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A Carbon-Centered Radical Unreactive Toward Oxygen:  Unusual Radical Stabilization by a Lactone Ring

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journal contribution
posted on 14.03.2000, 00:00 by J. C. Scaiano, Alan Martin, Glenn P. A. Yap, K. U. Ingold
A lactone ring confers unusual stability to a diphenylmethyl-like radical that is virtually unreactive toward oxygen. Thus, the radical derived from HP-136 is about 10 000 times less reactive than typical carbon-centered radicals. A reversible reaction with oxygen is proposed by analogy with triphenylmethyl; however, the association constant is about 1000 times smaller for HP-136 than for triphenylmethyl. While the lactone ring greatly influences the reactivity, the spectroscopy of the HP-136-derived radical is in line with that expected for a substituted diphenylmethyl radical.