Formation solvent-free environments

Formation, chemistry and structure of organomagnesium species in solvent-free environments... 

Gidden, J. Ferzoco, A. Baker, E. S. Bowers, M. T., Duplex formation and the onset of helicity in poly d(CG)(n) oligonucleotides in a solvent-free environment. Journal of the American Chemical Society 2004, 126, (46), 15132-15140. 

The only example of a reaction between two solids, under solvent-free and catalyst-free environment, was demonstrated by Varma et al. when the reaction of neat 5- or 8-oxobenzopyran-2(177)-ones with a variety of aromatic and heteroaromatic hydrazines provided rapid access to several synthetically useful heterocyclic hydrazones (Scheme 5) via the formation of a eutectic melt below the melting point of either of the reactants. ... 

If the nucleophilicity of the anion is decreased, then an increase of its stability proceeds the excessive olefine can compete with the anion as a donor for the carbenium ion, and therefore the formation of chain molecules can be induced. The increase of stability named above is made possible by specific interactions with the solvent as well as complex formations with a suitable acceptor 112). Especially suitable acceptors are Lewis acids. These acids have a double function during cationic polymerizations in an environment which is not entirely water-free. They react with the remaining water to build a complex acid, which due to its increased acidity can form the important first monomer cation by protonation of the monomer. The Lewis acids stabilize the strong nucleophilic anion OH by forming the complex anion (MtXn(OH))- so that the chain propagation dominates rather than the chain termination. 

Upon excitation at 295 nm, free tryptophan in aqueous environment shows a fluorescence maximum at 353 nm, whereas solvent-buried tryptophan residues have maxima at 330-335 nm. Therefore, the extent of solvent exposure of tryptophan residues can be estimated from the wavelength of the fluorescence maximum indicating the formation of aggregates. Accordingly, the quenching susceptibility using iodide has been used as indicator for compactness of aggregation of Sol 11 (Koppelman et al 2002). 

Spectral changes with the water content are attributed to the existence of aggregates which induce different environments surrounding the por phyrin and not to dimer formation (Brochette et al., 1985). The observation of an isosbestic point implies the existence of two different species of porphyrin, one associated with the interface and the other corresponding to the free porphyrin in the bulk organic solvent or water. This equilibrium is expressed by... 

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