322af06_e2_key

322af06_e2_key - CHEMISTRY 322aL/325aL Please Kc, \[ _ EXAM...

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Unformatted text preview: CHEMISTRY 322aL/325aL Please Kc, \[ _ EXAM NO' 2 Print Last Name OCTOBER 4, 2006 First Name First 4 digits of USC ID __ _ _ _ -X.XXX-XX TA's Name Grader — (1) (15) Lab Day a: Time (2) (20) .— (3) (20) __ (4) (15) __ (5) (10) .— (6) (10) __ (7) (10) _ (100) first letter olst ae I will observe all the rules of Academic Integrity while taking this exam. Chemistry 322a / 325a -2- Name _ Exam No. 2 (1) (15) Use information in the Appendix, as needed, to answer the questions below. (A) (9) Complete the reactions below by supplying the missing structures inside the boxes. In the shadow box above the arrow, indicate by "yes" or "no" whether the reaction proceeds spontaneously as written. \les (i) C6H5803H + NaOH fiat ) + CI- + CH3C02— Na+ (“H5 $03 a. + lo conjugate base conjugate acid CH3NHZ + CHSQOZH conjugate base Conjugate acid CH3CH3 conjugate base conjugate acid (B) (6) In the Lewis acid-Lewis base reactions below, formal charges in the reactants are shown, but nonbonding electron pairs are omitted. Add the missing nonbonding electron pairs and use the curved arrow formalism to show movement of the electron pairs that lead to the products. In the products, add missing formal charges and nonbonding electron pairs. On the lines below the structures, identify the Lewis acid and Lewis base. (i) (CH3)3chH (CH3)3c-o-CH3, Ltuxs QC \ & LQwsg b ng H (11) CH3CH2-CH——CH2 + CHBCH2.%1>{_CH3 + ~_ 1: U W Lung ack& “ Chemistry 322a/ 325a -3- Name _ Exam No. 2 (2) (20) (A) (6) Provide systematic or IUlPAC names for the structures below. Cl H3 C1 QH SIHZCH3 CH3CH2CHCH2CHCH3 CH3 §~ m var», \ -3” he 9+cvn o\ e r 5 +41. A—k¥\he 2+k‘h“ '3 c o\ '~L, «Pd rck\o ro —-\ ’L“dl ML\—\ kirch lynx“ 1 (B) (6) Provide condensed structural formulas inside the boxes for the names below the boxes. All structural details provided by the names must be correctly shown. mg I. B r CH 25H 1C\Q'§_C.H CH 3 cis-4—hexen-1-ol 5-bromo-3,3-dimethyl-1-pentyne (C) (6) There are three constitutional isomers of C5H12. Draw their condensed structural formulas in the boxes below according to the information provided below each box. On the line below each box, provide the IUPAC name of the isomer. '11. e "casomegA “ { fm ( . isomer B isomer C H contains only 1° + contains 1° and 2° H contains 10, 20‘ and 30 H or _ Ill’dt‘ ¢‘\’\n mOPQfl amk Ee'h'i‘ocm L 1-m1-‘c—Kcllbnfi-QMQ (D) (2) Which isomer above (A,B or C) has the highest melting point? Why? N10 pam‘VQ—VW . M031“ Cb Mgd"? S‘l—ru «Avg; Nu chglcj \3¢\~+h<' I'vx SQUL Siva“. , V \ ‘14.! J‘Mf A N g ‘J‘VP C(M pi Chemistry 322a / 325a -4— ame __ Exam No. 2 at (3) (20) Circle the correct answer for each question or statement below. (A) Carbon dioxide has a linear and symmetrical geometry. Which of the following modes are expected to be "ir active", that is, show an absorption in the infrared region, according to the selection rule? F _., _, _, l (circle answer below) O=C: O'Cz Q2019 land 11 only 11 symmetrical asymmetric stretch stretch bend @ 1,11 and III I II III (B) Characteristic absorptions in the infrared are seen for the OH stretch in alkanes, alkenes and alkynes, as shown below. An analysis by Hooke's law suggests this pattern is —¢-H =é—H EC—H 2850-2960 cm" 3010-3100 cm‘1 ~3300 cm-1 1 11 III \ (circle correct statement below) -due to the different geometries around the ue to t e increasmg orce constants (bond stren ths) for the OH bonds: III> — ue 0 en e ectronegativities of the hybrid or itals projected by the carbons in I, II and 111. -due to the different acidities of the H in I, II and III. (C) In each pair of carboxylic acids below, the stronger acid is CH3CH2COOH CH3CHC1COOH CH3CHFCOOH CH3CHC1COOH ‘ 11 , , 11 I I I ; A B » (circle answer) A I, B 1 A I, B 11 A II, B 11 (D) Consider the chemical reaction for the important industrial process to produce methanol below. The standard free energies of formation of the reactants and product are provided. Which statement below is correct about this reaction? + 2 H2(g) —> AG? (kcal/mol) -32.8 0 -38.7 (circle answer below) ~This reaction is spontaneous because of a favorable entro chan e. -Thi ' aneous espite an unfavorable entropy c ange. This reaction is not spontaneous u e 0 an un c ange. -This reaction is not spontaneous but has a favorable entropy change. Chemistry 322a / 3253 -5- Name __ Exam No. 2 (3) (Contd) 1 [\J (E) Which of the following anions can be used as nucleophiles or bases in water as the solvent? (circle answer below) only I only 111 CI HC c: CH3COZ' HzN I II III IV L1H, IV (F) Determine the stronger base in each pair of amines below from the available pKa and Ka values of the conjugate acids of these amines. \ ‘ (circle answer below) / A I, B I A I, B II - - | NH H . . 2 I CHzNHz A II, B 1 II I II pKa 5.25 11.27 Ka 2.34 x 10'5 4.67 x 10'10 gf—J a; A B (G) In the combustion of the following constitutional isomers of C6H12, the least amount of heat will be released in the reaction with (H) The name of the alkane shown in a Newman projection formu a elow is H3 C HK H (circle answer below) 2-methylpentane 2-methylbutane H 2,3-dimethylbutane ( 3-methylpentane ) CHZCH3 (I) Which of the following names are correct names for the structure below? CH3¢HCH2CI 2-methylpropyl chloride sec-butyl chloride (Cirde answer bealOW) I CHq II I and II II and IV ‘ isobutyl chloride 1—methylpropyl choride III IV 111 and IV (1) Three of the bond-line structural formulas below are the same compound. Which structure of the four is a different compound? /_\ (circle correctstructure) W < k/j/ M, Chemistry 322a/ 325a -6- Name Exam No. (4) (15) Compound A, an unsaturated hydrocarbon, reacts with excessH2 in the presence of a catalyst to produce an alkane, C4I-I10, compound B. This alkane has a highly symmetrical structure where all three C-C bonds are equivalent. Compound C, an unsaturated hydrocarbon, reacts with excess H2 in the presence of a catalyst to produce an alkane, C4H10, that is a constitutional isomer of B. Infrared spectra of the unsaturated hydrocarbons are provided below but need to be assigned to A and C. Use all the information provided to draw the correct structural formulas for A, B, C and D in the boxes below. Also, assign the ir spectra to A and C on the lines above the spectra. excess H2 ‘ catalyst A excess H2 CH CH CE C \4 5 a catalyst C D C4H10(/‘ '2 \ IR Spectrum I is compound A IR Spectrum II is compound _£_ INFRARED SPECTRUM INFRARED SPECTRUM "WWW “ 1 1 0.9 0,8 0.8 0.6 0.7 0.4 Relative Transmittance TRANSMITTANCE 0.6 0.2 0.5 3000 2000 1000 Wavenumber (cm~1) Wavenumber (cm-1) In the box below, comment on the characteristic features (ir bands) in each spectrum that allowed an assignment to either A or C. \R I: skews Q—H si-n‘t-cl.‘ gkarktgrw-HK or a“ Q\K0W\QQ~3\G¢_9CM‘\ . \ (I Skates Q—H- S-i-ra'H (~33oo CM“\ clock cac the-11k (~1Leo QM“) L‘fflxr‘ath t-CS'I‘TL o? ‘ firmtxe“ ' Chemistry 322a /325a -7- Name Exam No. (5) (10) Cyclopropane and propene are constitutional isomers of C3H6. Their heats of combustion measured under identical conditions are given in the table below. cyclogpane propene /\ AH" Comb - -491.8 in kcal /mol 4993 (A) (1) Complete a balanced equation for the combustion of C3H6 below. C3H6 + 3102 3C0; FjHr-Zé or 1C3Hb + o \——9 (ocoz + Cot—i113 _ (B) (6) Complete an energy 5 atefiiagram below that compares the combust10n react10ns of cyclopropane and propene. Note that the Y—axis is broken to more easily show the energy difference. Your diagram must show the starting and the product states (all properly labeled) and these states must be pr0perly positioned relative to each other according to the energy scale. Use arrows to show the AH changes between reactant and product states. ‘ cyclopropane propene L mfg. --‘-l‘l\. :- relative enthalpy (C) (1) According to the diagram, which constitutional isomer is more stable? pmtnyw— (D) (2) Briefly cite one factor to explain this stability difference. y—a—fi (\[c\o?1'o‘>a.-1\gls l'\\3k\7/ S‘l‘mcwi‘ Tho-c mm 1\kW\¢‘VCl’ZS 0C ~l-or—stowl Shut/vs caulk Musk SHIN“, f sh \ \D( C“ kz‘rfiom\‘_l OML KL fwe “Ltds \k‘d Chemistry 322a / 325a -8- Name Exam No. (6) (10) Answer the questions below. (A) (3) Draw in the box below, a Newman projection formula for the conformation in ethane that has no torsional strain. What is the name of this conformation? 9ng 3E h. A. f (B) (7) Draw in the box below, a Newman projection formula of the lowest energy conformation during rotation around the C2 -C3 bond (arrow) in 2-methylbutane. ( i VCJM 6M CH3qH—‘CH2CH3 or Mirror an H CH3 \MujL ( OK‘ Is the conformation shown in the box free of strain energy? Explain. No, Thu—L \3 W +l~d~ mm 4x . \m+r-oc.lo ( 1 5+1 vt¢ $+P¢LF 3 f Chemistry 322a / 325a -9- Name Exam No. (7) (10) The most stable conformation during rotation around the indicated bond in butane is the anti while the gauche is the most stable conformation during rotation around the indicated bond in 1,2-ethanediol. (A) (6) Draw Newman projection formulas of these conformations in the boxes below. CH3 Pm 5" 0" u 0H or H H 2%“; “GAO. 4&1 QR awe-An «A? anti conformation 3 gauche conformation 3 CH3CH2_CH2CH3 HOCHZiCHZOI-I (B) (4) What stabilizing factor in the gauche conformation could reasonably account for this being the most stable conformation in 1,2-ethanediol? \‘vd-t‘anokzc ukcacn k1 droykm ‘0beme ShXO..\Jj_(_3 FLQ 3Q” ka CDM‘BerHD/IA Q’l/xd Lo ,— q“\( 5+T‘C try\ («n Pg 7 QSSoc curb: A Q \4—\!\ 'TkQ & ecu uh; Cow‘Aer-Ho'wx. H" ‘3 O’KdJrNS S'HJfi “213 \~l\ 1/7! m (FL \gCul/N‘O\ ...
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322af06_e2_key - CHEMISTRY 322aL/325aL Please Kc, \[ _ EXAM...

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