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Origin of the [C 4 H 9 O] + ions in the mass spectrum of n ‐butyl ethyl ether
Author(s) -
Hudson Charles E.,
McAdoo David J.
Publication year - 1979
Publication title -
organic mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 0030-493X
DOI - 10.1002/oms.1210140210
Subject(s) - ether , chemistry , ion , isomerization , deuterium , metastability , mass spectrum , alcohol , medicinal chemistry , polyatomic ion , hydrogen , ethanol , ethylene , photochemistry , organic chemistry , physics , quantum mechanics , catalysis
The mechanisms of formation of m/z 73 ions in the mass spectrum of the ionized title compound were investigated by deuterium substitution and by examining the decompositions of metastable ions. Two routes to the [C 4 H 9 O] + ions were found in the normal spectrum. The ethyl lost by the major pathway contains the α‐ and β‐hydrogens and a γ‐hydrogen from the butyl group. The minor route involves the loss of ethylene from the [MH] + ion. There were metastable peaks for losses of ethyl, ethanol and methyl from the molecular ion. The ethyl contains the α‐ and β‐methylenes and a γ‐hydrogen, while the methyl is the δ‐methyl of the butyl group. The labeling data rule out a previous mechanistic proposal for the loss of ethyl and support a mechanism involving stepwise isomerization to the sec ‐butyl ethyl ether molecular ion. However, the metastable ion chemistries of the molecular ions from the n ‐ and sec ‐butyl ethyl ethers are highly dissimilar, perhaps due to decompositions from different electronic states. The n ‐pentyl methyl ether ions loses both ethyl and propyl, apparently following rearrangements to the 3‐pentyl and 2‐pentyl ether ions. Di n ‐butyl and n ‐butyl methyl ethers also give metastable peaks for loss of methyl, ethyl and the shorter chain alcohol.