112BMidterm2key2008 - Chemistry 1123: Midterm 2, Tuesday...

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Unformatted text preview: Chemistry 1123: Midterm 2, Tuesday April 15, 2008 Name: @_ U C SID : GS]: Question 1 (18 points) Question 2 (25 points) Question 3 (25 points) Question 4 (8 points) Question 5 (33 points) Question 6 (10 points) Question 7 (36 points) Question 8 (20 points) Total —————————— — --/ 175 points Question 1 (a) Predict 2 possible products of the following reaction (6 points). O—com ow " OMe lily/LO ——> AICI3, CH2CI2 (b) Provide a name for this type of reaction (2 points) :_&1§d§[:€£€{f§_ _é?éf//4/7'.vm (0) Provide a mechanism for the formation of one of the products from Part (a) (10 points). Question 2 (a) Provide a synthesis of B from A. (Hint: the sequence involves a diazotization reaction) (15 points) Multiple 3' NH2 Steps CN _—_> Br Br A B i (M C ’V i. (b) The amino group is normally an ortho/para director. However, in the following nitration reaction, a significant amount of meta product is formed, why? (10 points) 0 h \Lo’ g’o’H NHZ NH2 NH 1/ U HNo3 2 U —______> H2804 Q i . N02 1L N02 51% 47% Gfiflg LL 15/0/1- 1: Jud 9‘” Z c Question 3 (a) Provide a mechanism and transition states that rationalize the stereochemical outcome in the formation of A and B. Label the transition states endo or exo (20 points). Me 0 line” 0 “EneH o / I‘m/[L Diets-Alder I E \ H ———_> H H Me nine Isle A B 4? é; Ky )L H‘ Lin ~ “‘7 fl A l (“do 0 (H gr N€\/v H O H L 7 if“ 1 i W H 6X1) (b) Which is the major product (A or B)? (5 points) A Question 4 Explain with appropriate figures why the following resonance structures are not possible (8 points). —o«bflmls \ M‘l’l/Ufloflal +1) “(fl/vb f ' 1‘: l u 'm an sgz “VH1 am e“ Dr “N 1'" lacsva 9 ' Ami") a» W ‘ a l l (S anHanv‘Aa’ncl go vi ( i “CYlMN | 'Olllll’fll (Sui on? Question 5 (a) Provide mechanisms to explain the formation of A, B and C from D (25 points). \\H / (gr NaNHginNHa / NI"2 / ‘ v ———-——> $0 / HfW Heat / / NH2 Me D Me A Me B C Me (b) Give two reasons why an 8N2 reaction is unlikely to explain the formation of A in part (a). (8 points). limb/1: mm”; mm : «Cb- ’fi/Irdu LL SS‘bby fizzy flu I’lMcCLafll/wu, f0 dafffl 7 Q I ’5 [Mp0 I i i m Villa +— ' . If UL’ @ ‘F’Wb’jflull‘d Quinn M TS m WWW Mame «7 W714 1?er Question 6 (From London; Problem 16.36) (a) The 1H NMR spectrum of the sodium salt of cyclopentadiene (A) consists of a singlet, why? (5 points) H H A M amid/74h; 7e fill MSW-‘7an {WIN/wail e I :H “If eqbeVAUV/lf’ , . (H H H earn/Limth A (b) The methyl group in the following compound (B) has an unusual 1H chemical shift of 5 (—1.67), about 4 ppm lower than the chemical shift of a typical allylic methyl group, why? (5 points) B W sz/ gray/7 ,‘5 l7, 4% ybwwtw/ flyim Id! «fl/L4“ dram/1th 979mm Question 7 Provide a synthesis for E given that it begins With a Diels Alder reaction of A and B. Other steps could include an acid—catalyzed enol hydrolysis of the Diels Alder product (i .e., loss of two equivalents of methanol), a conjugate addition (with a cuprate formed from C) and other steps. Provide reagents and a complete synthesis using additional reactions of carbonyl and aromatic compounds that you have learned. Alternatively, you may also propose a synthesis of E from any starting material six carbons or less. (36 points) 0 MeO \ i OCH3 MeO MgBr Me 0 Mel OMe ‘3 A B C D MeO {441‘d'KAlA/,t fir] (DielS'MM’) MA Mobil/IQ“) E N a /—;- \ A i oCH3 HCiJHLO ll 2 0‘ MC. 0 \ am 0 C + {( M’s/attic ant/4W" ) 0\ Me I 8r M9 0 \, Dido” ) H10 Yaw W H 0W 61° 6 i 1- {Q I x 0 M0 M 0 Am? Question 8 (a) The Vilsmeier reagent can be formed from dimethylformamide (DMF) and oxalyl chloride. Draw a detailed mechanism for the formation of the Vilsmeier reagent (10 points). (Hint: this relies on a lot of the same mechanistic steps as acid chloride formation). CI A 55*“ Vilsmeier reagent (b) Formylations (the addition of an aldehyde) of benzene are not possible using the reactions we have learned so far. Instead the Vilsmeier—Haack reaction (using the Vilsmeier reagent as the electrophile) is employed. Using this information, draw a detailed mechanims for the following formylation (10 points). W 1. Vilsmeier reagent OMe 2. H20 workup OMe ———————> C {K H \ 5') ,‘R‘fL H 0 Gig / WM we | H /6 E) / ‘ ° VQ ‘“‘* C’ ‘ m k 1 0M 4 2 (+10 M 32 N Y .Dm 4—— /@\ ...
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112BMidterm2key2008 - Chemistry 1123: Midterm 2, Tuesday...

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