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31 Jan 2009 11:56:41 IST

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inductive effect and electromeric effect

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inductive effect and electromeric effect

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saharsha kumar keshkar

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31 Jan 2009 12:10:14 IST

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when an electron withdrawing group or electron releasing group is attached to carbon chain,

polarity is induced on yhe carbon atom and on substituent attached to it,it is known as INDECTIVE EFFECT>

In the presence of an electrophile,there is complete transfer of (pi) electrons,

from one atom to other to produce produce temporary polarity on atoms joined by multiple bonds.,

is known as ELECTRO MERIC EFFECT.

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Divya tryin 4 jee

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31 Jan 2009 12:24:39 IST

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hey! its very simple...........

let me explain you in simple words..

inductive effect

the permanent displacement of electron when an more electronegative group is attached to the carbon chain the electronegative difference increases and bond length decreases.this ia only there in single bonded compounds.it include 2 more effects

1]+I effect--- the group which releases the eleectron due to electronegative difference possess +I effect eg alkyl group

2]-I effect--- the group which accepts electron possess -I effect eg halogen.

electromeric effect

it is the temporary displacement of electron when an electrophyl or nucleophyl is attached to unsaturated compounds

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Bipin Dubey

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31 Jan 2009 16:12:48 IST

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The most basic way to explain it is that the inductive effect is used to explain how certain groups can "Push" and "Pull" charge that is next to them, the most common example is the Methyl (or similar alkyl group) that will "Push" negative charge from itself and toward whatever it is attached to, this is called a "+I" group because of this effect. The pushing of negative charge towards something that is positive will help make that species a little less positive then if it was all alone and therefore less unstable.

rtrikha

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31 Jan 2009 19:07:14 IST

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INDUCTIVE EFFECT

Whenever the withdrawing electron group (such as halogen) is attached to the end of a carbon chain, a permanent effect called inductive effect takes place. To understand this, consider a chain of carbon atoms having Cl atom at one end: C-C-C-C-Cl

Since chlorine (Cl) is more electronegative than C, the electron pair shared between C, and Cl is displaced towards the Cl atom, due its larger electronegativity. A partial negative charge (d-) is thus acquired by Cl and C acquires a partial positive charge (d+). The displacement is, not limited to C₁-Cl bond but is transmitted to other carbons along the chain. This happens due to the small positive charge on C, which attracts the of electrons of C₁-C₂ bond towards it. This displacement results in the positive charge on C₁ being partially neutralized while a small positive charge is developed on C₂. The charge on C₂ is less than that on C₁ (d'+ < d+).

Similarly, C₃ will acquire a small positive charge d +"<d+" < d+'). ( d= delta means small)

This process of electron displacement of electrons along the chain of carbon atoms is called inductive effect (or I-effect). This is a permanent effect and results due to the presence of a polar covalent bond at one end of the chain. An arrow as shown generally represents this effect:

It may be noted that this effect decreases sharply as we move away from the atoms involved in the initial polar bond. From the fourth atom onwards, the effect becomes negligible.

For comparing the relative effects, hydrogen is taken as the standard and atoms or groups are classified into the following two categories:

Atoms or groups of atoms that have a greater electron-attracting capacity than hydrogen are referred to as having -I (electron attracting) effect. For example,

NO₂>CN >COOH >F >Cl >Br >I>OH>OCH₃>C₆H₅>HI

Atoms or groups of atoms, having smaller electron attracting power than hydrogen are referred to as having +I (electron repelling) effect.

Inductive effect plays very significant role in understanding reactions of organic chemistry. Carbon of methyl chloride, for example, acquires partially positive charge due to shift of electrons towards chlorine and provides a site for attack by a negatively charged species (say OH).

Electromeric Effect

This is a temporary effect and takes place between two atoms joined by a multiple bond, i.e., a double or triple bond. It occurs at the requirements of the attacking reagent, and involves instantaneous transfer of a shared pair of electrons of the multiple bond to one of the linked atoms.

It is temporary in nature because the molecule acquires its original electronic condition upon removal of the attacking reagent.

For example, consider the carbonyl group, >C=O, present in aldehydes and ketones. When a negatively charged reagent say approaches the molecule seeking positive site, it causes instantaneous shift of electron pair of carbonyl group to oxygen (more electronegative than carbon). The carbon thus becomes deprived of its share in this transferred-pair of electrons and acquires positive charge. In the meanwhile oxygen takes complete control of the electron pair and becomes negatively charged. Therefore, in the presence of attacking reagent, one bond is lost and this negatively charged attacking reagent links to the carbon having positive charge.

This phenomenon of movement of electrons from one atom to another at the demand of attacking reagent in multibonded atoms is called electromeric effect, denoted as E effect. The electromeric shift of electrons takes place only at the moment of reaction. Like the inductive effect, the electromeric effect is also classified as +E and E:

When the transfer of electrons takes place towards the attacking reagent, it is called + E (positive electromeric) effect. For example,

When the transfer of electrons takes place away from the attacking reagent, it is called, -E (negative electromeric) effect. For example,

mohit gupta

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1 Feb 2009 09:34:17 IST

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if u need any mroe information realy worth reading , then you must visit>>>>http://en.wikipedia.org/wiki/Inductive_effect

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