Mass Spectrometry

   Hey guys, This is John Harbold and I will be discussing and analyzing one major part of Organic Chemistry 2.  This discussion will be about an area of Organic Chemistry that I have had difficulty with and how I've overcome the obstacles and become very knowledgeable in that area.  The area of Organic Chemistry that I have had multiple problems with has been identifying and understanding the plot of the mass spectrum and determining which compound is being plotted.
    An example of a compound that was difficult to correlate with the mass spectrum of the graph is 2-chloropropane.  To determine which graph correlates with the 2-chloropropane I first realized that I needed to calculate the molecular weight for each of the common isotopes for chlorine which are 35Cl and 37Cl.  When plotting a compound with chlorine in it there will be two peaks due to the two common isotopes.  Chlorine has a height ratio from the first peak(M peak) to the second peak(M+2 peak) of 3:1.  The mass of the molecular ion of 2-chloropropane with the 35Cl isotope is 78 which is the M peak while the mass of the molecular ion of 2-chloropropane with the 37Cl isotope is 80 which is the M+2 peak.  When plotting each of these in the graph the M peak will be at 78 while M+2 peak is at 80 and the M+2 peak is 1/3 the relative abundance of the M peak. 
    Reading throughout ch. 13 of the 2nd edition Smith Organic Chemistry book was very helpful in overcoming this problem and better understanding this concept.  Remember ALWAYS READ YOUR BOOK!