On the rearrangement and scrambling of hydrogen in the benzophenone oxime molecular ion

The losses of CO, hydrogen and CO, OH and HNOH radicals from the benzophenone oxime molecular ion have been studied by means of deuterium labelled compounds. Hydrogen scrambling and/or exchange and rearrangement reactions of interest, taking place prior to fragmentation, were observed.     

Ring cleavage and ring expansion of indoles by superoxide ion

The reaction of indoles ($\text{1}$) with superoxide ion resulted in ring cleavage to give $\text{o}$-formyl and $\text{o}$-acylaminoketones ($\text{6}$) or N-acylanthranilic acid ($\text{8}$) and ring expansion yielding 2-quinolones ($\text{7}$). All reactions are chemiluminescent except that of 2-methylindole ($\text{lh}$), which gave a coupled product ($\text{9}$).     

Moment functions of the hydrogen molecular ion

The moment functions of H⁺₂ are computed for internuclear distances up to 5a₀ from the dipole osciliator strengths.     

The mechanism of hydrogen randomization in the stilbene molecular ion

Hydrogen randomization of the stilbene molecular ion preceding the formation of the [M—methyl]-ion is discussed.     

Electron-impact induced hydrogen scrambling in cyclohexanol and methylcyclohexanols

Exact mass measurements and the mass spectral behavior of O-deuterated cyclohexanols, coupled with a re-evaluation of previously published data^1,2, show that the hydrogen attached to oxygen undergoes partial scrambling with the 2, 3, 5 and 6 position ring hydrogens prior to or during the formation of the major primary fragment ions.     

Ring H/hydroxyl H scrambling before loss of water from salicylic acid molecular ions

Scrambling before formation of the [M — 18] ion from salicylic acid is considerably reduced in comparison with scrambling before formation of the [M — 17] ion from benzoic acid.     

Bethe logarithm and Lamb shift for the hydrogen molecular ion

A variational method is used to evaluate Bethe logarithm for the ground electronic state of the hydrogen molecular ion. The trial function employed in the calculations analytically represents the singular behavior of the exact solution of the variational problem for high virtual photon energies. This ensures that the accuracy of six significant figures can be obtained with basis sets not exceeding 70 functions. For the equilibrium internuclear separation of 2.0 bohr, the calculated value of the Bethe logarithm, equal to 2.31936, lies outside the bounds 2.35 and 2.56, representing the best previous estimation of this quantity. The accurate values of the Bethe logarithm for internuclear separations ranging from 0.6 to 6.0 bohr are tabulated and used to calculate the radiative corrections to the rovibrational energy levels of H₂⁺, HD⁺, and D₂⁺. The influence of these corrections on the transition and dissociation energies is also examined.     

Deuterium labelling and thermochemical studies of dissociative ionization of methyl substituted monosilacyclobutanes. Ring expansion in the molecular ion of 1,1,3-trimethyl-1-silacyclobutane

Dissociative ionization of 1,1-dimethyl-1-silacyclobutane, 1,1-bis(trideuteromethyl)-1-silacyclobutane, 1,1,3-trimethyl-1-silacyclobutane, 1,1-bis(trideuteromethyl)-3-methyl-1-silacyclobutane and 1,1,2-trimethyl-1-sila-cyclobutane have been studied. Low energy electron impact fragmentation of 1,1-bis(trideuteromethyl)-3-methyl-1-silacyclobutane results mainly in the loss of ethene with the involvement of the C-methyl group from the rearranged molecular ion. No fragment ions indicating rearrangement of the molecular ion have been detected in mass spectra of 1,1-bis(trideuteromethyl)-1-silacyclobutane. The ionization energies for 1,1,3-trimethyl-1-silacyclobutane, 1,1,2-trimethyl-1-silacyclobutane and 1,1-dimethyl-1-silacyclopentane, and also the appearance energies for the [M ? 28]^+˙ and [M ? 42]^+˙ ions, have been measured by photoioniza-tion mass spectrometry. The heats of formation of these ions and of 1,1,3-trimethyl-1-silacyclobutane and 1,1-dimethyl-1-silacyclopentene molecules have been calculated as have the enthalpies of the transformation processes.     

Photodissociative formation of ion pairs from molecular hydrogen and the electron affinity of the hydrogen atom

Photodissociative production of ion pairs from H₂ has been observed in the wavelength range 706–718 A at spectral resolution of 0.4 and 0.22 A. From measured thresholds for production of H^? from H₂ molecules in each of the three lowest rotational states, the lower bound EA(H) ? 0.754 ± 0.002 eV is obtained, in excellent agreement with the theoretical electron affinity of 0.75421 eV. For formation of D^? from D₂, a threshold assigned to molecules in the rotational state J = 2 has been measured, from which the bound EA(D) ? 0.757 ± 0.005 eV is obtained. Negative ion yield curves are presented for hydrogen.     

Ultrafast hydrogen scrambling in methylacetylene and methyl-d3-acetylene ions induced by intense laser fields

Three-body Coulomb explosion processes of triply charged positive ions of methylacetylene (CH(3)-C≡C-H) and its isotopomer, methyl-d(3)-acetylene (CD(3)-C≡C-H), induced by an ultrashort intense laser field (790 nm, ～40 fs, 5.0 × 10(13) W cm(-2)) are investigated by the coincidence momentum imaging method. Two types of three-body decomposition processes accompanying the ejection of a proton are identified for methylacetylene, and six types of three-body decomposition processes accompanying the ejection of a proton or a deuteron are identified for methyl-d(3)-acetylene. From the observed momentum vectors of all the three fragment ions for each decomposition pathway, the proton and deuteron distributions are constructed in the coordinate space, and the hydrogen migration processes are investigated. It was shown that the hydrogen migration proceeds more efficiently from the methyl group than from the methine group. In addition to the decomposition pathways accompanying the migration of one H (or D) atom, the decomposition pathways accompanying the migration of two light atoms (H/D exchange and 2D migration) are identified. Furthermore, the decomposition pathways ascribable to the migration of three light atoms (H/D exchange followed by D migration) are identified, showing the high intramolecular mobilities of H and D atoms within methylacetylene and methyl-d(3)-acetylene in an intense laser field, resulting in the H/D scrambling.     

Ring opening of the molecular ion of 5(4H)-oxazolone

Quantum chemical calculations were carried out at several theoretical levels (semi-empirical, MNDO; ab initio, 3–21G SCF, 6–311G** SCF and DZP CISD) to investigate the ring-opening process of and the loss of CO from the molecular ion of 5(4H)-oxazolone. The ring-opening process is predicted to be slightly endothermic and the loss of CO from the open-ring molecular ion to be slightly exothermic. Detailed population analysis calculations suggest the weakening of the lactonic C? O bond in the closed-ring molecular ion and weak carbon—carbon and nitrogen—(formy)—carbon bonds in the open form. Both the open-ring molecular ion and the [M–CO]^+· ion are suggested to be of distonic type.     

Electropolymerization of 3-methylthiophene at liquid 3-methylthiophene | aqueous solution | graphite three-phase junction

Droplets of 3-methylthiophene are mechanically attached to the surface of paraffin-impregnated graphite electrode (PIGE) and immersed into aqueous solution of LiClO₄. It is demonstrated that the oxidative electropolymerization (observed in non-aqueous solutions) can be accomplished by potential cycling between −0.3 and 1.4 V vs. saturated calomel electrode (SCE). Since the droplets do not contain a dissolved electrolyte, the electrochemical reaction starts at the very edge of the three-phase junction organic droplet | graphite | aqueous electrolyte.     

3-甲基噻吩和3-氯噻吩的电化学共聚

3-甲基噻吩和3-氯噻吩首次三氟化硼乙醚溶液中实现了电化学共聚。共聚物的分子结构通过电化学分析、红外和拉曼光谱得到了证实。实验结果表明：单体投料比对共聚物的结构和电化学性质有很大的影响;共聚物比3-甲基噻吩和3-氯噻吩的均聚物具有更大的充放电电容和更可逆的氧化还原性质。     

Chain ion molecular mechanism of ascorbic acid oxidation with hydrogen peroxide. Cu3+ ion as a chain carrier

The kinetics and mechanism of ascorbic acid (DH₂) oxidation have been studied under anaerobic conditions in the presence of Cu²⁺ ions. At 10^?4 ≤ [Cu²⁺]₀ < 10^?3M, 10^?3 ≤ [DH₂]₀ < 10^?2M, 10^?2 ≤ [H₂O₂] ≤ 0.1M, 3 ≤ pH < 4, the following expression for the initial rate of ascorbic acid oxidation was obtained: where χ₂ (25°C) = (6.5 ± 0.6) × 10^?3 sec^?1. The effective activation energy is E₂ = 25 ± 1 kcal/mol. The chain mechanism of the reaction was established by addition of Cu⁺ acceptors (allyl alcohol and acetonitrile). The rate of the catalytic reaction is related to the rate of Cu⁺ initiation in the Cu²⁺ reaction with ascorbic acid by the expression where C is a function of pH and of H₂O₂ concentration. The rate equation where k₁(25°C) = (5.3 ± 1) × 10³M^?1 sec^?1 is true for the steady-state catalytic reaction. The Cu⁺ ion and a species, which undergoes acid–base and unimolecular conversions at the chain propagation step, are involved in quadratic chain termination. Ethanol and terbutanol do not affect the rate of the chain reaction at concentrations up to ≈0.3M. When the Cu²⁺–DH₂–H₂O₂ system is irradiated with UV light (λ = 313 nm), the rate of ascorbic acid oxidation increases by the value of the rate of the photochemical reaction in the absence of the catalyst. Hydroxyl radicals are not formed during the interaction of Cu⁺ with H₂O₂, and the chain mechanism of catalytic oxidation of ascorbic acid is quantitatively described by the following scheme. Initiation: Propagation: Termination:      

Ring expansion of isopropenyldihydrofuran derivatives

Lactonization of 2‐(hydroxymethyl)‐5‐isopropenyl‐4,5‐dihydrofuran‐3‐carboxylic acids 1a,b,c with dicyclohexylcarbodiimide gave the corresponding furano‐lactones, 5‐isopropenyl‐5,6‐dihydro‐1(3H)‐furo[3,4‐b]furanone 2a,b,c , which were readily converted to the corresponding oxepino‐lactones, 6‐methyl‐5,8‐dihydro‐1(3H)‐furo[3,4‐b]oxepinone 3a,b,c by respective thermal ring expansions.     

Mass spectrometry of aralkyl compounds with a functional group—IX: Hydrogen scrambling in the molecular ion of hydrocinnamaldehyde

The molecular ion of hydrocinnamaldehyde (C₆H₅CH₂CH₂CHO) chiefly loses fragments C₂H₂O and C₃H₄O. Mass spectra of specifically deuterated analogues show that in the loss of C₂H₂O an α-hydrogen atom (with respect to the aldehyde group) is transferred to the aromatic part. A shift of the aldehydic hydrogen to one of the ortho positions of the phenyl ring and loss of C₂H₂O by a McLafferty rearrangement is not observed. In the loss of C₃H₄O also an α-hydrogen atom migrates to the aromatic part. Both reactions appear to occur with an extensive randomization of all hydrogen atoms in the molecular ion.