Trends in alkyl substituent effects on nucleophilic reactions of carbonyl compounds: Gas phase reactions between ammonia and R1R2COCH3+ oxonium ionsElectronic supplementary information (ESI) available: proton affinities, geometries and energies of optimised structures, structures of the stationary points and a plot of experimental and RRKM ln(kae/ksub) against a-stabilisation constants. See http://www.rsc.org/suppdata/ob/b2/b209955c/
作者:Lihn Bache-Andreassen、Einar Uggerud
DOI:10.1039/b209955c
日期:2003.2.11
The reactivity of carbonyl substituted methyl oxonium ions (R1R2COCH3+) towards ammonia has been investigated using an FT-ICR mass spectrometer and ab initio calculations. The monosubstituted ions (R1 = H; R2 = H, CH3, C2H5 and i-C3H7) show different reaction patterns with variable degree of: (1) nucleophilic substitution, (2) addition-elimination and (3) proton transfer, when reacted with ammonia
Proton affinities and the site of protonation of enamines in the gas phase
作者:Mark R. Ellenberger、David A. Dixon、William E. Farneth
DOI:10.1021/ja00408a017
日期:1981.9
Unimolecular reactions of isolated organic ions. The importance of ion-dipole interactions
作者:Richard D. Bowen、Dudley H. Williams
DOI:10.1021/ja00528a038
日期:1980.4
Unimolecular reactions of the isolated immonium ions CH3CH = NH+C4H9, CH3CH2Ch = NH+C4H9 and (CH3)2C = NH+C4H9
作者:Richard D. Bowen、Alex. W. Colburn、Peter J. Derrick
DOI:10.1002/oms.1210251005
日期:1990.10
AbstractThe reactions of ten metastable immonium ions of general structure R1R2CNH+C4H9 (R1 = H, R2 = CH3, C2H5; R1 = R2 = CH3) are reported and discussed. Elimination of C4H8 is usually the dominant fragmentation pathway. This process gives rise to a Gaussian metastable peak; it is interpreted in terms of a mechanism involving ion‐neutral complexes containing incipient butyl) cations. Metastable immonium ions ontaining an isobutyl group are unique in undergoing a minor amount of imine (R1R2CNH) loss. This decomposition route, which also produces a Gaussian metastable peak, decreases in importance as the basicity of the imine increases. The correlation between imine loss and the presence of an isobutyl group is rationalized by the rearrangement of the appropriate ion‐neutral complexes in which there are isobutyl cations to the isomeric complexes containing the thermodynamically more stable tert‐butyl cations. A sizeable amount of a third reaction, expulsion of C3H6, is observed for metastable n‐C4H9+NHCR1R2 ions; in contrast to C4H8 and R1R2CNH loss, C3H6 elimination occurs with a large kinetic energy release (40–48 kJ mol−1) and is evidenced by a dish‐topped metastable peak. This process is explained using a two‐step mechanism involving a 1,5‐hydride shift, followed by cleavage of the resultant secondary open‐chain cations, CH3CH+ CH2CH2NHCHR1R2.
Site of gas-phase methylation of l-phenyl-2-aminopropane
作者:Herman Zagppey、Roel H. Fokkens、Steen Ingemann、Nico M. M. Nibbering、Helena Florencio
DOI:10.1002/oms.1210260610
日期:1991.6
AbstractThe regioselectivity of methyl cation transfer from (CH3)2F+, (CH3)2Cl+ and (CH3)3O+ to 1‐phenyl‐2‐aminopropane was studied by Fourier transform ion cyclotron resonance in combination with collision‐induced dissociation and neutralization‐reionization mass spectrometry of the stable [M + CH3]+ ions formed in a chemical ionization source. The (CH3)2F+ ion transfers a methyl cation to the NH2 group and the phenyl ring with almost equal probability. Predominant CH3+ transfer to the NH2 group is observed for the (CH3)2Cl+ ion whereas the (CH3)3O+ ion reacts almost exclusively at the amino group. The preference for methylation at NH2 is discussed in terms of a lower methyl cation affinity of the phenyl ring than of the amino group and the existence of an energy barrier for methylation of the phenyl moiety.