Charge Localization in the Carbonium Ions of Methylbenzanthracenes

Ercole Cavalieri, Melvin Calvin

Research output: Contribution to journalArticle

7 Scopus citations

Abstract

Covalent binding of aromatic hydrocarbons to cellular macromolecules, the first probable step in the tumor-initiating process, requires metabolic activation by monooxygenase enzyme systems. Acid-catalyzed proton-deuterium exchange was used as a model to simulate the electrophilic oxygen atom activated by such enzymes. Kinetics of exchange with deuterium ion for a series of carcinogenic and noncarcinogenic methylbenzanthracenes were studied by NMR in two sets of conditions, i.e., CCl4-CF3COOD (85:15 v/v and 50:50 v/v). Deuteration of the potent carcinogen 7,12-dimethylbenz[a]anthracene at the most basic position C-12 generated a carbonium ion with charge localized at the complementary 7 position, resulting in the specific deuteration of the attached methyl group. Similarly, selective attack of deuterium ion on C-6 in 3-methylcholanthrene produced a carbonium ion with a high degree of charge localization at C-12b and, consequently, specific deuteration at the adjacent methylene group. This study has revealed that charge localization in the carbonium ion renders this intermediate chemically reactive; such a distinctive property might play a role in the bioactivation of these compounds.

Original languageEnglish (US)
Pages (from-to)2676-2679
Number of pages4
JournalJournal of Organic Chemistry
Volume41
Issue number16
DOIs
StatePublished - Aug 1 1976

ASJC Scopus subject areas

  • Organic Chemistry

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