No real reaction between KBr and alkenes. KBr is a salt of the bromide ion, very similar to table salt, NaCl.

I think you mean something else, but I will let you think about it….

Stereospecific is a subset of stereoselective.

It’s like saying two people are siblings, and then later on saying that they are brothers. They are both siblings and brothers, but brothers is a subset of siblings.

[Worth noting: bromination of alkenes is technically an oxidation reaction, because each carbon goes from being bound to another carbon (0) to bromine (–1). The oxidation state of each carbon in ethene is +2; the oxidation state of each carbon in dibromoethane is +1. ]

This is in Section 8: Some Applications of Halogenation Reactions. Oxidation number should become more positive / less negative if carbon is being oxidized (which it is here). Looks like the numbers are right but the sign is incorrect. Thank you :)

The leaving group is excellent, first of all. The C-halogen bond length is much longer than a normal C-leaving group bond length. (e.g. 2.48 A for C-I in the iodonium vs 2.13 A for normal C-I).

Secondly, because of the 3-membered ring, the geometry on the carbons is not the same as in your typical tetrahedral carbon, so there is more “room” for the nucleophile to approach.

No, what happens is that you form the bromonium ion with Br2 and then Cl(-) is the active nucleophile which attacks the resulting bromonium ion at the most substituted position.
Kind of a strange question though, because they probably don’t mention solvent. NaCl is not going to dissolve in an organic solvent. Better choice would have been Bu4N+ Cl- .

I’m studying for a quiz and the problem I came across was an alkene addition with Br-Br and NaCl. I know that the Cl should add first but I can’t seem to figure out the mechanism for it.

See this post: https://www.masterorganicchemistry.com/2017/04/11/more-on-12-and-14-additions-to-dienes/