A series of laboratory and modelling experiments on the oxidation of propene in the gas phase has been undertaken to determine conditions which give high yields of propene oxide. The conditions under which the experiments were conducted were 505-549 K and up to 4 bar pressure. It is proposed that propene oxide is formed from propene by reaction with several peroxy radicals including HOz and CH3C03. However, one of the more important radicals is hydroxypropylperoxy. Its reaction with propene, under these conditions

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This paper presents the main findings of a field survey conducted in the United Kingdom into the human response to vibration in residential environments. The main aim of this study was to derive exposure-response relationships for annoyance due to vibration from environmental sources. The sources of vibration considered in this paper are railway and construction activity. Annoyance data were collected using questionnaires conducted face-to-face with residents in their own homes. Questionnaires were completed with residents exposed to railway induced vibration (N = 931) and vibration from the construction of a light rail system (N = 350). Measurements of vibration were conducted at internal and external positions from which estimates of 24-h vibration exposure were derived for 1073 of the case studies. Sixty different vibration exposure descriptors along with 6 different frequency weightings were assessed as potential predictors of annoyance. Of the exposure descriptors considered, none were found to be a better predictor of annoyance than any other. However, use of relevant frequency weightings was found to improve correlation between vibration exposure and annoyance. A unified exposure-response relationship could not be derived due to differences in response to the two sources so separate relationships are presented for each source.

Carbonyl compounds are the main products of the low-temperature gas-phase oxidation of alkenes. It is suggested that they are formed by consecutive addition of a hydroxyl radical and an oxygen molecule to the alkene, the hydroxy-substituted peroxyl radical subsequently decomposing to yield two molecules of carbonyl compounds and the chain carrier. A model system has been investigated, the fuel chosen being 2,3-dimethylbutan-2-01 which gives acetone as the major product at 578 K. In reactions with [180]-2,3-dimethylbutan-2-ol and oxygen, the ketone is enriched by ca. 50%. and this result is consistent with the decomposition of the radical (11).CARBONYL compounds are the principal products of the low-temperature oxidation of aliphatic alkenes in the gas p h a ~e . l -~ For example, acetaldehyde, acetone and acetaldehyde, acetone, 2-methylpropanal and formaldehyde, and acetone and formaldehyde are the main products from the oxidation of tram-but-2-ene,l2-methyl-b~t-2-ene,~J 3-methylbut-l-ene? and 2-meth~lpropene,~ respectively. Where different carbonyl compounds are formed from the alkene, it is apparent that one molecule of alkene decomposes to yield two molecules of carbonyl and the overall reaction may be expressed as (1)-The formation of the carbonyl compounds via a dioxetan is ruled out as the reaction is highly endothermic (AHo = 290 kJ mol-1),6 involving a spin-forbidden transition, as oxygen is in its ground state. Knox, on the other hand, suggested that the alkene first undergoes consecutive addition reactions with a hydroxyl or a hydroperoxyl radical and oxygen. ' We have suggested that it is the hydroxyl radical that is the

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