Chem460 Exam-2 2010 - CHEM460 Fall, 2010 Professor Sasaki...

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CHEM460 EXAM #2 Name . Fall, 2010 Professor Sasaki 100 points TOTAL Good Luck! Note: Only answers in the box will be graded. 1. (30) (a) 1 H-NMR of the following compound shows two unique protons at 9.28 and - 3 ppm. These chemical shifts are very different from typical vinylic protons (5 ~ 6 ppm). (i) Which peak (9.28 ppm or - 3ppm) is more shielded? (ii) In the structure, clearly indicate the protons that are responsible for the two peaks. (iii) Provide a brief explanation for their unusual chemical shifts. (i) (iii) (b) The following splitting pattern may represent the 2 protons of an AB system or the X proton of an A 3 X system. Briefly explain how it is possible to distinguish between these possibilities. (c) 1 H-NMR of 1,2,3-trichlorobenzene shows two unique protons at 7.356 and 7.138 ppm with a 3 J(H 4 , H 5 ) value of 8.2 Hz. (i) Calculate the frequency difference ( Δν ) of H 4 and H 5 protons when a 200 MHz instrument is used. (ii) Describe the spin system of 1,2,3- trichlorobenzene by using the Pople notation. Briefly explain your reasoning.
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2 2. (40) 1 H-NMR of glycerol acetonide is attached in the pages 4 and 5. Answer the
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This note was uploaded on 01/18/2012 for the course CHEM 460AB taught by Professor Sasaki during the Fall '11 term at University of Washington.

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Chem460 Exam-2 2010 - CHEM460 Fall, 2010 Professor Sasaki...

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