7693-26-7

Usage

Uses

Used in Organic Chemistry:
Potassium hydride is used as a strong reducing agent in organic condensations and alkylations, facilitating the formation of new chemical bonds and improving the yield of desired products.
Used in Super Base Preparation:
Potassium hydride is used in the preparation of super bases, such as RNHK and ROK, where R is an alkyl group. These super bases are highly reactive and have applications in various chemical reactions and processes.
Used in Potassium Hydride Dispersions:
Potassium hydride is sold as a 35 wt% dispersion in mineral oil, which helps to stabilize the compound and prevent its reaction with moisture and air. This form of potassium hydride is useful for various applications in the chemical industry.
Used in Hydroxy-Xanthone Derivatives Synthesis:
Potassium hydride is used in the preparation of hydroxy-xanthone derivatives via isoprenylation followed by Claisen rearrangement, starting from fluoroxanthone derivatives. This application is particularly relevant in the synthesis of complex organic molecules and pharmaceutical compounds.

Reactions

Potassium hydride acts as a base and as hydride donor. It is used for deprotonation, cyclization-condensation, elimination, and rearrangement reactions, and also as a reducing agent. Potassium hydride undergoes reaction quickly and quantitatively with acids, and of particular note is its capability to rapidly deprotonate tertiary alcohols where sodium hydride or potassium metal do so slowly or not at all. The reactions of metal hydrides take place at the crystal surface. The crystal lattice energies decrease from lithium to cesium hydride, and potassium hydride appears to have the optimal lattice energy and hydride radius for surface reactions. The presence of 18-crown-6 enhances the reactivity of potassium hydride, The crown ether can operate as a phase-transfer agent or as a simple “pickling” agent of the potassium hydride surface, dissolving the formed inorganic salts. Potassium hydride is usually superior to lithium and sodium hydride in the reactions. Unusually active potassium hydride can be prepared easily from hydrogen and superbasic reagents (t-BuOK-TMEDA) in hexane. “Superactive potassium hydride” is very active in deprotonation as well as in reduction. The reactivity of commercially available potassium hydride, which is prepared by the reaction of hydrogen gas with elemental potassium, depends upon the impurities in different lots (mainly potassium or its reaction products), thus leading to side reactions and variable yields. The superactive metal hydride contains no alkali metal.

Hazard

Dangerous fire and explosion risk, evolves toxic and flammable gases on heating and on expo- sure to moisture.

Health Hazard

Potassium hydride react with the moisture on skin and other tissues to form highly corrosive sodium and potassium hydroxide. Contact of these hydrides with the skin, eyes, or mucous membranes causes severe burns; thermal burns may also occur due to ignition of the liberated hydrogen gas.

Health Hazard

The toxicity data on potassium hydride arenot reported in the literature. In the pure state, Potassium hydride should be highly corrosiveby inhalation, ingestion, and skin contact.It yields potassium hydroxide, whichis also very corrosive, when reacted withmoisture.

Fire Hazard

Potassium hydride is flammable solid that ignite on contact with moist air. Potassium hydride presents a more serious fire hazard than sodium hydride. The mineral oil dispersions do not ignite spontaneously on exposure to the atmosphere. Sodium hydride and potassium hydride fires must be extinguished with a class D dry chemical extinguisher or by the use of sand, ground limestone, dry clay or graphite, or "Met-L-X ? " type solids. Water or CO 2 extinguishers must never be used on sodium and potassium hydride fires.

Flammability and Explosibility

Potassium hydride and sodium hydride are flammable solids that ignite on contact with moist air. Potassium hydride presents a more serious fire hazard than sodium hydride. The mineral oil dispersions do not ignite spontaneously on exposure to the atmosphere. Sodium hydride and potassium hydride fires must be extinguished with a class D dry chemical extinguisher or by the use of sand, ground limestone, dry clay or graphite, or "Met-L-X?" type solids. Water or CO2 extinguishers must never be used on sodium and potassium hydride fires.

Safety Profile

Dangerous fire hazard by chemical reaction. Ignites spontaneously in air. Moderate explosion hazard when exposed to heat or by chemical reaction. Wdl react with water, steam, or acids to produce H2 which then igmtes. Can react vigorously with oxidizing materials. To fight fire, use CO2, dry chemical. Potentially explosive reactions with 0-2,4- dnitrophenylhydroxylamine, fluoroalkenes. Ignites on contact with air, oxygen + moisture, fluorine. Incompatible with Cl2, acetic acid, acrolein, acrylonitrile, (CaC + Cl2), ClO2, (H202 + Cl2), (CHFL + CH,OH), 1,2-dchloroethylene, maleic anhydride, (n-methyl-n-nitrosourea + CH2Cl2), nitroethane, NCb, nitromethane, nitroparaffins, o-nitrophenol, nitropropane, n-nitrosomethylurea, (nitrosomethylurea + CH2Cl2), H20, trichloroethylene, tetrahydrofuran, tetrachlorethane. When heated to decomposition it emits highly toxic fumes of K2O. See also POTASSIUM and HYDRIDES.

storage

Safety glasses, impermeable gloves, and a fire-retardant laboratory coat should be worn at all times when working with these substances. These hydrides should be used only in areas free of ignition sources and should be stored preferably as mineral oil dispersions under an inert gas such as argon.

Incompatibilities

Potassium hydride and sodium hydride react violently with water, liberating hydrogen, which can ignite. Oil dispersions of these hydrides are much safer to handle because the mineral oil serves as a barrier to moisture and air. Potassium hydride may react violently with oxygen, CO, dimethyl sulfoxide, alcohols, and acids. Explosions can result from contact of these compounds with strong oxidizers. Potassium hydride is generally more reactive than sodium hydride.

Waste Disposal

Excess potassium or sodium hydride and waste material containing these substances should be placed in an appropriate container under an inert atmosphere, clearly labeled, and handled according to your institution's waste disposal guidelines. Experienced personnel can destroy small quantities of sodium hydride and potassium hydride by the careful dropwise addition of t-butanol or iso-propanol to a suspension of the metal hydride in an inert solvent such as toluene under an inert atmosphere such as argon. Great care must be taken in the destruction of potassium hydride because of its greater reactivity. The resulting mixture of metal alkoxide should be placed in an appropriate container, clearly labeled, and handled according to your institution's waste disposal guidelines.

InChI:InChI=1/K.H/q+1;-1

Synthetic route

hydrogen (1333-74-0) + potassium (7440-09-7) → potassium hydride (7693-26-7)

Conditions	Yield
In neat (no solvent) byproducts: H; Irradiation (UV/VIS); mixt. irradiation by frequency doubled and tripled Nd:YAG laser (404.4nm, 30 Hz, 300 μJ/pulse, oven temp. 500 K), according to P. D. Kleib er et al., J. Chem. Phys. 85 (1986) 5493; detection by LIF technique;
In neat (no solvent) using a six-armed heat pipe to deposit K metal, heating K metal in the oven (500 K, 100 mTorr), evacuating (to 1E-5 Torr prior introduction of H2) flowing H2 slowly through the chamber (< 5 Torr);
In neat (no solvent, gas phase) potassium was placed in the cell-furnace and subjected to vacuum extn. and slight heating; hydrogen was introduced at 10-20 torr; the cell was kept at 700 K;;
In neat (no solvent) production of hydride on discharge (2400 MHz, 150 mA, p(H2) = 1 Torr);

potassium hydride (7693-26-7) + lithium tetrahydridogallate → potassium tetrahydrogallate

Conditions	Yield
In diethyl ether byproducts: LiH; Ga-complex soln. treating with excess K-compd. (three-necked flask, roomtemp., stirring, 3 h), soln. decantation; ppt. washing (ether), treatment with diglyme, crystn. on soln. vac. evapn. (80°C), crystals washing (ether), vac. drying (90°C, 2 h); elem. anal.;	91%

potassium hydride (7693-26-7) + (C6H5)2Sn(CH2C(OH)(CF3)2)2 (210818-37-4) → (C6H5)2Sn(OC(CF3)2)2(CH2)(CH3)(1-)*K(1+)=(C6H5)2Sn(OC(CF3)2)2(CH2)(CH3)K

Conditions	Yield
In tetrahydrofuran room temp., 2 d;

Upstream product

• 1333-74-0 hydrogen 
• 7440-09-7 potassium 

Relevant academic research and scientific papers

Rotational population distribution of KH (v=0, 1, 2, and 3) in the reaction of K(52PJ, 6 2PJ, and 72PJ) with H2: Reaction mechanism and product energy disposal

Using a pump-probe method, we have systematically studied the rotational distribution of KH (v=0-3) produced in the reaction of K (5P, 6P, and 7P) with H2. The resulting rotational states fit roughly a statistical distribution at the system temperature, while the vibrational populations are characterized by a Boltzmann vibrational temperature of 1800, 3000, and 3100 K for the 5p, 6P, and 7P states, respectively. These results provide evidence that the reaction follows a collinear collisional geometry. This work has successfully probed KH from the K(5P) reaction, and confirms that a nonadiabatical transition via formation of an ion-pair K+H2- intermediate should account for the reaction pathway. The available energy dissipation was measured to be (68±4)%, (26±2)%, and (6±3)% into the translation, vibration, and rotation of the KH product, respectively. The energy conversion into vibrational degree of freedom generally increases with the principal quantum number, indicating that the electron-jump distance elongates along the order of 5P2 case, in which the electron-jump distances were considered roughly the same. Furthermore, a relatively large distance is expected to account for highly vibrational excitation found in the KH product. According to the classical trajectory computation reported by Polanyi and co-workers, the strong instability of the H2- bond, inducing a large repulsion energy, appears to favor energy partitioning into the translation.

Chemical dynamics of the reaction K*(5p2P) + H2→KH(v=0; J)+H: Electronic orbital alignment effects

We report results from scattering state spectroscopic studies of the excited state reaction K*(5p 2P) + H2→KH(ν″,J″)+H. The final state resolved action spectra allow a direct measurement of essential features of the excited state potential surfaces, including regions of local maxima and minima. We observe a pronounced blue-wing-red-wing asymmetry in the reactive to nonreactive branching ratio, peaking in the neighborhood of a strong blue wing satellite. These results show that the dominant reaction pathway passes over a small activation barrier (350 ± 100 cm-1) in Σ+-like orbital alignment. This result is consistent with an electron jump mechanism through a K+H-H ion-pair intermediate. In contrast, approach in Π-like alignment leads predominantly to nonreactive scattering. Our results suggest that a combination of steric and energetic effects determine the major quenching pathways for alkali metal atom-H2 systems.

The intensity behaviour of the laser-induced fluorescence spectrum in the KH molecule

Collosional processes involving changes in rotational and vibrational quantum numbers are detected in laser induced fluorescence spectrum of KH molecule.The knowledge of the Franck-Condon factors in the involved transitions allows us to evaluate a relative variation of R2e versus the ν'' vibrational quantum number.In the same context a population analysis was made for the ν'=7 vibrational level.

Spectroscopy of the NaH, NaD, KH, and KD X 1Σ+ ground state by laser excited fluorescence in a high frequency discharge

By laser excited fluorescence of the hydrides obtained in a discharge, the ground state vibrational levels of NaH, NaD, KH, and KD, have been observed up to v = 15, 20, 14, and 16, respectively , instead of v = 8,2 , 4, and 4 by conventional spectroskopy.Experimental values of Gv , Bv , and Dv are obtained.Spectroscopic parameters and RKR potential curves are calculated.In NaH and NaD, a comparison can be made with ab initio calculations.