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Information on possible reaction paths and products has been obtained from semiempirical molecular orbital calculations on the ozonization of C60. Results reveal the rate-determining step and the major product.

The article discusses research methods used to discover repeat substitute patterns of hererofullerene complexes.

The reorganization between the closed and open isomers of C60O and C60S are studied using semiempirical AM1 and MNDO methods. The results indicate that the interchange of the two isomers of C60O follows a two-step route involving an intermediate and two transition phases.

Abstract: In this work, we have put forward the conservation of generalized parity concerning the environment time-space, which involves the main points listed as follows: first, corresponding to the environment space with periodic symmetry the invariant is space-parity. Especially, for periodic translation the corresponding invariant is wave-parity. If the space periodic length approaches zero, the conservation of wave-parity will transform to the conservation of momentum. Second, corresponding to the environment time with periodic length the invariant is frequency-parity. If the time periodic length approaches zero, the conservation of frequency parity will transform to the conservation of energy. Third, for the environment time-space, if the time-space periodic length is very small but not null, we can get the formulae ΔEΔt≥h and ΔPΔx≥h, which are similar to the uncertainty principle. Finally, for an environment time-space with the measurable periodic length, we have analyzed the relative conservation rules. [Copyright &y& Elsevier]

A total of eight possible isomers of C50O, an oxide of fullerene C50 (D5h), have been investigated by B3LYP/3‐21G calculations. The isomer, which has an annulene‐like structure with oxygen bridging across a [5,6] type C—C bond at the site between the pole and the equatorial belt, is found being the ground state of C50O. Four isomers are relatively more stable and the energy differences between them are not large. This result indicates that more than one C50O isomer will coexist once C50O is synthesized. The relative stabilities of the C50O isomers may be determined mainly by the strain release and by the formation of the cyclic phenylene substructure at the equatorial belt of the cage. The calculated nucleus independent chemical shifts (NICS) of the C50O isomers will be useful because from them one can expect outstanding NMR properties that can lead to their identification and characterization. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005 [ABSTRACT FROM AUTHOR]

A systematic investigation on possible structures of heterofullerenes C70– nP n ( n=2–10) has been performed employing semiempirical MNDO and ab initio methods. The stabilities decrease with increasing number of heteroatoms. The structures whose carbon atoms are substituted in the para pattern across the equatorial hexagons correspond to the most stable isomers. The isomeric pattern of P-doped C70 systems follows our previously proposed correlation between the isomerism of the fullerene adducts C60X n/C70X n and those of the heterofullerenes C60– nN n or C60– nB n /C70– nN n or C70– nB n. The aromaticity of the most stable structures of heterofullerenes is studied to investigate the heteroatom doping effect on the electron delocalization of the fullerene cage. [ABSTRACT FROM AUTHOR]

Presents information on the attention received by nonlinear chemical reactions, mechanisms and complex phenomena in unhalogen aqueous reaction systems, while focusing on the interest in nonlinear reactions systems without halogen. Reasons for the design of hydrogen peroxide-thiocyanate-copper sulfate reaction; Reference to experimental results by Epstein and others; Detailed information on the study.

Discusses the use of the molecular mechanics method to estimate the thermochemical data of organic compounds. Reference to S.W Benson's group additivity method; Limitations of Benson's method; Definition of molecular mechanics; Information on the enthalpies of organic compounds.

An ab initio MO method has been used to calculate the potential energy surface for the formation of HF when H reacts with C1F. The various transition states possibly related to forming HF were optimized. An IRC calculation starting from the collinear F-centered transition state was performed and energies of a series of points with bending configurations were also calculated to determine the direct reaction path leading to HF product. Another IRC calculation starting from the H-centered transition state was run to determine the migratory path to forming HF. By doing so, the Polanyi’s assumption that it would involve the direct and a migratory mechanisms for the formation of HF when H reacts with CIF has been verified theoretically. [ABSTRACT FROM AUTHOR]

Kinetics of reaction between Na2S203 and peroxide compound (H202 or Na2S2O3) in a batch reactor and in a continuous stirring tank reactor (CSTR) were studied. Steady oscillations in uncatalyzed reactions in a CSTR were first discovered. In Na2S203-H2O2-H2S04 reaction system, Pt potential and pH of higher and lower flow rates beyond oscillation flow rates were in around the same extreme values. The reaction catalyzed by Cu2+ consists of the catalyzed oscillation process and the uncatalyzed osciliation one. On the basis of experiment, a reaction mechanism consisting of three stages was put forward. The three stages are H+ positive-feedback reactions, proton negative-feedback (uncatalyzed negative-feedback and catalyzed negative-feedback) reactions and transitional reactions. The mechanism is able to explain reasonably the nonlinear chemical phenomena appearing in the thiosulfate oxidation reaction by peroxide compounds. [ABSTRACT FROM AUTHOR]

Systematic studies on eight isomers of C70O were performed by means of INDO methods. It has been indicated that the O atom is mainly added to the C1-C2 or C3-C3 bond and an epoxide feature with Cs symmetry is formed. Based on the optimized geometries, the UV-Vis spectra were calculated. It has been found that the main peaks of C70O resemble those of C70 and the characteristic absorptions beyond 460 nm are produced, which is in agreement with the experimental results. Theoretical assignments about the absorptions were canied out and the reason for the red-shift of the absorptions was discussed. C70O is probably composed of four isomers according to the calculated results. [ABSTRACT FROM AUTHOR]

Presents information on column chromatography which is the chief method for separation and purification of C60/C70, while highlighting a method developed by Scrivens. Information on the stationary phases used in the method; Advantages and disadvantages of the method developed by Scrivens; Examination of a depressurizing column chromatography method; Detailed information on the experiment; Results and discussion.

Abstract: The 1,3-dipolar cycloaddition of methyl azide to C50 and the subsequent nitrogen elimination from the formed triazoline intermediate to yield the aziridine adduct have been studied using semiempirical AM1 methods. The results show that the cycloaddition of methyl azide to a [5,5] bond of C50 leading to a closed [5,5]-triazoline intermediate takes place through two stepwise pathways a and b: both of them starting from the formation of one C–N bond followed by the formation of the other C–N bond. The two pathways are competitive and the activation energy of each path is about 22kcalmol−1. The subsequent thermal loss of N2 from the closed [5,5]-triazoline takes place through two paths, I and II: path I includes three steps while path II includes two steps. And path I is the preferred one with a total activation energy of approximately 41kcalmol−1. There is also a pathway without the formation of triazoline, in which the formation of C–N bond between N3CH3 and C50 to give an intermediate is followed by the elimination of N2 together with the formation of the other C–N bond to form the closed [5,6]-C50NCH3, which is the preferred pathway among all the pathways with a total activation energy of about 14.5kcalmol−1. It is expected that the closed [5,6]-C50NCH3 is the main product from addition of N3CH3 to C50. The closed [5,6]-C50NCH3 isomer is more stable than its closed [5,5] isomer. The isomerization activation energy from the closed [5,6] isomer to the [5,5] isomer is 53.6kcalmol−1, and that for the reverse isomerization is 35.7kcalmol−1. This result indicates that the conversion of the two isomers can hardly take place at room temperature and some day both of them can have the chance to be actually isolated experimentally. [Copyright &y& Elsevier]

Abstract: The geometries and stabilities of mono-BN doped (5,5) armchair single-walled carbon nanotube (ASWCNT) isomers for a smaller C50H20 model are first investigated by both AM1 and HF/4-31G methods. The calculations suggest that both the two methods obtain similar results, demonstrating that the AM1 method is reliable in calculating the properties of BN-doped ASWCNT isomers. Then, the equilibrium structures and relative stabilities of the mono-, di-, and tri-BN doped isomers for a larger (5,5) ASWCNT model (C110H20) are further studied based on AM1 level. For mono-BN doped ASWCNT, the thermodynamic stabilities of its isomers in general decrease with the separation between two heteroatoms, and the isomer with two neighbored B and N atoms is the most stable one. For di- or tri-BN doped ASWCNT isomers, the N–N and B–B bonds should be avoided and the isomer with a B–N–B–N or B–N–B–N–B–N chain in same hexagon is the most stable one. The BN-doping generally enhances the redox and electron excitation properties of BN-doped ASWCNT isomers compared with their host tube, and their stabilities increase with their diameter enlargement on the whole. [Copyright &y& Elsevier]

Abstract: The calculations based on AM1 and PM3 methods suggest that the cycloaddition between the nitrene (HN:) group and (5,5) armchair single-walled carbon nanotube (ASWCNT) produces four isomers, and their thermodynamic stability can be described as follows, V-open >V-closed >S-open >S-closed. The kinetic analysis, however, suggests that the predominant forms are S-open and V-open in the mixture of HN

Abstract: Total of seven possible isomers for both methano- and imino-[50]fullerenes have been investigated by ab initio calculations. An insight into the relationship between structures and stabilities of these isomers is presented. The results show that the [5,6]-closed structure with CH2 group bridging across a [5,6] type of C–C bond near the equatorial belt is the ground state of C50CH2 while that of the C50NH is [5,6]-open fashioned with NH group bridging across a [5,6] type of C–C bond at the site between the pole and the equatorial belt. The underlying reason of this structural difference may be the larger atomic size and the greater Pauli repulsion of carbon atom compared with those of nitrogen atom. The relative stabilities of the isomers are determined by the strain of the cage, especially the strain at the equator. And although the contribution of the cyclic phenylene substructure at the equatorial belt to the stabilization of the favored isomers probably can not be ignored, the contribution of the conjugation effect to the stabilization is not competitive. Energy difference among three favored isomers is not very large, hence it can be expected that some isomers will co-exist in a mixture once methano- and imino-[50]fullerenes are synthesized. The calculated NICSs for the isomers of C50CH2 and C50NH will be useful for their identification and characterization. [Copyright &y& Elsevier]