Fragmentation 3-cleavag

Due to ring opening prior to fragmentation, 3>cleavage is as relevant as the a-cleavage. 

Fragmentational cleavage of C5 of 128 was reported to take place through rupture of the N4-C5 and C5-N6 bonds upon acid-catalyzed hydrolysis to give 70 (65JOC3601 93MI1 94JHC1503) (Scheme 49). 

Fragmentation Cleavage of bonds that are adjacent to the carbonyl group gives rise to R+, [RC O]and [OCH3]+. An intense peak in the mass spectra of C6-C26 methyl esters results from the McLafferty rearrangement ... 

Ring opening reactions are of considerable interest, particularly in view of the trend of using heterocycles as sources for other organic fragments. Cleavage of (5,5)-fused ring... 

Figure 8 Roepstorff and Fohlman92 notation for peptide fragmentation. For thex-, y-, and z-ion series, charge is retained on the C-terminus fragment and for the a-, fa-, and c-ion series, charge is retained on the N-terminus fragment. Cleavage of the C -C bond gives rise to the a and x ions (e.g., by EDD) cleavage of the C-N amide bond, the fa and y ions (e.g., CID) and cleavage of the N-C amine bond (e.g., by ECD or ETD), the c and z ions.

Heteroatoms in a molecular ion tend to promote fragmentation. Cleavage of the carbon-heteroatom bond and of the bond a to the heteroatom is common. n-Decanol, for example, has a relative molecular ion intensity nearly 1,000 times less than that of n-decane, and the expulsion of HCN from pyridine (Figure 2.58b) is considerably more facile than loss of C2H2 from benzene (Figure 2.58a), depicted by Equation 2.91. 

Arsene CG, Ohlendorf R, Burkitt W, Pritchard C, Henrion A, O Connor G, Bunk DM, Guttler B. Protein quantification by isotope dilution mass spectrometry of proteolytic fragments Cleavage rate and accuracy. Anal Chem 2008 80(11) 4154—4160. 

Fragmentation Cleavage at the azo group followed by loss of N2, giving rise to the dominant base peak. 

Fragmentation Cleavage of the bond next to CO, leading to [M-1]" (more significant than in saturated aldehydes), [M-29], and m/z 29. No McLafferty rearrangement occurs if the y-hydrogen atom is attached to a double bond or if there is a double bond in a,P-position. 

Fragmentation Cleavage of the bond next to CO, more favorably on the saturated side, is the most important primary fragmentation. The acyl ion then loses CO. The McLafferty rearrangement occurs neither when the unsaturated substituents are in a,p position nor when the only available y-hydrogen atom is attached to a double-bonded carbon. 

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