Question

The stability of carbonium ion depends upon:
(This question has multiple correct options)
A.) the polarity of the group to which it is attached
B.) the substrate with which it reacts
C.) the inductive effect of the attached group
D.) the tendency of the compound to react

Answer 1

The stability of a carbonium ion is more when an electron releasing group is attached to the carbonium ion and stability of carbonium ion is less when an electron withdrawing group is attached to it.

Complete step by step answer:
In this question, by carbonium ion we mean those cations which have positive charge on the carbon and this positive carbon is known as carbocation or carbonium ion. The carbocation is formed when a covalent bond between carbon and a more electronegative atom is broken by heterolytic fission. While heterolytic fission the more electronegative atom takes away the electron pair while the carbon atom loses its electron. Therefore, carbon acquires a positive charge on it. This can be shown by simple example of methyl chloride as follows:
$C{H_3} - Cl\xrightarrow{{Heterolytic{\text{ }}fission}}CH_3^ + + C{l^ - }$
In the carbonium ion, the carbon which has positive charge has six electrons in its valence shell.
The stability of carbocation depends upon the inductive effect of the attached group. The $+ I$ effect is shown by the species which have a tendency to donate electrons and the $- I$ effect is shown by the species which have tendency to withdraw electrons. When a group having $+ I$ is attached to the carbocation then the stability of carbocation increases because electron density on it increases. When a group having $- I$ is attached to the carbocation then the stability of carbocation decreases because electron density on it decreases.
The stability of carbocation also depends upon the polarity of the group to which it is attached . If the atom attached is negatively charged then the stability of carbocation increases and when the atom attached to carbocation is positively charged then stability of carbocation decreases.
Hence, A and C are the correct options.

Note:
Always remember that negatively charged group and negative inductive effect increases the stability of carbocation and positively charged group and positive inductive effect decreases the stability of carbocation.