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# 11-16 - An unknown has a formula of C4H8O2 an infrared...

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Unformatted text preview: 11/17/2009 An unknown has a formula of C4H8O2, an infrared spectrum that has a very strong absorption at 1742 cm-1 but shows no OH and the 1H NMR spectrum shown below. What is the structure of the unknown compound? Choose the structure of a compound with the formula C4H8O2 an infrared spectrum that has a very strong absorption at 1742 cm-1 but shows no OH and the following nmr spectrum. O A. D. HO O OH H B. B. E. HO O O O C. O O O 3 3 peak areas = 2 F. 3 H C H O H C H H C H H H 3 H C H H C H H peak areas = 2 1 2 Review: Review: Jbc = 1.67 Hz c b c b c c c c Jab a Jab a Jac Ha Ha Hb Hb Jab = 15.5 Hz Jac = 6.85 Hz Jab Jab = 15.5 Hz Jac = 6.85 Hz Jab Jbc ? 8 8 7 7 6 6 5 5 4 4 PPM 3 PPM ( ) 3 2 2 1 1 0 0 8 8 7 7 6 6 5 5 4 4 PPM 3 PPM ( ) 3 2 2 1 1 0 0 How many lines would be observed if Jab ~ Jac? Choose the major product of the following reaction. H O c b H O H H Br Br H H O H H or H H H H Br O O H H H H O Jab Jac c c Jab ~ Jac H H C H H O C H A H H B H H C H H C H H C H H C H H a Ha A. 2 B. 3 C. 4 D. 5 E. 6 F. 8 5 4 3 PPM ( ) 2 1 0 1 11/17/2009 Predict the 1H NMR spectrum for compound B. s = singlet, d = doublet, t = triplet, q = quartet singlet, H Br O H O H H H Predict the 1H NMR spectrum for compound B. A 1H s 3H q B 1H d 3H q C 1H q 3H d D 3H q 1H s E 3H d 3H s F 3H s 3H s 5 4 3 PPM 2 H H H H H H H H Br O O H H H H B B H 1 0 5 4 3 PPM 2 1 0 Choose the major product of the following reaction. H O What is a probable mechanism of this reaction? H O 1 O O H O Br Br H Br H H O H O H H H H or H H H H O Br O H H H H H O H O O H Br Br O O 2 O H O A H B Br O O O O Br Br O O H H H O O Which atom is more basic, C=C or O? Why? H Mass Spectroscopy M energy accelerate Which path would be predicted to be more favorable? H H C H + O C H C H H e +· M +· electric field magnetic field H H heavy ions C H O C H C H H e- O H H C H C H C H A m/z = 58 m/z = 43 H O 43 fragmentation of the radical cation often occurs light light ions 58 B O H H C H C+ C H C H H C H H 14 14 H m2+ m1+· M+· (parent ion) 13 15 m/z = 15 2 11/17/2009 Mass Spectroscopy MM MMM MM condensed phase M gas phase M+· molecular ion Mass spectroscopy has recently been applied to large molecules such as peptides and even proteins. m2+,m1+· fragments trypsin digestion M MALDI unknown protein peptide fragments (solution) gas phase for MS? (Matrix-assisted laser desorption/ionization) 15 Mass spectroscopy has recently been applied to large molecules such as peptides and even proteins. Mass spectroscopy has recently been applied to large molecules such as peptides and even proteins. trypsin digestion MALDI unknown protein peptide fragments (frozen matrix) gas phase peptide for MS What is the major product of the following reaction. Why is B the major product of this reaction? H H RO Br OR Br H H H or H H Br H H H RO Br OR H Br H H H or H H Br H H A 2 2 B Br H Br A H H or B 5 H 8 7 6 5 4 PPM ( ) 3 2 1 0 3 11/17/2009 Why is B the major product of this reaction? RO OR RO + OR H Br RO H + Br Br Br or H H H Why is this called a free radical chain mechanism? RO RO OR +H Br RO + RO OR H + H Br RO Br initiation H + Br H H RO Br OR Br H H H H H + Br + Br H A Br or B Br Br Br +H Br Br + Br propagation Br H Br + Br Br termination Why is this called a free radical chain mechanism? RO +H Br RO H + Br H Br Br initiation + propagation H Br Br Br Br + Br Br termination How are organo halogen compounds prepared? C C + H How are organo halogen compounds prepared? C C Cl Cl H C Cl C O H H C OH OH C + Cl + Cl Cl Cl Cl Cl Cl C + Cl Cl +H Cl Cl C H+ Cl Cl 27 Cl Cl Cl Cl C +H Cl Cl C H+ Cl Cl 28 4 11/17/2009 What is the reaction mechanism for free radical halogenation? How are the bonds being made and broken? Where did the Cl  come from? C H+ Cl Cl C +H Cl Cl C H+ Cl Cl C +H Cl Cl propagation C + Cl Cl Cl Cl C Cl propagation C + Cl Cl Cl Cl C Cl + Cl Cl + Cl Cl Cl Cl Cl Cl h or light Cl Cl + Cl Cl initiation 29 30 Which of the following reactions will terminate the free radical chain? A H H H C H+ Cl H H H C +H Cl What happens when two radicals in this mechanism react with each other? C H+ Cl Cl C +H Cl Cl B Cl Cl 2 Cl propagation H H C + Cl Cl H H C Cl + Cl H C H H D H C + Cl H H C Cl C + Cl Cl Cl Cl C Cl + Cl Cl H H Cl Cl h or light Cl + Cl initiation C +C C C termination C+ Cl Cl C Cl 32 Cl Cl Cl Cl h or light Cl Cl + Cl Cl initiation C H+ Cl Cl C +H Cl Cl propagation C + Cl Cl Cl Cl C Cl + Cl Cl C +C C C termination Chlorination. An example of a free radical chain reaction mechanism. 33 5 ...
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