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Ethylamine
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| Names | |||
|---|---|---|---|
| Preferred IUPAC name
Ethanamine | |||
| Other names
Ethylamine
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| Identifiers | |||
3D model (JSmol)
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| 505933 | |||
| ChEBI | |||
| ChEMBL | |||
| ChemSpider | |||
| ECHA InfoCard | 100.000.759 | ||
| EC Number |
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| 897 | |||
| KEGG | |||
| MeSH | ethylamine | ||
PubChem CID
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| RTECS number |
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| UNII | |||
| UN number | 1036 | ||
CompTox Dashboard (EPA)
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| Properties | |||
| C2H7N | |||
| Molar mass | 45.085 g·mol−1 | ||
| Appearance | Colourless gas | ||
| Odor | fishy, ammoniacal | ||
| Density | 688 kg m−3 (at 15 °C) | ||
| Melting point | −85 to −79 °C; −121 to −110 °F; 188 to 194 K | ||
| Boiling point | 16 to 20 °C; 61 to 68 °F; 289 to 293 K | ||
| Miscible | |||
| log P | 0.037 | ||
| Vapor pressure | 116.5 kPa (at 20 °C) | ||
Henry's law
constant (kH) |
350 μmol Pa−1 kg−1 | ||
| Acidity (pKa) | 10.8 (for the Conjugate acid) | ||
| Basicity (pKb) | 3.2 | ||
| Thermochemistry | |||
Std enthalpy of
formation (ΔfH⦵298) |
−57.7 kJ mol−1 | ||
| Hazards | |||
| GHS labelling: | |||
 
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| Danger | |||
| H220, H319, H335 | |||
| P210, P261, P305+P351+P338, P410+P403 | |||
| NFPA 704 (fire diamond) | |||
| Flash point | −37 °C (−35 °F; 236 K) | ||
| 383 °C (721 °F; 656 K) | |||
| Explosive limits | 3.5–14% | ||
| Lethal dose or concentration (LD, LC): | |||
LD50 (median dose)
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LC50 (median concentration)
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1230 ppm (mammal)[3] | ||
LCLo (lowest published)
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3000 ppm (rat, 4 hr) 4000 ppm (rat, 4 hr)[3] | ||
| NIOSH (US health exposure limits): | |||
PEL (Permissible)
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TWA 10 ppm (18 mg/m3)[2] | ||
REL (Recommended)
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TWA 10 ppm (18 mg/m3)[2] | ||
IDLH (Immediate danger)
|
600 ppm[2] | ||
| Related compounds | |||
Related alkanamines
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Related compounds
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Ethylamine, also known as ethanamine, is an organic compound with the formula CH3CH2NH2. This colourless gas has a strong ammonia-like odor. It condenses just below room temperature to a liquid miscible with virtually all solvents. It is a nucleophilic base, as is typical for amines. Ethylamine is widely used in chemical industry and organic synthesis.[4] It is a DEA list I chemical by 21 CFR § 1310.02.
Synthesis
[edit]Ethylamine is produced on a large scale by two processes. Most commonly ethanol and ammonia are combined in the presence of an oxide catalyst:
- CH3CH2OH + NH3 → CH3CH2NH2 + H2O
In this reaction, ethylamine is coproduced together with diethylamine and triethylamine. In aggregate, approximately 80M kilograms/year of these three amines are produced industrially.[4] It is also produced by reductive amination of acetaldehyde.
- CH3CHO + NH3 + H2 → CH3CH2NH2 + H2O
Ethylamine can be prepared by several other routes, but these are not economical. Ethylene and ammonia combine to give ethylamine in the presence of a sodium amide or related basic catalysts.[5]
- H2C=CH2 + NH3 → CH3CH2NH2
Hydrogenation of acetonitrile, acetamide, and nitroethane affords ethylamine. These reactions can be effected stoichiometrically using lithium aluminium hydride. In another route, ethylamine can be synthesized via nucleophilic substitution of a haloethane (such as chloroethane or bromoethane) with ammonia, utilizing a strong base such as potassium hydroxide. This method affords significant amounts of byproducts, including diethylamine and triethylamine.[6]
- CH3CH2Cl + NH3 + KOH → CH3CH2NH2 + KCl + H2O
Ethylamine is also produced naturally in the cosmos; it is a component of interstellar gases.[7]
Reactions
[edit]Like other simple aliphatic amines, ethylamine is a weak base: the pKa of [CH3CH2NH3]+ has been determined to be 10.8[8][9]
Ethylamine undergoes the reactions anticipated for a primary alkyl amine, such as acylation and protonation. Reaction with sulfuryl chloride followed by oxidation of the sulfonamide give diethyldiazene, EtN=NEt.[10] Ethylamine may be oxidized using a strong oxidizer such as potassium permanganate to form acetaldehyde.
Ethylamine like some other small primary amines is a good solvent for lithium metal, giving the ion [Li(amine)4]+ and the solvated electron. Such solutions are used for the reduction of unsaturated organic compounds, such as naphthalenes[11] and alkynes.
Applications
[edit]Ethylamine is a precursor to many herbicides including atrazine and simazine. It is found in rubber products as well.[4]
Ethylamine is used as a precursor chemical along with benzonitrile (as opposed to o-chlorobenzonitrile and methylamine in ketamine synthesis) in the clandestine synthesis of cyclidine dissociative anesthetic agents (the analogue of ketamine which is missing the 2-chloro group on the phenyl ring, and its N-ethyl analog) which are closely related to the well known anesthetic agent ketamine and the recreational drug phencyclidine and have been detected on the black market, being marketed for use as a recreational hallucinogen and tranquilizer. This produces a cyclidine with the same mechanism of action as ketamine (NMDA receptor antagonism) but with a much greater potency at the PCP binding site, a longer half-life, and significantly more prominent parasympathomimetic effects.[12]
References
[edit]- ^ Merck Index, 12th Edition, 3808.
- ^ a b c NIOSH Pocket Guide to Chemical Hazards. "#0263". National Institute for Occupational Safety and Health (NIOSH).
- ^ a b "Ethylamine". Immediately Dangerous to Life or Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
- ^ a b c Karsten Eller, Erhard Henkes, Roland Rossbacher, Hartmut Höke, "Amines, Aliphatic" Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2005.doi:10.1002/14356007.a02_001
- ^ Ulrich Steinbrenner, Frank Funke, Ralf Böhling, Method and device for producing ethylamine and butylamine Archived 2012-09-12 at archive.today, United States Patent 7161039.
- ^ Nucleophilic substitution, Chloroethane & Ammonia Archived 2008-05-28 at the Wayback Machine, St Peter's School
- ^ NRAO, "Discoveries Suggest Icy Cosmic Start for Amino Acids and DNA Ingredients", Feb 28 2013
- ^ Wilson and Gisvold's Textbook of Organic Medicinal and Pharmaceutical Chemistry, 9th Ed. (1991), (J. N. Delgado and W. A. Remers, Eds.) p.878, Philadelphia: Lippincott and 10.63.
- ^ H. K. Hall, Jr. (1957). "Correlation of the Base Strengths of Amines". J. Am. Chem. Soc. 79 (20): 5441–5444. doi:10.1021/ja01577a030.
- ^ "AZOETHANE". Organic Syntheses. 52: 11. 1972. doi:10.15227/orgsyn.052.0011.
- ^ Kaiser, E. M.; Benkeser R. A. Δ9,10-Octalin Archived 2007-09-30 at the Wayback Machine, Organic Syntheses, Collected Volume 6, p.852 (1988)
- ^ "World Health Organization Critical Review Report of Ketamine, 34th ECDD 2006/4.3" (PDF).
External links
[edit]Ethylamine
View on Grokipediafrom Grokipedia
Structure and Nomenclature
Molecular Structure
Ethylamine, with the structural formula CH₃CH₂NH₂, is a primary aliphatic amine consisting of an ethyl group (CH₃CH₂-) bonded to an NH₂ group. Both carbon atoms and the nitrogen atom exhibit sp³ hybridization, leading to tetrahedral local geometries around these atoms. The Lewis structure depicts a single bond between the two carbon atoms, a single C-N bond, two N-H bonds, and a lone pair on the nitrogen atom, which contributes to its nucleophilic character. In three-dimensional space, ethylamine adopts a staggered conformation around both the C-C and C-N bonds to minimize torsional strain and steric interactions between the methyl group and the amino hydrogens. Experimental gas-phase structural parameters, determined by electron diffraction, show the C-C bond length as approximately 1.53 Å and the C-N bond length as approximately 1.47 Å, with minor differences between the trans (C-C 1.531 Å, C-N 1.470 Å) and gauche (C-C 1.524 Å, C-N 1.475 Å) conformers. The H-N-H bond angle measures about 107°, reflecting the influence of the lone pair repulsion on the nitrogen pyramidality.[4] Relative to ammonia (NH₃), the ethyl group in ethylamine acts as an electron-donating substituent via inductive effects, slightly enhancing the basicity of the amine; the pKₐ of the ethylammonium ion is 10.6, compared to 9.2 for the ammonium ion.Names and Identifiers
Ethylamine, with the molecular formula C₂H₇N, is systematically named ethanamine as the preferred IUPAC name.[1] This nomenclature treats the compound as a derivative of ethane, replacing the terminal "-e" with "-amine" to indicate the primary amino group.[5] Common names for the compound include ethylamine and monoethylamine, the latter emphasizing its status as a simple primary amine.[1] In chemical databases and regulatory contexts, ethylamine is assigned the CAS Registry Number 75-04-7, the EC (EINECS) number 200-834-7, and the UN number 1036 for transport classification as a flammable gas. Additional identifiers include PubChem CID 6341 and the InChI string InChI=1S/C2H7N/c1-2-3/h3H2,1-2H3. Historically, the compound was commonly referred to as ethylamine in early chemical literature, reflecting its derivation from ethyl alcohol; however, the preferred IUPAC name ethanamine was formally established in the 1979 Recommendations of the International Union of Pure and Applied Chemistry (IUPAC) for the Nomenclature of Organic Chemistry, promoting systematic alkanamine naming for primary amines.Properties
Physical Properties
Ethylamine is a colorless gas at standard temperature and pressure, exhibiting a strong ammoniacal odor often described as fishy.[1][6] Its molecular weight is 45.08 g/mol.[1] The liquid density of ethylamine is 0.687 g/cm³ at 15 °C, while its vapor density relative to air is 1.56.[1] It has a melting point of -81 °C and a boiling point of 16.6 °C.[1][3] Ethylamine is miscible with water, ethanol, and diethyl ether, and it shows good solubility in organic solvents such as benzene.[1][2] The refractive index of the liquid is 1.366 at 20 °C.[1] Its liquid viscosity is approximately 0.3 cP near 0 °C, decreasing with temperature.[7]Chemical Properties
Ethylamine acts as a weak base in aqueous solution, characterized by a pK_b value of 3.36, corresponding to a pK_a of 10.64 for its conjugate acid at 25°C. This basicity arises from the lone pair on the nitrogen atom, enabling protonation according to the equilibrium:
The compound exhibits high stability under ambient conditions but undergoes thermal decomposition at temperatures exceeding 300°C, primarily yielding ethylene and ammonia through unimolecular pathways involving hydrogen, ammonia, or methane elimination.[8]
Spectroscopically, ethylamine displays a characteristic N-H stretching band in the infrared spectrum at approximately 3300 cm⁻¹, indicative of its primary amine functionality.[9] In the ¹H NMR spectrum, the methyl protons appear as a triplet at 1.1 ppm, the methylene protons as a quartet at 2.6 ppm, and the amino protons as a broad singlet at 1.2 ppm, reflecting the expected splitting patterns and hydrogen bonding effects.[10]
The polarity of ethylamine stems from the electronegative nitrogen, resulting in a dipole moment of approximately 1.3 D.[11] This property contributes to its moderate solubility in water and role as a nucleophile in various chemical processes.
Thermodynamic Properties
Ethylamine's thermodynamic properties are crucial for applications in process design, equilibrium predictions, and energy balance calculations in chemical engineering and synthesis. In the gas phase, the standard enthalpy of formation (ΔH_f°) is -50.03 kJ/mol at 298.15 K, reflecting the energy change when forming the compound from its elements in their standard states.[12] The standard Gibbs free energy of formation (ΔG_f°) is 36.3 kJ/mol, indicating the spontaneity of formation under standard conditions.[13] The standard entropy (S°) in the gas phase is 283.8 J/mol·K at 298 K, providing insight into the disorder associated with the molecule.[13] The molar heat capacity at constant pressure (C_p) for the gas is 71.5 J/mol·K at 25°C, while the enthalpy of vaporization (ΔH_vap) is 26.8 kJ/mol at the boiling point of approximately 289 K.[13][14] These values enable accurate modeling of phase changes and thermal behaviors. The C-N bond dissociation energy is approximately 305 kJ/mol, a key parameter for assessing molecular stability during bond-breaking processes.| Property | Value | Phase/Condition | Source |
|---|---|---|---|
| ΔH_f° | -50.03 kJ/mol | Gas, 298.15 K | ATcT[12] |
| ΔG_f° | 36.3 kJ/mol | Gas, 298 K | Engineering Toolbox[13] |
| S° | 283.8 J/mol·K | Gas, 298 K | Engineering Toolbox[13] |
| C_p | 71.5 J/mol·K | Gas, 25°C | Engineering Toolbox[13] |
| ΔH_vap | 26.8 kJ/mol | At boiling point (~289 K) | NIST WebBook[14] |
| C-N BDE | ~305 kJ/mol | Gas | LibreTexts |
Occurrence and Production
Natural Occurrence
Ethylamine has been tentatively detected in the interstellar medium toward the Galactic center molecular cloud G+0.693−0.027 through radio astronomical observations, marking it as one of the complex organic molecules present in such environments.[15] The derived column density corresponds to an abundance of (1.9 ± 0.5) × 10^{-10} relative to H₂, indicating its rarity but significance in astrochemistry.[15] Laboratory simulations replicating interstellar conditions further support its natural formation, showing that ethylamine arises from the irradiation of ices composed of ammonia (NH₃) and methane (CH₄) with energetic particles, such as those from cosmic rays.[16] This process highlights ethylamine's potential role as a prebiotic building block, contributing to the synthesis of proteinogenic α-amino acids in extraterrestrial settings.[16] On Earth, ethylamine functions as a metabolite in biological systems, primarily generated via the decarboxylation of alanine catalyzed by alanine decarboxylase (AlaDC).[17] In humans, it appears as a normal constituent of urine and is derived from amino acid breakdown, though in trace quantities.[1] Similarly, plants such as tea (Camellia sinensis) produce ethylamine through AlaDC-mediated alanine decarboxylation, where it serves as a precursor for compounds like theanine.[18] Microorganisms also generate ethylamine in small amounts during metabolic processes, underscoring its widespread but minor presence in terrestrial biochemistry.[19] In environmental contexts, ethylamine exists at low atmospheric concentrations, typically below levels that pose significant pollution risks, due to its short half-life of about 14 hours in the presence of hydroxyl radicals.[1] It emerges as a minor byproduct in natural fermentation, accumulating in trace amounts in beverages like wine, beer, and vinegar through microbial activity on amino acids.[20] These occurrences reflect its incidental role in organic decay and food-related processes rather than as a dominant environmental compound.[1]Industrial Production
Ethylamine is primarily produced industrially through the catalytic amination of ethanol with ammonia in the presence of hydrogen. This process employs a heterogeneous catalyst, typically consisting of copper, cobalt, and nickel supported on gamma-alumina (Al₂O₃), at temperatures ranging from 200 to 300°C. The reaction proceeds as CH₃CH₂OH + NH₃ → CH₃CH₂NH₂ + H₂O, achieving a selectivity of approximately 70% toward ethylamine under optimized conditions.[21] Alternative production routes include the reductive amination of acetaldehyde with ammonia and hydrogen over a suitable catalyst, represented by CH₃CHO + NH₃ + H₂ → CH₃CH₂NH₂.[22] In these processes, particularly the ethanol amination, diethylamine and triethylamine form as significant byproducts due to further alkylation of the primary amine. These are managed through distillation and decantation steps, with portions recirculated to the reactor to convert intermediates into higher-boiling compounds and prevent accumulation, ensuring efficient separation and recovery of the target ethylamine.[22] Global production of ethylamine stands at approximately 152,000 metric tons per year as of 2025, with major producers concentrated in Europe (e.g., BASF in Germany) and Asia (e.g., Balaji Amines in India). The overall ethylamine market, encompassing mono-, di-, and triethylamine variants, was valued at USD 3.17 billion in 2024.[23][24]Reactions
Acid-Base Reactions
Ethylamine acts as a base through protonation of its nitrogen atom, forming the ethylammonium ion according to the equilibrium CH₃CH₂NH₂ + H⁺ ⇌ CH₃CH₂NH₃⁺, where the acid dissociation constant for the conjugate acid is K_a = 10^{-10.63} (pK_a = 10.63 at 25°C).[25] This protonation is reversible and reflects the compound's moderate basicity in aqueous solutions. The protonated form readily forms salts with acids, such as hydrochloric acid, yielding ethylammonium chloride (CH₃CH₂NH₃Cl) via the reaction CH₃CH₂NH₂ + HCl → CH₃CH₂NH₃⁺ Cl⁻. This salt is highly soluble in water (approximately 280 g/100 g at 25°C), facilitating its use in the purification of ethylamine by converting the free base to a crystalline or soluble ionic form that can be separated from non-polar impurities, followed by basification to regenerate the amine.[26] Aqueous solutions of ethylamine exhibit basic pH values due to partial protonation of water, with a 0.1 M solution having a pH of approximately 11.8, calculated from its base dissociation constant K_b = 4.3 × 10^{-4}.[27] In acid-base titrations with HCl, the pH starts high (around 12), decreases gradually as the base is protonated, and shows a sharp drop near the equivalence point (pH ≈ 5.5–6.5), where the solution becomes dominated by the ethylammonium ion acting as a weak acid.[28] Compared to ammonia (pK_a of NH₄⁺ = 9.25), ethylamine is a slightly stronger base, as the electron-donating inductive effect (+I) of the ethyl group increases the electron density on the nitrogen, enhancing its ability to accept a proton.[29]Electrophilic Reactions
Ethylamine, as a primary aliphatic amine, readily undergoes acylation reactions with electrophilic acid chlorides to form N-ethylamides. The nucleophilic nitrogen attacks the carbonyl carbon of the acid chloride, displacing the chloride ion and yielding an amide after deprotonation. For example, the reaction of ethylamine with acetyl chloride proceeds as follows:
This reaction is typically conducted in the presence of a base to neutralize the HCl byproduct and is a standard method for amide synthesis from primary amines.[30][31]
Alkylation of ethylamine with alkyl halides occurs via nucleophilic substitution, where the amine acts as a nucleophile to displace the halide, forming higher-substituted amines. A representative example is the reaction with methyl iodide:
However, due to the increased nucleophilicity of the resulting secondary amine, overalkylation to tertiary amines and quaternary ammonium salts is a common challenge, often requiring excess amine or protective strategies to control selectivity.[32][33]
Ethylamine reacts with carbonyl compounds such as aldehydes to form imines, commonly known as Schiff bases, through nucleophilic addition followed by dehydration. This condensation typically requires mild acidic conditions or removal of water to drive the equilibrium toward the imine product. For instance, ethylamine and benzaldehyde form N-benzylideneethylamine. These imines serve as versatile intermediates in organic synthesis. In reductive amination, ethylamine condenses with an aldehyde or ketone to form an imine intermediate, which is then reduced (e.g., with NaBH₃CN or H₂) to yield a secondary amine, providing a selective route to alkylated products without overalkylation issues.[34][35]
Among other electrophilic reactions, ethylamine reacts with carbon dioxide to form ethylcarbamic acid, which can exist in equilibrium or as a carbamate salt under basic conditions. The mechanism involves nucleophilic attack by the amine nitrogen on CO₂, followed by proton transfer, often facilitated by a second amine molecule or solvent effects in aqueous media.[36] Additionally, ethylamine can be oxidized by hydrogen peroxide, typically under copper catalysis, to the corresponding imine, acetaldimine (CH₃CH=NH), via dehydrogenation, though this product is unstable and prone to hydrolysis.[37]