Tutors on net
Tutors on NetTutors on Net

Bond Polarization - Eletromeric Effects

Chemical Bonding Assignment / Homework Help
Unlike mesomeric and the inductive effects that are seen in compounds irrespective of the presence of the attacking agent, there are certain temporary effects that act only in the presence of the reacting agent. These effects include the electromeric effect and the hyperconjugation.


Electromeric Effect:

Electromeric effect can be defined as the transfer of electrons from a double bond or an atom with a lone pair of electrons to an adjacent single bond. π electrons are involved in the transfer process. This involves a complete transfer of electrons. Hence, complete negative and positive charges are formed on the molecule. However, this effect remains as long as the attacking molecule is present. The effect disappears as the attacking agent is removed. This effect can best be represented as follows.

Reagent
C=C ------ -----→ C +-C -
→   ←-----------
No reagent

As can be seen above, the transfer of electrons takes place towards a more electronegative atom. The atom obtaining the electrons attains a complete negative charge and the one that has lost the electrons develops a positive charge.

Like other effects electromeric effect represented by the letter E exists in two forms the +E effect and the -E effect. The +E effect is said to occur if the electrons are transferred towards the atom. The -E effect involves displacement of electrons away from the atom.

As the electromeric effect is seen only in the presence of an attacking agent, this effect is said to promote the reactions rather than inhibiting them. When the inductive effect and the electromeric effect operate in the same molecule, electromeric effect dominates the inductive effect. The most common attacking reagents that initiate the electromeric effect are the polar reagents. When these reagents are added to either C=C or C=O the displacement of the π electrons takes place.

Hyperconjugation:

Unlike the electromeric effect which involves the transfer of π electrons, hyperconjugation involves the displacement of both the sigma and π electrons. This type of effect is mainly seen in atoms with a hydrogen atom on the α-carbon atom attached to the unsaturated carbon atom i.e. (H-C-C=C). The extent of electron displacement depends on the number of H atoms attached to the α-carbon atom. Greater the number of hydrogen atoms attached to the carbon atom greater will be the electron release. Thus, methyl with three hydrogen atoms shows a greater effect when compared to ethyl with only two such hydrogen atoms.

Stability of the compounds such as alkenes can best be explained with the help of hyperconjugation. For example 2-methyl propene with six C-H bonds is more stable than propylene.

Solved problems
  • Methyl amine is considered stronger than ammonia. This is due to which of the following effects.
    • Electromeric effect
    • Inductive effect
    • Hyperconjugation
    • Mesomeric effect
    Answer: b
  • The set of structures that represent the true structure of a molecule but none of them alone can represent the molecule are called as
    • Resonating structures
    • Canonical structures
    • Different structures cannot combine to explain a single molecule
    • A and b
    Answer: d
  • Which of the following is a permanent effect
    • Inductive effect
    • Electromeric effect
    • Hyperconjugation
    • All
    Answer: a
  • The reactivity of alkyl halides and the strength of carboxylic acids can best be explained with which of the following bond polarization effects.
    • Electromeric effect
    • Inductive effect
    • Mesomeric effect
    • Hyperconjugation
    Answer: b
  • Which of the following effects are seen in unsaturated molecules with conjugative system?
    • Inductive effect
    • Mesomeric effect
    • Electromeric effect
    • Hyperconjugation
    Answer: b
  • Why are the electromeric and hyperconjugation effects termed as temporary effects?
    • As they occur only in the presence of a attacking agent and disappear as the attacking agent is removed
    • They exist only for certain time period.
    • They are not temporary effects but are permanent
    • none
    Answer: a

Online Live Tutor Electromeric Effect (Bond Polarization):

We have the best tutors in Finance in the industry. Our tutors can break down a complex Electromeric Effect (Bond Polarization) problem into its sub parts and explain to you in detail how each step is performed. This approach of breaking down a problem has been appreciated by majority of our students for learning Electromeric Effect (Bond Polarization) concepts. You will get one-to-one personalized attention through our online tutoring which will make learning fun and easy. Our tutors are highly qualified and hold advanced degrees. Please do send us a request for Electromeric Effect (Bond Polarization) tutoring and experience the quality yourself.


Online Inductive Effect of Hyperconjugation (Bond Polarization) Help:

If you are stuck with a Inductive Effect of Hyperconjugation (Bond Polarization) Homework problem and need help, we have excellent tutors who can provide you with Homework Help. Our tutors who provide Inductive Effect of Hyperconjugation (Bond Polarization) help are highly qualified. Our tutors have many years of industry experience and have had years of experience providing Inductive Effect of Hyperconjugation (Bond Polarization) Homework Help. Please do send us the Inductive Effect of Hyperconjugation (Bond Polarization) problems on which you need Help and we will forward then to our tutors for review.