Spring2011Exam2Key

Spring2011Exam2Key - CHEMISTRY 32231. Please K1 j EXAM N0....

Info iconThis preview shows pages 1–8. Sign up to view the full content.

View Full Document Right Arrow Icon
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 2
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 4
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 6
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 8
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: CHEMISTRY 32231. Please K1 j EXAM N0. 2 Print Last Name FEBRUARY 28, 2011 First Name USC ID No. TA‘s Name Grader (1) (15) W (2) (10) W (3) (15) W... (4) (20) ._...._ (5) (10) W (6) (15) ___.... (7) (15)W (100) first letter of last name I will observe all the rules of Academic Integrity while taking this exam. Chemistry 32231. ~2~ Name Exam Not 2 (1) (15) Answer the questions below. (A) (12) Provide IUPAC or systematic names for the two structures below on the lines below the structures. Provide condensed or bond-line structural formulas inside the boxes for the names below the boxes. Be sure to show stereochemical details, Where required. H3C H3 3 sea/k l ,..{ flack (grocer3 m of 0 HCE‘ECCH CH CHCH Cl 2 2 3 WA \‘Ck\0r° “3&3”df \c cfi,\o\&$¢~ng‘ 3-methylbut—2-en—Lol cis-2,3~dichloro-S—methyl-Zohexene (B) (3) Draw the condensed structural formula of 2-methylbutyl chloride inside the box. C HSQHLQH —-C\~\2.Q\ \ {H3 (2) (10) There are 5 constitutional isomers of Cal-114. Using the information below each box, provide the correct condensed structural or bond-line formula of the isomer inside each box. The "reaction" refers to a monosubsff’c‘iition reaction where Cl replaces an H atom yielding different constitutional isomer products C6H13 C1. Reaction provides two Reaction rovides four Reaction provides five products CGHBCI r products C6H13Cl products C6H13Cl :[U <<t+333c<eLcs3 Reaction provides three products Reaction provides three products C6H13Cl: two different primary and C6H13Cl: one primary and two one secondary. different secondary. Chennstry SZZaL. ~3~ Name Exam No. 2 (3) (15) Answer the following questions. (A) (5) Indicate whether each of the following compounds is chiral or achiral on the line below the structure or the name. OOH 2-pentanol ack‘m‘d (2&3;ng 1 r (‘j M ‘" 00 raga 3,3-dichloro-1-butene CH etc/\x '3 n: l SCH \ rq\ W (B) (10) Indicate on the line below each pair of structures whether they are enantiomers, diastereomers, or the same stereoisomer. CH2CH3 CeHs «fwa Mwa (:6H5 CHZCH3 mum‘o L3 h (2R,3$)-2—bromo—3-methylpentane and \‘ QM (2R,3R)-2~bromo—3—methy1pentane H3 H3 (:1 H 1 c1 c1 CH3 CH3 ggm yummy: Me r Chemistry 322aL Name Exam No. 2 WW «4. ole/lack), w: Mac ad- (4) (20) Circle the correct answer for each question or statemen below. (A) For the general reaction below (ignoring solvent effects), what is the expected sign (positive or negative) of the standard entropy change (A80) and what will be the influence (favorable or unfavorable) on the standard free energy change (AGO)? (circle answer below) A + B C AS" positive, AG" favorable AS" ositive, AG°unfavorable AS" negative, AG°favorable AS" negative, AG°unfavorable (B) An analysis of the heats of combustion of the following cycloalkanes shows that the least amount of heat per CH2 group is released by W, D E] E> @ O (C) A conformation that clearly is not involved during the interconversion of chair conformations in cyclohexane is (circle answer) b O H M lana half-chair pure boat twist boat (D) The more stable isomer (cis or trans) of the two t—butylcyclohexanols below is H H (circle answer below) I cis II cis I cis II trans Bu-t H311 I trans II cis I trans II trans 3-t—butylcycloheXanol 4-t-butylcyclohexanol I II (E) A Newman projection formula along the C1-C2 bond in equatorial- methylcyclohexane will reveal an anti relationship of the methyl group with the CH2 numbered (circle answer below) Chemistry 322211. Exam No. 2 Name \ -5- (4) (0mm) k 1246 51/ O V mg, (F) The maximum number of stereoisomers for the general structure below is (circle anwer below) cr—rzzcucuzcuacnacus 2 3 GD 6 (G) Assign (R) or (S) configurations to the stereocenters in A and B below. H H (circle anwer below) i ? A(R)B(R) A(R)B(S) C/(lYHs CHacuz/fimgcna coon CH=CH2 A (S) B (5) A B (H) A sample of 100% ee (S)-naproxen, an anti-inflammatory drug, has a specific rotation of [049 = +66° in chloroform at 25°C. What is the specific rotation of an optically impure sample that is 55% (R) and 45% (S) naproxen? liq OOH (circle answer below) CH3 / \CHs 36.30 400° +2970 (S)-naproxen (I) Dibromination of 1,3—diphenylpropane produces 1,3—dibromo-1,3—diphenylpropane as a mixture of three stereoisomers in equal amounts. These stereoisomers are the (R,R), (8,8) and the (R,S). Which statement below correctly describes the results when the product mixture is separated by gas chromatography? C6H5CHBrCH2CHBrC6H5 three stereoisomers produced in equal amounts 1,3—dibromo-1,3-diphenylpropane (R,R) (8,8) (R,S) (circle answer below) ~Three separable fractions. Each is optically active. —Three separable fractions, Two are optically active and one is not. — no a.......-.;, u .. 10 One IS ot1call active .. 9 one 15 not. ~Two separable fractions. Neither is optically active. . 0) Fischer formulas of the three stereoisomers of tartaric acid are shown below. If you find an incompletely labeled bottle of tartaric acid that is optically inactive, what may its stereoisomer composition be? OCH OCH OCH (circltle answer below) -can on y be I OH OH H H -can only be a racemic form of 11/11] COOH COOH f d a racemic form of 11/11 fOOH H -may be any Sing e s ereorsomer, I, II or III III Chemistry 322aL 6— Name Exam No. 2 (5) (10) The three constitutional isomers ofC5H12 are pentane, 2~methylbutane and neopentane (2,2—dimethylpropane), as shown below. The heats of combustion of these three isomers are provided in the table below. pentane 2-methylbutane neopentane Heats of Combustion, AH‘gomb (gas) (kcal/ mol) pentane 644.993; 0.23 2«methylbutane -8413: 0.22 neopentane $39.88;}; 0.23 Combustion reaction is scaled to one Calling) 3 02 "' " 5 C02 + 6 H20(g) mole of alkane. (A) (6) Show how the above combustion reaction allows an assessment of the relative stabilities of these isomers by drawing an energy state diagram below. Your diagram should clearly include the reactant and product states (properly labeled by isomer) and the enthalpy changes in state-to-state transformations. The diagram does not need to be to scale, but the relative positions of the reactant states must reflect the energy changes. M +30,“ .——_¥_.__. N4: 80')... >(+ 80 9—H: fig .— stitth kc‘il final ‘- teal M Co mmon/ Mdufift’ gA‘w‘k‘L Relative Enthalpy (B) (2) What is the stability order (most to least) of these isomers? N0 PaM'V‘ccmd. > 2-ml.+\~1ll3 u‘lfi'a'ni > PLn'hm L (C) (2) The standard enthalpy of formation (AI—10f) is the enthalpy change when compounds are formed from the elements under standard state conditions. The defining reaction for the C5,le isomers is shown below, along with the three standard heats of formation. On the line below each value, write the name of the constitutional isomer associated with each standard enthalpy of formation. 5C (graphite) + 6H2(g) *'—> C5H12 (g) AH? = —40.27 -36.84 -35.16 (in kcal/rnol) assignments “W W ,._Le_:‘_+£2_<’—_ Chemistry 322aL -7- Name Exam No. 2 (6) (15) Answer the following questions. (A) (4) Complete the Newman projection formulas of the lowest energy conformations during rotation around the C1~C2 bonds in 1-chloropropane and 2-chloropropane. H \A H‘ o r~ k complete the Newman formulas for the H H \+ u "l MC \ H Cl C '51, lowest energy conformations 1-chloropropane Z—chloropropane 6143 a» a est-ufl C s; l—d (B) (6) Draw the lowest energy conformations for trans—T24imethylcyclohex e (Box A) and cis-1,2-dimethylcyclohexane (Box B) below. A trans-1,2-dimethylcyclohexane B cis-1,2—dimethylcyclohexane L Which isomer (trans or cis) is more stable? ‘VVOM’XE (Hint: Compare the more stable chair for each isomer.) Won- L By how many gauche interactions? 26" (C) (5) The "pure" boat and chair conformations of cyclohexane are both free of angle strain, but the pure boat is still about 7 kcal/mole less stable because of other types of strain energy. What are two sources of strain energy in the pure boat conformation? Add the missing H in the drawing below to illustrate your answers. 4/” 3% Ha SAW/QM H I H l /\’\‘ ‘4 a f‘@ (ii) S'st‘urta SJYTOAM \;+or6k°ma{ Symbqu : H CCU (>3ch H Illustrate these answers in the drawing. ' pure boat 3 Chemistry 322aL ~8~ Name Exam No. 2 , *7 (15) An unsaturated hydrocarbon A i eacts with sodium amide to produce a salt B. Reaction of B with methyl bromide pro uces D. Compound A also reacts with two equivalents of H2 over a platinum catalyst to yield an alkane, C. Combustion of one mole of C produces 6 moles of C02 and 7 moles of H20. Alkane C contains 9 equivalent primary H, three additional equivalent primary H, and two equivalent secondary H. Provide structural formulas for A, B , C and D in the boxes below. (Hint: Read the entire roblem c fl.“ Suficient information is provided.) excess 02 complete combustion of one mole of C C s» we a m («e q W Wm / DVW z" W A) e M % 6 mm W [14 (Lt-6!?“ 0; COM; ...
View Full Document

Page1 / 8

Spring2011Exam2Key - CHEMISTRY 32231. Please K1 j EXAM N0....

This preview shows document pages 1 - 8. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online