Question

Treating trimethylamine with 2-chloroethyl acetate gives acetylcholine as its chloride. Acetylcholine is a neurotransmitter.

Short answer

The reaction between trimethylamine (CH3)3N and 2-chloroethyl acetate ClCH2CH2OC(O)CH3 is a nucleophilic substitution reaction, specifically an S_N2 reaction. In this reaction, trimethylamine attacks the electrophilic carbon attached to the chloride, replacing the leaving group (chloride ion). The product formed is acetylcholine chloride, represented as (CH3)3NCH2CH2OC(O)CH3(+) Cl(-). Acetylcholine is an essential neurotransmitter in the nervous system.

Step-by-step solution

Understand the reactants

Trimethylamine is a tertiary amine with the formula (CH3)3N, which has three methyl groups bonded to a nitrogen atom. 2-Chloroethyl acetate is an ester with a chlorine atom attached to an ethyl group, and its formula is ClCH2CH2OC(O)CH3.

Identify the reaction type

The reaction between trimethylamine and 2-chloroethyl acetate is a nucleophilic substitution reaction, specifically an S_N2 reaction. In this reaction, the nucleophile (trimethylamine) attacks the electrophile (2-chloroethyl acetate) and replaces the leaving group (chloride ion).

Mechanism of the reaction

In the S_N2 reaction, the nucleophile, trimethylamine, attacks the electrophilic carbon connected to the chloride in 2-chloroethyl acetate. The bond between the carbon and chloride breaks, and the chloride dissociates as a leaving group.

Formation of acetylcholine

After the nucleophilic attack, the nitrogen of the trimethylamine group is now connected to the ethyl group and acetate moiety, forming acetylcholine. The overall reaction can be written as: (CH3)3N + ClCH2CH2OC(O)CH3 -> (CH3)3NCH2CH2OC(O)CH3 + Cl-

Acetylcholine chloride

Since chloride ion is released during the reaction, the product formed is acetylcholine chloride, which is the salt of acetylcholine and can be represented as: (CH3)3NCH2CH2OC(O)CH3(+) Cl(-) In summary, the reaction between trimethylamine and 2-chloroethyl acetate is an S_N2 nucleophilic substitution reaction and results in the formation of acetylcholine chloride. Acetylcholine is an essential neurotransmitter involved in the functioning of the nervous system.

Key concepts

S_N2 Reaction

An S_N2 reaction stands for 'bimolecular nucleophilic substitution' and is a fundamental concept in organic chemistry where a nucleophile actively displaces a leaving group from an electrophilic carbon. This type of reaction is characterized by a single, concerted step where the bond formation and bond breaking occur simultaneously. An easy-to-visualize aspect of the S_N2 mechanism is the 'backside attack' concept, where the nucleophile approaches the carbon atom from the opposite side of the leaving group.

Since the process involves two reacting species coming together in one step, it is referred to as 'bimolecular'. What makes S_N2 notable is the inversion of configuration at the carbon center undergoing substitution—it's akin to an umbrella flipping inside out in the wind. This reaction is favored by primary and secondary alkyl halides and can be slowed or inhibited by steric hindrance around the electrophile.

Acetylcholine Synthesis

Acetylcholine synthesis in a laboratory setup, as illustrated by the exercise, involves creating this pivotal neurotransmitter through an organic reaction. Acetylcholine is typically synthesized from choline and acetyl coenzyme A in the biological setting. However, when we replicate the process synthetically, different starting materials can be used. In the given problem, acetylcholine is synthesized through the reaction of trimethylamine with 2-chloroethyl acetate.

This reaction is a great representation of how an understanding of organic reaction mechanisms can be applied to synthesize complex molecules like neurotransmitters. In the final product, acetylcholine chloride, the amine functional group from trimethylamine has formed a new bond with an acetyl group from the ester, emulating the natural structure of acetylcholine.

Organic Reaction Mechanisms

Understanding organic reaction mechanisms is crucial in the field of chemistry because it allows chemists to predict the behavior of molecules in a reaction. A mechanism is a detailed step-by-step description of how reactants are converted into products; it includes all the intermediates and transitions states that occur during the course of a reaction.

To fully grasp a mechanism, such as the one in our S_N2 reaction example, recognizing the role of different molecular players is essential. The nucleophile (trimethylamine) actively seeks out the electrophile (2-chloroethyl acetate), the transition state is the point at which old bonds are breaking and new bonds are forming, and the leaving group (chloride ion) exits the scene to complete the transformation. Understanding mechanisms is like following a recipe in cooking—it guides the chemist in combining ingredients to create the desired product.

Neurotransmitter Chemistry

Neurotransmitter chemistry is the study of how chemical messengers in the brain, like acetylcholine, work. These molecules are essential for transmitting signals between nerve cells and can affect everything from muscle movement to mood. Acetylcholine, specifically, plays a key role in activating muscle fibers, memory, and learning.

The synthesis of neurotransmitters can occur naturally in the body or synthetically in the lab as we've seen with acetylcholine. Understanding how these compounds are created, how they interact with receptors, and what effects they produce helps scientists and doctors to develop new drugs and therapies for treating various neurological disorders. The investigation into neurotransmitter chemistry spans numerous scientific disciplines, including organic chemistry, neurobiology, and pharmacology.