Question

In Mass Spectrometry (MS) the molar mass of compounds can be determined. The so-called "molecular ion" corresponds to the molecular mass when Electron Impact Mass Spectrometry (EIMS, one of several common MS techniques) is used. It is important to realize, though, that the mass detected by MS depends on the isotopes present in the molecule. The questions below try illustrate the impact of isotope distribution in a molecule. What is the molar mass of the compound shown below? What is the molar mass if only^35 Cl isotopes are present in the molecule? What is the molar mass if 90 % of all carbon atoms consist of^12 C, 10% of^13 C isotopes? When molecules are subjected to Electron Impact Mass Spectrometry (EIMS), some bonds will break and smaller ionic parts (fragments) will form. Only cationic fragments can be detected. As a rule of thumb, the more stable a cation, the more likely it will form and will be detected in the instrument. For the molecule given in question 1), which cationic fragments are likely to form in an EIMS instrument? Show at least two structures, and calculate mass of the fragment ion. In Nuclear Magnetic Resonance Spectroscopy of protons (^1 H-NMR) each hydrogen atom that has a unique chemical environment generates a separate signal. Each signal can consist of a number of lines. How many signals do you expect to see in the^1 H-NMR spectrum of the compound below? For the three highlighted atoms in the molecule, how many lines do you expect to see for each of the signals of H_a, H_b, or H_c if the number of lines in each signal were to be equal to the number of neighboring H's located on immediately neighboring carbon atoms?

Answer 1

CR lolo C-12 260 aImol