F07 midterm2 key

F07 midterm2 key - NAME ; 1E BEAM Student ID# _ Circle your...

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Unformatted text preview: NAME ; 1E BEAM Student ID# _ Circle your TA’s name: José Ryan Amy Ben CHEM 30A Fall 2007 Midterm Exam #2 November 21, 2007 Please sign the following HONOR STATEMENT below before beginning. No regrade requests will be honored if the signature space is left blank. The answers in this examination booklet are entirely my own work. I neither gave nor received information or assistance in writing this examination. I understand that sharing information during this examination, or using materials not explicitly allowed by the instructor, will result in a failing grade on this exam, and possibly in additional action that may affect my ability to continue attending UCLA. SIGNATURE PLEASE READ THE FOLLOWING INSTRUCTIONS BEFORE BEGINNING. 1. Please verify that your cell-phone and/or pager are OFF. If your device rings or vibrates during the exam, 5 points will be deducted from your score. 2.The exam consists of 9 questions on 10 pages. Please verify NOW that you have all pages, and raise your hand for assistance if you do not. 3. Please write your name at the top of EVERY page NOW. 4. To receive full credit, your answers must be legible, structures readable, chemical names spelled and punctuated correctly, and numerical answers given to the correct number of significant figures. To receive partial credit on problems for which it is given, you must show your work. .Always indicate clearly if your work continues onto the back of a page! If there is no such indication, graders will not look at the page backs. R:8.314J-K“mol'1 m R = 0.0821 L - atm - mor 1K" _ lkcal =4.184 kJ kB = 1.381 ' 10—23J ' K’1 lerg=10’7J 1 L'atm = 101.325 .I l Noggin = 142.1 cm3 AG”. = AH — TAS AG =AG°+ RTan AG" = —RT1nK k = Ae—Ea /RT 1 _ i? k=Ce AG /RT 50 Scaled to 100 and rounded up AGfxn : WE... AG? _ mg... AG? NAMEM__ Page 2 of 10 1. (18) a) (5) A new plant species has just been discovered. The sample contains both (+)—carvone and (—)—carvone, with the (+)—enantiomer present in 80% e.e. What is the ratio of (+)—carvone to (—)-carvone in the sample? 8090 excess (+3 Wmawrk 20%; \‘s rammsc 009069110300)», $090369 a]; \ l O 0 b) (5) Using the E,Z system, name the following alkane — [é " " l1 8% 9— 061-- -m CI E." (5) ’ IA-chwom bl 'S—méflog- 4-odeye1 Is this compound cis or trans? 4L— 0) (3) M—Farnesene is found in apple skins. How many isoprene units is it made from? 3 0c —Farnesene d) (3) What is the full name for DMSO? gs SM‘I‘COX I‘d. E , e) (2) True or false: Branched alkanes have lower boiling points than unbranched ones with the same number of carbon atoms. TR uE" Name lQE. BRUHM Page 3 of 10 2. (20) Read this question carefully! In each part below, an acid—base equilibrium reaction is shown. the statement below the reaction that best describes the position of the equilibrium. No explanation is necessary. a) (4) 0H + H30; 0- + H2304 ... . . wbfi? E u111br1um favors roducts l1es to the r1 ht. \ orq p ( g ) HzSCDK \S a Slmés“ ““3 quilibrium favors reactants (lies to the left). CI n @o ' e e b)(4) CHsCH20H + iCECH<-——‘ CHsCH20 + HCECH 7 WM . Equilibrium favors products (lies to the right . C\'\3CH10\9\' \ S 51 5“ WNQ‘“ or and "(rlnuh cud—mt H. Equilibrium favors reactants (lies to the left). c) (4) Rank the following with respect to relative acidity. Put a 1 under the molecule that is most acidic and a 4 under the molecule that is least acidic. T o 'r T‘ T' /° 1* T” H—C—C/< H—C—C—Cl H—C—'C / H—‘C—C—H I OH | l | \ I | H H H H OH H H N relative rank: _‘l__\_; d) (4) Rank the following with respect to relative nucleophilicity in aprotic solvents. 1 = most nucleophilic, 4 = least nucleophilic. CH3CO[ NH4+ H20 CN" relative rank: Z i l e) (4) The equilibrium constant (Km) for the reaction shown below is. . .? (multiple choice) ——A Acid + Base “— Conjugate Acid + Conjugate Base pKa= _2 pKa: 2 A: 10,000 B: 0 C: —1 D: 4 E: 0.0001 Name QOE BR MIA.) Page 4 of 10 3. (12) 21) Assuming that the reaction of l—methylcyclohexene with D—Br (the deuterium labeled version of H—Br) proceeds with absolute Markovnikov selectivity, what will the major product(s) of the reaction be? DBr _———> 9 Ether (solvent) \' \ N .~ . : Br Only 3 and 4 Only 2 and 4 Only 1 and 2 All of them Only 1 and 3 HUOUU> b) The major product(s) of the reaction of the trans—alkene shown below with bromine in water are? [Note Ph 2 © ] Me Brz 9 —-——> H20 . Br 2H 2H Br Me g Me Me k/Me Ph Ph/\/ Fri/Y Ph OH Er 3' 8” 1 2 3 4 A Only 2 and 3 B Only 2 ._.___._... C Only 3 I: D Only 1 and 4 E Only 3 and 4 c) What is the major product of the reaction shown below? (Pick one from the choices below.) / HCl —> Ether (solvent) A 1—chloro—3—methylpentane 2—chloro—3—ethylbutane 3—chloro—3—methylpentane 3—chloro—2—methylpentane 2—chloro—3—methylpentane HUGO-‘1 Name M Page 5 of 10 4. (22) a. (4) Rank the following in order of decreasing reactivity toward nucleophilic substitution by the SN2 mechanism. 1 = most reactive, 4 = least reactive H Br /\/\Br flifi AAF M A B C D relative rank ‘ _ ‘ 3 2- Please answer the following questions, using word definitions or structures as requested. b.(4) Define hyperconjugation. K J \ lVl’rem c‘l 10”“ c)? eledrons m A SlW— mam? whim MI w [W M Vam M' Z? oflofifl 0? am “A 34(pm— $051?! char (WWW, '. \eaw clelomh-t-eoclw», V\‘m ovlmlad overlap - (“me 52,523239594 \oondm3 arbfioil 40 cm adjmeni' unfilled «finial-J c.(4) Give an example of keto—enol tautomerism. Show structures, but not the detailed mechanism. OH I 1 cugcu=cau5 : c l+3cuz~ c045 eho\ kc}:va d.(4) What is a stereospecific reaction (definition)? Pr rem-hon m Mm‘cln ems. slerem‘swnorrs «2va (or éefimoedi) Jro fine exclusirm cf all o‘lhers. 3.(6) Draw the molozonide that forms Draw the ozonide that then forms: after ozone reacts with propene: \———v f Name M Page 6 of 10 5. (12) The phenoxide anion reacts with l—bromopropane to form an ether, as shown below. 669 O K + /\/Br ___> + KBr DMSO O—\ In the box below: 1) Draw the energy profile for this reaction. 2) Draw the structures of any proposed transition states or intermediates and label them TS or INT as appropriate. 3) Label any activation energy barriers to show AG:. 4) Label the Gibbs free energy change (AG°) associated with the reaction. > O) I- (D C a) d) a: L I.— reaction coordinate Name 305 UV) Page 7 of 10 6. (27) (3 to 5 points each) For each of the following, complete the reaction with the predominant product or products. You must indicate stereochemistry with wedges and dashes. If a racemic mixture is created, you must write “racemic” under the structures. If no reaction, write “NIR-a, \ H ,Pt Mi 2 YE: 1) 03 2) MeZS HCI c1 N NH 4—2— #> M ' R . H so , 1) BH3 2H26 2) HZOZ/NaOH Name £805 BRUVU Page 8 of 10 7.( 12) For each of the following, write in the box the reagents, conditions, and additional reactants (if any) needed to convert the reactant into the product. CI Cl Name W Page 9 of 10 8. (15) READ THESE DIRECTIONS CAREFULLY! Carefully examine the reaction in the box. a) Write the products in the designated box. b) In the large box, write the mechanism for the formation of one of the products. Use arrows to show how pairs of electrons are moved to make and break bonds during the reaction. Make sure to draw all lone pairs of electrons, all formal charges, and all products produced at each step. _______> racemic mixture + HBr Products: 0! {3W Drown 4 ‘Jv/ offoéarnfly We» 4W . Kt" 13‘47‘07" 8/4 Me Me, ‘Q/J'f . Name _ Page 10 0f10 9. (12) For each of the following reactions, indicate in the box at right whether it proceeds by an SNl mechanism, SN2 mechanism, or that there is no reaction, NR. 21. AA ethanol AA M ——>Nal M b' OTs DMSO | 3/0 Z CH3OH C. WE .___> WO\ Br (1. 1 NaBr acetone 3 M Z ...
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