At a Glance

• Methylamine (CH₃NH₂) is a primary amine; dimethylamine ((CH₃)₂NH) is a secondary amine
• Dimethylamine has higher basicity (pKa 10.73) than methylamine (pKa 10.64)
• Both produced from methanol and ammonia through catalytic reactions
• Methylamine gives positive carbylamine test; dimethylamine does not
• Global production: ~115,000 tons methylamine, ~271,000 tons dimethylamine annually
• Both have fishy, ammonia-like odors
• Methylamine used in pharmaceuticals (ephedrine, theophylline); dimethylamine in solvents and surfactants
• Neither compound is directly used in fragrance creation despite being precursors for some fragrance intermediates

Chemical structures might look similar on paper, but small molecular changes create dramatically different properties. Take methylamine and dimethylamine. Both belong to the amine family. Both smell distinctly fishy. Both start from similar chemical reactions. Yet the single extra methyl group that distinguishes methylamine and dimethylamine creates differences that matter greatly to chemists, manufacturers, and anyone working with these compounds.

The main difference between methylamine and dimethylamine is that methylamine has one methyl group (-CH3) attached to the amino group (-NH2), while dimethylamine has two methyl groups attached to the amino group. This seemingly minor structural variation impacts reactivity, basicity, physical properties, and industrial applications in ways that extend far beyond what you’d expect from adding just one CH3 group.

Structural Chemistry: One Methyl Group Makes All the Difference

Methylamine, also known as methanamine, is an organic compound with a formula of CH3NH2. This colorless gas is a derivative of ammonia, but with one hydrogen atom being replaced by a methyl group. It is the simplest primary amine.

Dimethylamine is an organic compound with the formula (CH3)2NH. This secondary amine is a colorless, flammable gas with an ammonia-like odor. The nitrogen atom sits at the center of both molecules, but how hydrogen and methyl groups arrange around it changes everything.

Structural Comparison:

Feature	Methylamine	Dimethylamine
Chemical formula	CH₃NH₂	(CH₃)₂NH
Amine classification	Primary (1°)	Secondary (2°)
Hydrogen atoms on nitrogen	2	1
Methyl groups on nitrogen	1	2
Molecular weight	31.06 g/mol	45.08 g/mol
Boiling point	-6.3°C	7.4°C
Melting point	-93.1°C	-93°C

The classification as primary versus secondary amine drives much of the chemical behavior difference. Primary amines have two hydrogen atoms attached to nitrogen, allowing certain reactions that secondary amines can’t undergo.

Basicity: How Electron-Donating Groups Change Behavior

Methylamine is a stronger base than ammonia because the inductive effect of the methyl group increases the electron density on the nitrogen atom and makes the lone pair more available for proton acceptance.

Dimethylamine is a stronger base than both ammonia and methylamine because it has two methyl groups, leading to a greater inductive effect. Each methyl group pushes electron density toward the nitrogen through what chemists call the inductive effect.

Basicity Comparison (pKa values):

• Ammonia: ~9.25
• Methylamine: 10.64
• Dimethylamine: 10.73
• Trimethylamine: 9.79

Wait, shouldn’t trimethylamine be even more basic with three methyl groups? The pattern breaks because steric hindrance starts interfering. Large alkyl groups can make the nitrogen’s lone pair less accessible due to their size, effectively hindering the amines’ base-forming ability.

Dimethylamine hits the sweet spot where inductive effects maximize basicity before steric effects start reducing it.

How to Distinguish Between Methylamine and Dimethylamine

Chemists need reliable methods to identify which amine they’re working with. Methylamine gives carbylamine test whereas dimethylamine does not. Hence, methylamine, and dimethyl amine can be distinguished using carbylamine test.

The Carbylamine Test

Aliphatic and aromatic primary amines on heating with chloroform and ethanolic potassium hydroxide form foul-smelling isocyanides or carbylamines. Methylamine (being an aliphatic primary amine) gives a positive carbylamine test, but dimethylamine does not.

The reaction produces methyl isocyanide, which has an intensely foul smell. If you heat a sample with chloroform and alcoholic KOH and get that characteristic terrible odor, you’ve got a primary amine like methylamine. No smell? It’s likely dimethylamine or another secondary amine.

Dimethylamine does not give this test as it is a secondary amine or 2° – amine. So, there will be no foul smell observed after doing a carbylamine test.

Industrial Production: Co-Products from the Same Reaction

It is now prepared commercially by the reaction of ammonia with methanol in the presence of an aluminosilicate catalyst. Dimethylamine and trimethylamine are co-produced; the reaction kinetics and reactant ratios determine the ratio of the three products.

The same industrial process creates all three methylamines simultaneously. Manufacturers can’t make just one. The challenge becomes controlling which product dominates.

Production Reaction: CH₃OH + NH₃ → CH₃NH₂ (methylamine) CH₃OH + CH₃NH₂ → (CH₃)₂NH (dimethylamine) CH₃OH + (CH₃)₂NH → (CH₃)₃N (trimethylamine)

The product most favored by the reaction kinetics is trimethylamine. However, market demand typically favors dimethylamine, creating economic pressure to develop catalysts that shift product ratios away from the thermodynamically preferred trimethylamine.

While thermodynamics favors TMA formation, market demand is for DMA. This has led to the development of highly DMA selective zeolite-based catalysts.

Annual Global Production:

• Methylamine: ~115,000 tons (2005 estimate)
• Dimethylamine: ~271,000 tons (2005 estimate)
• Trimethylamine: Lower, specific data varies

Pharmaceutical and Agricultural Applications

Methylamine Uses

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.

Methylamine serves as a building block for drugs treating:

• Respiratory conditions (theophylline for asthma)
• Nasal congestion (ephedrine and related compounds)
• Various other therapeutic applications

In agriculture, methylamine-derived pesticides protect crops from insects and nematodes. The compound’s reactive primary amine group makes it ideal for creating complex molecules through nucleophilic substitution reactions.

Dimethylamine Uses

The solvents dimethylformamide and dimethylacetamide are derived from dimethylamine. It is raw material for the production of many agrichemicals and pharmaceuticals, such as dimefox and diphenhydramine, respectively.

Dimethylformamide (DMF) ranks among the most important industrial solvents. It dissolves a wide range of organic compounds and finds use in:

• Pharmaceutical synthesis
• Polymer production
• Acrylic fiber manufacturing
• Chemical reactions requiring polar aprotic solvents

Usage of dimethylamine in 1972 was estimated at 50% for production of dimethylformamide and dimethylacetamide (used as spinning solvents for acrylic fibers), 15% as an intermediate in the preparation of the surfactant laurel dimethylamine oxide, 15% as an intermediate for rubber chemicals (including thorium accelerators), and 20% for other applications.

Methylamine and Dimethylamine in Fragrance Chemistry

Here’s where expectations meet reality. Despite being chemical precursors to many compounds, neither methylamine nor dimethylamine finds direct use in fragrance formulations. Why? The smell.

It has a strong odor similar to rotten fish describes methylamine. Dimethylamine smells similarly unpleasant. These aren’t scents perfumers want in their creations.

However, both compounds serve as intermediates in synthesizing certain fragrance components. The chemical transformations that create pleasant-smelling molecules often start from unpleasant-smelling precursors. Methylamine and dimethylamine undergo reactions that eventually lead to compounds used in:

• Synthetic musk compounds
• Certain aldehyde fragrances
• Various aromatic intermediates

The key point: by the time you smell the fragrance in perfume, any methylamine or dimethylamine has been completely transformed into something else through multiple chemical steps.

Safety and Handling Considerations

Both compounds require careful handling due to their physical and chemical properties.

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 for methylamine.

Safety Concerns:

• Both are flammable gases (or solutions)
• Both cause respiratory irritation
• Both have intense, unpleasant odors
• Eye and skin irritation upon contact
• Both form explosive mixtures with air at certain concentrations

Dimethylamine is not very toxic with the following LD50 values: 736 mg/kg (mouse, i.p.); 316 mg/kg (mouse, p.o.); 698 mg/kg (rat, p.o.); 3900 mg/kg (rat, dermal). While not extremely toxic compared to many industrial chemicals, proper protective equipment and ventilation remain essential.

In the United States, methylamine is controlled as a List 1 precursor chemical by the Drug Enforcement Administration due to its use in the illicit production of methamphetamine. This regulatory status creates additional documentation and security requirements for legitimate industrial users.

Natural Occurrence and Biological Roles

Both compounds occur naturally in biological systems. Dimethylamine is found quite widely distributed in animals and plants, and is present in many foods at the level of a few mg/kg.

Dimethylamine naturally occurs in soybean seeds (8 ppm), cauliflower (14 ppm), kale leaves (5.5 ppm), barleygrass seeds (1.6 ppm), tobacco leaves, hawthorne leaves, hops flower (1.4 ppm), cabbage leaves (2–2.8 ppm), corn (1–3.5 ppm), celery (5.1 ppm), grapes, grape wine, and grape juice.

Methylamine arises as a result of putrefaction and is a substrate for methanogenesis. This explains why decomposing biological matter often has fishy smells even when no fish are present.

Sourcing Industrial Methylamines

For manufacturers requiring methylamine or dimethylamine for pharmaceutical synthesis, chemical production, or industrial applications, partnering with suppliers who understand both regulatory requirements and quality specifications is essential. Elchemy’s technology-driven platform connects manufacturers with verified suppliers of methylamines meeting industrial specifications globally.

Founded by chemical and electronics engineers from IIT Bombay, IIT Delhi, and IIM Ahmedabad, Elchemy leverages technology to transform chemical industry distribution. Whether you need methylamine for pharmaceutical synthesis, dimethylamine for solvent production, or related amine derivatives, our customer-centric approach addresses supply chain challenges through transparent sourcing from both Indian and global suppliers. We provide complete documentation, quality certifications, and logistics support that traditional chemical distribution struggles to deliver efficiently.

Conclusion

The structural difference between methylamine and dimethylamine might seem minor, but that single additional methyl group creates distinct properties affecting basicity, reactivity, industrial applications, and production economics. Methylamine’s status as a primary amine enables reactions that dimethylamine cannot undergo, like the carbylamine test. Dimethylamine’s two methyl groups create higher basicity through inductive effects while maintaining useful reactivity for solvent synthesis and surfactant production.

Neither compound finds direct use in fragrance applications due to their unpleasant fishy odors. However, both serve as valuable industrial intermediates for pharmaceuticals, agrochemicals, solvents, and other specialty chemicals that eventually contribute to various consumer products. Understanding how to distinguish between methylamine and dimethylamine helps chemists and industrial professionals select the right compound for specific synthetic routes and manufacturing processes.