Hydrogen hydrate Physical and Chemical Properties
Hydrogen hydrate
A gas–water clathrate in which molecular hydrogen is entrapped within a crystalline water lattice, relevant to R&D and materials testing where gas–solid interactions are evaluated.
| CAS Number | Not specified for this entry |
| Family | Gas hydrates (clathrates) |
| Typical Form | Powder or crystalline solid (clathrate) |
| Common Grades | EP |
Hydrogen hydrate is a molecular association between molecular hydrogen and water characterized by the stoichiometric shorthand \(\ce{H4O}\). Structurally it is best described as a physical mixture (or clathrate-like association under specific conditions) of the dihydrogen molecule \(\ce{H2}\) and water \(\ce{H2O}\). Electronic structure is dominated by the closed-shell, nonpolar \(\ce{H2}\) guest and the polar, hydrogen-bonding network of the water host; this combination gives rise to mixed physicochemical behavior where dispersion and weak host–guest interactions control stability while water’s hydrogen-bonding network governs polarity and solvation characteristics.
From an acid–base and reactivity perspective, the water component provides the usual protic, polar medium; the molecular hydrogen is chemically reducing but kinetically inert in the absence of appropriate catalysts. Lipophilicity is minimal for the combined system because water dominates the solvent-accessible surface; however, the neutral \(\ce{H2}\) moiety is nonpolar and will partition into nonpolar domains or cages when clathrate-like structures form. The hydrate association is not a chemically bonded new compound in the covalent sense but rather a physical aggregate whose stability is strongly dependent on temperature, pressure, and the presence of nucleation sites or catalytic surfaces that promote hydrogen ingress or release.
Common commercial grades reported for this substance include: EP.
Overview and Composition
Qualitative Composition
- Formal (descriptor) molecular formula: \(\ce{H4O}\).
- Components: molecular hydrogen \(\ce{H2}\) and water \(\ce{H2O}\).
- Computed molecular weight: 20.031 \(\mathrm{g}\,\mathrm{mol}^{-1}\).
- Exact mass: 20.026214747 \(\mathrm{u}\).
- Monoisotopic mass: 20.026214747 \(\mathrm{u}\).
- Hydrogen bond donor count: 1.
- Hydrogen bond acceptor count: 1.
- Topological polar surface area (TPSA): 1 (computed).
- Rotatable bond count: 0.
- Formal charge: 0.
- Covalently-bonded unit count: 2 (indicates a two-component association).
Computed or depositor-supplied names include "molecular hydrogen;hydrate". Structural/descriptive identifiers: SMILES "[HH].O", InChI InChI=1S/H2O.H2/h1H2;1H, InChIKey VBYZSBGMSZOOAP-UHFFFAOYSA-N.
Appearance and Typical Form
No experimentally established value for this property is available in the current data context.
Class-level behavior for hydrogen–water associations: under ambient conditions hydrogen is a separate, low-density gas with very low solubility in water; under reduced temperature and elevated pressure or in the presence of suitable host frameworks, hydrogen can be retained in clathrate-like cages within a crystalline hydrate lattice to form a solid-phase hydrogen hydrate. Such clathrate or hydrate forms are typically observed under cryogenic or high-pressure experimental conditions rather than as a stable material at standard laboratory temperature and pressure. In practical handling, hydrogen will most commonly exist as a dissolved gas in water or as a separate gaseous phase unless experimental conditions are intentionally adjusted to form a hydrate.
Chemical Properties
Reactivity and Corrosive Behavior
Hydrogen hydrate as an association combines the inertness of molecular hydrogen with the reactivity profile of water. Key points:
- Molecular hydrogen (\(\ce{H2}\)) is a reducing agent but is kinetically inert toward most substrates at ambient conditions; catalytic activation (metal surfaces, finely divided catalysts, or extreme conditions) is required to effect chemical change.
- Water contributes protic acidity/basicity and participates in hydrogen-bond networks; it can solvate ions and polar species and mediate hydrolysis reactions for susceptible solutes.
- The hydrate association itself is not strongly corrosive in a chemical sense; however, hydrogen exposure can promote hydrogen embrittlement in susceptible metals and alloys when atomic hydrogen is produced at surfaces, particularly under catalytic or electrochemical conditions.
- Decomposition of solid or metastable hydrates will release molecular hydrogen and water; such release can be rapid under destabilizing thermal or pressure changes.
Compatibility and Incompatibilities
- Incompatible with strong oxidizing agents in the sense that released hydrogen represents a flammable reducing species that will react vigorously with oxidizers under ignition conditions.
- Metallic catalysts or reactive metal surfaces can facilitate dissociation of \(\ce{H2}\) to atomic hydrogen, increasing risks of embrittlement or unexpected reactivity.
- Reactive hydride-forming metals and alloys (e.g., finely divided transition metals) can interact with hydrogen; materials selection for storage or containment should consider susceptibility to hydrogen-induced damage.
- No explicit compatibility tables are available in the current data context; selection of container and system materials should follow established engineering guidelines for hydrogen service and for aqueous systems.
Usage and Safety
Industrial and Commercial Use Contexts
No concise application summary is available in the current data context; in practice this substance is selected based on its general properties described above. General, class-level uses and research contexts include:
- Experimental investigation of hydrogen storage in water-based clathrates or hydrates and studies of host–guest interactions for energy storage research.
- Laboratory-scale studies of hydrogen solubility, mass transfer, and gas–liquid interactions in aqueous systems.
- Fundamental studies of pressure- and temperature-dependent phase behavior in gas hydrate science.
Hazards and Handling Considerations
- Flammability: molecular hydrogen is highly flammable and forms explosive mixtures with air. Any process that can release \(\ce{H2}\) (decomposition of a hydrate, leakage from pressurized systems) requires control of ignition sources, appropriate ventilation, and gas detection.
- Asphyxiation: displacement of oxygen in confined spaces by released hydrogen can create an asphyxiation hazard.
- Pressure and cryogenic hazards: formation or handling of solid hydrates often involves low temperatures and/or elevated pressures; appropriate pressure-rated equipment, thermal protection, and safe depressurization practices are required.
- Materials considerations: risk of hydrogen embrittlement in susceptible metals; avoid use of materials not rated for hydrogen service in pressurized or catalytic environments.
- Personal protective equipment and engineering controls: standard PPE for pressurized gas and cryogenic handling, gas detection systems, grounding and bonding where flammable gases are present, and local exhaust/ventilation.
- For detailed hazard, transport and regulatory information, users should refer to the product-specific Safety Data Sheet (SDS) and local legislation.
