Why does the Torah name the Nasi of Merari before saying where they encamped, as it does in connection with K'has and Gershon?
Moshav Zekenim (in Pasuk 23): Gershon and K'has encamped in the west and the south, near the Degalim of Efrayim and Reuven, who are called Bechorim. Merari encamped in the north, near the Degel of Dan, who was a Ben Shifchah, so the Torah delays saying where they encamped.
Malbim (in Pasuk 22): The Torah also mentions first the primary matter that it is coming to teach. For K'has and Gershon, it primarily teaches where they encamped, so it mentons it first. For B'nei Merari, we already know that they must camp in the north, so it primarily teaches the name of the Nasi. 1
We do not yet know if they are in the east! The Torah teaches that Moshe and the Kohanim are it is not the east only in verse 38! Perhaps it was known that they will be in the east, by the opening of the Mishkan, or because the east is most esteemed (Yehudah was in the east). (PF)