“Oxazepine” refers to any seven-membered ring containing an oxygen and nitrogen atom. The 1,3-oxazepine is a branch of many types of the heterocyclic oxazepine [1–7]. The core structure of 1,3-oxazepane-4,7diones consists of a sevenmemebred ring along with two carbonyl group. Over the years, the syntheses of oxazepine derivatives have been investigated and documented. The result is important of heterocyclic compounds having significant biological uses [8– 13]. Recently, we prepared a variety of 1,3-oxazepinediones in order to study the spectroscopic and liquid crystal properties [14]. In this paper, we present the structural elucidation by 1D and 2D NMR experiments of 3-alkyl- 2-(3-hydroxyphenyl)-1,3-oxazepane-4,7-diones with general formula(HOC6H4)CONCnH2n+1CH-CH(CO)2 (where n = 2, 4, 6, 8, 10, 12, 14, 16, and 18). Here, the hydroxyphenyl and the terminal alkyl chain are attached to the oxazepane ring.