539-89-9Relevant articles and documents
Chemical Ionization Mass Spectra of Urethanes
Wright, Andrew D.,Bowen, Richard D.,Jennings, Keith R.
, p. 1521 - 1528 (2007/10/02)
Chemical ionization mass spectra using methane as the reagent gas are reported for 33 urethanes of general structure RNHCO2C2H5 nH2n+1 (n=1-8), CH2CH=CH2, cyclo-C6H11, Ph, PhCH2, PhCH2CH2, and Ph(CH3)CH> and R2NCO2C2H5 nH2n+1 (n=1-4)>.Abundant MH+ ions are present in all the spectra, accompanied by satellite peaks corresponding to + and +.Four classes of fragment ions are of general importance in the spectra.Two of these, + and +, are associated with the CO2C2H5 group.The other two, corresponding to alkane and alkene elimination from MH+, arise from the RNH or R2N function.The mechanisms whereby these fragment ions are formed are discussed and their analytical utility is illustrated by reference to the spectra of the four isomeric C4H9NHCO2C2H5 and the eight isomeric C5H11NHCO2C2H5 compounds.The results of 2H-labelling studies are presented and a comparison is made between the methane and ammonia chemical ionisation spectra of selected urethanes.
Low-energy, Low-temperature Mass Spectra. 10-Urethanes
Bowen, Richard D.,Maccoll, Allan
, p. 113 - 122 (2007/10/02)
The 12.1 eV, 75 deg C electron impact mass spectra of 24 urethanes, RNHCO2C2H5 nH2n+1 (n = 1-8), CH2=CHCH2, Ph, PhCH2 and PhCH2CH2>, and seven symmetrically disubstituted urethanes R2NCO2C2H5 (R = CnH2n+1 (n = 1-4) are reported and discussed.All 31 spectra show appreciable molecular ion peaks.For n-CnH2n+1NHCO2C2H5, M+. usually is the most abundant ion in the spectrum.A peak at m/z 102 of comparable intensity also is present; this corresponds to formal cleavage of the bond connecting the α- and β-carbon atoms in the N-alkyl group, though it is unlikely that the daughter ion has the structure (1+).In the RNHCO2C2H5 series, branching at the α-carbon atom enhances the relative abundance of the ion arising by notional α-cleavage at the expense of that of M+..Formal cleavage of the bond between β- and γ-carbon atoms occurs to some extent for +. ions; this reaction provides information on the degree of branching at the β-carbon, especially if metastable molecular ions are considered.The higher n-CnH2n+1NHCO2C2H5 (n = 5-8) urethanes exhibit two other significant ions in their mass spectra.First, there is a peak at (1+).Secondly, a peak is present at m/z 90; the most plausible structure for this ion is (1+), arising by double hydrogen transfer from the alkyl group and expulsion of a nH2n-1>. radical.Ions originating from secondary decomposition of the primary ionic species are generally of only very low abundance in these spectra.
Ion-Dipole Complexes in the Unimolecular Reactions of Isolated Organic Ions. Effect of N-Methylation on Olefin and Amine Loss from Protonated Aliphatic Amines
Bowen, Richard D.,Harrison, Alex G.,Reiner, Eric J.
, p. 1009 - 1014 (2007/10/02)
The slow unimolecular fragmentation reactions os 18 gaseous protonated aliphatic amines of general formula R1NH(1+)R2R3 (R1=Prn, Pri, Bun, Bui, Bus, or But; R2,R3=H,CH3) are reported and discussed.Two decomposition routes are observed for a metastable ions R1NH(1+)R2R3.The first involves elimination of a neutral amine, R2R3NH, and formation of a carbocation, R1(1+), via a mechanism involving an incipient cation bound to the developing amine by an ion-dipole attraction.Rearrangement of the cation, to give thermodynamically more stable isomers, is feasible in these ion-dipole complexes.Further reorganization of the complexes leads to a species in which an incipient olefin 1-H> and an amine 2R3NH> are co-ordinated to a common proton.Dissociation of these proton-bound complexes, with retention of the proton by the developing amine, results in olefin loss, which is the secondreaction undergone by metastable ions R1NH(1+)R2R3.The relative abundance of amine expulsion is greater for protonated amines containing a primary alkyl group, R1, than is the case for isomeric ions containing secondary or tertiary alkyl groups.Progressive methylation of the nitrogen atom decreases the relative abundance of amine loss from R1NH(1+)R2R3, regardless of the nature of the principal alkyl group.These two trends are explained in terms of the energetics of the intermediates and products involved in the decomposition of the protonated amines.
