Steric factors in the kinetically controlled direction of elimination of secondary and tertiary esters in the gas phase. The pyrolysis of 4,4-dimethylpent-2-yl acetate

1981 ◽  
Vol 13 (6) ◽  
pp. 577-589 ◽  
Author(s):  
Gabriel Chuchani ◽  
Rosa Maria Dominguez
Keyword(s):  
Gas Phase ◽  
Kinetically Controlled ◽  
Steric Factors

Multi-color perovskite nanowire lasers through kinetically controlled solution growth followed by gas-phase halide exchange

2017 ◽  
Vol 5 (48) ◽  
pp. 12707-12713 ◽  
Author(s):  
Xianxiong He ◽  
Peng Liu ◽  
Suning Wu ◽  
Qing Liao ◽  
Jiannian Yao ◽  
...  
Keyword(s):  
Gas Phase ◽  
Solution Growth ◽  
Controlled Growth ◽  
Kinetically Controlled ◽  
Halide Exchange ◽  
Nanowire Lasers

We report multi-color perovskite nanowire lasers on arbitrary substrates through kinetically controlled growth followed by gas-phase halide exchange.

The photolysis of tetrahydrofuran and of some of its methyl derivatives at 185 nm

1980 ◽  
Vol 58 (24) ◽  
pp. 2819-2826 ◽  
Author(s):  
Nuray Klzilkilic ◽  
Heinz-Peter Schuchmann ◽  
Clemens von Sonntag
Keyword(s):  
Liquid Phase ◽  
Quantum Yield ◽  
Gas Phase ◽  
Carbonyl Compounds ◽  
Quantum Yields ◽  
Product Analysis ◽  
A Value ◽  
Steric Factors ◽  
Methyl Derivatives ◽  
Group 1

The uv photolysis of tetrahydrofuran, 1, 2-methyltetrahydrofuran, 2, cis-2,5-dimethyltetrahydrofuran, 3, trans-2,5-dimethyltetrahydrofuran, 4, and 2,2,5,5-tetramethyltetrahydrofuran, 5, has been investigated by product analysis in the liquid phase, and quantum yields have been determined. The photolysis of tetrahydrofuran itself was also studied in the gas phase at pressures ranging from 1 to 120 atm (pressurizing gas N2); and very little difference was found between the photolytic behaviour of the vapour at 120 atm and that of the liquid. The major products are in ail cases the cyclopropanes and the corresponding carbonyl compounds, as well as the olefinic alcohols and the carbonyl compounds that are isomeric with the starting material. These products are considered to be formed by the two major primary processes [i] and [ii].[Formula: see text]The cyclopropanes formed in reaction [i] retain some excess energy (apparently more than is needed to realize the trimethylene form), and in the photolysis of tetrahydrofuran vapour the hot cyclopropane rearranges to a considerable extent into propene. The propene to cyclopropane yield ratio falls strongly with increasing pressure, to a value of 0.065 at 120 atm. A similar value is observed in the liquid phase photolysis.The five-membered oxyl alkyl diradical from reaction [ii] is the likely intermediate in the cis-trans photoisomerization that is observable with the 2,5-dimethyltetrahydrofurans [Formula: see text]. The photolysis of these compounds also demonstrates that steric factors have a strong bearing on the course of the reaction, e.g. the quantum yield of methylcyclopropane from the cis compound is 0.22, vs. 0.08 from the trans compound.Molecular hydrogen is produced if the tetrahydrofurans carry hydrogen in α-position. Its production is enhanced if the α-position is shared with a methyl group (1 gives a hydrogen quantum yield of 0.07, 2 of 0.17, 3 of 0.27, 4 of 0.29, and 5 of zero).

A comparative study of gas phase aromatic desilylation and detertbutylation by charged electrophiles

1988 ◽  
Vol 66 (12) ◽  
pp. 3099-3107 ◽  
Author(s):  
Fulvio Cacace ◽  
M. Elisa Crestoni ◽  
Giulia De Petris ◽  
Simonetta Fornarini ◽  
Felice Grandinetti
Keyword(s):  
Comparative Study ◽  
Ab Initio Calculations ◽  
Ab Initio ◽  
Gas Phase ◽  
Mass Spectrometric ◽  
Para Position ◽  
Ring Carbon ◽  
Steric Factors ◽  
Comparable Effect ◽  
The Stability

Aromatic desilylation and detertbutylation by CH5+, C2H5+, i-C3H7+, and t-C4H9+ ions have been studied in the gas phase by mass spectrometric and radiolytic techniques. The higher rate of desilylation than of dealkylation is traced to the step involving the formation of ipso arenium ions, protonated at the ring carbon bearing the SiMe3 or the CMe3 substituent. The latter has been shown by ab initio calculations at the SCF STO-3G level to selectively depress the basicity of the ipso position, hence the stability of the corresponding arenium ion relative to its protomers, e.g. the basicity of the ipso position of PhCMe3 is lower by ca. 11 kcal mol−1 than of the para position. The SiMe3 group has no comparable effect, very close basicities being computed for the para and the ipso position of PhSiMe3. The different effects of the CMe3 and SiMe3 groups are traced to electronic and steric factors.

Steric factors in the gas phase elimination kinetics of ethylN-benzyl-N-cyclopropylcarbamate and ethyl diphenylcarbamate

2001 ◽  
Vol 34 (1) ◽  
pp. 67-71 ◽  
Author(s):  
Marniev Luiggi ◽  
Rosa M. Dominguez ◽  
Alexandra Rotinov ◽  
Armando Herize ◽  
Mary Cordova ◽  
...  
Keyword(s):  
Gas Phase ◽  
Elimination Kinetics ◽  
Steric Factors ◽  
Kinetics Of ◽  
Phase Elimination

UV-Absorptionsspektren methylsubstituierter Phenylcyclopropane / UV absorption Spectra of Me thy I substituted Phenylcyclopropanes

1980 ◽  
Vol 35 (1) ◽  
pp. 137-143
Author(s):  
Nuhudh D. Bhaya ◽  
Muthana Shanshal
Keyword(s):  
Excited State ◽  
Excitation Energy ◽  
Gas Phase ◽  
Absorption Spectra ◽  
Electronic Excitation ◽  
Uv Absorption ◽  
Uv Absorption Spectra ◽  
Steric Factors ◽  
Excitation Processes

Abstract The UV absorption spectra of phenyl-cyclopropane(l), 267 nm, 1-methyl-1-phenyl-cyclopro-pane(2), 259 nm, o-tolyl-cyclopropane(3), 264 nm, m-tolyl-cyclopropane (4), 270 nm, and p-tolyl-cyclopropane(5), 280 nm are recorded in the gas phase, in methanol and in n-hexane. The hypsochromic shifts in the spectra of both 2 and 3 are explained in terms of a twisting of the phenylring out of the bisected conformation which causes an increase in the excitation energy. The spectra of 4 and 5, in which no steric factors are expected to twist the phenylring, show typical inductively caused bathochromic shifts. The vibronic structuring of all the absorption spectra are analyzed and found to include the frequencies 984, 964 and 1100 cm-1 that are attributed to the and the νas vibrations of the ν̃s cyclopropyl ring in the excited state. The results of the analysis confirm a recent assumption of a strong participation of the ⊿as Walsh MO of these Molecules in their electronic excitation processes.

Residual Gas Reactions in the Electron Microscope: I. Qualitative Observations on the Water Gas Reaction

1968 ◽  
Vol 26 ◽  
pp. 292-293
Author(s):  
Richard E. Hartman ◽  
Roberta S. Hartman ◽  
Peter L. Ramos
Keyword(s):  
Electron Beam ◽  
Electron Microscope ◽  
Gas Phase ◽  
Absolute Temperature ◽  
Residual Gas ◽  
Gas Reactions ◽  
Image Position ◽  
The Right ◽  
Water Gas ◽  
Thinning Rate

The action of water and the electron beam on organic specimens in the electron microscope results in the removal of oxidizable material (primarily hydrogen and carbon) by reactions similar to the water gas reaction .which has the form:The energy required to force the reaction to the right is supplied by the interaction of the electron beam with the specimen.The mass of water striking the specimen is given by:where u = gH2O/cm2 sec, PH2O = partial pressure of water in Torr, & T = absolute temperature of the gas phase. If it is assumed that mass is removed from the specimen by a reaction approximated by (1) and that the specimen is uniformly thinned by the reaction, then the thinning rate in A/ min iswhere x = thickness of the specimen in A, t = time in minutes, & E = efficiency (the fraction of the water striking the specimen which reacts with it).

Integration of Core-Edge Spectroscopy Methods for the Study of Polymers

1996 ◽  
Vol 54 ◽  
pp. 154-155
Author(s):  
E. G. Rightor
Keyword(s):  
Excited State ◽  
Polymer Blends ◽  
Gas Phase ◽  
Spatial Resolution ◽  
High Spatial Resolution ◽  
Electronic States ◽  
Core Electron ◽  
Bulk Solids ◽  
Development Application

Core edge spectroscopy methods are versatile tools for investigating a wide variety of materials. They can be used to probe the electronic states of materials in bulk solids, on surfaces, or in the gas phase. This family of methods involves promoting an inner shell (core) electron to an excited state and recording either the primary excitation or secondary decay of the excited state. The techniques are complimentary and have different strengths and limitations for studying challenging aspects of materials. The need to identify components in polymers or polymer blends at high spatial resolution has driven development, application, and integration of results from several of these methods.

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