19. The coupling constant, J, between the protons of chloroethane is 7 Hz when the spectrum is obtained at 250 MHz. What is the coupling constant between these protons when the spectrum is acquired at 500 MHz? 3.5 Hz a. b. 7 Hz c. 14 Hz d. 21 Hz 20. Which of the following is true for pair of diastereotopic protons? 1. 2. They will appear at the same chemical shift in an achiral (i.e., nonchiral environment) They will appear at the same chemical shifts in a chiral environment a. only 1 b. only 2 c. neither I nor 2 d. both 1 and 2 Chapter 14 21. What is the principle that allows us to use mass spectrometry to determine the molecular weight of a compound? a. higher molecular weight compounds are less volatile b. higher molecular weight compounds are more dense c. a beam of higher molecular weight cations is deflected less by a magnetic field d. ions with higher molecular weight absorb higher frequencies of light 22. Which of the following is the definition of the base peak of a mass spectrum? a. the peak corresponding to the most abundant ion b. the peak corresponding to the ion with lowest m/e c. the peak corresponding to the molecular ion peak d. the peak corresponding to the ion arising to loss of a proton from the molecular ion 23. What are products of the collision between high energy electrons and methane? a. CH4 +2 e b. CH3 +H c. CH4+ + 2e d. CH3 +H+2e 24. Which of the following sets of molecular ions does a dibromoalkane possess? a. two molecular ions in a 2:1 ratio separated by two mass units b. two molecular ions in a 1:1 ratio separated by two mass units c. three molecular ions in a 1:2:1 ratio, separated by two mass units d. two molecular ions in a 3:1 ratio separated by two mass units