225Sp08 Test 6 Key - CHEMISTRY 225 TEST #6 JUNE 20, 2003 '...

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Unformatted text preview: CHEMISTRY 225 TEST #6 JUNE 20, 2003 ' 1. (31) A ‘ 2. (18) NAME \A va 1? 1/ C17 3. _H___ (16) 4. (10) TOTAL (75) GOOD LUCK! 1. (31 Points) ORGANIC REACTIONS. a. ( u t 7) Consider the reactivity of trans-1-bromo—4-methylcyclohexane (below). As a secondary alkyl halide it is susceptible to various reaction types depending on the reagent and reaction conditions. o (4) Ethoxide and acetate are both oxygen nucleophiles, but ethoxide is by far the stronger base. Use this information to the major product in each of the two reactions of trans-l-bromo-4- methylcyclohexane. (o , . . __._____ (1 Br 0 H (—3 Cch—O ;' (71° 2' CH3 - (3) Write structures for the two substitution products formed when trans—l—bromo—4— methylcyclohexane is heated up in aqueous acetone (equation below) (‘2 1+ ' '6 1+ Br 1 H20 —‘h— acetone l (EH3 2 b. ( t 24) Complete six of the following organic reactions with structures for the reactant, product, or reagent as required. Pay due attention to stereochemistry and regtochemtstw in those cases where such characteristics are important. If no reaction is expected under the reaction conditions, write “NR.” and explain briefly why the reaction fails. If you complete more than six reactions, please be sure to indicate clearly which six you wish to have graded. Each problem carries equal point value. OH CH3 in . i 1. 030 5 ' 3 #__w_____)_' 1 5p 2. H20,N32803 E P = protecting group, not involved in reaction H OH 1. H OAc ,HO,THF Gt )2 2 HCHS 2. NaBH4 3 H Br 9 | CH3CH20 CH3CH20CH2CH3 —"'+ | CchHZOH ' CHZCH3 ‘i’Ha H/ D2, PdIC ma..- —" / | /l\/\ OH X». (only product) (Intramolecular reaction) H+ -. (W ‘O :1, H3O CH3 2. [18 Points) ORGANIC REACTION MECHANISMS 7. a. ( WK 8) Consider the chemical behavior of 1-bromo-§-ethy]eyeIOpentane when it is warmed up in ethanol solution (equation below). “HE-El <1 —— -—v OCHQCHg H c H < c 3 H23 /( CH20H3 - (5) Provide a detailed, stepwise reaction mechanism to account for the formation of the ether product in the reaction below. A complete reaction mechanism will include structures for all intermediates and curved mechanistic arrows to depict the “flow” of an electron pair. _ - a "1 o (I) Write the rate law for the above reaction. Q€tfi€ 7" L L; Q“; <3ng i 4 o (2) For the reaction on the previous page provide a structure for an additional unsaturated product that would be formed under the reaction conditions. EV CH3CH=CHCHCH3 Step' val-e “d (Lu Sfll .r 34,... i;- w: lexical ~l’C’ End MM ‘flsa CavL’dC‘cLi-E‘u ‘nwlevwr-zii'ak. 714 we’th “.1 Catalina.) m V-al-r‘ (LYN/L) (lite-aermigh “Yr 0. 4-6 coda”? dll7LsL L4 1(3voric-nex9 0‘- Uf‘ry b. ( f 3) Account for the fact that 4-bromo—2—pentene (compound to the right) is an unusually reactive secondary alkyl halide under conditions favoring the SN] process. IHNT: consider the product of the rate-determining attic. C‘ex-‘lteh- 2r Lé co.qu m fL—gi—3!__ E“; (Q It . ‘1 l \I - '- H— @ K‘l-éuc. car\7 A 00oz all _ “C”; (F) qufltwgwiq c. ( I 7") Formation of the (err-butyl cation by the 'r' _ .HIBr' " (+3 unimolecular dissociation of 2-bromo-2-mcthylpropane (equation [(CHslscBr —" (CHslsc to the right) is an endothermic process. 0 (3) Use the Hammond Postulate to speculate on the nature of the transition state for this process. Underline the correct description. In the transition state: - The central carbon bears an almost fully developed positive charge is nearly electrically neutral is almost fully intact is almost completely broken almost trigonal planar very nearly tetrahedral — The carbon-bromine bond ~ The geometry at carbon is o (4) Which of the following terms describes the tert-bu l cation (circle all that apply). 3. (16 Points) HIGHLIGHTS FROM THE WORLD OF ORGANIC CHEMISTRY RESEARCH. ' on Bronsted aci weak nucleophile a. ( _ r 3) As reported in the May 12 issue of Chemical & Engineering News chemists at MIT have deve10ped a new procedure for the Suzuki reaction. The procedure involves coupling of an organoborane reagent with an alkyl halide in the presence of a nickel catalyst. The preparation of this organoborane reagent by electrophilic addition of 9-BBN to an alkene is shown below. Complete the synthesis with a structure for the alkene reactant. W 5 h. ( ___ i’ 3) Why even bother doing the reaction? The elusive molecule P2 (the phosphorus analogue of M) has recently been prepared. Chemists in Japan have carried out quantum mechanical calculations on the reactivity of P2 including its addition to double bonds (generic equation to the upper right). The calculations reveal that the reaction should be a syn addition, with retention of H3C P configuration ofthe alkene [Tetrahedron Len. 2003, —-9- )— 49, 35738]. Complete the reaction to the right with a ' CH3 structure for the product that shows its stercochemistry clearly. c. ( i4, BONUS QUESTION) As reported in the May 26 issue of Chemicai & Engineering News scientists at Cal Tech have found that in the lungs ascorbic acid (vitamin C) reacts with ozone gas to form a potentially harmful ozonide. The structure of this ozonide is shown below. ' ' o (I) Directly on the structure of ascorbic ozonide circle two carbon atoms that are at the same oxidation state. o (3) Complete the equation below with a structural formula for ascorbic acid. OH i o 1. 03, —78° HO\/ Z/O —h~ o 0 2. warm to 0 HO, f HOH o—o Ascorbic ozonide 04 - \ H’OVvO- 9&0 ascorbic acid d. (m_ K 7) Chemists at the University of Mumbai used styrene oxide, structure below, as a reactant in a series ofnucleophilic ring opening reactions [Tetrahedron Lett. 2008, 49, 36W]. C374 0 OH‘,H20 I r A PLCM was styrene oxide (:5, 003:4 I Pi- CH = CH; alkene reactant o [4) Write an equation (showing reactant and reagent) for a one-step synthesis of styrene oxide from an alkene. - (3) Complete the synthetic Sequence with a structure for the hydrolysis product of styrene oxide. 6 e. ( f 3) As reported in Chemical & Engineering News on June 2, orchids release certain alkenes to lure male bees to facilitate their own pollination. One such alkene is (Z)-7-heneicosene (structure below). Complete the reaction of (Z)-7—heneicosene with a structure of the bromination product. For simplicity you may use the condensed formulas ~C6H13 and —C13H27 to represent the two alkyl groups in the structure of the product. 4. (10 points) MULTIPLE CHOICE. By now you know what to do. Q 1 Which of the following describes the regiochemistry of the E2 reaction? A. Hammond Postulate B. Markovnikov’s Rule C. Zaitsev Rule D. Murphy’s Law A Which reagent would serve to accomplish the transformation to the right? > M 2 —)v / A. if B. OH‘ C. NaH D. H2, PdfC Q Which addition reaction is correctly described? A. Electmphilic bromination: an anti addition via a cyclic bromom'um ion intermediate. B. Direct epoxidation with a peroxy acid: an anti addition Via two mechanistic steps. C. Catalytic hydrogenation: a stepwise process via a carbocation intermediate. D. Addition of hydrogen bromide: a syn addition with anti-Markovnikov regiochemistry. @ Deduce the structure of an unknown hydrocarbon, C10H16, that would be converted to the compound to the right by ozonolysis. OHC CH0 Hac—Q-CHa H2c=c»—<:>—.CH=CH2 HcEc’O—CECH ;b C. D. A. B. C/ For which two compounds below are the underlined carbon atoms in the same oxidation state? OH o | n 1. CH30H2§H=NH u. CH3CH2§H2CI m. CH30H2§HOCH3 IV.CH3CH2QNH2 A. I and II B. H and III C. I and III D. Hanle ...
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225Sp08 Test 6 Key - CHEMISTRY 225 TEST #6 JUNE 20, 2003 '...

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