ISSN:
0030-493X
Keywords:
Chemistry
;
Analytical Chemistry and Spectroscopy
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The low resolution mass spectra of α-dimethylaminoacetophenone and γ-dimethylaminobutyrophenone are compared to those of δ-methylhexanophenone and dimethyl n-butylamine as well as to those of α-dimethylaminoacetonitrile and γ-dimethylaminobutyronitrile. Analysis indicates that significant fractions of the fragmentations of the aminoketones are directed by the carbonyl. In particular, McLafferty rearrangement of the γ-aminoketone is favored over α-cleavage from nitrogen at ionizing voltages below 15 eV. Although the overall fragmentation patterns are presumably determined both by the distribution of charge and by the relative rates of the fragmentation processes available to the two ionized groups, the intrinsic rates for α-cleavage at ionized nitrogen and at ionized carbonyls appear to be very similar. Kinetic analysis suggests that 26% of the charge resides on the carbonyl in the γ-aminoketone molecular ion. The extent of delocalization of charge in any aminoketone may be partially controlled by the extent of spatial overlap of the two groups. Correlations of mass spectral behavior with photochemical behavior are thus limited because electronic excitation is more localized in the lowest excited states of molecules than charge is in electron-impact produced molecular ions.
Additional Material:
4 Tab.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/oms.1210031010
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