11-20 - 11/20/2009 2 hydrogens are 3.5 times more reactive...

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Unformatted text preview: 11/20/2009 2 hydrogens are 3.5 times more reactive than 1 hydrogens. 400 kJ/mol H C C C C H H H H 2 hydrogens are 3.5 times more reactive than 1 hydrogens. 400 kJ/mol H C C C C H H H H 413 kJ/mol C C C H H H 421 kJ/mol C H C H H H 413 kJ/mol C C C H H H 421 kJ/mol C H C H H H 3° 2° 1° 3° 2° 1° Predict the major product of the following reaction. Predict the major product of the following reaction. 4  3.5 14 6 statistical 6 predicted 70% 30% predicted 2 1 2 hydrogens are 3.5 times more reactive than 1 hydrogens. 400 kJ/mol H C C C C H H H H 413 kJ/mol C C C H H H 421 kJ/mol C H C H H H In addition to many other compounds, four isomers with the formula C3H6Cl2 are produced in the following reaction. 3° CH3 H3C C CH3 H + Cl2 initiator 2° CH3 H3C C CH3 Cl + 1° CH3 H3C C H2C H Cl + H reactivity 37 63 /9 3° 1° 5 Cl Cl Cl Cl Cl Cl Cl Cl Cl Cl Cl 37% 63% Predict the major product of the following reaction. A. A. Very sure this is true B. B. Somewhat sure this is true C. Maybe this is true D. Maybe this is false E. Somewhat sure this is false F. Very sure this is false 4 70% 30% predicted 3 What is the selectivity of bromination in this reaction? 400 kJ/mol H C C C C H H H H What is the mechanism of these reactions? CH3 H3C C CH3 CH3 H3C C + Cl H+ 421 kJ/mol C C H H H 400 kJ/mol Cl H3C CH3 C CH3 CH3 H3C C CH3 432 kJ/mol Cl +H H° = 400  432 = -32 kJ/mol 243 kJ/mol Cl 349 kJ/mol Cl + Cl H° = 243  349 = -106 kJ/mol reactivity 3° 1° 5 1 3° CH3 H3C C CH3 H + Cl2 initiator CH3 H3C C CH3 Cl + 1° CH3 H3C C H2C H Cl + H 3° reactivity 1° Cl CH3 CH3 H3C C CH3 H + Cl2 37(9) 63 5 initiator CH3 H3C C CH3 Cl + H3C CH3 C H2C H Cl + H Cl 37 63 /9 37% 63% 37% 63% Is the first step exothermic? CH3 H3C C CH3 H + Br2 initiator CH3 H3C C CH3 Br + H3C CH3 C H2C H Br 5 A. yes B. no + H Br 99.4(9) 1600 0.6 6 99.4% 0.6% 1 11/20/2009 What is the CH3 H3C C CH3 CH3 H3C C + Cl H+ Cl H for the overall reaction? CH3 H3C C CH3 CH3 H3C C CH3 CH3 H3C C CH3 Cl + H3C CH3 C H2C H Cl + H Cl 400 kJ/mol 432 kJ/mol Cl What is the difference in CH3 H3C C CH3 H+ 400 kJ/mol Cl H3C +H H° = 400  432 = -32 kJ/mol CH3 C CH3 432 kJ/mol Cl H° of the first two steps? H° = 400  432 = -32 kJ/mol +H 243 kJ/mol Cl 349 kJ/mol Cl + Cl H° = 243  349 = -106 kJ/mol CH3 H3C C H2C CH3 H3C C CH3 H + H+ H 421 kJ/mol Cl H3C CH3 432 kJ/mol C H2C CH3 H3C C CH3 Cl + H +H Cl H° = 421  432 = -11 kJ/mol CH3 CH3 H3C C CH3 H + Cl2 initiator Cl2 initiator CH3 H3C C H2C H Cl + H Cl energy C H Cl C H Cl energy C H Cl C H Cl H° = 21 kJ/mol H° = -138 kJ/mol reaction 7 reaction 8 What is the reactivity of 3to 1 if CH3 H3C C CH3 CH3 H3C C H2C H+ H H+ 400 kJ/mol Cl H3C CH3 C CH3 432 kJ/mol Cl H* = 21 kJ/mol? H° = 400  432 = -32 kJ/mol Why isn't chlorination more selective? CH3 H3C C CH3 CH3 H3C C H2C H+ H H+ 400 kJ/mol Cl H3C CH3 C CH3 432 kJ/mol Cl +H 3/ 1 H° = 421  432 = -11A = kJ/mol +H H° = 400  432 = -32 kJ/mol 421 kJ/mol Cl H3C CH3 432 kJ/mol C H2C CH3 H +H Cl 1 5 50 500 5000 5000 421 kJ/mol Cl H3C CH3 432 kJ/mol C H2C H +H Cl H° = 421  432 = -11 kJ/mol B= C= D= E= CH3 H3C C H2C H H3C C CH3 C H C H Cl Cl C H Cl 3° 1° 5 1 energy C H Cl C H Cl energy H* = 21 kJ/mol transition state theory (Ch 6) Keq = 1021/5.7 = 103.7 5000 C H Cl C H Cl H° = 21 kJ/mol H° = 21 kJ/mol reaction 9 reaction 10 For a reactivity ratio of 5/1 what is the approximate CH3 H3C C CH3 CH3 H3C C H2C H+ H H+ 400 kJ/mol Cl H3C CH3 C CH3 432 kJ/mol Cl H*? Is the first step of bromination exothermic? CH3 H3C C CH3 H+ 400 kJ/mol Cl H3C +H H° = 400  432 = -32 kJ/mol CH3 C CH3 432 kJ/mol Cl CH3 C CH3 CH3 C H2C H+ H H+ 400 kJ/mol Br H3C CH3 C CH3 366 kJ/mol +H Br +H H3C 421 kJ/mol Cl H3C CH3 432 kJ/mol C H2C H +H Cl H° = 421  432 = -11 kJ/mol CH3 H3C C H2C H+ H 421 kJ/mol Cl H3C CH3 432 kJ/mol C H2C H +H Cl H3C 421 kJ/mol Br H3C CH3 C H2C 366 kJ/mol H +H Br C H C H Cl Cl C H Cl H* = ? Keq = 10 ?/5.7 Keq = 10?/5.7 5 5 Keq = 104/5.7 A ~4 B ~ 40 energy C H C H Cl Cl C H Cl 3° 1° 5 1 C H Br C H Br Br C H Br 3° 1° 1600 1 H° = +55 kJ/mol energy energy C ~400 D ~0 E ~-8 F ~-80 C C H Br H Br C H Cl C H Cl C H Cl C H Cl H° = +34 kJ/mol H° = 21 kJ/mol reaction reaction reaction 12 2 11/20/2009 Why is the H* for bromination larger than that for chlorination? Hammond's postulate The transition state for an exothermic step resembles the reactants. The transition state for an endothermic step resembles the products. Hammond's postulate C H C H H* = 4 kJ/mol C H Br H* = 18 kJ/mol C H Br Br C H Br Hammond's postulate C H Cl Cl C H Cl C H C H C energy energy energy C C H Br H Br H C H energy C H Cl C H Cl C H C H energy C H H° = 21 kJ/mol reaction H° = 21 kJ/mol reaction 13 reaction reaction reaction 14 The addition of H-Br to 1-butene in the presence of peroxides gives 1-bromobutane. Give a mechanism for this reaction consistent with this observation. The The addition of H-Br to 1-butene in the presence of peroxides gives 1-bromobutane. Give a mechanism for this reaction consistent with this observation. Predict the major products of the following initiation reaction. ? A. 1 + 3 B. 2 + 4 C. 2 + 3 D. 3 + 4 E. 1 + 4 15 Predict Predict the major product, A or B, of the following reaction. The The addition of H-Br to 1-butene in the presence of peroxides gives 1-bromobutane. Give a mechanism for this reaction consistent with this observation. initiation initiation initiation A B A B 17 18 3 11/20/2009 The addition of H-Br to 1-butene in the presence of The peroxides gives 1-bromobutane. Give a mechanism for this reaction consistent with this observation. Organic bromides are easily reduced using tri n-butyl tin hydride in a free radical chain process. initiation initiation -Bu3 Sn H = Sn H propagation termination 19 20 What is the mechanism of this reaction? What is the mechanism of this reaction? What is the initiation step in this reaction mechanism? What are the two propagation steps in this reaction mechanism? initiation review: H H C H H H C H + Cl Cl H H + Cl H H C H H C H Cl + Cl + H Cl propagation What is the mechanism of this reaction? What is the mechanism of this reaction? What are the reactants of last propagation step in this reaction mechanism? initiation H propagation + -Bu3 Sn A. 1 + 3 B. 2 + 4 C. 2 + 3 D. 3 + 4 E. 1 + 4 4 11/20/2009 Predict the major product for the following reaction. F3C I + Predict the major product of the following reaction. h + F3C F3C F3C F3C I ? I F3C I CF3 I CF3 F3C I A B C D 26 Propose a mechanism consistent with the following reaction. Choose the weakest C-H bond in linoleic acid. F3C F3C F3C + I F3C 27 28 29 5 ...
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This note was uploaded on 12/25/2009 for the course CHE 320 taught by Professor Ff during the Spring '09 term at SUNY Stony Brook.

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