O'connor 140B midterm

O'connor 140B midterm - CHEMISTRY 140B NAME(please print...

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CHEMISTRY 140B NAME (please print) MIDTERM EXAM 1 FIRST LAST A UG 20, 2007 (V OLLHARDT 5 TH E D , C P 10-12) SIGNATURE ID NUMBER LAST NAME OF PERSON SEATED TO YOUR RIGHT : LAST NAME OF PERSON SEATED TO YOUR LEFT : DO NOT OPEN THE EXAM UNTIL YOU ARE TOLD TO DO SO . - Please sign your name on the top of pages 1 through 6. - Please check that you have 8 pages (including this one; page 8 is blank for your scratch work). Page 7 contain tables of NMR data. - Answer only in the space provided. Do not write answers on the back of a page. _____________________________________ Question Points Score _____________________________________ 1. 30 _____ 2. 20 _____ 3. 25 _____ 4. 25 _____ _____________________________________ Total 100 _____ _____________________________________ H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn
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NAME:________________________________ 2 1a. (16 pts) On the lines provided indicate the number of hydrogen and carbon environments for each molecule (assume all spectra are recorded at room temperature): O O H C H C H C H C Br Cl Cl Br Br Cl Br Br 1b. (8 pts) On the line provided indicate the number of doublets expected in the 1 H NMR spectrum of each molecule. Assume that hydrogens in two different environments will exhibit different coupling constants to hydrogens in a third environment. Also assume that allylic and geminal couplings will be observable. HO HO (assume a pure sample) Br S S O O H H H 1c. (6 pts) On the line provided indicate the number of singlets expected in the 13 C NMR spectrum (the hydrogen-coupled spectrum) for the two molecules shown below. MeO O O Cl Br
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NAME:________________________________ 3 2. (20 pts) Shown below is the 1 H NMR spectrum for a compound of molecular formula C 4 H 8 O. The relative number of hydrogens (based on the integration) for each resonance are indicated on the spectrum. i) ( 1 pt ) How many degrees of unsaturation are there for this molecule? ______ ii) ( 1 pt ) How many different hydrogen environments are there for this molecule? ______ iii) ( 7 pts ) In the box provided draw the structure for this compound. iv) ( 2 pts ) How many carbon resonances are expected in the 13 C NMR spectrum of this molecule? ______ v) ( 9 pts ) In your structure clearly label the hydrogens which give rise to resonances A, B, and C in the spectrum.
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NAME:________________________________ 4 3a. (20 pts) For each of the following one-step transformations, use curved-arrow notation (electron pushing) to show the movement of electrons. Show all formal charges. i) ii) HOEt + + + H H Me Me OEt Me H Cl Cl H H H O O O O Me Me + C H H O O iii) R H O H O O O R + CO 2 H iv) + C Cl Cl Cl Cl C Cl Cl 3b. ( 5 pts ) Is 1-methylcyclohexene more stable than methylenecyclohexane ( A )? ______ Is 1-methyl-cyclopropene more stable than methylenecyclopropane ( B )? _______ A B
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NAME:________________________________ 5 4a. ( 15 pts) Predict the major product(s) for each of the following reactions. Write " NO REACTION " where appropriate. Show stereochemistry where appropriate. Assume all chiral starting compounds are optically pure (a single enantiomer). For any product that exists as a racemic mixture write “plus enantiomer” under your product structure.
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