Electromeric Effect

As with electrochemical effects like the electromeric effect and hypercoagulation, organic redox reactions are frequently affected by electrochemical effects. Compounds with similar formula units and structures can behave differently because of electronic factors.

Examples of Electronic Effects are:

• Electromeric effect
• The inductive effect
• Resonance
• The mesomeric effect
• Hypercoagulation

What is the Electromeric Effect?

Electrons in Pi (π) bonds can be easily polarized, making them a good choice for conducting experiments. Electrophiles and nucleophiles, which are reacted chemically with an atom’s nucleus, will cause the electrons to polarize and move toward one of the atom’s constituent parts. The underlying mechanism is electrostatic attraction and repulsion. One atom becomes more negatively charged and the other more positively charged as a result of the transfer of electrons from one atom to the other. A reversible reaction in which a pi-electron pair is completely transferred can be induced by an electrophile or a nucleophile. Taking away the attacking reagent eliminates the effect. No matter how you look at it, the electromeric effect is always working in your favor during a reaction. In the presence of an electron-attacking reagent, the electromeric effect (E effect) is also known. When electrons move from one location to another, the curved arrow notation is also used.

Direction of the Shift

There will be a forward movement of an electron pair in the following direction:

If the groups linked to multiple bonds are similar enough, it is possible to shift in either direction

• When groups other than homologous link the ends of a double bond, the inductive effect determines the electron pair’s shift

The mechanism of an electromeric reaction can be explained in this way. In the presence of an electrophile E+, the two pi electrons that make up a pi bond are transferred to an atom in a double or triple bond. Dipole formation occurs immediately when the shared pi electrons are transferred.

Effects of Electromagnetism; There are two types of electromeric effects:

• The positive electromeric effect, or the +E effect, as it is also known
• The negative electromeric effect, or -E effect, is another name for this phenomenon

+E Effect or Positive Electromeric Effect  A similar effect occurs when the attacking reagent moves the electron pair of the pi bond closer to the reagent. Adding acid to alkenes causes the +E effect to become more prominent. When a pair of electrons are exchanged, the attacking reagent latches onto the atom that received it. When an electrophile comes into contact with a positively charged atom, it typically produces the +E effect by transferring pi electrons to the target atom. For example, the +E effect is demonstrated by the protonation of ethene. -E Effect or Negative Electromeric Effect As soon as the electron pair of the pi bond is moved away from the attacking reagent, this effect takes place. As soon as a negatively charged atom loses its electron pair, the attacking agent attaches itself to it, binding to the positively charged atom. Nucleophiles often exhibit the -E effect, in which the pi electrons are transferred to an atom that the attacking reagent will not bond to. This is known as the -E effect. The- E effect is observed when nucleophiles are introduced to carbonyl compounds.

Examples of the Electromeric Effect

• An alkene and Br₂ reaction in CCl₄

In response to the reagent bromine approaching an alkene, the C₂ atom becomes negatively charged while the C1 atom becomes positively charged. Alkenes are attacked by Br+ to produce cyclic bromonium ions as an intermediate step. Br attacks the cyclic bromonium ion, and vicinal dibromide is formed  

• Incorporating hydrogen halides into an existing formulaProton and nucleophiles are found in hydrogen halides, which are both electrophilic and nucleophilic (halide). After a double bond is broken, the electrons of the electrophile are taken up and attached to the newly formed molecule (carbocation). This reaction generates a brand-new molecule.  
• Nucleophilic addition reaction  Negatively charged nucleophiles will polarize the positively charged carbonyl group if they are in close proximity, and the nucleophiles will then attack the positively charged molecule.
  • Electrophilic addition reaction
  When H+ is used to activate the carbon-carbon double bond, the symmetrical alkenes or alkynes become polarized.
  • Electrophilic substitution reactions of benzenoids
  When an electrophile attacks benzene, it undergoes these polarization reactions.

  Differences Between Electromeric Effect and Inductive Effect:

  When it comes to effects, the electromeric and inductive are poles apart. Inductive effects, on the other hand, cannot be reversed. The latter has the effect of altering the magnetic field permanently. Therefore, the electromeric effect takes precedence when both inductive and electromeric effects are present at the same time.

  Conclusion

  Organic compounds must have at least two bonds to see the Electromeric Effect. An abrasive agent has a short-term effect on a substance when exposed to it. The Electromeric effect transfers all the shared pi-electron pairs in an organic molecule to a single nucleus, resulting in a dipole in the molecule. At least one multiple bond is required for this effect to occur in organic compounds. An attack on atoms in this multiple bond results in a complete transfer to one of the two atoms of this bond of one pi bonding pair of electrons. Once an organic compound has been exposed to the attacking reagent, the electromeric effect will continue to take place. Once the agent has been removed, the polarised molecule returns to its original form.