How do I convert Ethanamine to N,N-diethylethylamine?

How do I convert ethanamine to N,N-diethylethanamine also known as triethylamine or TEA? This question is quite a common one and needs to be answered. Read our two methods to synthesize N,N-diethylethanamine.

The production of N,N-diethylethanamine, also known as triethylamine or (C₂H₅)₃N, is quite an important process and is widely used in agrochemicals and during different other industrial processes. Another chemical called ethanamine or C₂H₅NH₂ can be used to convert it into triethylamine by using two different methods. Although different, both still use a general principle of alkylation in which an ethylating agent is used.

How do I convert ethanamine to N,N-diethylethanamine?

In the first method, ethylamine is reacted (first alkylation) with excess ethyl halide, denoted as C₂H₅X, in the presence of a base, forming diethylamine (C₂H₅)₂NH.

C₂H₅NH + C₂H₅X > (C₂H₅)₂NH + HX

It undergoes another alkylation and forms (C₂H₅)₃N. This reaction also leads to byproducts that are not needed, including ammonium salts [(C₂H₅)₄N⁺X⁻].

(C₂H₅)₂ + C₂H₅X > (C₂H₅)₄N + X^-

The unwanted byproducts are in fact quaternary ammonium salts, which pose purification challenges at the end of conversion. Distillation with triethylamine or washing with water or organic solvents can help remove these byproducts, which happen to be highly toxic. The ethyl halides used are also very volatile and on the higher spectrum of toxicity.

In the second method, diethylamine is reacted with ethylene oxide while keeping the presence of a catalyst like zeolites, alumina, and some nickel-based catalysts. In the controlled catalytic conditions, the diethylamine reacts with ethylene oxide to form N-diethyl ethanolamine.

(C₂H₅)₂NH + C₂H₄O > (C₂H₅)₂NCH₂CH₂OH

The second method removes the production of ammonium salts, but it is worth mentioning here that the ethylene oxide is highly reactive and requires controlled conditions with careful handling, more suitable for industrial environments. For lab study and educational demonstration, the first method is much more practical despite its lower efficiency.

They also act great when used as a buffering agent in drug formulations where precise pH control is crucial. It does that by acting as a pH adjuster and chemical buffer in the solution in drug formulations, particularly in injectable solutions. It is also a quite important substance used during the production of important drugs, including many antimicrobial and anti-fungal drugs, during which it acts as an intermediate for synthesizing pharmaceutical compounds.

It also acts as a precursor for compounds used in pesticides and also helps stabilize the active ingredients of herbicides. TEA produced from the second method is also used in many other industrially important reactions like the Friedel-Crafts alkylation and acylation reactions, where it helps stabilize acidic compounds. It is also widely used for the production of detergents.

The first method stated above is also used at some scale in the industrial sector but generates serious halide waste, which uses scrubbing systems and other related waste-naturalizing systems to handle these halides. The conversion itself is also notoriously inefficient due to the fact that the first step releases strong acid, which interferes in the second step, making it hard for TEA to form. On the other hand, the second method is a high-purity one and is used for selective amine synthesis to gain high levels of TEA.

The first method can also be done by alkylation of ethanamine with excess chloroethane (C₂H₅Cl), which reacts with it in a nucleophilic substitution or SN2 fashion. In this reaction, the C₂H₅NH₂ or (C₂H₅)₂NH behaves as a nucleophile, replacing the chlorine atom with an ethyl group. This reaction also forms amine salts (diethylammonium chloride being the most common), which are usually dealt with a base that can help them dissociate back to the free amines. Their reaction is written as:

(C₂H₅)₃N + C₂H₅Cl > (C₂H₅)₄N^+Cl⁻

In case of excess chloroethane, this process can keep going to gain tertiary amine or triethylamine to quaternary ammonium salts, tetraethylammonium chlorides in this case. This method, just like the first one explained above, also makes unwanted salts, unlike the second one, which has a higher operational cost but gives more yield without salt waste. Thus, making it a more preferable way to make N,N-diethylethanamine.