O'connor 140B midterm

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

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Unformatted text preview: CHEMISTRY 140B NAME (please print) FIRST SIGNATURE ID NUMBER MIDTERM EXAM 1 LAST AUG 20, 2007 (VOLLHARDT 5 TH ED , CP 10-12) 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. 2. 3. 4. 30 20 25 25 _____ _____ _____ _____ _____________________________________ Total 100 _____ _____________________________________ H Li Na K Rb Cs Be B Mg Al Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Ba La Hf Ta W Re Os Ir Pt Au Hg Tl He C N O F Ne Si P S Cl Ar Ge As Se Br Kr Sn Sb Te I Xe Pb Bi Po At Rn NAME:________________________________ 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 Cl Br H C H C Cl Br Br H C H Br Cl Br C 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. H HO HO Br H S O S H O (assume a pure sample) 1c. (6 pts) On the line provided indicate the number of singlets expected in the 13C NMR spectrum (the hydrogen-coupled spectrum) for the two molecules shown below. O MeO Cl Br O 2 NAME:________________________________ 2. (20 pts) Shown below is the 1 H NMR spectrum for a compound of molecular formula C4 H8 O. The relative number of hydrogens (based on the integration) for each resonance are indicated on the spectrum. i) ii) iii) (1 pt) How many degrees of unsaturation are there for this molecule? ______ (1 pt) How many different hydrogen environments are there for this molecule? ______ (7 pts) In the box provided draw the structure for this compound. iv) v) (2 pts) How many carbon resonances are expected in the 13C NMR spectrum of this molecule? ______ (9 pts) In your structure clearly label the hydrogens which give rise to resonances A, B, and C in the spectrum. 3 NAME:________________________________ 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) O Me Me O O H H Me O O Me + H O C H ii) Cl H Me H H H + OEt + + HOEt Cl iii) RH O H CO2H O O R O + iv) Cl C Cl Cl 3b. Cl C Cl + Cl (5 pts) Is 1-methylcyclohexene more stable than methylenecyclohexane (A)? ______ Is 1-methyl-cyclopropene more stable than methylenecyclopropane (B)? _______ A B 4 NAME:________________________________ 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. a) (3 pts) Et Me H2 Pt b) (3 pts) KOBut OTs tBuOH c) (3 pts) cat. H+ d) (3 pts) 1) 1 equiv BH3 2) HOOH HO e) (3 pts) Br2 excess NaN3 5 NAME:________________________________ 4b. (10 pts) For each transformation shown below, indicate the reactions that are required to generate the indicated product. You need not show mechanisms, but show all reagents and give the structure of the product for each reaction that you employ. a) (5 pts) O b) (5 pts) OH OH OH 6 NAME:________________________________ Typical Hydrogen Chemical Shifts in Organic Molecules Type of Hydrogen (in itallics) Chemical Shift d in ppm Primary alkyl, RCH 3 0.8 1.0 Secondary alkyl, RCH 2 R' 1.2 - 1.4 Tertiary alkyl, R3 CH 1.4 1.7 Allylic, R2 C=C(R')CH 3 1.6-1.9 Benzylic, ArCH2 R 2.2 2.5 Ketone, RC(=O)CH3 2.1 2.6 Alkyne, RCCH 1.7 3.1 Chloroalkane, RCH 2 Cl 3.6 3.8 Bromoalkane, RCH 2 Br 3.4 3.6 Iodoalkane, RCH2 I 3.1 3.3 Ether, RCH2 OR' 3.3 3.9 Alcohol, RCH 2 OH 3.3 4.0 Terminal alkene, R2 C=CH 2 4.6 5.0 Internal alkene, R2 C=CHR' 5.2 5.7 Aromatic, ArH 6.0 9.5 Aldehyde, RC(=O)H 9.5 9.9 Alcoholic hydroxy, ROH 0.5 5.0 Thiol, RSH 0.5 5.0 Amine, RNH2 0.5 5.0 Coupling Constants Around a Double Bond Type of Coupling Name J Range (Hz) H H Vicinal, cis 6 - 14 C C Typical J (Hz) 10 16 2 6 H C H C C H Vicinal, trans Geminal None 11-18 0-3 4 - 10 C H C H C H C C H C C H H C C H C C Allylic (1,3-cis or trans) 1,4 or long range Aromatic Meta (4-bond Coupling) 0.5 3.0 0.0 1.6 1.2 3.1 2 1 2 H R H 7 NAME:________________________________ 8 CHEMISTRY 140B NAME (please print) FIRST SIGNATURE ID NUMBER MIDTERM EXAM 2 LAST SEPT 4, 2007 (VOLLHARDT 5 TH ED , CP 13-16) 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 7 pages (including this one; page 7 is blank for your scratch work). - Answer only in the space provided. Do not write answers on the back of a page. _____________________________________ Question Points Score _____________________________________ 1. 2. 3. 30 40 30 _____ _____ _____ _____________________________________ Total 100 _____ _____________________________________ H Li Na K Rb Cs Be B Mg Al Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Ba La Hf Ta W Re Os Ir Pt Au Hg Tl He C N O F Ne Si P S Cl Ar Ge As Se Br Kr Sn Sb Te I Xe Pb Bi Po At Rn NAME:________________________________ 1a. (6 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 O O H (assume a pure sample) 1b. (21 pts) Indicate on the lines provided whether the following statements are true (T) or false (F). (i) Both E- and Z-haloalkenes (e.g. cis- and trans-RCH=CBrR) eliminate with base to give an alkyne. ______ (ii) Alkynyl and alkenyl Grignard reagents (e.g. RC CMgBr and RCH=CHMgBr, respectively) participate in SN2 reactions with primary alkyl halides. ______ (iii) (iv) SN2 reactions of allylic halides with good nucleophiles are faster than those of the corresponding saturated haloalkanes. ______ In Friedel-Crafts alkylation, Lewis acid catalysts are used to enhance the nucleophilic power of the alkyl halide. ______ Enol-keto tautomerization is a key transformation in the Hg catalyzed hydration of alkynes, the hydrobromination of alkynes, and the hydroboration-oxidation of alkynes. ______ The Diels-Alder reaction involves the s-cis conformation of 1,3-butadiene even though the s-cis conformataion is less stable than the s-trans conformation. ______ UV-Vis spectroscopy tells us about the extent of delocalization in an extended pisystem, with a decrease in l max as the delocalization increases in a series of compounds. ______ 2+ (v) (vi) (vii) 1c. (3 pts) List the three limitations of Friedel-Crafts alkylation: 1. 2. 3. 2 NAME:________________________________ 2a. (12 pts) For each of the following one step transformations show the movement of electrons by using the standard curved arrow notation. Show all formal charges for each structure on the left and right of the reaction arrow. a) H Br Br b) CN CN c) H + Br Br FeBr3 H Br d) MeO2C H MeO2C + 3 NAME:________________________________ 2b. (18 pts) Circle each of the following structures that exhibit aromatic character and place a box around any structures that are not aromatic (i.e. either non-aromatic or antiaromatic). H (a) P CH3 (f) (b) B H (g) O N (c) (h) 2c. (10 pts) For each of the following compounds, circle the ones which will exhibit a p to p* excitation in the UV-vis spectrum and place a box around any that would not exhibit a p to p* excitation in the UV-vis spectrum. Finally, write "longest" under the structure that would exhibit the longest wavelength l max. H3C O O OH H2C CH3 CH3 4 NAME:________________________________ 3. (30 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. a) (3 pts) O 1. 2. EtMgBr 3. H+, H2O D b) (3 pts) O Me Et Zn/Hg Heat, HCl c) (3 pts) EtCCH Na NH3(l) d) (3 pts) NC + NC D e) (3 pts) HNO3 O 2N H2SO4 5 NAME:________________________________ f) (3 pts) Li O g) (3 pts) NBS hn, CCl4 h) (3 pts) HBr heat i) (3 pts) nPrBr MeO AlBr3 j) (3 pts) 1. Mg Cl 2. D2O 6 NAME:________________________________ 7 To pick up your graded exam from a box outside 5100A Pacific Hall sign here: ________________________________ CHEMISTRY 140B FINAL EXAM SEPT 7, 2007 NAME (please print) FIRST LAST SIGNATURE ID NUMBER LAST NAME OF PERSON SEATED IN FRONT OF YOU: LAST NAME OF PERSON SEATED BEHIND YOU: DO NOT OPEN THE EXAM UNTIL YOU ARE TOLD TO DO SO. - Please sign your name on the top of each page. Please check to see that you have 10 pages (including this one). The one blank page may be used for scratch work, but DO NOT use the scratch page for answers. Answer in the space provided. Do not write answers on the back of a page. Question Points Score _________________________________________ 1. 2. 3. 4. 65 45 50 40 _____ _____ _____ _____ __________________________________________ Total 200 _____ __________________________________________ H Li Na K Rb Cs Be B Mg Al Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Ba La Hf Ta W Re Os Ir Pt Au Hg Tl He C N O F Ne Si P S Cl Ar Ge As Se Br Kr Sn Sb Te I Xe Pb Bi Po At Rn NAME:__________________________ 1a. (20 pts) For each of the following interconversions indicate if K > 1, K = 1, or K > 1, by circling the correct answer. K is the equilibrium constant. i) OH H+ K>1 O K=1 K<1 ii) H+ K>1 K=1 K<1 iii) HBr H Br K>1 K=1 K<1 iv) O Cl3C v) H2O H HO OH H CCl3 K>1 K=1 K<1 O H OH H OH- O 2 H K>1 K=1 K<1 1b. (15 pts) Indicate on the lines provided whether the following statements are true (T) or false (F). (i) (ii) (iii) Alkynyl Grignard reagents (e.g. RCCMgBr) participate in SN2 reactions with secondary alkyl halides. ______ In Friedel-Crafts alkylation, Lewis acid catalysts are used to enhance the electrophilicity of the alkyl halide. ______ Aldehydes are readily converted (by a single reaction in some cases followed by aqueous acid work-up) to a variety of functional groups including alcohols, carboxylic acids, hydrates, hemiacetals, acetals, and alkenes. ______ UV-Vis spectroscopy tells us about the extent of delocalization in an extended pi-system, with a decrease in lmax as the delocalization increases in a series of compounds. ______ The thermodynamic stability of ketones is typically greater than that of aldehydes. _______ (iv) (v) 2 NAME:__________________________ 1c. (15 pts) Shown below are three sets of four structures. Within each set of structures, list the compounds in order of increasing acidity. OH OH OH OH < CH3 A OMe B CF3 C D < < HO H O O C R A B O H < D < < < A B C D < < 1d. (15 pts) Show three different types of bromination reactions that meet the requirements indicated below. Give starting materials, reagents, and products. You need not show mechanism. Be sure to clearly indicate regiochemistry. i) (a substitution reaction) ii) (an addition reaction that involves free radical intermediates) iii) (an addition reaction that involves ionic (charged) intermediates) 3 NAME:__________________________ 2a. (20 pts) Provide an efficient synthesis for each of the following compounds from the indicated starting materials. Do not show mechanisms. Give the product structure for each of the reactions that you employ. i) O H Br ? H O OH ii) OH ? O O 4 NAME:__________________________ 2b. (25 pts) In the boxes provided, draw the structure of the starting material need for each of the following transformations. a) H+ - H2O b) O O H N Me Me pH 4.8 - H2O Me Me N c) O Me OLi Me Me Me Et d) Et H2NNH2 OH-, D NH2 e) cat. OH- H Me OH H O 5 NAME:__________________________ 3. (50 pt) 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. a) O 1. D 2. MeMgBr 3. H+, H2O b) O Me Br2 FeBr3 c) EtCCH Na NH3(l) d) NC + NC D e) OHOH O D 6 NAME:__________________________ f) Li O g) OH H+ O OH h) O CH2PPh3 i) NMe2 nPrBr j) Mg Cl 7 NAME:__________________________ 4a. (20 pts) For each of the following one step transformations show the movement of electrons by using the standard curved arrow notation. Show all formal charges for each structure on the left and right of the reaction arrow. a) Et O O O O b) O PPh3 O PPh3 c) O O O O d) Me MeO O N O O H O N O e) N Me Me N Me Me NH2 O H H N H O H 8 NAME:__________________________ 4b. (10 pts) Draw a reaction coordinate diagram for the reaction of benzene with D2SO4 to give C6H5D. Clearly show the relative energy levels for starting materials, products, all intermediates, and all transtion states. Label each intermediate as "I" and each transtion state as "TS". E reaction coordinate (6 pts) Draw all the resonance structures for each intermediate in the above diagram. (4 pts) Would the related reaction of nitrobenzene give an intermediate(s) of lower or higher energy than in the above reaction? 9 NAME:__________________________ 10 ...
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This note was uploaded on 10/17/2008 for the course CHEM 140B taught by Professor Nefzi during the Fall '06 term at UCSD.

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