tailieunhanh - Ebook Solutions manual to accompany - Organic chemistry (8th edition): Part 2

(BQ) The solutions manual to accompany Organic Chemistry provides fully-explained solutions to all the problems that feature in the second edition of Organic chemistry. Intended for students and instructors alike, the manual provides helpful comments and friendly advice to aid understanding, and is an invaluable resource wherever Organic chemistry is used for teaching and learning. | CHAPTER 13 Spectroscopy SOLUTIONS TO TEXT PROBLEMS The field strength of an NMR spectrometer magnet and the frequency of electromagnetic radiation used to observe an NMR spectrum are directly proportional. Thus the ratio T 200 MHz is he same as T 60 MHz. The magnetic field strength of a 60 MHz NMR spectrometer is T. The field strength of a 920 MHz instrument is T. The ratio of H and - C resonance frequencies remains constant. When the ll frequency is 200 MHz 13c NMR spectra are recorded at MHz. Thus when the H frequency is 100 MHz 13c NMR spectra will be observed at MHz. a The 1NMR chemical shift 8 of bromoform CHB1 3 recorded at 300 MHz is s 2065 Hz 6 __ ----- 2----xio ppm 300x10 Hz b When measured at 400 MHz the chemical shift would be the same for bromoform ppm. c The frequency of the measured absorption at 400 MHz for bromoform is 2752 Hz. This is usually measured by the spectrometer. However using the equation in pint a and replacing the value of 2065 Hz withy replacing 300 X 1 o6 with 400 X 106 and then solving fory one may calculate this value. _ X 400 X 106Hz _ y ------------ 7-------2752 Hz 1 X1O 371 372 CHAPTER 13 Spectroscopy b Electronegative atoms such as chlorine exert an electron-withdrawing effect on the protons that are separated from them by the fewest bonds. The effect is cumulative and two chlorines will exert a greater effect than one. The proton on C-l will be the least shielded and those on C-3 will be the most shielded. Least shielded Most shielded S Cl Ù iLz C12CHCHCH3 5 c The protons on the carbons adjacent to the oxygen of tetrahydrofuran will be less shielded than those separated from the oxygen by more bonds. More shielded 5 3 ---- Less shielded o The least shielded most deshielded protons are those directly attached to the double bond. The protons on the ring that are closer to the double bond are less shielded than those farther away. 5 b .