At This Level You Should Always Focus Analysis On The Molecular Ion Please Note That There Are Often Tiny Peaks On The 1 (34.5 KiB) Viewed 38 times
At This Level You Should Always Focus Analysis On The Molecular Ion Please Note That There Are Often Tiny Peaks On The 2 (60.23 KiB) Viewed 38 times
At this level, you should always focus analysis on the molecular ion. Please note that there are often tiny peaks on the Mass Spectrum; they should generally be ignored (see exception for isotope effects below). There are three basic bits of information to be gained from MS: 1. Molecular Mass: The largest peak which is farthest to the right in the mass spectrum is usually the Molecular Ion. (see exceptions for isotope peaks below). What would be the Molecular weight for the compound in the MS above? 2. Odd or Even Number of Nitrogen atoms in the Molecule: Once you have found the molecular ion, check to see if its molecular weight is odd or even. If the mass is even, then there will be an even number of Nitrogen atoms in the molecule (e.g. 0,2,4,…, etc.) If the mass is odd, then there will be an odd number of Nitrogen atoms in the molecule (e.g. 1,3,5, etc) Practice to prove to yourself that this is correct. What are the molecular weights of each molecule on the next page? Do the odd MW molecules have an odd number of N's? Do the even MW molecules have and even number of N's? (Note: when calculating molecular weight for MS, use only real, wholenumber values for the weight of each atom - do not use the averages printed on a periodic table.)
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