Is something an electrophilic addition because of the first step or slowest step?

[Michael_Phillipi_1I]

In examples when HBr is added and it is an electrophilic addition, it says that because H^+ is an electrophile it is an electrophilic reaction. However, the slower second step involves adding a Br nucleophile. So is it an electrophilic addition because the first step, adding the H^+ is an electrophilic addition is slower, or simply because it is the first step?

[Britney Pheng 1L]

Hi Michael!

It is an electrophilic addition reaction because step 1 involves the addition of an electrophile (which in this case is H^+) to the other molecule in the first step. For general electrophilic addition reactions, a pi (double) bond is broken and two sigma (single) bonds are formed. The bonds H-C and Br-C are those two sigma bonds. So basically the name speaks for itself :)