CHEM 2402 Midterm 1 Answers

@leotn* @l,uc/ Your student number: Your lab day and time (a.m. or P.m.): Mid-Term Test DALHOUSIE yrglYFs$lT_y Chemistry 2402 ,2014 12 February {rt *ft i t"i.trg &4i nd-s 1 D. J. Burnell (50 minutes) Read the questions completely and carefully. Answer all the questions on these sheets. This test marked out of 40. will be I explain why the major IIZ marksl. Draw the complete mechanism for the nitration of anisole, and products are the ortho- andpara-products. euestion OCH. ocH d l" ,,\ HN03, H2SOa V Noz Generation of tre electrophile: P)? H_O-Nlt o Hra + ocH3 HO ,5.1qi Ho HO € u_---+ ffi: @ H NO2 (b*r, )A._ -,,to, [..-)-H <'-> tertiary ocH3 tu; X: is any species with a lone pair that can assist with the removal of H*. 1n tnis case it would be wata.) CgcH, t?t" ocH3 ,\ I )*o, nitonium ion O ,,\ * [,\-H @ NOz A >aY <...._> t" A A € H NOz H tertiary charge on €?t*' ocH" oba H NO2 O Noz ?"" a Noz para X: ?c" ?cH, q).I":*,OX* o*o' charge on O gcH. gcH. I 'd,*-#r, NOz NOz I _l are much favored over meta since the intermediates are lower energy / more stable, i.e., the intermediates for para and ortho form more quickly than for meta. The intermediates for the para and ortho reactions are stabilized by four resonance structures, including a tertiary carbocation and a cation on oxygen. ln contrast, the meta reaction's intermediate is stabilized by three resonance structures that are all just secondary carbocations. Para and ortho 1600 .3200 3500 .t -0t .27s0 2900 -2700 2300 -2200 O-H (alcohol) G-H (alcohol) N_H O-H (acid) C-H (sp-carbon) C-H (sp2-carbon) C-H (sp3-carbon) C-H (aldehyde) C=N strong.-\.r0. one or two peaks 2250 -2100 C=C C=O C=C weak .o0 -t.3000 3000 .3200 3300 . broad. sharp medium medium medium./^__\ " I \_0.00 tll 1a00 ln6 glHgltm 2200 & l.1540 1300 .2J.t -0t -oJ -tJ - .a4 T T \s41'2fT? - I lt ir l5 16 tt rale .2800 33s0 -32s0 3200 . Which structure belongs to spectrum A and which structure belongs to spectrum B? (Make sure your answers are clear. These are labelled A and B. 0!l . These belong to two of six structures drawn below.t loe o o -[t 3 -0r s -0. \\ .0 2s ttI I al I tlm /1'* | -0-t I 1 -02 no C=O -0: -Ort -o. a3!o ro0o rao aas lam ril s 2t00 2t00 e.0€ v.7 ! -0J -m { 0ll aro {. two peaks weak stong medium medium weak medium c{l c-o stong stong C-Br strong -0.0 tpo 300 e0 80 il00 22m e0 r&o I lt00 YAYEXT'SIBS ro ltl t20o lm i! -eo a6 Table of typical IR absorptions Wavenumber (cm-l) Bond Typical intensity 37s0 .00 ta !0@ l: s tm It 310 . Here are two infrared specta. 2.1660 . sharp for free OH strong.o? 11 7.) A: .10s0 1780 1680 1650 750 630 - 650 550 C=N C=C (aromatic) N=O (nifto) strong extremely broad medium.1580 r6t0 .3500 3500 . broad for H-bonded OH medium.E -0.Question 2 [6 marks].?. 7s + zJ ?ll a'c? {t5 I $cioLs tl I T tl tl t6 r0 rr rrf.n6 so ao 3..a0 aa6 ar6 .t -0.1600 1570 . li /_\ s _. --. ether -"-ocH3 H 2. 'o wca' IH H.-_. "tt-t I H I It... O O ------> 2. Hrfo* *. Devise synthetic sequences to carry out the following tansformations.r"''0to" . racemic m-CPBA .3 uestion [6 marks]. that have intermediates of all the structures and draw on rurows... H*.. H. H...* X. Mechanisms are not required!) euestion 4 CH"-OH : (/"'".. H2SOa (sulfonylation) ."* " (..-n 1.."O alkylationl (ortho-para directoQ conc. LiAlHa. Indicate reagents and conditiorrs significant lifetimes.. *ro OH c(H (by-product) (More than one [6 marks]. H*.!ocH3 --+ --+ f H \H H 'lo 'lo H*AI-H + I H HocH3 ..Al- oocH.... i"p * requirea."D-to" cHel'Alclg (Friedel-Crafts cftMsBr' (Sp2 attack to open epoxide) (epoxidation) B' 1' ' *. What is the mechanism of this reaction? 'ilo -l OH l.'H lJr c....llr o')- o") 11*i-ocH3 llc. H2O A of -.. t. (C-C bond formation with organocuprate) 1. G.HzO H.D _ ? (iodination . (benzylic J.Question 5 [10 marks]. -? (oxidation of alcohol) \. H.Br -1--\ . Noz o E 1. H*. ether 3. excess CH3MgBr. A. HCI ? (Friedel-Crafts acylation then reduction) Br Br2. - 3. H2O (reduction of aldehyde) rOH F. NaOCl.Z bromination) PBr3. D. . H20 (double addition of organomagnesium to acid chloride) c. reagents/conditions and products. B. H242. pyridine (Sr'r2) \ . o HzSO+ . (cHgcHz)zcu\i. CH3OH -^-^* AtoH 2.l-. CH3CO2H -l-=. Oa-t' Jo . NaBHa. CH3CH2-C-Cl .electroRh$c aromatic substitution) 1. AlCl3 Z. Provide the missing starting compounds. Zn(Hg). H*.OH t: t- hv To \A.C CH" O ? ^x". 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