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Unformatted text preview: 11/16/2010 In a 10g sample of rapamycin approximately how many grams would have a 13C at the indicated methyl group?
HO HO O What would the size of 13C 1H coupling constants compared to the 1H 1H coupling constants be for the following methyl group ? A. Larger HO HO B. Smaller
O Natural Natural abundance of
N O OH OH O O O O O OH O 13C 12C = 1%
N O O O O OH O Most carbon, 99%, is O O A. 0.01 g C. 1.0 g B. 0.1 g D. 5 g OH OH O O O O Most Most 13C spectra are recorded using proton decoupling so that carbon atoms appear as single lines. rapamycin
C51H79NO13 What are the maximum number of adsorptions that could be observed for the 13C spectrum of rapamycin? A. 1 HO HO B. 25 O C. 51 D. 102 E. >500 O O OH
N O OH OH O O O O O Give the structure of C5H10O.
Each Each chemically different carbon atom in a structure results in one absorption The The position of a carbon atom absorption depends upon its chemical environment
O H O pure chemical compound C5H10O
O O A B O C D E O C51H79NO13 What is the product of the following reaction? A. B.
2° What is the product of the following reaction? A. B.
13C spectrum of product. 1 11/16/2010 What is the mechanism of the following reaction?
initiation propagation termination
8 The chlorination of methane. When a bond is broken two radicals are produced. A
H H C H H H C H Cl H C H H C H B
H Which C-H bond of propane, A or B, is stronger? 9 10 Which radical is more stable? Which radical is more stable?
H H C H H C H C H H H H C H H C H H C H H C H H H H H H C H H C H H C C 1° H + H H H H C H H C H H C H H C H H H C H C H H H H H H C H H C H H C H H C C H C H H 1° H + H H H C H H A
H C C H H A
H C C H H 2° H C H H+ H 2° H C H H+ H B H B
H H H H C H C H H C H
12 H 11 2 11/16/2010 Which Which reaction has the larger BDE (∆H˚)? Using Using bond dissociation energies (BDE) estimate the ∆H° of the following reaction.
+ + H H C H H C H H C H H C H H H H H H C H H C H H C H H C H C H C A. 1° H + H H BDE (∆H˚)
423 kJ/mol H C H H B. B. 2° H C H H+ H 413 kJ/mol bonds of reactants (440 + 243) 683 - bonds of products (352 + 432) 784 C. -101 = heat of reaction = -101 kJ/mol
14 F. 0 13 A. -784 B. +682 D. +439 What is the ∆H° of the first step in the accepted mechanism of the chlorination of methane?
+ The chlorination of methane involves two steps?
+ H C HH
+ 432 kJ/mol H C HH
+ 432 kJ/mol ∆H° = +8 H C HH
+ + H
243 kJ/mol 352 kJ/mol C HH + + 243 kJ/mol 352 kJ/mol What is the ∆H° of the second step in the accepted mechanism of the chlorination of methane? A. -440 B. +109 C. -8 D. +8 E. -109
15 F. +440 A. -440 B. +109 C. -8 D. +8 E. -109 16 F. +440 What is the overall ∆H° for the chlorination of methane?
+ C HH + ∆H° = +8 H C HH
+ + ∆H° = -109 ∆H° = -101 17 3 ...
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