3294 I. M. HUNSBERGER, H. s. GUTOWSKY, W. POWELL, L. ~IORIN AND \'. BANDURCO vel. 80 ... [CONTRIBUTION FROM THE DEPARTMENT OF CHEMISTRY, FORDHAM USIVERSITY; DEPARTMENT OF CHEMISTRY, ANTIOCki COLLEGE; AND THE NOYES LABORATORY, UNIVERSITY OF ILLISOIS] The Determination of Double-bond Character in Cyclic Systems. IV. Tetrahydronaphthalene. Steric Facilitation of Chelation1