Jan A. Herman

Radiolysis of Ethane + Sulfur Hexafluoride and Ethylene + Sulfur Hexafluoride Gaseous Systems. Formation of SF5• Radical and its Reactivity

Neutralization processes of ions in radiolysis of ethane or ethylene + sulfur hexafluoride systems lead to the formation of the SF5• radical. Compounds of the general formula RSF5 are formed as a result of recombination reactions with hydrocarbon radicals. In the mixture ethane +0.3% sulphur hexafluoride the radiochemical yield of SF5• is The presence of ammonia decreases to ca. 0.2, suggesting that the neutralization process of NH4+(NH3)n with SF6− ions follows some unknown path. In the present work some reactions of the SF5• radical are studied. Preliminary results indicate that the presence of SF6 influences very little, if at all, the yield of atomic hydrogen.

Photoionization study of ion-molecule reactions in isobutylene

Abstract Ion—molecule reactions of gaseous isobutylene were investigated in a high-pressure photoionization mass spectrometer up to a pressure of 3 torr. With increasing pressure the reaction sequence is complicated by the occurrence of many condensed ionic species, which can be grouped into four families: [C 4 H 9 (C 4 H 8 ) n ] + , [C 9 H 15 (C 4 H 8 ) m ] + , [C 7 H 15 (C 4 H 8 ) p ] + and [C 10 H 21 (C 4 H 8 ) q ] + . The last two families of ionic species seem to originate from the [C 4 H 9 (C 4 H 8 ) n ] + ions by elimination of neutral ethylene or isomeric pentene fragments during condensation steps. On the other hand, the C 9 H 15 + ion, which starts the [C 9 H 15 (C 4 H 8 ) m ] + polymerization sequence, seems to result from the interaction of the C 8 H 14 + with neutral isobutylene molecules.

Photoionization study of clustering reactions in diamines: ethane-1,2-diamine, propane-1,2-diamine and propane-1,3-diamine

Solvation of the protonated diamines species, [R(NH2)2]H+, has been studied in the systems C2H4-(NH2)2, 1,2-(NH2)2C3H6 and 1,3-(NH2)2C3H6 by high-pressure photoionization spectrometry. Clusters [R(NH2)2]nH+ up to n= 4 have been observed and the 2,3 and 3,4 equilibria of the reversible reaction [R(NH2)2]n–1H++ R(NH2)2⇌[R(NH2)2]nH+ have been examined. Thermodynamic quantities for the 2,3 and 3,4 equilibria have been determined.

Photoinisation study of the ion/molecule reactions of pent-1-ene and pent-2-ene

Abstract The ion/molecule reactions of gaseous pent-1-ene and pent-2-ene up to a pressure of 3 torr have been investigated in a high-pressure photoionisation mass spectrometer. With increasing pressure the reaction sequence is complicated by the presence of many condensed ionic species, which can be grouped into several families for each normal pantene isomer studied. For both normal pantene isomers the condensation of neutral molecules on the parent ion (C5H10)n+ is a major reaction path at low pressures. Besides this family of ions all other ion families seen to originate from secondary ion species formed either in proton- or hydrogen-transfer processes [(M−2)+), (M−1)+) and (M+1)+], or in fragmentation of the adducts proceeding via rupture of the weakest CC bond. At high pressure (0.5 torr), reactive collisions between the association dimer ion C10H20+ and neutral pantene lead to the formation of C8H14+ and C8H15+ (and in smalleramounts. C8H 16−) ionic species which are unreactive toward the neutral molecules and in accumulate in the system. Some mechanisms for the formation of the condensed species are proposed.

Ion—molecule reactions in gaseous allylamine

Abstract Ion—molecule reactions of gaseous allylamine were studied as a function of pressure in the range from 0.1 to 4 Torr. The parent ions were produced by photoionization at 10.03 and 10.64 eV. The stepwise solvation of the protonated allylamine ion, C3H5NH+3, into C3H5NH+3(C3H5NH2)2 and C3H5NH+3(C3H5NH2)3 ions has been observed. These ions undergo a further decomposition into C9H21N+2 and (C3H5)2NH2+·C3H5NH2 ions respectively, and from each of the latter ions a reaction sequence begins. The effects of temperature and electric field strength on ionic processes have been studied. Enthalpy changes for a number of ionic reactions occurring in the system were estimated.

Fourier transform ion cyclotron resonance mass spectrometry measurements of rate constants of ion/molecule reactions with continuous ejection of product ions. Reactions of CH3ClH+ with methyl chloride

Abstract The measurement of rate constants for ion/molecule reactions in systems where a continuous ejection of secondary ions interfering in reverse processes is performed requires the use of absolute intensities of primary and secondary ions in the kinetics determination. A general kinetic formalism allows the calculation of the rate constants in the presence of unknown concentrations of impurities, provided that their ion products formed in reaction with the primary ion are well established. The use of this kinetic formalism to study ion/molecule reactions of protonated methyl chloride, CH 4 Cl + , with neutral methyl chloride gave the following rate constants values:

Photoionization study of ion/molecule reactions in allene

Abstract Ion/molecule reactions of gaseous allene up to 3.5 Torr were investigated in a high-pressure photoionization mass spectrometer. On increasing the pressure, the reaction sequence was complicated by the presence of many condensed ionic species, which could be grouped into several families, but only two were important: C 6 H 7 + (C 3 H 4 ) n and C 7 H 7 + (C 3 H 4 ) m . In the case of C 7 H 7 + and C 10 H 11 + , their behaviour suggests that these ionic species undergo isomerization reactions, most probably through collisionally induced processes.

Photoionization study of ion-molecule reactions of but-1-ene and but-2-ene

Abstract Ion-molecule reactions of gaseous but-1-ene and but-2-ene up to a pressure of 3 torr are investigated in a high-pressure photoionization mass spectrometer. With increasing pressure the reaction sequence is complicated by the presence of many condensed ionic species, which can be grouped into four families for each butene isomer studied. In the case of but-1-ene one can distinguish [C 4 H 9 (C 4 H 8 ) n ] + , [C 6 H 11 (C 4 H 8 ) m ] + , [C 5 H 11 (C 4 H 8 ) p ] + and [C 11 H 23 (C 4 H 8 ) q ] + species besides the C 8 H 15 + ion, which is fairly unreactive towards the neutral parent molecule. In but-2-ene one finds (C 4 H 8 ) r + , [C 6 H 11 (C 4 H 8 ) s ] + , [C 7 H 15 (C 4 H 8 ) t ] + , [C 5 H 11 (C 4 H 8 ) w ] + and two unreactive ions, C 8 H 15 + and C 10 H 21 + . Several mechanisms for the formation of condensed species are proposed.

Radiolysis of vinyl iodide. Part 3.—Formation of polymer in carbon tetrachloride solutions

The polymerization by 60Co gamma-rays of vinyl iodide in carbon tetrachloride solutions was studied. The infra-red spectrum of the polymer shows the existence of a CCl3 group per macromolecule independently of the monomer concentration in solutions from which the polymer is formed. Moreover, the polymerization shows a relatively constant M.W., around 7500, a negative temperature coefficient and an intensity exponent of ∼1.0. It is assumed that initiation of polymerization is due to hot CCl3 radicals or CCl+3 ions, while termination is by deactivating transfer on solvent and on monomer.

Fragmentation and isomerization of [(CH3)2CHCHCH3]+ ions in gas-phase radiolysis

A study has been made of the influence of different additives on the radiolysis of gaseous mixtures of hydrogen, 3-methyl-but-1-ene and oxygen. In these systems the [(CH3)2CHCHCH3]+ ion is formed by proton transfer from the XH+ ion to the olefin. For X = H2 the secondary pentyl ion is formed with sufficient internal energy to decompose, producing mainly ethylene. When X is CO2, CH4, N2O or CO the secondary pentyl ion partially isomerizes into the tertiary pentyl ion. This isomerization has been investigated in the mixture of xenon, methane, 3-methyl-but-1-ene and nitric oxide between –10 and + 110°C. If it is assumed that the rate of isomerization (internal hydride-ion displacement) is a function only of the temperature, the measured activation energy of the process [(CH3)2CHCHCH3]+→[(CH3)2CCH2CH3]+ is Ea= 8.8 ± 0.4 kJ mol–1(2.1 ± 0.1 kcal mol–1 or 0.092 ± 0.005 eV).