Exam 1--Fall 2005.pdf

Chemistry 215 Name ___________________________________ First Examination please print clearly please print clearly October 5, 2005 Signature ________________________________ (1.5 hr; 120 points) ID No. _______________________ Put an ?X? here if you are not in Chem 216: _____ Please CHECK OF your laboratory section: 130 T 1-5 PM A636 Chen, Jinhui 131 T 1-5 PM A618 Cychosz, Katie 150 W 12-4 PM A606 Chen, Jinhui 151 W 12-4 PM A612 Norton,Zikiya 152 W 12-4 PM A618 Cychosz, Katie 153 W 1-5 PM A624 Haber, Andrea 170 TH 1-5 PM A606 Feng, Kai 171 TH 1-5 PM A612 Norton, Zikiya 172 TH 1-5 PM A618 Chanowski, Eric 230 T 1-5 PM A624 Chen, Jiumei 231 T 1-5 PM A630 Casey, Ryan 232 T 1-5 PM A612 Feng Kai 252 W 1-5 PM A636 Geisert, Wiliam 270 TH 1-5 PM A630 Casey, Ryan 272 TH 1-5 PM A624 Chen, Jiumei Prob Pts Score GSI I 28 \__ _/ ___ II 23 \__ _/ ___ III 25 \___/ ___ IV 28 \___/ ___ V 16 \___/ ___ Total 120 \__ _/ ___ Please read each question carefuly and answer it completely and clearly. Complete Lewis structures are aceptable for answers unles you are given other specific instructions. Precision in drawing is an important skil in the comunication of organic chemistry concepts. Double-check any thre-dimensional representations to ensure you are implying an unequivocal direction of bonding. Do not forget to include important features such as nonbonding lone electron pairs and formal charges when apropriate. Individual point values are given in the corner of each answer space. The exam has 6 pages in adition to this cover page. A pK a table is on the last page. Name ______ Pg 1 (F.05.215E1p) I. (28 points) Complet the folwing reaction sequencs, including sterochemistry, as required. (a) JOrg Chem 205 70 459 C O H Br Br N H ClrO 3 CH 2 l 2 OOH Ts ! (c) Org Let 205 74095 HO H 8 PCl 3 C H 8 C (d) JOrg Chem 205 70 4865 C Si(CH 3 ) C O H CH 32 CH 22 Br Mg H 3 O 4 4 4 4 4 4 4 Name ______ Pg 2(F.05.215E1p2) I. (23 points) Imidazole (shown below) is ahetrocylic aromatic organic ompound. It is further clsifd a alklid. Ti ring stem is pesnt i imprtant bilgical bilding blocks uh as histidne n histamie. Imidazol ca ct as base (cojuate id pKa = 7.0) and as wek acis (pKa = 14.5). N N H H H H (A) imidazole What is the expectd hybrization of te nitrge atms i iidazole? (a) N H H H H (b)One f the nitrogen atoms i signifcantly more basic than the other; (i) give an example of a cid tat shuld be ble to cmpletl ptnte imidzl, (i) daw th structre f th conjugte cid, an (i) prvide abrif exlatio for the difernce in reactivty btwen the two nitroge toms. an cid t prtnate iidazole conjugate cid of imidazoleexplain difernce in N atoms Although te raction betwen disopryl amine (pK a 35) and sodium hydrie (NaH) gives a cnjat acid whs pK a is arly identicl to that of the ipryl ain, th rection cn be ofidently preicted to g to cmpltio (al te wy t t right) as how below. Briefly xplain this bsrvation. [(CH 3 ) 2 CH] 2 N + NaH[(CH 3 ) 2 CH] 2 Na + H (B) Draw the Lwis tructre for aC 6 O isomer it t foling prortis: (a) l closed shel atoms b l atm uncrged (c) no leclar dipol oent d asigl C-NMR signal (C) 4 4 4 4 4 1 1 Name ______ Pg 3(F.05.215E1p3) I. (25 points) Provide acomplet, step-wise curved arow mechanism for the folwing transformation. You may use HB nd B- for any Brontd aci nd bas tt you ned t use (J O Che 205 70 4863). OH HO C 3 OH Ph C H O acid catlyst O O CH 3 OH Ph H 13 hemiacetal intermediate (i) draw the mechanism through te formation f the miacetal intermediate (i) draw the mechanism through te formation f the product 9 3 O O CH 3 OH Ph H Ph C H O Name ______ Pg 4 F.05.215E1p4 IV. (28 points) When R-2brombutane is treatd with sodium ethoxide (NaOCH 3 ), some of the xpectd S N 2 product is fred log with considerable aount f th tre difernt E2 byproduts. What is the strtre of th S N 2 prduct and what r th strctres of t E2 products. (a) BrH NaOCH 3 CH 3 O S N 2 E2 E2 E2 (b) In aother atempt o cary out he preartion f the dsired product, an S N 1 substiution reaction ws tmptd with R-2btanl, instd. A racemic ixtur f the sbstiution prodct frmd i the S N 2 reaction as oservd, alog with nothr prodct wos moleclar frmula nd NMR carctristis are givn blow. What is te structre f this ther prdut? OH H CH 3 O H 2 SO 4 racemic ixture of the prdct sn i the S N 2, above plus Experimental dat: (a) C 5 H 12 O (b) -NMR shows 2signals (c) H- ignal rtio i 1:3 (i.e, 3:9) (d) C-NR shows 3signals (c) JOrg Chem 205 70 420 O Ph Ph H Ph PhCH 2 N 2 140?C intaly formed intermediate product, after potn transfers 4 4 4 4 4 4 4 Name ______ Pg 5 F05.215E1p5 V. (21 points) Prvide the structres a caled for by the dscriptions. (a) JOrg Chem 205 70 4695 Cl HO O CH 3 1) excs NaH 2) H 3 O OH O O O CH 3 + Cl HO O CH 3 NaH deprotnation intramolecular substiutin conjugate base f phnol (PhOH) O HO O CH 3 H 3 O protnation nucleophilc rig openig (b) JOrg Chem 205 70 459 OO H 2 NH 2 Experimental dat (a) C 9 H 14 N 2 (b) 5-MR signals (c) 3H-N il + 2H 2 O 4 4 4 4 5 bcoppola1 Microsoft Word - 215E1.1.doc