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The hydride adds to an electrophilic center, typically unsaturated carbon. Hydrides such as sodium hydride and potassium hydride are used as strong bases in organic synthesis. The hydride reacts with the weak Bronsted acid releasing H 2. Hydrides such as calcium hydride are used as desiccants, i.e. drying agents, to remove trace water from ...
Binary hydrogen compounds in group 1 are the ionic hydrides (also called saline hydrides) wherein hydrogen is bound electrostatically. Because hydrogen is located somewhat centrally in an electronegative sense, it is necessary for the counterion to be exceptionally electropositive for the hydride to possibly be accurately described as truly behaving ionic.
The distance between the metal and the hydrogen is typically 1.8–2.3 Å, and the M┄H−C angle is in the range of 90°–140°. The presence of a 1 H NMR signal that is shifted upfield from that of a normal aryl or alkane, often to the region normally assigned to hydride ligands.
The hydrogen anion is the dominant bound-free opacity source at visible and near-infrared wavelengths in the atmospheres of stars like the Sun and cooler; [2] its importance was first noted in the 1930s. [3] The ion absorbs photons with energies in the range 0.75–4.0 eV, which ranges from the infrared into the visible spectrum.
One hydride serves as the hydride source, and the other serves as a proton source. [2] In the case of ionic hydrogenation, a dihydride complex is regenerated by hydrogen gas following hydrogenation. Typical catalysts are tungsten or molybdenum complexes. An example of such a catalyst is CpMo(CO) 2 (PR 3)(OCR' 2)]+ where M = W or Mo. [7]
Hydrogen (1 H) has three naturally occurring isotopes: 1 H, 2 H, and 3 H. 1 H and 2 H are stable, while 3 H has a half-life of 12.32(2) years. [3] [nb 1] Heavier isotopes also exist; all are synthetic and have a half-life of less than 1 zeptosecond (10 −21 s). [4] [5] Of these, 5 H is the least stable, while 7 H is the most.
Other strong non-nucleophilic bases are sodium hydride and potassium hydride. These compounds are dense, salt-like materials that are insoluble and operate by surface reactions. Some reagents are of high basicity (pK a of conjugate acid around 17) but of modest but not negligible nucleophilicity.
Extraplanetary material, such as lunar and asteroid regolith, has traces of 3 He from solar wind bombardment. To become superfluid, 3 He must be cooled to 2.5 millikelvin, ~900 times lower than 4 He (2.17 K). This difference is explained by quantum statistics: 3 He atoms are fermions, while 4 He atoms are bosons, which condense to a superfluid ...