Chem 51A S02 QUIZ - S King Name CHEMISTRY 51A Quiz II...

Unformatted text preview: S. King Name CHEMISTRY 51A Quiz II February 1, 2002 ID number , , -_Hl¢ |—'-_‘ ‘ '. '— (please PRINT, iast name first) Seat #___ Read these instructions carefully: mm»—- 9‘.“- . DO NOT OPEN THIS EXAM UNTIL TOLD TO START. . THIS IS A CLOSED BOOK EXAM. Please put away all notes, books, other papers away NOW. . LOOKING AT PAPERS OF OTHER STUDENTS CON STITUTES AN ACT OF CHEATIN G AND WILL RESULT IN IMMEDIATE EXPULSION FROM THE LECTURE HALL AND AN (F) GRADE FOR THE COURSE. You must'stop work when asked to do so by the proctors. You shOuId attempt all of the questions, so do not spend too long On any one question. This Box is to be used if you request regrading to correct a grading error. STUDENT STATEMENT: I request that my test be reviewed to correct a grading error. I attach a note to indicate what I think the error was. I Sign here to indicate that I have NOT ALTERED OR ADDED TO THIS TEST IN ANY WAY. I understand that alteration of this exam and submitting it for regrading constitutes an act of cheating and that the instructor assigns an (F) grade for the course to any student found to be cheating in this course and places a letter in the student‘s permanent file. Signed 51A Practice Problems #2 Winter, 2002 1. For each of the following compounds, assign the hybridization states (sp, spz, sps) for the indicated atom. (EH3 CH3\ H\ «\H k K CH3 K H3C/ R CH3 2. Identify the shape, hybridization type, and bond angles of each of the following compounds: 7:1.CH3+ b. CH 3* c. HCI—ZCH d. CH3OCH3 3. Indicate by mow the longest C-C bond, the shortest C-C bond, and the shortest C—H bond. H l1 — —"C=C—CEC—H I H—c ll HH 2—0—11 4. Circle and name the functional groups in each of the following molecules: CH3 (“3 a. CH3C==CHCCH3 b. CH3CH2$HCH=CH2 c. CH3EOCH2CH20CH3 Br 0 5. Which of the following molecules is expected to have the smallest energy gap (AE) between a filled and unfilled electronic energy level? H\ H a. Ec=c< b. CH3CH3 c. CH3§H d. /c=o e. CH3}in H H 6. Calculate AHr for the following reactions, using the average bond energies given in Table 2.4. CH3 CH3 H3CHC-—-OH + H—Cl —*> H3CHCWCI + H—OH CH3 CH3 7. Draw a 3-dimensional structural formula for CH3CN, using lines, dashed lines, and wedges to indicate 0 bonds, and showing the actual orbitals involved in IE bonds. Nonbonding electrons may be shown in lobes ( a ) or at the end of wedges ( ’5) or dashed lines ( ._‘“\°-) to indicate direction. Also indicate which orbitals overlap to make each bond. 51A Practice Problems #5 Winter, 2002 1. Draw an energy diagram for the addition of H1 to l-butene. Let one curve on your diagram show the formation of 1-iodobutane and another curve on the same diagram show the formation of 2—iodobutane. Label the positions for all reactants, intermediates, and products. Which curve has the higher-energy carbocation intermediate? Which curve has the higher first transition state? Make sketches of the transition-state structures involved in the reaction. CH3CH2CH=CH2 + HI —-—> CH3CH2CHCH3 + CH3CH2CH2CH2 i l 1 1 l-Butene 2-Iodobutane l-Iodobutane 2. The mechanism of the electrophilic addition of H30+ to an alkene is analagous to the mechanism of the electrophilic addition of HBr to an alkene, except for one additional deprotonation step. Write the mechanism of the following reaction, using curvy arrows to show the movement of electrons. FK/H 65H HH c~—*(‘\ + H— H/ H H @0\ 3. Supply a reagent that will give the chemical change shown in each of the equations below. Identify the reagents as electmphiles or nucleophiles. c, a. CH3CH==CH2 'r CH3|CHCH3 N3 ? b. CH3CH=CH2 :- CH3|CHCH3 OH ? ? c. CH3OH > CH3O Na 1» CH3CH20CH3 4. There are three possible cationic intermediates possible when the following alkene reacts with HCl. Draw the three possible intermediates, and rank them according to their anticipated rate of formation (fastest ~> slowest). H3co\ H / C: C He: 9 / \ H CH3 5. Draw the Newman projection formula for the following compound, viewing from the direction indicated. Make sure that you have not changed configuration in going from the 3-D formula to the Newman projection. (CH3)2CH [email protected] => \cuc'l‘CHs H“? \ CH3 CH3 6. Draw the lowest energy and highest energy conformation of the following compound, both as Newman projections and 3-D formulas. CH3 7. How many different groups of equivalent H’s would you expect for the following compound? How many different types of C’s? H C H H H_};_l;__£...£..H l1 1'; £1 51A Practice Problems #6 Winter, 2002 1. Write the correct IUPAC name for the following compounds: ('31 l|3r ICHZOH a. CH3-H- (IJ—ICH- CF3 b. Qf—CHz-CH—CH3 C1 OH Br OH CH C. W (1. 2. Determine if the following pairs of Newman projections represent identical or different compounds. \ CH3 H CH3 H3C CH3 f I_ a. and g \ H CH3 H CHZCH3 \ CHZCH3 H3 H b. and ' H3C H \ H H . H CH3 CH3 CH(CH3)2 CH3 CH3 (2. and H3C H H H CH(CH3)2 CH3 3. Draw structural formulas for the two chair conformations of iodocyclohexane. Which chair conformation has the lowest energy and why? 4. Which of the following compounds are chiral? Star any sterocenters. H fll 1; ’CH3 CH3 CH3 H‘VR. / C\ Br CH3O H OH I cwfk 51A Practice Problems #7 Winter, 2002 1. In one stereoisomer of 2-isopropy-l-methylcyclohexane, the isopropyl group is trans to the methyl group. a) Draw the two chair conformations for the compound, and indicate which conformer would be more stable. Clearly draw the substituents in axial and equatorial positions. b) Does trans—4-isopropyl-l-methylcyelohexane have any stereocenters? o) Is trans-4-isopropyl- l-methylcyciohexane a meso compound? 2. Write a 3-D formulas for (R)-2-iodo-3-methylbutane, showing the proper stereochemistry: 3. For each of the following structures: a. Star any stereocenter or chiral carbon atoms. b. Label each chiral carbon as (R) or (S). a. If b. if ,CH3 c. CH3 CImuv C\ C\ 0,, CH3()/ CH3 H Hgch Br "0H 4. Draw all possible stereoisomers of 3-bromo-2-butanol and assign (R,S) configuration at each stereocenter. Identify the enantiomeric pairs. 5. Draw the most stable conformation of: a) cis-I -ten—buryi-2-methyleyelohexane b) ciS-l-tert-butyl-3-methylcyclohexane e) trans— l -tert-butyl—4—methylcyclohexane 6. For each of the following pairs, give the relationship between the two compounds. Making models will be helpful. a. (2R, 3S)-2,3-dibrom0hexane and (ZS, 3R)—2,3-dibromohexane 131-E CH3 H CH3 H "- B b Ck”; H and I.” ctr; B I, CH3 Br CH3 H Bra CH3 H, /CH3 H '.' B <- c 7: CWOH and ‘fic (sci/OH CH3 H CH3 H C1 and Cl ” Br f. Brm/H and Im/H H Br H 1'31, Br H H Br Br H g. and H3 I H BT CH3 ...
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