Chemistry INDUCTIVE EFFECT

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INDUCTIVE EFFECT

Inductive Effect :

In a covalent bond between the two dissimilar atoms, the electron pair forming the bond is never shared absolutely equally between the two atoms but is attracted a little more towards the more electronegative atom of the two, eg. the electron pair forming the `C- X` bond is somewhat more attracted towards the atom `X` with the result - it attains a partial negative charge (`-delta`) while the carbon atoms attain a partial positive charge(`+delta`).

`-> C : X` or `-> overset(delta^(+))(C)-overset(delta^(-))(X)`

In a covalent bond between the two dissimilar atoms, the electron pair forming the bond is never shared absolutely equally between the two atoms but is attracted a little more towards the more electronegative atom of the two, eg. the electron pair forming the `C- X` bond is somewhat more attracted towards the atom `X` with the result - it attains a partial negative charge (`-delta`) while the carbon atoms attain a partial positive charge(`+delta`).

`-> C : X` or `-> overset(delta^(+))(C)-overset(delta^(-))(X)`

Negative Inductive Effect (`-I` Effect) :

This is due to electron-attracting groups (`X`); it develops positive charge on the chain and is said to exert a negative inductive effect denoted by (`-I`) . `overset(delta^(+))(C) -> overset(delta^(-))(X)`

`*` (`-I`) effect decreases as one goes away from group `X` (electron attracting)

`underset(3)overset(delta delta delta ^(+))(C)-underset(2)overset(delta delta ^(+))(C)-underset(1)overset(delta ^(+))(C)->X^(delta^(-))`

`C_1(delta_1+) > C_2(delta delta +) > C_3(delta delta delta +)` and after third carbon charge is negligible

`*` (` - I`) effect is in order

`text( )^(+)NH_3 NO_2 > F > COOH > Cl > Br > I > OH > C_6H_5`

Due to (`-I`) effect (electron-withdrawing nature) electron-density decreases, hence

- basic nature is decreased

- acidic nature is increased

`*` Chloro acetic acid is stronger than acetic acid since `Cl` shows (`-I` effect, electron-density is decreased and `O - H` bond is weakened causing ionisation of `(-COOH)` to a greater extent than `CH_3COOH`. See fig.1.

`*` `NH_3` is a base due to lone-pair on nitrogen. Phenyl group is electron-withdrawing. What happens to electron-density of nitrogen in aniline? Naturally electron-density is decreased. Hence aniline is weaker base than `NH_3`. See fig.2.

Similarly acidic nature of phenol is greater than `H_2O` due to electron-withdrawing nature of phenyl group. See fig.3.

This is due to electron-attracting groups (`X`); it develops positive charge on the chain and is said to exert a negative inductive effect denoted by (`-I`) . `overset(delta^(+))(C) -> overset(delta^(-))(X)`

`*` (`-I`) effect decreases as one goes away from group `X` (electron attracting)

`underset(3)overset(delta delta delta ^(+))(C)-underset(2)overset(delta delta ^(+))(C)-underset(1)overset(delta ^(+))(C)->X^(delta^(-))`

`C_1(delta_1+) > C_2(delta delta +) > C_3(delta delta delta +)` and after third carbon charge is negligible

`*` (` - I`) effect is in order

`text( )^(+)NH_3 NO_2 > F > COOH > Cl > Br > I > OH > C_6H_5`

Due to (`-I`) effect (electron-withdrawing nature) electron-density decreases, hence

- basic nature is decreased

- acidic nature is increased

`*` Chloro acetic acid is stronger than acetic acid since `Cl` shows (`-I` effect, electron-density is decreased and `O - H` bond is weakened causing ionisation of `(-COOH)` to a greater extent than `CH_3COOH`. See fig.1.

`*` `NH_3` is a base due to lone-pair on nitrogen. Phenyl group is electron-withdrawing. What happens to electron-density of nitrogen in aniline? Naturally electron-density is decreased. Hence aniline is weaker base than `NH_3`. See fig.2.

Similarly acidic nature of phenol is greater than `H_2O` due to electron-withdrawing nature of phenyl group. See fig.3.

Positive Inductive Effect (`+ I`) :

This is due to electron-releasing group (`Y`). It develops a negative charge on the chain and is said to exert a positive inductive effect denoted by (`+I`).

`C^(delta^(-)) leftarrow Y^(delta^(+))`

`*` (`+I`) effect also decreases as we go away group `Y` (electron-releasing)

`underset(4)(C)-underset(3)overset(delta delta delta -)(C)-underset(2)overset(delta delta -)(C)-underset(1)overset(delta -)(C)-Y^(delta^(+))`

`C_1(delta-) > C_2 (delta delta -) > C_3(delta delta delta -)`

(`+I`) effect is in order.

`(CH_3)_3 C- > (CH_3)_2CH- > CH_3CH_2- > CH_3-`

See Table.

Take example of `H_2O`, `CH_3OH` and `C_6H_5OH`

See fig.

This is due to electron-releasing group (`Y`). It develops a negative charge on the chain and is said to exert a positive inductive effect denoted by (`+I`).

`C^(delta^(-)) leftarrow Y^(delta^(+))`

`*` (`+I`) effect also decreases as we go away group `Y` (electron-releasing)

`underset(4)(C)-underset(3)overset(delta delta delta -)(C)-underset(2)overset(delta delta -)(C)-underset(1)overset(delta -)(C)-Y^(delta^(+))`

`C_1(delta-) > C_2 (delta delta -) > C_3(delta delta delta -)`

(`+I`) effect is in order.

`(CH_3)_3 C- > (CH_3)_2CH- > CH_3CH_2- > CH_3-`

See Table.

Take example of `H_2O`, `CH_3OH` and `C_6H_5OH`

See fig.

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