HALOGEN MIGRATION AND ELIMINATION IN THE CLAISEN REARRANGEMENT OF ALLYL 2,6-DIHALOPHENYL ETHERS

1963 ◽  
Vol 41 (12) ◽  
pp. 2917-2930 ◽  
Author(s):  
E. Piers ◽  
R. K. Brown
Keyword(s):  
Dielectric Constant ◽  
Lewis Acids ◽  
Claisen Rearrangement ◽  
Stannous Chloride ◽  
Ionic Species ◽  
Thermal Rearrangement ◽  
Polar Solvents ◽  
Factors Affecting ◽  
Competitive Reduction ◽  
Catalytic Effects

A study has been made of some factors affecting the migration or elimination of halogen in the Claisen rearrangement of allyl 2,6-dihalophenyl ethers.In the thermal rearrangement of allyl 2,6-dichlorophenyl ether, carried out in a number of solvents of different dielectric constant, halogen migration proceeds somewhat better in highly polar solvents. However, a competitive reduction to the monohalogenated allylphenol occurs in the presence of oxidizable solvents and/or products. The reaction is also complicated by the catalytic effects of certain solvents and the phenolic products, which give results similar to those obtained with Lewis acids. Stannous chloride acts as a Lewis acid and catalyzes the rearrangement of allyl 2,6-dichlorophenyl ether with simultaneous halogen rearrangement. As well, a competitive reductive removal of the halogen takes place. Results from the rearrangement of allyl 2,6-dibromophenyl ether with zinc chloride and of allyl 2,6-dichlorophenyl ether with zinc bromide, as well as those from the stannous chloride reactions indicate that the halogen migration takes place not only by an allylic shift but also via a competitive halogen substitution probably occurring by an Sn2′ pathway possibly assisted by a zinc halide bridge mechanism and/or an ionic species such as [Formula: see text].

Efficient Catalytic Effects of Lewis Acids in the 1,3-Dipolar Cycloaddition Reactions of Carbonyl Ylides with Imines

2005 ◽  
Vol 70 (26) ◽  
pp. 10782-10791 ◽  
Author(s):  
Hiroyuki Suga ◽  
Yasutaka Ebiura ◽  
Kazuaki Fukushima ◽  
Akikazu Kakehi ◽  
Toshihide Baba
Keyword(s):  
Lewis Acids ◽  
Dipolar Cycloaddition ◽  
Cycloaddition Reactions ◽  
Catalytic Effects

FURTHER OBSERVATIONS ON THE DETERMINATION OF PHOSPHATE BY PHOTOELECTRIC COLORIMETRY

1939 ◽  
Vol 17b (6) ◽  
pp. 178-191 ◽  
Author(s):  
G. R. Smith ◽  
W. J. Dyer ◽  
C. L. Wrenshall ◽  
W. A. De Long
Keyword(s):  
Ferric Iron ◽  
Stannous Chloride ◽  
Reducing Agent ◽  
Factors Affecting

A study of factors affecting the ceruleomolybdate reaction for phosphate is reported. The concentrations of stannous and stannic ions, the presence of extraneous salts, and temperature are important factors affecting the intensity and stability of the blue colour.The stannous chloride reagent should be preserved from oxidation by storing it under hydrogen.The interference by ferric iron is due largely to its reaction with the reducing agent, and may be avoided by diluting the sample to contain 0.1 p.p.m. of phosphorus and using two or three times the usual quantity of stannous chloride.

Dielectric constant of fluorized graphite intercalated with polar solvents

1989 ◽  
Vol 40 (6) ◽  
pp. 759-760 ◽  
Author(s):  
E B Amitin ◽  
V G Bessergenev ◽  
A A Varchenko ◽  
S S Ilyasov ◽  
N F Yudanov
Keyword(s):  
Dielectric Constant ◽  
Polar Solvents

Catalytic effects of Lewis acids on 1,3-DC reaction: A luminescent study

2012 ◽  
Vol 132 (6) ◽  
pp. 1456-1461 ◽  
Author(s):  
Tandrima Chaudhuri ◽  
Manas Banerjee
Keyword(s):  
Lewis Acids ◽  
Catalytic Effects

scholarly journals On the Role of Enthalpic and Entropic Contributions on the Conformational Free Energy Landscape of MIL-101(Cr) Structural Building Units

2019 ◽  
Author(s):  
Loukas Kollias ◽  
David Cantu ◽  
Vassiliki-Alexandra Glezakou ◽  
Roger Rousseau ◽  
Matteo Salvalaglio
Keyword(s):  
Free Energy ◽  
Metal Organic Framework ◽  
Energy Landscape ◽  
Ionic Species ◽  
Free Energy Landscape ◽  
Materials Synthesis ◽  
Factors Affecting ◽  
Enthalpy And Entropy ◽  
Conformational Free Energy

The thermostructural behavior of metal-organic framework (MOF) precursors is responsible for regulating the introduction of MOF structure defects during synthesis. In this paper, we evaluate factors affecting the flexibility of MIL-101(Cr) half – secondary building units (half-SBUs) in solution using enhanced sampling methods. In particular, we calculate entropic and enthalpic contributions to the conformational free energy landscape of isolated MIL-101(Cr) half-SBUs, in water, in the presence and absence of ionic species (Na<sup>+</sup> and F<sup>-</sup>), and in N, N-dimethylformamide (DMF). We find that the interplay between enthalpy and entropy determines the most probable conformational state for half-SBUs. Furthermore, we investigate the role of enthalpy and entropy in the conformational rearrangement of an SBU in water, noting that entropic contributions are essential to stabilize configurations that depart from those coherent with the MIL-101(Cr) crystal structure. Our analysis highlights the importance of explicitly considering entropic effects on the configurational ensembles of MOF building units, as such effects can significantly impact the relative stability of structurally different conformers, which ultimately can be responsible for the formation of defects during materials synthesis.

scholarly journals On the Role of Enthalpic and Entropic Contributions on the Conformational Free Energy Landscape of MIL-101(Cr) Structural Building Units

2019 ◽  
Author(s):  
Loukas Kollias ◽  
David Cantu ◽  
Vassiliki-Alexandra Glezakou ◽  
Roger Rousseau ◽  
Matteo Salvalaglio
Keyword(s):  
Free Energy ◽  
Metal Organic Framework ◽  
Energy Landscape ◽  
Ionic Species ◽  
Free Energy Landscape ◽  
Materials Synthesis ◽  
Factors Affecting ◽  
Enthalpy And Entropy ◽  
Conformational Free Energy

The thermostructural behavior of metal-organic framework (MOF) precursors is responsible for regulating the introduction of MOF structure defects during synthesis. In this paper, we evaluate factors affecting the flexibility of MIL-101(Cr) half – secondary building units (half-SBUs) in solution using enhanced sampling methods. In particular, we calculate entropic and enthalpic contributions to the conformational free energy landscape of isolated MIL-101(Cr) half-SBUs, in water, in the presence and absence of ionic species (Na<sup>+</sup> and F<sup>-</sup>), and in N, N-dimethylformamide (DMF). We find that the interplay between enthalpy and entropy determines the most probable conformational state for half-SBUs. Furthermore, we investigate the role of enthalpy and entropy in the conformational rearrangement of an SBU in water, noting that entropic contributions are essential to stabilize configurations that depart from those coherent with the MIL-101(Cr) crystal structure. Our analysis highlights the importance of explicitly considering entropic effects on the configurational ensembles of MOF building units, as such effects can significantly impact the relative stability of structurally different conformers, which ultimately can be responsible for the formation of defects during materials synthesis.

Sign in / Sign up

Export Citation Format

Share Document