In 1984, what happened to Syme? How is his fate connected to the secret O'Brien reveals to Winston and Julia?

After having
a conversation in the canteen with Syme,has a flash of insight in which he realizes Syme will be
vaporized because he's too intelligent. Their canteen conversation had been about the Newspeak
dictionary Syme was working on. Syme had waxed enthusiastic about reducing the number of words
in the language to the fewest possible. Syme had grasped that reducing people's vocabulary to a
bare minimum reduced people's capacity to have subversive thoughts, and he talked about this
knowledge openly with another person. In other words, he grasped the big picture in a way that
violated the rules of doublethink, in which he was both to know and simultaneously remain
unaware of what he was doing. Syme ends up disappearing, almost certainly vaporized.  ,
apparently aware that Winston has talked to Syme, uses a mention of this "friend" of
Winston's (since Syme has been vaporized O'Brien can't use his name) to suggest to Winston that
he, O'Brien, might be a conspirator against the regime. 

O'Brien reveals a
secret when he gives Winston a copy of The Book, laying bare the logic of Oligarchic
Collectivism. The Book confirms what Syme had said about dumbing down the language: The Book
reveals the importance of crimestop, or stopping any subversive thought before it can even
occur. Syme clearly did not practice crimestop and, like Winston after reading The Book, he knew
too much to be allowed to continue unchecked.