Monomethyl selectivity, dimethyl carbonate

The carbon nanotubes can be useful in the separation of molecules not only with different sizes (monomethyl naphthalenes) but also those with different shapes (dimethyl naphthalenes) as demonstrated with a tube of inner diameter of 7.3A. The above results have clearly indicated that the application of carbon nanotubes for gas separation is in very early stage of a technology with far-reaching consequences. The important point brought out is the fact that computational techniques such as MD and CG methods are efficient for screening and designing of carbon nanotubes for selective adsorption and separation of molecules. 

The monomethylation of carbanions derived from 1,3-cyclohexanedione and acetylacetone has been described (eqs 1 and 2) Selective monomethylation of (3-diketones is dependent upon the base employed variable amounts of O-methylation, dimethylation, and carbon-carbon bond cleavage may occur. The tetraethylammonium enolate of p-diketones reportedly provides higher yields of C-methylation without competing side reactions (eq 3). Dimethylation is sometimes a desired reaction pathway. In this case, a large excess of both methyl iodide and base favors the dimethylated product (eq 4). Recently, the combination of a potassium base and a catalytic amount of 18-Crown-6 (eq 5) has been described to provide a higher yield of dimethylation, ... 

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