Fragmentation of molecular ions of fatty acid methyl esters into methoxycarbonylalkyl ions by electron impact

Sonneveld, W.; Steen, Dorika; Pabon, H. J. J.

doi:10.1002/recl.19680871003

Cited by 4 publications

(2 citation statements)

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“…esters, where both H and C rearrangements abound. 15 We prepared the 6-13 C labelled derivative of non-8-enoic acid in order to distinguish between these possibilities. If carbon skeletal rearrangement is occurring in this negative ion system, both ' 12 C 3 13 parent anion.…”

Section: Methodsmentioning

confidence: 99%

Competitive charge-remote and anion-induced fragmentations of the non-8-enoate anion. A charge-remote reaction which co-occurs with hydrogen scrambling

Dua¹,

Bowie²,

Cerda³

et al. 1997

J. Chem. Soc., Perkin Trans. 2

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The non-8-enoate anion undergoes losses of the elements of C 3 H 6 , C 4 H 8 and C 6 H 12 on collisional activation. The mechanisms of these processes have been elucidated by a combination of product ion and labelling ( 2 H and 13 C) studies, together with a neutralisation reionisation mass spectrometric study. These studies allow the following conclusions to be made. (i) The loss of C 3 H 6 involves cyclisation of the enolate anion of non-8-enoic acid to yield the cyclopentyl carboxylate anion and propene. (ii) The loss of 'C 4 H 8 ' is a charge-remote process (one which proceeds remote from the charged centre) which yields the pent-4enoate anion, butadiene and dihydrogen. This process co-occurs and competes with complex H scrambling. (iii) The major loss of 'C 6 H 12 ' occurs primarily by a charge-remote process yielding the acrylate anion, hexa-1,5-diene and dihydrogen, but in this case no H scrambling accompanies the process. (iv) It is argued that the major reason why the two charge-remote processes occur in preference to anion-induced losses of but-1-ene and hex-1-ene from the respective 4-and 2-anions is that although these anions are formed, they have alternative and lower energy fragmentation pathways than those involving the losses of but-1-ene and hex-1-ene; viz. the transient 4-anion undergoes facile proton transfer to yield a more stable anion, whereas the 2-(enolate) anion undergoes preferential cyclisation followed by elimination of propene [see (i) above].

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Section: Methodsmentioning

confidence: 99%