The conformational properties of the 3-halogenated-1-benzoxepins (compounds6–9) have been studied by1H and13C dynamic nuclear magnetic resonance. The results show that for the heavier halogen derivatives (Cl, Br, and I), only two chair forms (CaandCe) are observed while for the F substituent, three forms (Ca,Ce, andTB) are detected. This is in contrast with the 3-halogenated-1,5-benzodioxepins (2–5), which were shown to exist as a mixture of three forms for the heavier halogens (Cl, Br, and I) and, show only two forms (CaandTB) for the F substituent. The results for these two systems characterize the conformational effects produced by one and two O—C—C—X vicinal interactions between polar bonds, which shed light on the nature of the intramolecular stereoelectronic σ–σ* orbital interactions operative in both families of molecules.Keywords: 3-halogenated-1-benzoxepins, conformational properties, nuclear magnetic resonance, stereoelectronic orbital interactions