E1 E2 Comparison

Let's compare E1 and E2 in the following aspects:
  1. Base
  2. Substrate
  3. Solvent
  4. Leaving Group
  5. Kinetics
  6. Stereochemistry
  7. Rearrangements 
Base
E1: As the base abstracts the proton only after the carbocation intermediate is formed, it does not affect the rate of reaction, hence not important.
E2: A strong base is indeed needed to promote the one-step reaction.

Substrate
E1: A more substituted substrate stabilizes the carbocation intermediate. 
E2: A more substituted substrate forms a more substituted alkene. 

 Solvent
E1: A polarizing solvent enhances the rate of ionization as it pulls the cation and anion apart. 
E2: The transition state is less sensitive to the solvent as the transition state has its negative charge shared over the whole molecule. 

Leaving Group
Both reactions need a good leaving group. 

 Kinetics
E1: The rate is only determined by the substrate as it is the only molecule that ionizes.
E2: Both the substrate and the base affects the rate of the concerted reaction.

 Stereochemistry
E1: It actually does not have a specific geometry, but it follows the Zaitsev's rule. 
E2: As it is a concerted reaction, an anti-coplanar orientation between the base and the leaving group is required as it is the lowest energy state.

 Rearrangements
E1: A methyl group or a hydride ion can shift to stabilize the carbocation intermediate before a base attacks.
E2: No rearrangements as there is no intermediate to be stabilized. 

 *Both E1 and E2 follow the Zaitsev's rule: 
 In elimination reactions, the most substituted alkene usually predominates.
E1 E2 Comparison Chart


Our team at Chemistery uses NordVPN every day and we highly recommend it.



Comments

Post a Comment

Popular posts from this blog

What is Pepsin?

Image
In Your Body... Pepsin is a digestive enzyme that performed the best in the acidic condition (pH 2) produced by the gastric juice. It digests and breaks down protein (e.g. meat, seeds, eggs, dairy products, etc.). Keep in mind that pepsin digests proteins (not carbohydrates, not fat) into peptides. These peptides are then either absorbed in the intestine or further break down by enzymes from pancreas. In small intestine (pH around 7), pepsin is no longer effective and no longer digests proteins. Hormones Hormones that regulate digestion and hunger such as gastrin and secretin stimulates the production of pepsinogen, the proenzyme of pepsin. In other words, when pepsinogen is activated, it becomes pepsin.
Read more

The structure of Chimeric Antigen Receptor (CAR) III - Transmembrane Domains

Image
Transmembrane Domains Among the four components of a chimeric antigen receptor (CAR), the transmembrane domain is the least studied one. How different transmembrane domains affect and contribute to each other's functions is also not well studied. That being said, we will go through the function of a transmembrane domain of a CAR, the CD3ζ transmembrane domain, and the CD8α transmembrane domain.  Introduction of the transmembrane domain The transmembrane domain is where the transmembrane proteins are located. In a CAR, the transmembrane domain has the function to anchor the CAR to the T cell membrane. How strong the CAR is anchored to the T cell membrane affects the CAR expression level and stability.  Currently, the commonly used transmembrane domain is derived from proteins such as CD3ζ, CD4, CD8α, and CD28. The CD3ζ transmembrane domain Among the transmembrane domains mentioned, the CD3ζ transmembrane may improve CAR-mediated T cell action as the CD3ζ transmembrane medi...
Read more

The structure of Chimeric Antigen Receptor (CAR) I - Extracellular Target Antigen Binding Domains

Image
Antigen Binding Domains The antigen-binding domain of a chimeric antigen receptor is like the head of a train. It determines the target antigen specificity.  The antigen-binding site is made up of a heavy chain and a light chain joined together to form a single-chain variable fragment (scFv).  Single-chain variable fragment (scFv) scFv targets extracellular surface cancer antigens, the biomarkers of the tumor cells. Classically, CD19 is presented in B cells in leukemia. Hence, CD19 is the biomarker that we want the CAR to recognize and bind with it. Once the scFv of a CAR binds with the target antigen, the immune response, major histocompatibility complex (MHC)-independent T cell activation, results. This is when a cascade of molecular signaling starts to trigger an immune response to kill the tumor cells.  MHC-dependent, T cell receptors (TCR)-mimic CARs Some may call it an improvement, but a T cell receptor (TCR)-mimic CAR functions well when it targets intracellular tu...
Read more