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The direct dimetalation of phenylacetylene and of (1-naphthy1)acetylene at the acetylenic as well as the ortho position can be achieved by an equimolar mixture of n-butyllithium and potassium tert-butoxide. Metalation at the ortho position was shown by subsequent reaction with trimethylchlorosilane (TMSC1) resulting in the formation of the ortho-silylated disilyl compounds o-TMSC6H4CeTMS and 2-TMS-1-Cl&C%CTMS. Under similar conditions C6H5C=CBut and 1-CloH7C=CBut gave the meta-silylated compound and a mixture of 3-, 4-, and 5-silylated derivatives, respectively. Ab initio calculations show that the ortho metalation of ethynylbenzene and 1-ethynylnaphthalene can be explained by the much higher coordination energy of the metalating reagent with the CECM rather than with the C=CR moiety.

In the Netherlands, there is a vigorous debate on ammonia emissions, atmospheric concentrations and deposition between stakeholders and research institutions. In this article, we scrutinise some aspects of the ammonia discourse. In particular, we want to improve the understanding of the methodology for handling experimentally determined ammonia emissions. We show that uncertainty in published results is substantial. This uncertainty is under-or even unreported, and as a result, data in national emission inventories are overconfident by a wide margin. Next, we demonstrate that the statistical handling of data on atmospheric ammonia concentrations to produce national yearly atmospheric averages is oversimplified and consequently atmospheric concentrations are substantially overestimated. Finally, we show that the much-discussed 'ammonia gap'either the discrepancy between calculated and measured atmospheric ammonia concentrations or the difference observed between estimated NH 3 emission levels and those indicated by atmospheric measurementsis an expression of the widespread overconfidence placed in atmospheric modelling.