Water rearrangements

Ammonium cyanate, NTUNCO, in water rearranges to produce urea, a common fertilizer, (NH2)2CO ... 

Where multiple products are possible, the CMR and MBR have been employed to optimize conditions for formation of specific components of a reaction sequence. Examples discussed below, were obtained by heating organic substrates such as allyl phenyl ether [46] and carvone [47] in water. Rearrangements, addition or elimination of water and isomerizations occurred, with each transformation favored under tightly defined conditions. 

It has been established that in the Dimroth rearrangement of 2-imino-pyrimidines, water plays an essential role (65JCS7071). In water the imine is, in fact, in equilibrium with its hydrate, the carbinolamine 39. That participation of the hydrate is important is shown by the experimental fact that in dry tetrahydrofuran, acetone, dioxane, or ether, the imine is quite stable and is not inclined to undergo rearrangement. However, on addition of a little water, rearrangement occurs its rate is proportional to the concentration of the water (65JCS7071). 

Having found equilibrium constants for the series of bases, we may now use them to characterize the proton-donating ability of any mixture of sulfuric acid and water. Rearranging Equation 3.30, we have... 

Andres, G. O., Cabrerizo, F. M., Martinez Junza, V., Braslavsky, S. E., A Large Entropic Term Due to Water Rearrangement is Concomitant with the Photoproduction of Anionic Free base Porphyrin Triplet States in Aqueous Solutions, Photochem. Photobiol. 2007, 83, 503 510. 

Quantitatively, we also know that the concentration of the ions in solution is given by their solubility product or Ksp. This is nothing more than the equilibrium constant for the salt in water, rearranged to take up the activities of the pure water and the pure solid salt ... 

Keywords AFM Desorption Inherent elasticity Macromolecules Mechanochemistiy Molecular motor Non-covalent interactions Polymer models QM calculations Single-molecule elasticity SMFS Supramolecular chemistry Supramolecular polymer Water rearrangement... 

By excluding the effects of salt and poor solvent types, the deviation was attributed to the water rearrangement upon elongation [26]. At the free state (F = 0), there is more bound water around ssDNA. Upon elongation, the distances between the H-bond donors and acceptors of ssDNA are increased, which caused a... 

In fact, the water rearrangement around the ssDNA chain can be expressed in another form, i.e., it can be regarded as a partial dehydration process ... 

When the membrane is placed in liquid water, rearrangement and a phase-transition occur. This could be due to surface rearrangements wherein the fluorocarbon-rich skin of the membrane is repelled from the interface between the water and membrane. What this means is that in order to minimize the energy of the system the side chains and backbone of the polymer reorient so that the chains are now arranged at the membrane/ water interface. This hypothesis agrees with the data that show that the water contact angle on the membrane surface becomes more hydrophilic after the membrane is placed in liquid water [32]. The presence of liquid water also results in the removal of a vapor-liquid meniscus, which could also aid in the above rearrangements [28]. 

---