Well, there is an absolute form of the noun תָּ֫וֶךְ [tawekh] "midst, middle, interior", but I would always expect the compound form with the preposition ב, i.e. after בְּתוֹךְ־ a noun or a suffix is always expected.
PS. Well, it exists. There is Gen. 15:10 ויקח לו את כל אלה ויבתר אתם בתוך ויתן איש בתרו לקראת רעהו ואת הצפר לא בתרו "And he took him all these, and divided them in the midst, and laid each half over against the other: but the birds divided he not."