Methylamine: Synthesis, Properties, Uses

Introduction

Methylamine, a chemical compound with the molecular formula CH3NH2, have an important role in various industrial processes and applications. This article delves into the multifaceted aspects of methylamine, exploring its physical and chemical properties, synthesis methods, legal status, applications, storage, disposal, and the rules governing its handling.

Methylamine structure

Methylamine Physical Properties

Methylamine exists as a colorless gas with a distinctive, ammonia-like odor similar to rotten fish. It is highly soluble in water (1008 g/L at 20 °C),methanol, ethanol, tetrahydrofuran. Its boiling point is -6.3 °C (-21.3 °F), melting point is −93.10 °C (−135.58 °F). Methylamine's density as a gas is approximately 0.6562 kg/m³, making it significantly lighter than air. These nuanced physical properties play a pivotal role in determining the appropriate storage, transportation, and utilization methods for methylamine in various industrial contexts.

Methylamine hydrochloride (powder form)

Methylamine is highly flammable and has a flashpoint of -10°C, making precautions necessary during transport and use. It is mixed with portions of methanol, ethanol, oxolane, and water to be sold as a solution. Anhydrous Methylamine gas is also transported in pressurized metal containers.

Methylamine Chemical Properties

Methylamine, a primary amine denoted by its molecular structure containing a nitrogen atom bonded to three hydrogen atoms, exhibits a rich array of chemical properties that underpin its versatility in diverse applications. The presence of the amino group imparts distinctive reactivity to methylamine, rendering it both a base and a nucleophile.

Methylamine Lewis structure

In chemical reactions, methylamine engages in processes such as nucleophilic substitution, addition (condensation) and various transformations vital in organic synthesis. Its role as a precursor is particularly noteworthy, facilitating the creation of pharmaceuticals, agrochemicals, and other complex organic compounds. Furthermore, methylamine's amine nature allows it to participate in acid-base reactions, forming salts with acids.

Methylamine Synthesis Ways

Methylamine was first prepared in 1849 by Charles-Adolphe Wurtz via the hydrolysis of methyl isocyanate and related compounds. An example of this process includes the use of the Hofmann rearrangement, to yield methylamine from acetamide and bromine gas.

Laboratory ways

In the laboratory, methylamine hydrochloride is readily prepared by various other methods. One method entails treating formaldehyde with ammonium chloride.

[NH₄]Cl + CH₂O → [CH₂=NH₂]Cl + H₂O

[CH₂=NH₂]Cl + CH₂O + H₂O → [CH₃NH₃]Cl + HCOOH

The colorless hydrochloride salt can be converted to an amine by the addition of a strong base, such as sodium hydroxide (NaOH):

[CH₃NH₃]Cl + NaOH → CH₃NH₂ + NaCl + H2O

Another method entails reducing nitromethane with zinc and hydrochloric acid.

CH₃NO₂ + 2HCl + Zn → CH₃NH₂ + ZnCl₂

Another method of methylamine production is spontaneous decarboxylation of glycine with a strong base in water.

Industrial way

Methylamines are produced commercially by aminating methanol in the presence of aluminosilicate catalysts (Zeolites). Ammonia reacts with methanol in the vapor phase to produce separate products, namely- MMA(Monomethylamine), DMA(Dimethylamine) & TMA(Trimethylamine). The reaction process and equation are shown below:

CH₃OH + NH₃ → CH₃NH₂ + H₂O

Methylamine reaction process

Methylamine is also produced by the reaction of formaldehyde with ammonium chloride salt. Both gaseous and liquid methylamines are used as intermediates in the production of pharmaceuticals, pesticides, laboratory reagents, and tanning agents. Agrochemicals are the main drivers of the methylamine industry.

With a primary amine group attached to it, methylamine acts as a good nucleophile.

Methylamine Applications

Representative commercially significant chemicals produced from methylamine include the pharmaceuticals ephedrine and theophylline, the pesticides carbofuran, carbaryl, and metham sodium, and the solvents N-methylformamide and N-methylpyrrolidone (NMP). Such valuable for industry substances are also produced from methylamine: N-methyl-2-pyrrolidone, methylformamide, caffeine, and N,N'-dimethyl urea. The preparation of some surfactants and photographic developers require methylamine as a building block.

Methylamine is widely used in drug manufacturing syntheses like MDMA, bk-MDMA, methamphetamine, mephedrone (4-MMC) and its isomers, Ephedrine and others. The most of them are represented on BB Forum.

Methylamine Legal Status

Methylamine holds a complex legal standing globally, primarily due to its association with illicit activities, especially in the illegal production of methamphetamine. Governments and regulatory bodies have imposed stringent controls and regulations on the manufacturing, distribution, and sale of methylamine to curb its diversion for unlawful purposes.

In many jurisdictions, methylamine is classified as a controlled substance under narcotics or precursor chemical laws. This classification imposes strict restrictions on its production, import, export, and distribution. Individuals and entities involved in handling methylamine must comply with licensing requirements and adhere to comprehensive record-keeping procedures to ensure transparency and traceability.

Moreover, international cooperation plays a pivotal role in regulating methylamine due to its potential for cross-border trafficking. Various conventions and agreements, such as the United Nations Convention Against Illicit Traffic in Narcotic Drugs and Psychotropic Substances, include provisions addressing the control of precursor chemicals like methylamine.

Storage

Safe and responsible storage of methylamine is a critical aspect of its management due to its unique physical properties and potential hazards. Typically encountered in its gaseous state, methylamine is stored in high-pressure cylinders designed to withstand the specific conditions associated with its transportation and storage.

To minimize the risks associated with methylamine, storage facilities must adhere to stringent safety protocols. Proper ventilation systems are essential to prevent the accumulation of gas and ensure a controlled environment. Additionally, temperature control measures are implemented to maintain stability and prevent fluctuations that could compromise the integrity of the storage containers.

Given methylamine's affinity for aqueous solutions, storage facilities must account for potential reactions with moisture. Facilities are equipped with moisture control systems, and stringent monitoring is in place to prevent unintended reactions that may compromise the quality and safety of the stored methylamine.

Methylamine hydrochloride salt has solid state at normal conditions. This aspect make this methylamine form more attractive and convenient for transportation and postal delivery.

Disposal

Disposing of methylamine requires adherence to environmental regulations. Treatment methods may include neutralization, chemical degradation, or incineration in approved facilities. Careful consideration must be given to prevent environmental contamination and ensure the safe disposal of by-products.

Toxicity and rules for handling the substance

Methylamine poses health risks, primarily through inhalation or skin contact. It can cause irritation to the respiratory system, eyes, and skin. Proper personal protective equipment, including respiratory protection, is crucial when handling methylamine. Additionally, adherence to established safety protocols, including proper ventilation and emergency response procedures, is essential to minimize the risks associated with its use.

The LD50 (mouse, s.c.) is 2.5 g/kg.

The Occupational Safety and Health Administration (OSHA) and National Institute for Occupational Safety and Health (NIOSH) have set occupational exposure limits at 10 ppm or 12 mg/m3 over an eight-hour time-weighted average.

Conclusion

In summary, methylamine emerges as a compound of significant versatility, finding applications across industries, both legitimate and otherwise. Appreciating its diverse properties, legal intricacies, and the importance of safe handling becomes paramount for those engaged in its synthesis, distribution, and use. A comprehensive understanding of methylamine is vital not only for fostering responsible industrial practices but also for mitigating potential risks associated with its multifaceted applications.

Bibliography

Corbin, David R., Stephan Schwarz, and George C. Sonnichsen. "Methylamines synthesis: A review." Catalysis today 37.2 (1997): 71-102. https://www.sciencedirect.com/science/article/abs/pii/S0920586197000035