Question

Rank the following anions in order of increasing basicity.

Rank the following anions in order of increasing basicity.

Answer 1

Concepts and reason

Basic strength depends on the strength of its conjugate acid; if the conjugate acid is more acidic, then the carbanion is less basic.

Acidic strength depends on the electronegativity of the hydrogen bonded carbon atom. If the electronegativity of the carbon atom increases, the acidic strength of that compound increases.

Fundamentals

Electronegativity: The tendency to attract the bonded pair of electrons towards one atom is called the electronegativity of that atom.

Electronegativity of an atom can also be explained through the percentage of s-character present in its hybridized orbital.

If the s-character present in hybridized orbital is more, electronegativity will be more for that atom.

Given carbanions are as follows:

, ,

And their conjugate acids are , and .

All these hydrocarbons show different type of hybridizations.

: This hydrocarbon is a saturated hydrocarbon; only sigma bonds are present in this structure. Therefore, the hybridization is. The s-character is 25%.

: This hydrocarbon is an unsaturated hydrocarbon; two pi-bonds are present with the sigma bonds. Therefore, the hybridization is and the s-character is 50% .

: This hydrocarbon is an unsaturated hydrocarbon; one pi-bond is present with the sigma bonds. Therefore, the hybridization is and the s-character is 33.3%.

s-character = 25%

s-character = 50%

s-character = 33.3%

If the s-character present in hybridized orbital is more, the electronegativity will be more for that atom.

In these compounds, hybridized carbon atom is the most electronegative and the hybridized carbon atom is the least electronegative in nature.

Therefore, thehybridized carbon atom containing compound is the most acidic among the all compounds and the hybridized carbon atom containing compound is the least acidic among all the compounds.

We know that, if the conjugate acid is more acidic, then the carbanion is less basic.

Therefore, is the least basic and is the most basic.

Basic order of the given carbanions is as follows:

Ans:

The increasing basicity order of the provided anions is as follows: