Master of Science (MS)
Semester of Degree Completion
David H. Buchanan
Rate constants of cleavages of fourteen alkyl-aryl ethers with HI, KI, or LiI in pyridine at 50-150°C were determined under pseudo first order conditions. The following ethers which have a six-membered ring intramolecular hydrogen bond underwent a bimolecular nucleophilic displacement by iodide ion in pyridine: 8-methoxy-1-naphthalenol, 8-ethoxy-1-naphthalenol, 2-methoxybenzoic acid, and 2-hydroxybenzyl methyl ether. The following ethers which lack a six-membered ring hydrogen bond were not cleaved or underwent cleavage slowly compared with the hydrogen bonded compounds: 1,8-dimethoxynaphthalene, 1,8-diethoxynaphthalene, 1-methoxynaphthalene, 4-methoxybenzoic acid, methyl 2-methoxybenzoate, 2-methoxybenzyl methyl ether, and 4-methoxybenzyl methyl ether. The pattern of ether reactivity indicated that a six-membered ring hydrogen bond to the ethereal oxygen atom can enhance the nucleophilic cleavage of ethers by iodide ion in a basic solvent such as pyridine.
Ethers such as 2-methoxybenzyl alcohol, 2-hydroxybenzyl methyl ether, and 4-hydroxybenzyl methyl ether which can react via elimination to a quinone methide also reacted, but apparently not by direct nucleophilic displacement.
Takemura, Nobumi, "Enhancement of Ether Cleaving Reactions by Intramolecular Hydrogen Bonding" (1986). Masters Theses. 2648.