Methylene. IV. Gas phase reactions with 2-chloropropane

1969 ◽  
Vol 312 (1509) ◽  
pp. 163-179 ◽  
Keyword(s):  
Carbon Monoxide ◽  
Reaction Mechanism ◽  
Hydrogen Atom ◽  
Transition State ◽  
Gas Phase ◽  
Chlorine Atom ◽  
Halogen Atom ◽  
Gas Phase Reactions ◽  
Alkyl Radicals ◽  
Singlet Methylene

As in earlier studies in this series, the reaction mechanism has been investigated by identi­fication and estimation of the products formed by the interaction of methylene, prepared by the photolysis of ketene, and the chloroalkane. The reaction was examined over a range of initial pressures, with different wavelengths of photolysing light, and in the presence of oxygen and carbon monoxide. Both insertion and abstraction processes are important, but insertion into C—Cl bonds is negligible under our conditions. Singlet methylene, which is responsible for insertion, is again found to be highly selective in its abstraction reactions, the ratio of the relative rates of abstraction of chlorine and hydrogen exceeding 12. The results are consistent with the mechanism suggested earlier (part II), according to which singlet methylene behaves as an electrophilic reagent, and forms a bond with a chlorine atom involving the vacant p-orbital of CH 2 and a filled p-orbital of Cl. Stereo­chemical considerations suggest that the transition state of this reaction is such that no bond­ing between the C atom of CH 2 and that of C—Cl, and hence no insertion into C—Cl, can occur. We believe that insertion into a C—H bond involves interaction of singlet CH 2 with the electrons of the bond, with a triangular transition state. The effect of a chlorine atom in generally reducing the probability of insertion into neighbouring C—H bonds is thought to be the result of the rapid competing reaction between singlet methylene and the halogen atom. A five-centre transition state in which singlet CH 2 is bonded to Cl through its vacant p-orbital and to a hydrogen atom on C 2 through its filled sp 2 -orbital may be partly respon­sible for chloromethane formation. Triplet methylene has been shown to resemble alkyl radicals in its abstraction reactions.

Methylene II. Gas phase reactions with ethyl chloride

1968 ◽  
Vol 306 (1485) ◽  
pp. 135-158 ◽  
Keyword(s):  
Carbon Monoxide ◽  
Gas Phase ◽  
Energy Content ◽  
Incident Light ◽  
Hydrogen Abstraction ◽  
Relative Concentration ◽  
Radical Mechanism ◽  
Gas Phase Reactions ◽  
Free Radical Mechanism ◽  
Singlet Methylene

In this work methylene was prepared by the photolysis of ketene, and the experiments include observations of the effects of changing the wavelength of the photolysing light and of introducing foreign gases. Results are consistent with a free-radical mechanism in which CH 2 abstracts a chlorine or a hydrogen atom from C 2 H 5 Cl: CH 2 +CH 3 CH 2 Cl→ k cl ĊH 2 Cl+CH 3 ĊH 2 , CH 2 +CH 3 CH 2 Cl→ k h1 ĊH 3 +ĊH 3 CH 3 Cl, } CH 2 +CH 3 CH 2 Cl→ k H2 ĊH 3 +CH 3 ċHCl. } ( k H ) All the fourteen products of the radical recombinations have been identified. Disproportionation of radicals and decomposition of excited molecules formed by recombinations yield additional products. Methylene insertion does not appear to play a significant role. When the incident light contains wavelengths in the region 2450 to 4000Å we find that k Cl / k H =1·62, k H1 / k H2 =0·098. If shorter wavelengths are excluded, or if nitrogen is added, lower values of k Cl / k H are obtained. On the other hand, in the presence of carbon monoxide the value of k Cl / k H may be greatly increased. It is suggested that these findings are attributable to differences in reactivity between singlet and triplet methylene. At longer wavelengths, or when nitrogen is present, the relative concentration of the singlet is reduced, but in the presence of carbon monoxide the triplet is removed preferentially (De Graff & Kistiakowsky 1967). Singlet methylene appears to be highly discriminating in its reactions, abstracting chlorine preferentially, while the triplet discriminates in favour of hydrogen abstraction. A kinetic analysis based on these ideas and consistent with the experimental observations shows that k S Cl / k S H >16·3, k T Cl / k T H <0·14. The selectivities shown by the two species of methylene are thought to be a result of differences in electronic structure rather than energy content.

Methylene. III. Gas phase reactions with 1-chloropropane

1969 ◽  
Vol 312 (1509) ◽  
pp. 141-161 ◽  
Keyword(s):  
Gas Phase ◽  
Rate Constants ◽  
Hydrogen Abstraction ◽  
The Other ◽  
Gas Phase Reactions ◽  
Other Hand ◽  
Chlorine Substituent ◽  
High Degree ◽  
Singlet Methylene

The work described in this and the following paper is a continuation of that in parts I and II, devoted to elucidation of the mechanism of the reactions of methylene with chloroalkanes, with particular reference to the reactivities of singlet and triplet methylene in abstraction and insertion processes. The products of the reaction between methylene, prepared by the photolysis of ketene, and 1-chloropropane have been identified and estimated and their dependence on reactant pressures, photolysing wavelength and presence of foreign gases (oxygen and carbon mon­oxide) has been investigated. Both insertion and abstraction mechanisms contribute significantly to the over-all reaction, insertion being relatively much more important than with chloroethane. This type of process appears to be confined to singlet methylene. If, as seems likely, there is no insertion into C—Cl bonds under our conditions (see part IV), insertion into C2—H and C3—H bonds occurs in statistical ratio, approximately. On the other hand, the chlorine substituent reduces the probability of insertion into C—H bonds in its vicinity. As in the chloroethane system, both species of methylene show a high degree of selectivity in their abstraction reactions. We find that k S Cl / k S H >7.7, k T Cl / k T H < 0.14, where the k ’s are rate constants for abstraction, and the super- and subscripts indicate the species of methylene and the type of atom abstracted, respectively. Triplet methylene is discriminating in hydrogen abstraction from 1-C 3 H 7 Cl, the overall rates for atoms attached to C1, C2, C3 being in the ratios 2.63:1:0.

The Gas Phase Reactions of Recoil Sulfur Atoms with Carbon Monoxide and Carbon Dioxide1

1964 ◽  
Vol 68 (2) ◽  
pp. 318-322 ◽  
Author(s):  
Edward K. C. Lee ◽  
Y. N. Tang ◽  
F. S. Rowland
Keyword(s):  
Carbon Monoxide ◽  
Gas Phase ◽  
Gas Phase Reactions

Laboratory measurements of gas‐phase reactions of polyatomic carbon ions C+n(n=1–6) and CnH+(n=2–5) with carbon monoxide

1987 ◽  
Vol 87 (12) ◽  
pp. 6934-6938 ◽  
Author(s):  
Diethard K. Bohme ◽  
Stanisl/aw Wl/odek ◽  
Leslie Williams ◽  
Leonard Forte ◽  
Arnold Fox
Keyword(s):  
Carbon Monoxide ◽  
Gas Phase ◽  
Carbon Ions ◽  
Laboratory Measurements ◽  
Gas Phase Reactions

scholarly journals The HNO− radical anion: A proposed intermediate in diazeniumdiolate synthesis using nitric oxide and alkoxides

2018 ◽  
Vol 25 (1) ◽  
pp. 82-85 ◽  
Author(s):  
Zhe-Chen Wang ◽  
Ya-Ke Li ◽  
Sheng-Gui He ◽  
Veronica M Bierbaum
Keyword(s):  
Nitric Oxide ◽  
Reaction Mechanism ◽  
Gas Phase ◽  
Radical Anion ◽  
Room Temperature ◽  
Hydrogen Transfer ◽  
Gas Phase Reactions ◽  
Ionic Product

The strategy of synthesizing diazeniumdiolates (X–N(O)=NO−) through the coexistence of nitric oxide and alkoxides (RO−) was introduced by Wilhelm Traube 120 years ago. Today, despite the wide use of diazeniumdiolate derivatives to release nitric oxide in the treatment of cancer, the first step of the reaction mechanism for diazeniumdiolate synthesis remains a mystery and is thought to be complex. We have studied the gas-phase reactions of nitric oxide with alkoxides at room temperature. An electron-coupled hydrogen transfer is observed, and the radical anion HNO− is the only ionic product in these reactions. HNO− can further react with nitric oxide to form N2O and HO−.

Gas-Phase Reactions between Diborane and Carbon Monoxide:  A Theoretical Study

2003 ◽  
Vol 107 (46) ◽  
pp. 9974-9983 ◽  
Author(s):  
Shao-Wen Hu ◽  
Yi Wang ◽  
Xiang-Yun Wang ◽  
Ti-Wei Chu ◽  
Xin-Qi Liu
Keyword(s):  
Carbon Monoxide ◽  
Gas Phase ◽  
Theoretical Study ◽  
Gas Phase Reactions

Bimolecular Homolytic Substitutions at Nitrogen: An Experimental and Theoretical Study on the Gas-Phase Reactions of Alkyl Radicals with NF3

2015 ◽  
Vol 21 (44) ◽  
pp. 15826-15834 ◽  
Author(s):  
Paola Antoniotti ◽  
Paola Benzi ◽  
Stefano Borocci ◽  
Chiara Demaria ◽  
Maria Giordani ◽  
...  
Keyword(s):  
Gas Phase ◽  
Theoretical Study ◽  
Gas Phase Reactions ◽  
Alkyl Radicals
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