Answer
(a) Putrescine - $NH_{2}-CH_{2}-CH_{2}-CH_{2}-CH_{2}-NH_{2}$
1,4-diaminobutane
(b) Cadaverine - $NH_{2}-CH_{2}-CH_{2}-CH_{2}-CH_{2}-CH_{2}-NH_{2}$
1,5-diaminopentane
Work Step by Step
(a) The compound has a four-carbon chain. Amino group ($–NH_{2}$) is present on carbon 1 and carbon 4. The prefix di- is used to represent the presence of two amino groups in the compound.
(b) The compound has a five-carbon chain. Amino group ($–NH_{2}$) is present on carbon 1 and carbon 5. The prefix di- is used to represent the presence of two amino groups in the compound.