Linked Life Data

16320290

Source:http://linkedlifedata.com/resource/pubmed/id/16320290

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
12
pubmed:dateCreated
2005-12-6
pubmed:abstractText
Ionization of esters of carboxylic acids RCOOR' (R = H, alkyl; R' = alkyl) within the air plasma of the Atmospheric Pressure Chemical Ionization (APCI) source occurs largely via H(+)-transfer and, to a minor extent, via NO(+) association. The protonated ester MH(+) is normally observed as M(2)H(+) and as higher aggregates (M(3)H(+), M(3)H(+)(H(2)O)) also at high source temperature. The behavior of M(2)H(+) upon collisional activation is consistent with the reported dissociation of proton-bound dimers to MH(+) species that, in turn, fragment according to the known paths of lowest energy. In addition, other important product ions form within the plasma, some in very high relative abundance, which are attributed to ion-molecule condensation reactions between neutral M and either MH(+) or M(2)H(+) resulting in the elimination of CO, R'OH, alkene from the alkoxy moiety of the ester and HCOOH. A general scheme is proposed to account for the experimental observations, which suggest that the encounter complex formed between MH(+) and M or between M(2)H(+) and M may either collisionally relax to the protonated dimer or trimer, respectively, or react via covalent bond forming and cleaving steps to eliminate stable neutral molecules. The proposed scheme is supported by both the observed concentration dependence and the temperature dependence of the products relative abundances within the plasma. Such reactions can be the dominant process, as in the case of formate esters. A second significant ionization route involves addition of NO(+) to form M(n)NO(+) (n = 1, 2, 3). An additional product corresponding to [M(2)NO(+) - CO(2)] is also observed with iso- and n-butyl formate esters.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Dec
pubmed:issn
1076-5174
pubmed:author
pubmed:issnType
Print
pubmed:volume
40
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
1583-9
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed:year
2005
pubmed:articleTitle
Positive ion chemistry of esters of carboxylic acids in air plasma at atmospheric pressure.
pubmed:affiliation
Dipartimento di Scienze Chimiche, Università di Padova, Via Marzolo 1, Italy.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't