Subject oxygen—hydrogen bonds

Not so much attention is given to the form of the hydrated hydroxide anion, which is also subject to hydrogen bonded interactions and does exist in some crystals as H3O2- or (H20)0H and has a symmetrical [HO-H-OH]" hydrogen bonded structure. Recent work5 has shown that the most probable form of the hydrated hydroxide ion is (h O OH-, in which the hydroxide oxygen atom participates in hydrogen bonds with three water molecules. Exclusively, the hydrated hydroxide ion is formulated as OH (aq) in chemical equations. 

In the epoxidation of acyclic allylic alcohols (Scheme 6), the diastereoselectivity depends significantly on the substitution pattern of the substrate. The control of the threo selectivity is subject to the hydroxyl-group directivity, in which conformational preference on account of the steric interactions and the hydrogen bonding between the dioxirane oxygen atoms and the hydroxy functionality of the allylic substrate steer the favored 7r-facial... 

As water is subjected to temperatures and pressures above its critical point (374.2°C, 22.1 MPa), it exhibits properties that differ from both liquid water and steam. At the critical point the liquid and vapor phases of water have the same density. When the critical point is exceeded, hydrogen bonding between water molecules is essentially stopped. Supercritical water sustains combustion and oxidation reactions because it mixes well with oxygen and with nonpolar organic compounds. Some organic compounds that are normally insoluble in liquid water become completely soluble (miscible in all proportions) in supercritical water. Some water-soluble inorganic compounds, such as salts, become insoluble in supercritical water. 

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