Linked Life Data

20704298

Source:http://linkedlifedata.com/resource/pubmed/id/20704298

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
35
pubmed:dateCreated
2010-9-2
pubmed:abstractText
The rate coefficients for the removal of the excited state of methylene, (1)CH(2) (a(1)A(1)), by acetylene, ethene, and propene have been studied over the temperature range 195-798 K by laser flash photolysis, with (1)CH(2) being monitored by laser-induced fluorescence. The rate coefficients of all three reactions exhibit a negative temperature dependence that can be parametrized as k((1)CH(2)+C(2)H(2)) = (3.06 +/- 0.11) x 10(-10) T ((-0.39+/-0.07)) cm(3) molecule(-1) s(-1), k((1)CH(2)+C(2)H(4)) = (2.10 +/- 0.18) x 10(-10) T ((-0.84+/-0.18)) cm(3) molecule(-1) s(-1), k((1)CH(2)+C(3)H(6)) = (3.21 +/- 0.02) x 10(-10) T ((-0.13+/-0.01)) cm(3) molecule(-1) s(-1), where the errors are statistical at the 2sigma level. Removal of (1)CH(2) occurs by chemical reaction and electronic relaxation to ground state triplet methylene. The H atom yields from the reactions of (1)CH(2) with acetylene, ethene, and propene have been determined by laser-induced fluorescence over the temperature range 298-498 K. For the reaction with propene, H atom yields are close to the detection limit, but for acetylene and ethene, the fraction of H atom production is approximately 0.88 and 0.71, respectively, at 298 K, rising to unity by 398 K, with the balance of the reaction with acetylene presumed to be electronic relaxation. Experimental constraints limit studies to a maximum of 1 Torr of bath gas; master equation calculations using an approach that allows treatment of intermediates with deep energy wells have been carried out to explore the role of collisional stabilization for the reaction of (1)CH(2) with acetylene. Stabilization is calculated to be insignificant under the experimental conditions, but does become significant at higher pressures. Between pressures of 100 and 1000 Torr, propyne and allene are formed in similar amounts with a slight preference for propyne. At higher pressures propyne formation becomes about a factor two greater than that of allene, and above 10(5) Torr (300 < T (K) < 600) cyclopropene formation starts to become significant. The implications of temperature-dependent (1)CH(2) relaxation on the roles of (1)CH(2) in chemical mechanisms for soot formation are discussed.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Sep
pubmed:issn
1520-5215
pubmed:author
pubmed:issnType
Electronic
pubmed:day
9
pubmed:volume
114
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
9413-24
pubmed:meshHeading
pubmed:year
2010
pubmed:articleTitle
Temperature dependent kinetics (195-798 K) and H atom yields (298-498 K) from reactions of (1)CH(2) with acetylene, ethene, and propene.
pubmed:affiliation
School of Chemistry, University of Leeds, Leeds, LS2 9JT, United Kingdom.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't