i believe the ans. is two.
however, i know why people have said there could be 3 isomer.
but then again, there are many types of isomers, like conformation isomer, and stereoisomer etc..
to the mods: i know this is a place where everyone can freely speak their mind. but looking through pre-dent. forum, i see few members (but others, in no doubt, are great folks) w/ consistant negative opinion that i see as a flaw in this community. i'm not saying you should banned them or anything, but should there be at least some limit as to what kind of comments are given?
i know of a forum (which is not academic btw) that does such a thing. i see this forum as more prestigious community, and i think there should be some type of monitoring little bit more. i'm just little concerned about "why are you so stupid, go die" types of comments.
just my 2 cents
😉