Accession Number : AD0710991

Title :   THE MICHAEL REACTION IN NON-ALKALINE MEDIA. V. EFFECT OF STRUCTURE ON THE RATE AND MECHANISM OF ADDITION OF 1,1-DINITROCARBANIONS TO METHYL ACRYLATE,

Corporate Author : NAVAL ORDNANCE LAB WHITE OAK MD

Personal Author(s) : Kaplan,Lloyd A. ; Pickard,Hugh B.

Report Date : 15 JUL 1970

Pagination or Media Count : 27

Abstract : The kinetics of the addition of a series of substituted 1,1-dinitromethide ions to methyl acrylate were studied in 50% dioxane and in water. The requirement for acid catalysis in these Michael additions was defined as a lowering of the free energy of the transition state for the reversal of the initially formed carbanion RC(NO2)2CH2CHCO2CH3. This can be accomplished by a substituent R which is able to delocalize negative charge by a resonance interaction. For borderline cases, the rate of protonation of the carbanion RC(NO2)2CH2CHCO2CH3 may be a deciding factor in effecting a change from an acid catalyzed to an uncatalyzed reaction. A comparison of the specific rate and activation parameters for fluorodinitromethide ion with alkyl, chloro and hydrogen dinitromethide ions shows that the 2000-fold increase in rate for R = F is due to a 5 kcal./mo1 decrease in Delta H*. This enhanced nucleophilicity is attributed to a destabilization of an sp2-hybridized carbon by an alpha-fluorine substituent. (Author)

Descriptors :   (*ALKENES, *ADDITION REACTIONS), ESTERS, ORGANIC NITROGEN COMPOUNDS, REACTION KINETICS, MOLECULAR STRUCTURE

Subject Categories : Organic Chemistry

Distribution Statement : APPROVED FOR PUBLIC RELEASE