Dialkyl group

Adsorption of a surfactant on solids is dependent, among other things, on the structure of both the hydro-phobic and hydrophilic portions of it. There are a number of mechanisms proposed for surfactant adsorption and an understanding of the effects of the structure of the surfactant can help in elucidating the role of these mechanisms. In this study, the effect on adsorption on alumina of some structure variations of sulfonates (chain length and the branching and the presence of ethyoxyl, phenyl, disulfonate and dialkyl groups) is examined above and below CMC as a function of surfactant concentration, pH and salinity. Co-operative action between an ionic alkyl sulfonate and a nonionic ethoxylated alcohol is also studied. 

Fig. S Selectivity-reactivity relationship, p vs. log A plots, for solvolyses of a,a-dialkylbenzyl OPNB in 80% aqueous acetone at 25 C plots of ,a-dialkylbenzyl-OPNB carrying dialkyl groups structurally unspecified, otherwise specified O, benzyl-OPNBs squares denote 2-norbomyl derivatives, exo- and enrfo-isomers , benzyl-OPNBs having conjugative a-substituents.

Polyindanes have been obtained from a variety of monomers which are capable of forming benzyl carbenium ions stabilized with dialkyl groups upon the appropriate initiation. Linear polymers containing indane units in the main chain have been obtained by the BClj-initiated polymerization of 1,4-diisopropenylbenzene [Eq. (6)] [8]. Polyindanes with structural unit IS have also been obtained when difunctional monomers capable of forming a,a-dimethylbenzylic carbenium ions upon treatment with an initiator [8-12] (Fig. 4). 

Scheme 6 Stabilisation of the positive charge by N,N-dialkyl groups in the intermediate...

Dialkyl metallocenes and other dialkyl Group 4 transition metal complexes are useful as precatalysts in combination with co-catalysts such as tris(perfluoro-aryl)boranes or tetrakis(periluoroaryl)borate salts [18]. Recently, an expedient procedure for the production of dimethyl metallocenes and Cp-amido dimethyl metal complexes in high yields and purity has been reported. The direct synthesis of Group 4 dimethylmetallocenes [19] consists of the one-pot reaction between the r-ligand, a 2-fold excess of MeLi, and MtCU. This simple method produces the dimethylated complexes in higher overall yield, and saves on reaction time and solvents, compared to the classic two-step route, which consists in the synthesis of the metallocene dichloride followed by its methylation with 2 equiv. MeLi. 

Crystal structures of four dioxastannolanes76 and one dioxastannanane have been determined. All four of the dioxastannolanes are associated, but the degree of association depends on the steric requirements of the 1,1-dialkyl groups and on the substituents on the methylene groups of the ring. 

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