THE DETERMINATION OF DOUBLE-BOND CHARACTER IN CYCLIC SYSTEMS IV — TETRAHYDRONAPHTHALENE STERIC FACILITATION OF CHELATION*

The strength of the intramolecular hydrogen bond between the carbonyl group of an aromatic aldehyde, ketone, or ester and an ortho-hydroxyl group varies with the amount of double-bond character exhibited by the aromatic bond joining the ring carbon atoms holding the substituents. The strength of such a hydrogen bond is measured by Δv(C=O). This paper records the results of a study of the bond structure of tetrahydronaphthalene on this line and a comparison of these results with our earlier work on indan and o-xylene, thus permitting a rather comprehensive evaluation of the Mills-Nixon effect. The twelve compounds required for this study were the 5,6,7,8-tetrahydro derivatives of 1- and 2-naphthaldehyde, 1- and 2-acetonaphthone, methyl 1-and 2-naphthoate, 2-hydroxy-1- and 3-naphthaldehyde, 2-hydroxy-1- and 3-acetonaphthone, and methyl 2-hydroxy-1- and 3-naphthoate.