Ethyl Ethenesulfonate Synthesis through Elimination and Sulfonylation

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1. E2 elimination

E2 elimination은 유기 화학의 제거 반응의 일종으로, 1-step mechanism을 따라서 bimolecular하게 일어난다. 따라서 반응 속도는 RX와 base의 농도의 영향을 받아 second order로 결정된다. 이 반응은 C-H와 C-X 사이의 결합이 끊어지는 것과 C=C 이중 결합이 형성되는 과정이 단일 단계로 일어난다. 따라서 E2 메커니즘을 따르는 반응은 antiperiplanar 배향으로 일어나고, 에너지 상태가 낮은 staggered conformation의 전이상태를 선호한다.
2. Zaitsev product vs non-Zaitsev product

Zaitsev's rule은 일반적인 Elimination 반응 결과 생성되는 major한 product를 예상하는데 사용되며, 이 법칙에 따르면 일반적인 Elimination 반응에서는 H의 수가 적은 탄소에서 H를 제거했을 때 생성되는 가장 많이 치환된 product가 major product가 된다. 반면 Hoffman product는 non-zaitsev product로, 가장 적게 치환된 alkene을 의미한다. 열역학적 관점에서 수소화열이 더 작아지는 것을 통해 더 많이 치환된 알켄일수록 안정하다는 사실을 알 수 있으며, 이는 alkyl group에 의한 induced effect, Alkyl의 HOMO와 이중 결합의 LUMO 사이의 상호작용(hyperconjugation) 등을 통해 설명될 수 있다.
3. Making tosylates from alcohols

Alcohol은 OH- ion이 강한 염기라서 매우 나쁜 이탈기로 작용한다. 따라서 OH group을 다른 group으로 바꾸면 alcohol은 더 좋은 이탈기로서 작용할 수 있다. 이 때 활용하는 방식이 p-toluenesulfonyl group(p-Ts)를 활용해서 tosylate group을 만드는 방법이다. Tosylate group은 -OTs group으로 표기하기도 하는 작용기로, p-toluenesulfonate group을 말한다. Alcohol은 p-toluenesulfonyl chloride와 반응해서 tosylate를 만들 수 있는데, 이 경우 더 좋은 이탈기로 작용하며 substitution이나 elimination 반응에 참여할 수 있다.
4. Coupling constant of vinyl group

Vinyl group은 R-CH=CH2 형태의 작용기로 SP2 hybridized orbital을 갖는 화학종을 일컫는다. 1H NMR에서 vinylic proton은 결합 배열 양상에 따라 0Hz에서 18Hz의 coupling constant를 갖는다. 일반적으로 Trans configuration을 갖는 경우에는 11~18Hz로 J-coupling constant가 가장 크고, Cis는 3~10Hz, geminal의 경우에는 0~3Hz로 나타난다. 이렇게 J constant가 다르게 나타나는 것은 Karplus Equation을 통해서 설명될 수 있다.
5. Reaction mechanism

이번 실험의 반응은 2-chloroethanesulfonyl chloride과 Ethanol의 Sulfonylation 단계와 TEA에 의한 Elimination 두 단계에 걸쳐서 일어난다. 먼저 첫번째 단계에서는 ethanol의 O가 nucleophilic attack을 통해 S와 결합을 형성하고 Cl이 이탈한 뒤 deprotonation을 통해 Sulfonate를 형성한다. 그리고 두번째 단계에서는 TEA가 base로서 proton을 제거하고, Cl이 이탈하면서 product가 생성된다.

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1. E2 elimination

E2 elimination is an important organic reaction that involves the removal of a hydrogen atom and a leaving group from adjacent carbon atoms, resulting in the formation of a carbon-carbon double bond. This reaction is commonly used in the synthesis of alkenes and is particularly useful in the context of eliminating halides or other leaving groups from alkyl halides or other substrates. The E2 mechanism proceeds through a concerted process where the base abstracts the hydrogen atom and the leaving group departs simultaneously. The stereochemistry of the reaction is typically anti, meaning that the leaving group and the hydrogen atom are removed from opposite sides of the molecule. The factors that influence the rate and selectivity of the E2 elimination include the strength of the base, the nature of the leaving group, the steric hindrance around the reaction center, and the stability of the resulting alkene product. Understanding the E2 elimination mechanism and its applications is crucial for organic chemists in the design and synthesis of complex organic molecules.
2. Zaitsev product vs non-Zaitsev product

The Zaitsev product and the non-Zaitsev product refer to the two possible alkene products that can result from an E2 elimination reaction. The Zaitsev product is the more substituted alkene, which is typically the thermodynamically more stable product. This is because the more substituted alkene can better stabilize the resulting carbocation intermediate through hyperconjugation and other stabilizing effects. In contrast, the non-Zaitsev product is the less substituted alkene, which is often the kinetically favored product due to steric factors. The selectivity between the Zaitsev and non-Zaitsev products depends on various factors, such as the nature of the substrate, the strength and type of the base, the reaction conditions, and the relative stability of the possible alkene products. Understanding the factors that influence the Zaitsev vs. non-Zaitsev selectivity is crucial for organic chemists in the context of controlling the regiochemistry of elimination reactions and designing efficient synthetic routes.
3. Making tosylates from alcohols

The conversion of alcohols to tosylates (p-toluenesulfonates) is a widely used synthetic transformation in organic chemistry. Tosylates are valuable intermediates in organic synthesis as they can serve as excellent leaving groups in a variety of reactions, such as nucleophilic substitutions, eliminations, and rearrangements. The process of making tosylates from alcohols typically involves the reaction of the alcohol with p-toluenesulfonyl chloride (tosyl chloride) in the presence of a base, such as pyridine or triethylamine. The resulting tosylate can then be isolated and used in subsequent steps of a synthetic sequence. The advantages of using tosylates include their stability, ease of handling, and the ability to control the stereochemistry of the resulting products. Additionally, tosylates can be used to activate primary, secondary, and even tertiary alcohols, making them a versatile tool in organic synthesis. Understanding the methods for preparing tosylates and their applications is crucial for organic chemists in the design and execution of complex synthetic routes.
4. Coupling constant of vinyl group

The coupling constant of a vinyl group, also known as the vicinal coupling constant, is an important parameter in 1H NMR spectroscopy that provides valuable information about the stereochemistry and conformation of alkenes. The coupling constant between the two hydrogen atoms on the vinyl group (the cis and trans protons) is typically in the range of 8-18 Hz, with cis-configured alkenes exhibiting a smaller coupling constant (8-12 Hz) and trans-configured alkenes exhibiting a larger coupling constant (12-18 Hz). This difference in coupling constant arises from the different dihedral angles between the cis and trans protons, as dictated by the Karplus relationship. Knowing the coupling constant of a vinyl group can help organic chemists determine the stereochemistry of the alkene, which is crucial for understanding the reactivity and selectivity of subsequent transformations. Additionally, the coupling constant can provide insights into the conformation and rigidity of the molecule, which can be important for understanding structure-activity relationships in the context of medicinal chemistry and drug design. Mastering the interpretation of vinyl coupling constants is a valuable skill for organic chemists in the characterization and structural elucidation of organic compounds.
5. Reaction mechanism

Understanding reaction mechanisms is a fundamental aspect of organic chemistry, as it allows chemists to predict the course of a reaction, rationalize the observed products, and design new synthetic routes. Reaction mechanisms describe the step-by-step process by which a chemical transformation occurs, including the formation and breaking of bonds, the movement of electrons, and the generation of intermediates. Analyzing reaction mechanisms is crucial for organic chemists as it enables them to: 1. Understand the factors that influence the rate and selectivity of a reaction, such as the nature of the reactants, the presence of catalysts or other additives, and the reaction conditions. 2. Propose reasonable pathways for the formation of desired products and anticipate the formation of potential side products or byproducts. 3. Design new synthetic routes by leveraging their knowledge of mechanistic principles to devise efficient and selective transformations. 4. Rationalize experimental observations, such as stereochemical outcomes, kinetic data, and spectroscopic evidence, in the context of the proposed mechanism. 5. Predict the reactivity of new substrates or functional groups based on their understanding of the underlying mechanistic principles. Mastering the analysis and interpretation of reaction mechanisms is a fundamental skill for organic chemists, as it underpins their ability to design, execute, and optimize synthetic strategies for the preparation of complex organic molecules.