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The differential mass spectrometry (Dif MS) and the computational chemistry. II. Dif MS and MO semiempirical analyses of exo-and endo-5,10-methylene-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-11-ols

Domenii publicaţii > Chimie + Tipuri publicaţii > Articol în revistã ştiinţificã

Autori: N.Dinca, M.D.Stanescu, E.Sisu, M.Mracec

Editorial: Rev.Chim., 55(5), p.346-350, 2004.

Rezumat:

Comparative analysis of the electronic imapct mass spectra (EI-MS)of the exo-and endo-5,10-methylene-10,11-dihydro-5H-dibenzo[a,d,]cyclohepten-11-ols revealed a similar fragmentation of these compounds. The paper presents a method for the correlation of the experimentally obtained differential mass spectrum Pms with the heats of formation calculated by the semiempirical methods AM1, PM3,MINDO3 and MNDO for the ions resulted in the mass spectrometer. This methodology allows an attribution of the pozition exo- and endo-for the hydroxyl group in these structures without the help of standards or spectra libraries, but only based on spectra of the two diastereoisomers. The methodology for the calculation of the differential mass spectra Pms, the correlation matrix and the drawing of the fragmentation diagram are represented. One may conclude that the AM1 and PM3 semiempirical methods are the best for the heats of formation estimate of this compounds and DifMS are efficient for the energetic profile description of the mass spectrometry ionization.

Cuvinte cheie: DifMS,computational chemistry,quantum chemical semiempirical MO methods,AM1,PM3,MINDO3,MNDO