Hydrocarbon species, formation

The C2H polymerisation reaction shown below results in the formation of long-chain hydrocarbon species that form part of the liposphere. 

Formally related reactions are observed when anthracene [210] or arylole-fines [211-213] are reduced in the presence of carboxylic acid derivatives such as anhydrides, esters, amides, or nitriles. Under these conditions, mono- or diacylated compounds are obtained. It is interesting to note that the yield of acylated products largely depends on the counterion of the reduced hydrocarbon species. It is especially high when lithium is used, which is supposed to prevent hydrodimerization of the carboxylic acid by ion-pair formation. In contrast to alkylation, acylation is assumed to prefer an Sn2 mechanism. However, it is not clear if the radical anion or the dianion are the reactive species. The addition of nitriles is usually followed by hydrolysis of the resulting ketimines [211-213]. 

Another interesting application of MDGC is in the rapid determination of isoprene (the most reactive hydrocarbon species) and dimethyl sulfide (DMS) (the major source of sulfur in the marine troposphere and a precursor to cloud formation) in the atmosphere (16). The detection limits were 5 and 25 ng F1, respectively. 

Multi-component hydrocarbon standards to provide accurate calibration of instruments (generally gas chromatographs) used to monitor the concentrations of a wide range of volatile organic hydrocarbon compounds (VOCs) in ambient air. These standards currently contain 30 different hydrocarbon species that are important to photochemical ozone formation, with concentrations ranging down to a few parts per billion by molar value. They are disseminated widely in the United Kingdom and the rest of Europe as calibration standards, and as test mixtures for assessment of the quality of international ambient hydrocarbon measurements (often under the auspices of the European Commission - EC). 

The activity and selectivity of catalyst HZSM5-1 was constant over 1 hour on stream although the formation of a linear hydrocarbon species at the catalyst was noticed. The IR spectra suggest that this species is a linear aliphatic hydrocarbon (coke precursor) increasing in concentration with time on stream [13], It is concluded that this species is adsorbed at the (catalytically inactive) Si-OH groups of the catalyst. During our measurements, the catalytically active Si-OH-AI groups were not blocked by this surface species and the product selectivity was not altered... 

The transition metal chemistry of y-carbenes (14) is of interest because of the possible involvement of such species in Fischer-Tropsch synthesis (15) and alkene metathesis (16,17). However, apart from y-CH2 and one example of y-CHMe, simple hydrocarbon species have, until the work described here, been generally unavailable and the reactivity of y-carbenes is effectively unexplored. An opportunity was therefore presented for such study, in which carbon-carbon bond formation has taken precedence. 

Third, GPC of very dilute solutions of asphaltenes and their fractions clearly confirm the above implications and demonstrate that these materials represent a dynamic, time-dependent system that changes to MW entities of the size of polyaromatic hydrocarbons and similar materials. This in turn indicates that the forces involved in the apparent high MW species formation are not fully understood and questions the tenability of formulations based on (r-bonded polymers to explain the apparent high MW of the aggregates. 

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