Exam2Fall2004 - cmzmsmy 322aL/325aL I EXAM NO 2 7 Print...

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Unformatted text preview: cmzmsmy 322aL/325aL I ' EXAM NO. 2 7 Print Last Name OCTOBER 6, 2004 First Name USC ID No. TA‘s Name Grader (1) (10) ~ (2) (10) __ (3) (15) ~ - lay & Time ‘_ (4) (10) __ __ (5) (20) __ (6) (15) ~ __ (7) (15) ~ (8) (05) .— (100) terlte I will observe all the rules of Academic Integrity while taking this exam. “‘— Chemistry 322a/ 325a -2- Name Ekam No. 2 (1) (10) (A) (6) For the acid-base reactions below, provide the missing structures inside the boxes ' according to the descn'ptive terms below the boxes. (See information 1n the Appendix as needed.) Where metal' ions £2 shown, be gun: to include them in your Mucus Condensed formulas are a ytable for e 7products. 214790“ cf? C ’7 'L 65 (i) CH CHEH + CH3CH N112: 3 2 CH3CHL kit-t3 «\le OH __.p (m) + HCECCHZCOH .— conjugate acid (B) (4) In the reacu'on below, add all missing nonbonding pairs, and use the curved arrow formalism to show the movement of an electron pair as the reactants transfonn to products. Add all missing formal charges to the structures and identify the Lewis acid and Lewis base on the lines below the reactants. Chemistry 322a/ 325a —3— Name Exam No. 2 (2) (10) When ammonia gas (NH3) is cooled to -33°C, it liquefies. Liquid ammonia is a polar solvent (much like water) that is used for certain organic reactions at low ' temperature. Describe the chemical behavior of materials in liquid ammonia by writing the chemical equations inside the boxes. Refer to the information in the Appendix, as needed. If there is no reaction, write "no reaction" inside the box. A reaction that produces only an insignificant amount of product is considered "no reaction." If there is a significant reaction, write a complete chemical equation inside the box that describes the chemical change. Use condensed structural formulas in your chemical equations. Be careful that your equation is complete and shows all the reactants and products. (A)(2) One equivalent of ethyne is added to liquid ammonia. C . DOT heC) HCE CH ’h o rec-cc“ 0 M / ethyne 6 1 d C , ,3”— “1” ”V (B) (3) One equivalent of sodium amide (NaNHZ) is added to the soluu'on formed from adding ethyne to liquid ammonia. CH3CHZOH ethyl alcohol (D) (3) To the solution that results from step (B) is added one equivalent of ammonium chloride, NH4C1. Chemistry 322a/ 325a -4- Name Exam No. 2 (3) (15) (A) (12) Provide systematic or IUPAC names for the structures, or provide structures inside the boxes for the names, as requested below. CH 2 3 .— CH3CHC1C'ZHCH2 CH3 CH3C =CCH2CH(CH3)2 CH3 3/‘LJ 7-”Cvao -—-3 C— . 1.9x ‘5\-&\\& S.- ‘ " hQ W/ a CH3 t'rans-2~methyl-3-penten-1-ol 1,3-dimethylcyclohexene (B) (3) I am a hydrocarbon, C5H12. When I react to produce monochloro substitution products of the formula C5H11Cl, four different constitutional isomers are produced. Draw my condensed structural formula in the box below and provide my IUPAC name on the line below the box. Note: Do not place the structures of C 5H11Cl in the box. Chemistry 322a/ 325a -5- Name Exam No. 2 (4) (10) Heat of combustion data for cyclohexane, cyclopentane and methylcyclopentane are given below. 3 heat of combustion cyclohexane cyclopentane . methylcyclopentane 0 (in kcal/mol) -936.6 -786.7 -941.3 omb Use data in the above table to estimate the difference in strain energy between a cyclohexane and cyclopentane ring. You do not need to use all the data in the table, but clearly explain below how you are using the data and why you must use it in that way. A numerical answer without an explanafion will not receive full credit. If appropriate, draw an energy diagram. Place your esfimate of the strain energy difference in the box. .. ML+¥O£ A “(do lam—KI. Mi Mch'kylfitlo Pam'FQa-y‘g (Mag cams-l-fi‘u‘fim lSDNx-‘5 a“; \(u.\eL +‘\L Sank Qr-Oclucb 3+d~e “NCO..ka ska“. (cu +q0L~w6C°L*-€H._o ' . ‘ WSQH, HMS:- kLers-s 0“- Cnmb- (jt-‘ioz +970L {1qu ca Atrng’t “£3.5qu 04- {4‘9}? T‘L\c.;l-'tue sthKt-H.§ _ Cycloltqun \S hot-L 8+!»le +'ha.~\ Mukkf ltslclo PQ“+Cg1\k B W"! Kc~kl-o\ A “Oh: ekrs «Scrtlenv:L 4° 34m)“ cm". h: 7’ l'K (L CYC‘D PfifKAfi‘A—xi he“ . “We ‘3 “— hdrs 0‘? mamas“; «momma WA CY¢\O?‘~’V\*‘¢L~\L Cmfiwl- lot. <\\nc+—\7 COKPQMA. 30+. +ka. {Nu-t: og- \‘c‘c— 91‘,— Cx-ll grog)? (CNN ‘1 c-a‘k?‘rd. Cyckokuaamn. ”Was/g 2-. mm Cyclope-n‘bcwz‘. ‘135-7/8 : \31-3 T\~¢_ firqb-‘nc awe—,3? 5% lug”? N4;- -qx..c, NA;— 4?“ v 6 Co ._+ C Hap ulcww\ H M53 *‘v \ P‘N— CHL V7\ C7 Ck Tag“ 011 5 Which cycloalkane has more oescfi LeA fins Sin-OJ «vx wan “37’ ‘ strain energy and what is our estimate? By flu rm— Wed. , +Lk +°Jrz~\ y woumfi- OC— 3*T‘CVW‘IM (\{do-Qs- M‘V‘umg— Cre.\¢:\-\V._ +3 cycloLgycak¢\ \S erz—xcsfl ‘(x :— : G, kccA/rxo (, Chemistry 322a/325a -6- e ExamNo.2 ( ) a _ (5) (20) Circle the correct answer for each question or statement below. (A) Among the triatomic molecules below, which ones have a symmetrical stretch that is "ir active"? Hint: First use VSEPR theory to determine the geometries. (circle answer below) all of them BCFZ C02 H20 502 only H20 0 l i ' ; d H O on] H o and so2 (B) In an infrared spectrum, a band at 3000 cm'1 shows a T = 0.10. The intensity of this band on the absorbance scale is A = (circle answer) 0.1 10 100 (C) In the reacfion below, + CH3c=CH2 + HI —> CH3C'ZCH3 + 1' CH3 C3'13 isobutene (circle answer below) (D) According to information in the Appendix, the strongest oxygen base (as defined by the magnitude of Kb below) among dimethyl ether, methyl alcohol and water is CH3COOH CICHZCOOH CIZCHCOOH Cl3CCOOH pKa- 4.75 2.86 1.29 0.65 an inductive effect a leveling effect a steric effect a resonance effect (circle answer) Chemistry 322a/ 325a -7- Name Exam No. 2 A] "(5) Cami—U (F) The AC0 values for the ionization' in water of three carboxylic acids are given below. V According to these values, the order of acid strength (strongest to weakest) is + - o for HA + H20 <— H3O + A at25 C (circle answer below) CGHSCOOH CH3CH2COOH HCOOH benzoic > propanoic >formic benzoic acid propanoic acid formic acid pro-anoi > ' ic > formi ormic > benzoic > propan01c propan01c > I enzorc > ormic AG" (kcal/mol) +5.7 +6.6 +5.1 (G) Consider the two acid-base reacfions below. According to information in the Appendix, the directions of the spontaneous reactions are (i) CH3OH2+ + I‘_' ‘— CH3OH + HI (circle answer below) (i) right (ii) right (i) right (ii) legft +941 (i - ri ht (ii) CH3CCH3 + H30+ ‘1‘ CH3CCH3 + H20 m (H) Among the structural representations of C7H16 below, the two that are, in fact, the same constitutional isomer are H3 CH3qHCH2qHCH3 . (Circle answer below) CH3 H HCHZCH3 CH3 II CH3 (1 and E In and IV 1-13 I (EH H3 3 CH3CH5CH3 CH3CIZHCHCH3 II and III I and III H2013 CHZCH3 III IV (I) The name of the chloroalkane shown in a Newman projection formula below is (circle answer below) CH 1 1-chlorobutane CH3 H tert-butyl chloride isobutyl chloride (J) The barriers to rotation (in kcal/ mol) around the carbon-carbon bonds in ethane and ethene (see below) are approximately R1 :H H\ (circle answer below) q/ «H H7CI H'C HC‘H I ~50,II ~1oo C 1-3, II ~60 ) I ~ 10, II ~ 10 I ~50, II ~10 Chemistry 322a / 325a -8- - Name Exam No. 2 - (6) (15) (A) (12) The infrared spectra of three constitutional isomers of C5H8 (A,B and C) are shown below. Assign structures to A, B and C from among the 5 chOices below based on the infrared spectra and information provided next to the spectra. Identify your choice in the answer box by the Roman numeral below the structure of your €111;be CpmpoundA_ SPLC ~H {FVC m H V V Reaction of A with H2 yields a hydrocarbon, C5Hm I that contains only secondary H. 2000. 1000. 3000 structure of A CmeOundb Sf Cfl'fl" f 1L" 7!: LL 0.99 0.93 0,97 0.96 Reaction of B with H2 yields a hydrocarbon, C5I-112 fl: that contains primary and secondary H. 570“ C __/_/ [fresbécfireofB 0.92 0.38 2000. 1000. p.996 Em Reaction of Cwith H2 yields page a hydrocarbon! CSI-IIZ ' that contains primary and fl secondary H. 3000. 2000. 1000. structure of C 0.904 choices of constitutional'isomers of C5H3 CH o A—a ra— M n I II IV V III (B) (3) When the above alkenes and alkynes undergo hydrogen 'on, is the standard enthalpy change (AHO) positive, negative or zero? $4, I; ( “Q (fl Is the hydrogenation reaction exothermic or endothermic. m IM I 'C 1 . 7‘ «7% 6% A H‘w. Chemistry 322a/ 325a -9- Name Exam No. 2 (7) (15) Answer the following questions about rotations around the indicated carbon- carbon bonds in the alkanes below. (A) (3) What is the relative order of the rotational barriers (largest to smallest) around the indicated C~C bonds in the alkanes I,II,III and IV? Identify the barriers by the Roman numerals of the alkanes. 'IEE >33|Z> 31>: largest lama-W smallest barrier @ /@ (B) (6) Answer the following questions about rotation around the C-C bond in I. (i) (3) Draw a Newman projection formula in the box below of the conformation of I with the lowest energy. On the line next to the box, write the name of this conformation. H H H «9 as: H H H @5‘ (ii) (3) Write the name of the conformation at the top of the energy barrier to rotation on the line below. In the box to the right give a descriptive name of the energy barrier. 0“ hn|bfiQ—\ SW?“ K'nu‘57/ Chemistry 322a/ 325a -10— Name Exam No. 2 . (7) Contd. (C)(6) Answer the following questions about rotation around the indicated C—C bond in 111. (i) (4) Draw Newman projection formulas of the lowest energy d highest xergy conformations in the designated boxes below. a C CHs [4 ’f‘ H lowest energy conformation highest energy conformation (ii) (2) What two sources of strain energy are found in the conformation at the top of the energy barrier to rotation in III? +°T‘$\O’V\‘l\ Walt!“ Ohfil. S'l‘irlq S‘h’l‘h @MA / (8) (05) When acetic acid dissociates in water to acetate and hydronium ions, is the standard entropy change positive, negative or zero? Provide a brief but clear explanation of I TkL Ago \S ‘Yxtscr‘flvg- Thu \omg PT‘OAQC1A. \h‘kvgcb mow-g Ser—o—KE i m? fidd‘C" V‘O\uU \OSJVNM JV‘J" “mm-A mask—1‘: «Ltd. TL: fiRN-‘iT'C‘f‘g sa\\fi'n'\‘- $O\U‘\'¢ K’W‘V'Lt'tcv‘QAO’KS O; H-‘DOMA—tmj KflA i°“~ ‘QPka («k—FoAULL ROFL 015-44" “N 4‘4“" .\0“r\ fiafi‘k A how. Order-A VTJDGIVG+ Sh-‘vk He“: \OMP 'fi‘w‘rro (>7- Thus, i-kc— dist—Asa \~\ 7.76% 97’ 0 BS, \3 fluéacl-RVU ...
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