Sodium acetylide (Na(C2H)) (1066-26-8) Physical and Chemical Properties
Sodium acetylide (Na(C2H))
Highly nucleophilic acetylide salt used as an alkynylating reagent in specialty and process chemistry, typically handled and stored under dry, inert conditions for R&D and manufacturing.
| CAS Number | 1066-26-8 |
| Family | Acetylide salts |
| Typical Form | Suspension (slurry) |
| Common Grades | EP, USP |
Sodium acetylide is an inorganic-organic salt of the acetylide (ethynide) monoanion; it is classed as an acetylide and a metal-organic salt. Structurally it comprises the acetylide unit and a sodium countercation and can be written by its molecular formula \(\ce{C2HNa}\). In condensed representation the ionic constituents are usefully depicted as \(\ce{C2H-}\) and \(\ce{Na+}\); structural descriptions emphasize a linear carbon–carbon triple bond in the acetylide fragment with formally anionic charge localized on the terminal carbon, giving pronounced nucleophilicity and basicity in aprotic media.
Electronically the acetylide fragment is a strong base and a soft-to-intermediate donor ligand: the anionic carbon has high s-character from the sp-hybridized orbital and a concentrated negative charge that favors tight ion pairing with alkali cations in low-dielectric environments. The material is essentially nonpolar as a discrete ion pair in nonprotic organic media but behaves as a highly reactive, water-sensitive ionic species on exposure to protic or aqueous environments. Hydrolysis or protonation produces acetylene gas and is exothermic; contact with water therefore produces flammable gas and may be violently reactive under some conditions.
As a reagent class, alkali acetylides are routinely used as sources of acetylide nucleophiles and as ligands or transmetallation intermediates in organometallic synthesis. Industrial handling typically employs suspensions or slurries in aprotic hydrocarbon media to moderate reactivity and to facilitate transfer; an 18% slurry in xylene is one documented commercial form. Common commercial grades reported for this substance include: EP, USP.
Basic Physical Properties
Solubility and Hydration
Sodium acetylide is strongly moisture-sensitive and reacts on contact with water to liberate acetylene gas; it is not handled as a freely water-soluble salt in conventional aqueous media. Practical preparations and commercial formulations are frequently distributed as suspensions or slurries in aprotic aromatic or hydrocarbon solvents (e.g., xylene). One documented physical description is: "Suspension in 82% xylene: Grey liquid with an aromatic odor." Attempting to dissolve the neat salt in protic solvents results in rapid protonation (hydrolysis) rather than formation of a stable solvated ionic solution.
Thermal Stability and Decomposition
No experimentally established value for melting point or boiling point is available in the current data context. Thermally and chemically, sodium acetylide decomposes by protonation/hydrolysis to produce acetylene (a flammable gas) and sodium-containing byproducts; exposure to moisture or protic impurities is the principal chemical decomposition pathway. Elevated temperature in the presence of contaminants or oxidants can increase the rate of decomposition and gas evolution; standard industrial practice is to maintain inert, dry atmospheres and avoid sources of moisture or strong oxidants.
Chemical Properties
Complex Formation and Coordination
The acetylide anion is a competent σ-donor and π-acceptor to transition metals and forms a range of terminal and bridging coordination modes in metal complexes. With hard alkali cations (e.g., \(\ce{Na+}\)), tight ion-pairing and cluster or polymeric aggregates are common in the solid state and in low-polarity solvents; in coordinating solvents or in the presence of complexing ligands, ion separation and formation of discrete metal–acetylide coordination complexes are observed. Transmetallation from alkali acetylides to transition-metal centers is a common synthetic route to organometallic alkynyl complexes.
Reactivity and Stability
Sodium acetylide behaves as a strong base and nucleophile in aprotic solvents: it readily deprotonates weakly acidic C–H bonds and adds to electrophilic carbon centers (e.g., carbonyls, activated halides) to form new C–C bonds. In protic environments it is instantly protonated to give acetylene; in the presence of water it releases flammable gas and can react violently with moisture. It causes severe skin and eye damage on contact and can produce corrosive vapors if heated or decomposed. The compound should be considered highly moisture-sensitive, corrosive, and reactive toward protic and oxidizing agents.
Molecular Parameters
Molecular Weight and Composition
- Molecular formula: \(\ce{C2HNa}\)
- Molecular weight: 48.02
- Exact mass: 47.99759431
- Monoisotopic mass: 47.99759431
- Heavy atom count: 3
- Covalently-bonded unit count: 2
These values reflect the empirical composition of the sodium acetylide ion pair and are consistent with a three‑heavy‑atom unit (two carbon atoms and one sodium atom) plus one hydrogen.
LogP and Ionization State
No experimentally established value for logP is available in the current data context. The substance exists as an ionic species in which the acetylide moiety carries negative charge and sodium is the countercation; in condensed notation the ionic constituents are represented as \(\ce{C2H-}\) and \(\ce{Na+}\). The acetylide anion is a strong base and will be protonated by sufficiently acidic media to yield acetylene; no definitive \(\mathrm{p}K_a\) value for the conjugate acid is provided here.
Additional computed descriptors: topological polar surface area (TPSA) 0; hydrogen bond donor count 0; hydrogen bond acceptor count 1; rotatable bond count 0; formal charge 0 (neutral overall ionic pair); complexity 10; canonicalization reported as Yes.
Note: three-dimensional conformer generation may be restricted for mixtures and salts in certain force-field-based workflows.
Identifiers and Synonyms
Registry Numbers and Codes
- CAS number: 1066-26-8
- European Community (EC) Number: 213-908-9
- ChEBI ID: CHEBI:55387
- DSSTox Substance ID: DTXSID50910044
- Nikkaji Number: J52.068C
- Wikidata: Q17417384
Synonyms and Structural Names
Selected synonyms and names that appear in supplier and registry listings include: Sodium acetylide; monosodium acetylide; sodium ethynide; sodium ethyne; ethynyl sodium; ethynylsodium; sodium;ethyne; C2HNa; sodium acetylide suspension; Sodium Acetylide Suspension (18 wt. % slurry in xylene). The computed IUPAC name is "sodium ethyne".
Structural identifiers (inline code):
- SMILES: C#[C-].[Na+]
- InChI: InChI=1S/C2H.Na/c1-2;/h1H;/q-1;+1
- InChIKey: SFDZETWZUCDYMD-UHFFFAOYSA-N
Industrial and Commercial Applications
Use as Salt Form or Excipient
Sodium acetylide is not used as an excipient; it is principally handled and traded as a reactive reagent. Commercial handling commonly involves suspensions in aprotic hydrocarbon solvents (xylene or related media) to moderate reactivity and facilitate metered addition to reaction mixtures. The substance is listed as commercially active in industrial chemical inventories for use in manufacturing and synthetic applications.
Common commercial grades reported for this substance include: EP, USP.
Representative Use Cases
Representative uses reflect the chemistry of acetylide anions: generation of carbon–carbon bonds via nucleophilic addition to electrophiles, formation of alkynylated intermediates and transmetallation to transition metals for synthesis of metal–alkynyl complexes. Industrial shipments and handling protocols favor inert, moisture-free formulations (slurries) for safe transport and dosing. If no concise application summary is available in specific procurement documentation, selection is typically driven by the need for a strong alkynyl nucleophile or a source of acetylide for organometallic synthesis.
Safety and Handling Overview
Toxicological Considerations
Sodium acetylide is corrosive and causes severe skin burns and eye damage (GHS hazard H314). It is highly reactive with water and, on contact, releases flammable gas (GHS hazard H261). Documented adverse effects include dermatotoxin (skin burns) and toxic pneumonitis risk from inhalation of corrosive gases or decomposition products. Hazard classifications reported include: Water-react. 2 (90.7%) and Skin Corr. 1B (100%). Relevant precautionary measures include control of moisture, use of appropriate personal protective equipment, and readiness to manage flammable gas evolution.
Noted GHS hazard statements and precautionary phrases (as used in supplier classification summaries) include:
- H261 (90.7%): In contact with water releases flammable gas.
- H314 (100%): Causes severe skin burns and eye damage.
- Precautionary codes: P231+P232, P260, P264, P280, P301+P330+P331, P302+P361+P354, P304+P340, P305+P354+P338, P316, P321, P363, P370+P378, P402+P404, P405, P501.
For detailed toxicology and exposure limits consult product-specific safety documentation.
Storage and Handling Guidelines
Store and handle under anhydrous, inert atmosphere conditions; avoid all contact with water and protic solvents. Typical engineering controls include dry nitrogen or argon blanketing, use of sealed transfer systems, and adequate ventilation to control any liberated gases. Personal protective equipment should protect against corrosive contact (chemical-resistant gloves, face shield, eye protection and appropriate protective clothing). Commercially, suspensions in aprotic hydrocarbon media (e.g., xylene) are used to reduce dusting and moderate reactivity during transfer.
For detailed hazard, transport and regulatory information, users should refer to the product-specific Safety Data Sheet (SDS) and local legislation.
