mliou2
Registered: 10/08/09
Posts: 15
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Reply with quote | #1 |
To start off, I have a head cold, so I blame my illness for not being able to understand this...
But why is it that for M+2 relative intensities, we cannot use the same rules as M+1?
To clarify, for PP #5 (a), why can't we say that its M+2 is (1 x 0) + (1 x 24.23)? Why does this rule only apply for M+1?
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NelM
Registered: 10/01/09
Posts: 15
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Reply with quote | #2 |
mliou2 - For M+2 relative intensities, we cannot use the same rules as finding M+1 relative intensities, because the M+2 intensities MAINLY give information about the presence of "sulfur, 4%, chlorine - 33%, or bromine - 100%" (Lecture Supplement, page 94/95). This is because Sulfur, Chlorine, and Bromine are the only main 3 atoms that show important M+2 peaks. The rest of the atoms under the M+2 contributors, such as the hydrogen in PP#5 (a), have a natural abundance of "parts per million" (lecture supplement, page 91), which is too small, and thus insignificant (also, according to page 111 of the Thinkbook, "the contribution from titrtium [3H] is negliglble, because this isotope is radioactive with a half-life of 12.3 years"). Therefore, we cannot use the same rules as finding M+1 relative intensities for finding M+2 relative intensities because some of the atoms under M+2 are too small to be added in, such as 3H. Sulfure, bromine, and Chlorine, however, have significant M+2 peaks (so we use those 3 atoms to base what M+2 relative intensities we have).
Hope that helped!
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