# Mass Spectrum * Fragmentation:

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In summary, the conversation discusses the difficulty in determining the m/z value for fragmentation in mass spectrometry. The individual is confused about how to calculate these values for compounds that are not given in the textbook. They receive help in understanding that the molar mass per charge is what is needed to calculate the m/z value. The conversation concludes with the individual realizing their mistake and thanking for the clarification.

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[SOLVED] Mass Spectrum * Fragmentation:

1. The problem, I've been having is how to tell a certain m/z (mass per a charge) value for fragmentation. Like the examples they give in the book have the values, but then we are expected to know the values of diffrent compounds, that aren't even in the book, thus I think there must be a method in finding that m/z value without any experimental test.

Example they give in the book is like 2,2-dimethylpropane and 2-methylbutane, which I know, one fragmentation will form a tertiary, which value they give is m/z = 57 and then the second one will form a primary and a secondary fragmentation m/z = 71, but I'm confused how they get the m/z values.

Thanks for any help given, its just confuses me, they don't even tell how they got that value, just give it.

Please elaborate. For a given fragment you just calculate its molar mass and divide it by the fragment charge. Fragment charge is always a low integer - like 1 or 2. But I don't think that's what you are asking.

You know I just figured it out while looking at it, heheh. The word molar mass got to me figure that out and go ohhh, they want the molar mass per a charge, hehe, ok I got it now :+)

Sorry about the confusing question, but I got it now, thanks :+)