electrons Anti-bonding (AB) b. Based on your analysis, can you explain the high reactivity or cyclobutadiene? Orbims wl‘hA unpaired dawns are Mme, l wi‘l’ln. {Mt/W. Sew M an: +wo Mao‘s eaten wl‘l’h om. unpaired e," qwls mu.le is W'ko mamve. ...
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