Step 1: Identify required conversion.
\[
CH_3CONH_2 \rightarrow CH_3NH_2
\]
This is conversion of an amide to an amine with one carbon less. Step 2: Name of reaction.
This is Hofmann bromamide reaction (Hofmann rearrangement). Step 3: Reagent used.
Hofmann rearrangement uses \(Br_2\) in presence of strong base \((NaOH)\) which forms \(NaOBr\) in situ.
Thus reagent is \(NaOBr\). Final Answer:
\[
\boxed{NaOBr}
\]