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322as09_e1_key - CHEMISTRY 322aL Please Kg 1 EXAM NO.V1...

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Unformatted text preview: CHEMISTRY 322aL Please Kg 1 EXAM NO.V1 Print Last Name FEBRUARY 9, 2009 First Name USC ID name of TA Grader (1) (20) _ (2) (20) _ _ (3) (15) __ _ (4) (20) __ _ (5) (10) _ __ (6) (15) _ _ (100) first letter of last name I will observe all the rules of Academic Integrity while taking this exam. Signature Chemistry 322a -2— Name Exam NO- 1 (1) (20) Answer the following questions. (A) (4) Provide detailed (dash) structural formulas for the two organic molecules below written as condensed formulas. Your structures must show all the atoms and all the bonding and nonbonding electron pairs. Each pair of bonding electrons must be shown in the dash or line formulation, while nonbonding electron pairs must be shown in the dot convention. Place your answers in the boxes. CH3OCH2CHC1CH=C(CH3)2 (B) (3) Draw inside the box a bond-line (abbreviated) structure of the condensed formula written below the box. \ CH3CH2CHC1CH=C(CH3)2 (C) (5) In the structures below, assign any missing formal charges immediately next to the atoms on which they reside. All valence~level electrons, both bonding and nonbonding, are shown. (D) (8) Identify the four functional groups in the structure to the right. H2CH2C0NH2 Place your answers on the lines. I do.) gent 411.9; Chemistry 322a -3— Name Exam No. 1 (2) (20) Answer the questions below. (A) (12) There are 4 constitufional isomers of C3H9N. Draw their condensed structural formulas in the boxes below, carefully noting the prompts below the boxes. 0n the line below each box, provide proper alkyl group names for the structures. constitutional isomers of C3H9N CHACHLCHLN H7. a primary amine a primary amine L Wins— 0 re m «Q CH “sun.“ Hat-l3 Q4353 3 CH 3 a secondary amine a tertiary amine .mflz-Amlf’gum‘k ‘rrl net-k g (B) (8) Indicate whether the structures in each pair below are the same compound, constitutional isomers, or completely different compounds that are not isomers. 9‘ M CICHZCHZQHCI CH3CH2CHCICH2CH2C1 MAL. CHZCH3 E C<’ZH3 <0nsi.',+ufljo~na\ «suckers CH3CH2CH=CH2 0:0 0 WE. H Chemistry 322a -4- Name Exam No. 1 (3) (15) Answer the questions below. (A) (9) Provide the products of the following acid-base reactions in the appropriate boxes below. In the shadow box above the arrow, indicate if the reaction is spontaneous (yes or no) in the direction it is written, left to right. Consult a table of pI<al values in the Appendix, as neeld—ed.f_ A X 0 _. f “A a + CHscH'LOH‘L ‘ \3CH1N Hz. + (i) CH3CH2NH3C1' + CH3CH20H conjugate acid conjugate base _ [3-2:] ., (in CH3CHZCECH + CH3CH201<* H3 “A“ + “awé‘f conjugate acid conjugate base _ =93 9 (iii) CH3CH2 Li+ + CHaCHzCECH —’ CH3C'H3 + CHfo“ conjugate acid conjugate base (B) (6) The pI<a values of methanesulfonic acid and acetic acid are given below. CHyg'OH CH3-C-OH O methanesulfonic acid (pI<a = -6) acetic acid (PK: = 4.75) (1) Circle the stronger base: CH3SO3' or (5) Draw the three important resonance structures for the methanesulfonate anion in Box A below. Show charges and all valence-level electrons. In Box B, draw the structure of the hybrid of the methanesulfonate anion with a quantitative assessment of the charge. Chemistry 3223 , -5- Name Exam No. 1 1 Wk (4) (20) Circle the correct answer for each question or statement below. (A) The molecular formula of the structure below' 1s H (circle answer below) 0 M C10H100-C10H14O C10H16O (B) What are the relationships of the structures in the pairs A and B shown below? ' . :?.H : : :Q.:- . CH3— -1'\'IHCH3 erg-c: NCH3 , ‘CHs' -CH=CH2 CHa—C=CH-CH1 , A B (circle answer below) (i) A constitutional' isomers and B constitutional isomers (C) What are the "hybridizations" of the carbon atoms that use the atomic orbitals shown below. Pure atomic p'mrbitals are shad'ed. Select your answers on a single horizontal line. (circle answer below) 0 j ' A sp B Sp c sp3 as 850 A sp3 B sp C sp A A sp2 8 sp C sp3 (D) In each of the three pairs of structures below (A,B,C), select the compound with the higher boiling point. (circle answer below) 0:0 =O|:>'OH OHEH>O AI 31 C1 AI,BII,CII \—I—v—I’ \._I_T_H_J a; AILBILCI (E) According to the VSEPR model, the geometries around each carbon atom in the three hydrocarbons below are (circle answer below) ethane ethene ethyne 1 trigonal planar, II tetrahedral, III linear I 11 III Itetrahedral, 11 linear, III trigonal planar I trional -lanar, II linear III tetra ~ - . I tetra edral, II trigonal planar, III linear Chemistry 322a -6- Name Exam N0. 1 2' M L (4) Contd. (F) In the structure below, the order of acidity (strongest to weakest) of the bolded H is B ”N A . A (circle answer below) A H . I Q (EEC-H C A>B>C B>A>C (’ A>C>B ) C>A>B (G) Noting that the benzene ring is planar, circle the aromatic compound below that has the largest molecular dipole moment. (“we W ”W. © c(©c :JCEZ (H) The Standard free energy chancgles (AGo) for the dissociation of three acids are given below. (1) H-X + H20 <_' H3O+ + X' AG° = -2.0 kcal/mol (2) H—Y + H20 ‘_' H3O“ + Y‘ AG° = +2.0 kcal/mol (3) H-Z + H20 ._' H3O+ + Z‘ AG° = +1.0 kcal/mol Which statement below is correct? (circle your answer.) -All three com-ounds have K v . - - >1 and HY is the strongest acid of the three. -Only H-Y and H- ave a va ues >1 and H-Y is t e strongest acid. -All three compounds have Ka values <1 and H-X is the strongest acid. (I) Among the small molecules below, which ones have a symmetrical stretch that is active in IR spectroscopy? Hint: First determine the geometries by VSEPR theory. (circle your answer) All of them. Only Bed: and H20. Only BCI3 and H20. Only H20. (J) Correctly assign the three infrared spectra (A, B and C) in the Appendix to structures 1, II and III below. 30;; BeC12 H20 C02 (circle your answer) AI,BII,CIII AII,BI,CIII HC ECHZCHZCHg, A 11, 3 III, c 1 I 11 III Chemistry 322a -7- Name Exam No. 1 (5) (10) Answer the questions below. (A) (5) Below are the melting and boiling points for two pairs of isomeric alkyl chlorides Isomers of C4H9Cl CH3CH§CH2CH2C1 (CH3)3CC1 mp = -123°C mp = -25°C bp = 784°C bp = 52°C Isomers 0fC5H11C1 CH3CH2CH2CH2CH2C1 (CH3)3CC§-12Cl mp=-99°C mp=- 0 C bp = 107.8°C bp = 843°C (i) What patterns are apparent in the physical properties within each isomer pair? kg, mg" s «H. \rug Ltr ‘Fur- +4”, V‘OR (among-1— sky-.‘Hl-r“ \D .3. And 5? ‘s 1H. lush .- 14.. +L¢ N N ,_\.-S§+._A\ s’rrus“f¥ (ii) Explain these differences by referring to specific intermolecular forces. “(1 Thec ‘mfiku- Me‘ 5 e-l- +‘NK N9"- “*6“? 3"”‘+UNS ‘ . 51111 f‘ o. “G ' ‘K+V\g so“ edit-1b kf‘LA— +" s“ :L' $7 ‘ MN:\£ ‘ «*3 +1: isms-XL” P. \l Alf“ 66 O.\“- 'FT‘O bk 5*0 “3"— HT Sud-“K 1711; . t9 , (9 (B) (5) The two aromatic compounds'bzdow, phenol and chlorobenzene, are derivatives of benzene (CGHG) with very different acidities. A mixture of 50 g each of phenol (a white solid) and chlorobenzene (a liquid) needs to be separated. Show how this is accomplished in the scheme below where the mixture is washed with 100 mL of a strongly basic water solution, which is then brought to pH = 7 by treatment with acid. Provide the missing structures inside the boxes. aqueous KOH and ’ s wash with 100 mL of \ separate I ____________________ J \ organic residue phenol pKa = 10 chlorobenzene pKa 3 35 mp = 43°C mixture mp = 45°C in aqueous solution a white precipitate . . acidification . 1n the aqueous solution Chemistry 322a -8- Name Exam No.1 (6) (15) Answer the questions below. (A) (6) Add all missing nonbonding electron pairs in the structures below (except for those around Cl), taking into account the formal charges that are shown. Then use the curved arrow formalism to show movement of electron pairs. On the lines, identify each reactant as an electrophile or nucleophile. 3 (4, t - 91 ‘ . 7C1 . (l) CH3ng-Cl SEAL c1 1% IVA e: t . Cl . . oh“; (.9 Ebc\‘- S \sgfiofi>\\k CH3 H3 flat r5, fig! . CHfiéi-Ia i fix < 'p/tf/S/ (ll) CngNHZ C6}{5_¥tH W’/Ar( [{l ’96—va dam: m_'-_'-\¢-'12l\'t l l\ H “If 40 . I (B) (9) Butanal (I) and 1-buten-1-ol (II) are constitutional isomers with very different acidities: I, pKa = 18 and II, pKa = 14. CH3CH2CH23-l + H20 L" CHaCH2CH£H + H30" 1 butanal pKa = 18 III _ :éH —. f H 0+ CH3CH2CH=CH + H20 .— CHaCH2CH= H + 3 II 1-butene-1-ol pKa = 14 IV Box (1) What is the relationship of structures III and IV? nsencmc t 5+?” CE" W s (2) Draw a more realistic representation of the conjugate base structures (11! and IV) inside the Box above. (6) The incomplete free energy diagram below represents the acid dissociation of I and II. Complete this diagram by supplying the missing structures for states A, B and C on the lines. Be sure to include all the chemical components in each free energy state. D" ® Free Energy Appendix Infrared Spectra for Problem (4) (1). Spectrum A INFRARED SPECTRUM \ ., um 3000 2000 1000 Wevenumber (cm-1) Spectrum 3 1 INFRARED SFICTRUM v 0.8 0.0 0.4 may. tannin-Ice 0.2 3000 2000 1000 Wevenumber (cm- 1) Spectrum C INFRARED SPECTRUM 3000 2000 1000 Wavenumbor (cm-1) ...
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