Methylammonium (17000-00-9) Physical and Chemical Properties
Methylammonium
Protonated methylamine (small organic cation) commonly handled as salts or aqueous solutions and used as a reagent and building block in synthesis, materials and analytical workflows.
| CAS Number | 17000-00-9 |
| Family | Alkylammonium cations |
| Typical Form | Aqueous solution or crystalline salt |
| Common Grades | EP |
Methylammonium is the simple primary alkylammonium cation derived from protonation of methylamine; its molecular formula is \(\ce{CH6N+}\). Structurally it is a small, strongly solvated cation featuring a single methyl-substituted nitrogen with three equivalent N–H bonds when protonated. Electronically it is a localized, positively charged nitrogen center that engages in strong ion–dipole interactions and conventional hydrogen bonding (as donor) with polar solvents and anionic counterions.
Because it is a primary ammonium ion, methylammonium behaves as the conjugate acid of a weak base: it is favored in neutral to acidic aqueous media and exists predominantly in the protonated cationic form under physiological conditions (major species at \(\mathrm{pH}\) 7.3). The combination of small size, a single positive charge and a modest topological polar surface area yields high aqueous solubility, low lipophilicity and efficient ionic pairing with inorganic and organic anions. Chemically it is stable as a salt but will equilibrate with free methylamine under sufficiently basic conditions.
Common commercial grades reported for this substance include: EP.
Molecular Parameters
Molecular Weight and Formula
- Molecular formula: \(\ce{CH6N+}\).
- Molecular weight: 32.065 (as provided).
- Exact/monoisotopic mass: 32.050024196.
- Heavy atom count: 2. The simple composition (one carbon, one nitrogen, six hydrogens formally) accounts for the low molecular complexity.
Charge State and Ion Type
- Formal charge: 1 (monocation).
- Ion type: primary alkylammonium cation (protonated methylamine).
- Hydrogen-bonding: H-bond donor count = 1; H-bond acceptor count = 0. The N–H motif on the ammonium center functions as a hydrogen-bond donor to polar solvents or anionic partners.
- Rotatable bond count = 0, reflecting the minimal internal conformational flexibility of this monofunctional cation.
LogP and Polarity
- XLogP: -0.7 (reported). The negative XLogP indicates low lipophilicity and preference for aqueous phases when present as the free cation or as readily dissociating salts.
- Topological polar surface area (TPSA): 27.6, consistent with high polarity for a species of this size and supportive of good aqueous solvation.
Structural Identifiers (SMILES, InChI)
- SMILES:
C[NH3+] - InChI:
InChI=1S/CH5N/c1-2/h2H2,1H3/p+1 - InChIKey:
BAVYZALUXZFZLV-UHFFFAOYSA-O - The compound is a canonicalized single covalently-bonded unit with low structural complexity.
Acid–Base Behavior
Conjugate Acid and Speciation
Methylammonium is the conjugate acid of methylamine (\(\ce{CH5N}\)). In aqueous solution the equilibrium between methylammonium cation and free methylamine is governed by proton availability; the cationic form predominates at neutral and acidic \(\mathrm{pH}\), while deprotonation yields the neutral amine under sufficiently basic conditions. It is reported to be the major species at \(\mathrm{pH}\) 7.3, consistent with typical primary-alkylammonium speciation trends.
Acid–Base Equilibria and Qualitative pKa Discussion
No experimentally established value for this property is available in the current data context.
Qualitatively, primary alkylammonium cations are formed by protonation of the corresponding amines and undergo reversible deprotonation as the medium becomes more basic. Speciation in mixed-solvent systems or in nonpolar media will be strongly influenced by counterion identity and solvent dielectric, with ion pairing reducing the effective degree of dissociation in low-dielectric environments.
Chemical Reactivity
Chemical Stability
As a discrete cation, methylammonium is chemically robust with respect to simple hydrolytic cleavage (there is no hydrolyzable bond intrinsic to the cation itself). Stability considerations are dominated by its tendency to form salts and crystalline phases with anions; crystallographic studies report numerous solid-state structures for methylammonium salts and complexes. Under oxidative or high-energy conditions, organic nitrogen-containing species can undergo oxidation or N-dealkylation, but such pathways are context-dependent and require specific reagents or conditions.
Formation and Hydrolysis Pathways
Methylammonium forms directly by protonation of methylamine in acidic media. The reverse process—loss of a proton to regenerate methylamine—occurs under basic conditions. In practical synthetic and industrial contexts methylammonium is typically encountered as a counterion in salts (e.g., pairing with inorganic anions, organic carboxylates or halides) rather than as an isolated free cation.
Identifiers and Synonyms
Registry Numbers and Codes
- CAS number: 17000-00-9
- ChEBI: CHEBI:59338
- DSSTox Substance ID: DTXSID20937723
- Nikkaji numbers: J135.954A; J2.161.655I
- Wikidata: Q27104851
- InChIKey: BAVYZALUXZFZLV-UHFFFAOYSA-O
Synonyms and Structural Names
Depositor- and computed synonyms reported include (selection): - Methylammonium - Methanaminium - methylazanium - Methylammonium ion - N-methylammonium - Monomethylammonium - methanaminium cation - methylaminium cation - Methylammonium cation - Protonated methylamine - Monoprotonated methylamine - primary methyl ammonium ion
(These names reflect alternative systematic, common and depositor-supplied labels for the protonated methylamine species.)
Industrial and Commercial Applications
Role as Active Ingredient or Intermediate
Methylammonium functions primarily as a simple monovalent counterion in salts and ionic materials and as an intermediate/protonated form of methylamine in chemical and biochemical contexts. It is also encountered as a human metabolite in biological systems. In synthesis it serves conceptually as the protonated partner when preparing amine salts or when stabilizing anionic species in crystalline form.
Representative Application Contexts
Representative contexts where methylammonium cations appear include: - Formation of crystalline salts for structural chemistry and materials research. - Use as the cationic component in ionic compounds and as an intermediary in synthetic sequences involving methylamine. - Presence in biochemical and metabolic studies where protonated small amines are relevant.
No concise application summary is available in the current data context; in practice this substance is selected based on its general properties described above.
Safety and Handling Overview
Toxicity and Biological Effects
Methylammonium is a low-molecular-weight primary ammonium cation and is reported to occur as a human metabolite. As with small protonated amines, exposure considerations focus on irritation potential to eyes, skin and respiratory tract for concentrated solutions and salts. Systemic toxicity and metabolic fate depend on dose, counterion, and route of exposure; small alkylammonium species are metabolically labile compared with quaternary ammonium compounds.
Storage and Handling Considerations
Handle methylammonium-containing materials using standard industrial chemical hygiene measures: appropriate eye and skin protection, use of gloves resistant to the formulation, and engineering controls to minimize inhalation of aerosols or dust. Store salts and concentrated solutions in well-closed containers, protected from strong bases (which will deprotonate the cation) and incompatible oxidizers. For detailed hazard, transport and regulatory information, users should refer to the product-specific Safety Data Sheet (SDS) and local legislation.
