322as05_e2_key

322as05_e2_key - CHEMISTRY322aL Please K9 1 EXAMNO.2 Print...

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Unformatted text preview: CHEMISTRY322aL Please K9 1 EXAMNO.2 Print Last ame FEBRUARY 28, 2005 Grader (1) (10) __ __ (2) (15) __ __ (3) (10) __ .— (4) (20) __ __ (5) (10) __ _ (6) (15) _ (7) (10)_ __ (8) (10)_. (100) first letter of last name I will observe all the rules of Academic Integrity while taking this exam. Chemistry 32a -2- Name Exam No. 2 (1)(10) Answer the following questions about acid-base reactions. (A) (4) For each reaction below where reactants (left side) and products (right side) are given, use the information provided to determine the direction of the spontaneous acid- base reaction. Draw an arrow in the box to show the direction of the spontaneous reaction, @ (i) CH3C02H + C13cc02-Na+ CH3C02'Na" + C113CC02H pKa = 4.75 pKa = 0,63 @(fi)ceHsNH2 + CeHsoH C6HS§H3 + W (B) (6) The reaction of acetic acid and sodium bicarbonate to produce sodium acetate and carbonic acid has a standard Gibbs free energy change of AG0 = -2.0 kcal/mol. AG° = -2.0 kcal/ mol CH3C02H + HOCOZ'Na” —> C113,C02'Na’r + HOgOH acetic acid carbonic acid Provide the free energy diagram for this reaction below. Use horizontal lines for the starting and product states that are positioned properly according to the energy scale. Clearly label these two states in your diagram. Draw an arrow between the states to indicate the standard Gibbs free energy change for the above reaction. kcal/mol According to the standard free energy change for this reaction, which is the stronger acid: acetic or carbonic acid? flSQ+fL & C A P redo Q‘T‘ $‘\"°~‘\‘L 4 % Mm Relative Gibbs Free Energy Chemistry 32a -3- Name Exam No. 2 (2) (15) Answer the questions below. (A) (12) Provide systematic or IUPAC names for the structures, or provide structures inside the boxes for the names, as requested below. a (b H 3 f r HC’ECCHZ CH3 2CHa H, CH3 - LL‘f~ (LI‘ML't-kylczdo 9 y 5- .V ‘bt‘DMO‘ L‘- cl-k --)- htyflqfiL Cl \ CH3 3-chloro-1-methylcyclohexene cis-l-bromo—3—hexene B) (3) Draw the detailed structure of 1,1-dimethylpropyl chloride \ inthe box. cuquzci-q CH3 (3) (10) Answer the questions below. PrOVide the IUPAC name Draw in the box below the most stable conformation of the compound drawn of cis-l-tert-butyl—4-methylcyclohexane. in a Newman projection formula below. lack \O’Vk Chemistry 322a M/ -4— Nam Exam No. 2 Q \ . fl (rt/ma, flage/ (4) (20) Circle the correct answer for each question or statement below. (A) Sodium amide (NaNHz) is a commonly used reagent in organic chemistry. In which of the following solvents may this reagent be used successfully? e circl be] ethyl alcohol liquid ammonia acetone hexane (11] 1mg“ oW) . 0 y qui ammonia PK. 16 38 19 >50 H .d “uh cetone dhexane liuid ammonia and hexane only ethyl alcohol (B) The compound triacetone triperoxide decomposes explosively to three molecules of acetone and one molecule of ozone, as shown below. Which statement is true about this reaction? 0/ ___>’ 3 X + 03 triacetone triperoxide -The standard entropy change for this reaction is negative which make a favorable contribution to the standard free ene :4 1,; ‘ e ge or ' reaction is positive which make a favorable free energy chan e. . ge or i' n. ea - on is negative which make an unfavorable contribution to the standard free energy change. - The standard entropy change for this reaction is positive which make an unfavorable contribution to the standard free energy change. (C) The order of acid strength (strongest to weakest) of the carboxylic acids below is CH3CHZCHZCOOH CH3CI-12CHC1COOH CI-I3CI-12CC12COOH I II 111 (circle answer) 1>11>m II>III>I III>I>II (D) In the two compounds below, the most acidic H are H A C‘' (A (C NHr (circle answer) 2 H0012 EC-H HCEC LC; ILA ‘\ CH3\ 1, A; 11,c 1,3; ILA 1 3 II B Chemistry 322a ' -5- Name Exam No. 2 g\ A “a (4) Contd. (E) An alkane, C7H16, has 12 equivalent primary H, two equivalent secondary H, and two equivalent tertiary H. Which alkane below fits this description? (circle answer below 2,2—dimethylpentane 2,3-dimethylpentane 2,4-dimethylpentane ,3—dimethylpentane (F) The cycloalkanes below that have some degree of torsional strain, in the conformations shown, are (circle answer) V V V m only I I II III Iv flifib all of them (G) In the chair conformation of cis-1,2-dimethylcyclohexane, the number of gauche interactions (G) associated with the methyl groups is 1c; 26 @ 4G (H) Identify the isomers of the three dimethylcyclohexanes shown below in chair conformations. 3 (circle answer) CHa H Claw CH 3 I trans; II cis; III cis CH3 H I trans; IItrans; III cis I II III Icis;IItrans;IIIcis (I) Among the chair conformations 1,11 and 111 above in (H), which is (or are) free of steric strain? (circle answer) I and III I and II ( only I > none of them (I) The heats of combustion of the three isomeric C5H12 alkanes are shown below. Based on this information, the stability order (most stable to least stable) of these isomers is GiaCIlzCHZCI-IZCI-Ig, G13CH(CH3)CHZCH3 (CHg)4C AHcomb -838.80 kcal/ mol -837.57 kcal/ mol -835.18 kcal/ mol (circle answer below) pentane>2—methylbutane> neopentane 2—methylbutane>neopentane>pentane neopentane>pentane>2-methylbutane eopentane>2~methylbutane>pentane Chemistry 322a -6- Name Exam No. 2 (5) (10) Larger organic compounds are often synthesized from smaller organic compounds. Using reagents] reactions already discussed in lecture, provide a multi-step synthesis of hexane from propyne and 1-bromopropane. Each step in the synthesis from starting materials to final product must be shown as a chemical equation with needed reagents above or below the arrow. To begin, provide the - ctures of the starting materials in the boxes below. c uscugsze r 1-bromopropane Proposed Synthesis of Hexane (Provide complete chemical structures for all organic compounds.) CH3CECH + NLNHLWS “53°C. QR EEC—LC N CL C\—\ 15:21: N on -\— QHSCRf—Hflgv QR mg CHSC‘EC‘CHLCHV—CHS ~13° (_ _ «cuss H c H393: qtfl+§a3 P+ fl? Chemistry 32a -7- Name ExamNo.2 2 «(Lt JW (6) (15) Answer the questions below. / m A m M (A) (12) Provide detailed structures for A -D below based on the information provided. Give the IUPAC name for each compound on the line below the box. \ CH 3g CA4: Loss CH3 ‘ 0 A CsHlo pKa=25 B CeHu 98‘1"?“ H 3eqmv1°H 2equiv2°H 3.3- dFmL+~\\yl—-\-\>o’t~|xg 2.1- d\m¢_-\-\\j| bw‘t‘ocme new a C CsHlo pKa=44 . D €6le 12 equier Minam— C'xclgb 15g mg (B) (3) Compound A (above) is added to a mixture of sodium amide (NaNHZ) in liquid ammonia at 63°C. After a few minutes, the temperature of the mixture is allowed to warm to room temperature. The ammonia evaporates leaving a white solid (CgHgNa). Deuterium oxide (D20) is added to the white solid and the resulting mixture is worked up yielding an organic compound C6HgD. Provide a detailed structure of the product in the box.. A NaNHz warmuE C a (:6le PKa = 25) HQ NHsr "33°C Chemistry 32a -8- Name Exam No. 2 (7)(10) Analysis of the heat of combustion data for cycloalkanes provides a measure of the "ring strain" in these structures. The data for cyclohexane and cyclopropane are given below. cyclohexane AH comb = -944.5 kcal/ mol cyclopropane AH - 499.8 kcal/ mol comb _ (A)(4) Assuming that cyclohexane is free of "ring strain," use the above heat of combustion data to calculate the total "ring strain" in cyclopropane. You must clearly show how you use the data. A simple memorized number will not be accepted. Place your answer in the («\CT:;+\ a,“ .Q— kmf’t’mflo\w_d 92v CHl \—V\ cYcloksqum‘L .- ~°\H'~(.§ Kca(/mv\ /(p 1— \57' ‘l' \4“‘\/CHW For— s-‘rr-mm"(ix-m~ Cyclopw PA’KK exud-z 27.0, "' - . KG} /Mo‘ . kCaX/M \ .. \S7H ‘l‘ 3 - Ll"l‘2. ’1. O Q$+M\ S+T¢1~x ‘2. ‘3 vWA—QgAC, 1' Li'TZIL: "27.Q \CCoJ/ . (B) (6) Degcrige‘the two types of strain energy that contribute HEW-IE""‘ri'n—g—strai1’?"o htfiu L i cyclopropane. lust giving the names of these types of strain energy will receive no credit. on must describe/explain them. Strain Energy 1 in cyclopropane Rang L W63 ’V\ TL‘L \AQ alt mi Ami—VAN; Ark\ ¢o Nee-H1 \0 Do \xav 9\ \xfim\ uni his a Q (D9-Co- \M C7 DV‘K‘O PQMKI +\~¢— Jr‘vKogvxé U\6kf\ iQoman‘ Rag (thtT'mocX Q'V‘j [0-3] dL-CT «LA by +\-¢ I-vx‘itr— ’Yw (Ac—eu- N—TSI 0 4’ 6,00 « TLtS Com-truck? v-V\ ‘90 V\ lO‘iS" +0 (20° \5 Ca.\\o.A Q. [L S'V‘I‘Ll’h' C $00 «a qéic Strain Energy 2 in cyclopropane Towns! am.) 5*- M.‘\ ’V\ (YdOYWPa‘eK \NA Ck 9\«-v\ar jun/«#1 whim ‘-L\\ H 0W3. \’Y\ QATPSQA COM-QPN+t0—KS +\r\o:5\_ Cons-tribud‘K H My. ‘ H Sven-1‘“. Ar0‘\*$\ om‘,\ .SJr‘raj '7\ . Chemistry 322a .9- Name ' ' Exam No. 2 (8) (10) Answer the questions below about rotation around a C-C bond in isobutane, (CH3)2CHCH3. (A) (4) In the box below, draw a Newman projection formula of a staggered conformation during rotation around a CC bond in isobutane. H CH3 CH3 or can a can \) a “Sr H H Newman projection formula (B) (6) Sketch the conformational energy diagram below for rotation around the CC bond in isobutane. Start your diagram at a rotation of 0 degrees with a staggered conformation. Label all locations in your diagram where the staggered or eclipsed conformations occur. Add values to the energy scale to show the approximate height of the energy barriers. 5 — boevrwJ-s C_\osL 310 Lk KQa.\/Mo\ ...
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322as05_e2_key - CHEMISTRY322aL Please K9 1 EXAMNO.2 Print...

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