Evidence for positive hole delocalization over two double bonds separated by 6 .ANG. in the cation radical of a nonconjugated diene: a consequence of laticyclic hyperconjugation

1989 ◽  
Vol 111 (18) ◽  
pp. 7259-7261 ◽  
Author(s):  
Anna M. Oliver ◽  
Michael N. Paddon-Row ◽  
Martyn C. R. Symons
Keyword(s):  
Cation Radical ◽  
Double Bonds ◽  
Positive Hole

Addition of thianthrene cation radical to non-conjugated dienes—Part II: Addition to two double bonds

2006 ◽  
Vol 27 (2) ◽  
pp. 139-147 ◽  
Author(s):  
Bing-Jun Zhao ◽  
Henry J. Shine ◽  
John N. Marx ◽  
Anna T. Kelly ◽  
Cristina Hofmann ◽  
...  
Keyword(s):  
Cation Radical ◽  
Conjugated Dienes ◽  
Double Bonds

Kinetic of Oxidative Polymerization of Benzylidene-Phenylenediamines and Investigation of their Thermal Properties

2019 ◽  
Vol 816 ◽  
pp. 124-128
Author(s):  
Timur A. Borukaev ◽  
A.Kh. Shaov ◽  
R.M. Otarova ◽  
L.R. Pashtova ◽  
A.Kh. Salamov
Keyword(s):  
Thermal Properties ◽  
Heat Resistance ◽  
Chemical Structure ◽  
Oxidative Polymerization ◽  
Cation Radical ◽  
Kinetic Studies ◽  
Chain Growth ◽  
Double Bonds

Oxidative polymerization of benzylidenephenylenediamines produced polymers containing conjugated double bonds. Kinetic studies of the processes of oxidative polymerization of benzylidenephenylene diamines were carried out. The obtained kinetic dependencies allowed us to suggest the mechanism of oxidative polymerization of benzylidenephenylenediamines, which flows through the stage of formation of the cation radical, dimmer, tetramer, leading eventually to the formation of the polymer. In this case the limiting stadia is the formation of cation-radical, and chain growth occurs by N-C. A study of the thermal properties of the polymers showed that polybenzylidenephenylenediamines is characterized by rather high values of heat resistance. It was found that the process of destruction of most of the synthesized polymers occurs in several stages and depends on the chemical structure of the macromolecule.

Gold liposomes

1996 ◽  
Vol 54 ◽  
pp. 898-899
Author(s):  
James F. Hainfeld
Keyword(s):  
Direct Methods ◽  
Important Class ◽  
Double Bonds ◽  
Membrane Phospholipids ◽  
Essential Ingredient ◽  
Lipid Structures

Lipids are an important class of molecules, being found in membranes, HDL, LDL, and other natural structures, serving essential roles in structure and with varied functions such as compartmentalization and transport. Synthetic liposomes are also widely used as delivery and release vehicles for drugs, cosmetics, and other chemicals; soap is made from lipids. Lipids may form bilayer or multilammellar vesicles, micelles, sheets, tubes, and other structures. Lipid molecules may be linked to proteins, carbohydrates, or other moieties. EM study of this essential ingredient of life has lagged, due to lack of direct methods to visualize lipids without extensive alteration. OsO4 reacts with double bonds in membrane phospholipids, forming crossbridges. This has been the method of choice to both fix and stain membranes, thus far. An earlier work described the use of tungstate clusters (W11) attached to lipid moieties to form lipid structures and lipid probes.

Stereoselective Synthesis 1 Stereoselective Reactions of Carbon—Carbon Double Bonds

2011 ◽  
Author(s):  
J. G. de Vries ◽  
K. Muñiz ◽  
G. Franciò ◽  
W. Leitner ◽  
P. L. Alsters ◽  
...  
Keyword(s):  
Stereoselective Synthesis ◽  
Double Bonds ◽  
Stereoselective Reactions

On the Reaction of 2,5-Dihydroxy-[1,4]-benzoquinone with Diamines – Strain-induced Reactivity Effects

2020 ◽  
Vol 24 ◽  
Author(s):  
Hubert Hettegger ◽  
Andreas Hofinger ◽  
Thomas Rosenau
Keyword(s):  
Nucleophilic Substitution ◽  
Product Structure ◽  
Carbonyl Groups ◽  
Reaction Products ◽  
Double Bonds ◽  
Oh Groups ◽  
Natural Geometry ◽  
Quinoid Structure ◽  
Bond Localization

: The regioselectivity of the reaction of 2,5-dihydroxy-[1,4]-benzoquinone (DHBQ) with diamines could not be explained satisfactorily so far. In general, the reaction products can be derived from the tautomeric ortho-quinoid structure of a hypothetical 4,5-dihydroxy-[1,2]-benzoquinone. However, both aromatic and aliphatic 1,2-diamines form in some cases phenazines, formally by diimine formation on the quinoid carbonyl groups, and in other cases the corresponding 1,2- diamino-[1,2]-benzoquinones, by nucleophilic substitution of the OH groups, the regioselectivity apparently not following any discernible pattern. The reactivity was now explained by an adapted theory of strain-induced bond localization (SIBL). Here, the preservation of the "natural" geometry of the two quinoid C–C double bonds (C3=C4 and C5=C6) as well as the N–N distance of the co-reacting diamine are crucial. A decrease of the annulation angle sum (N–C4–C5 + C4–C5–N) is tolerated well and the 4,5-diamino-ortho-quinones, having relatively short N–N spacings are formed. An increase in the angular sum is energetically unfavorable, so that diamines with a larger N–N distance afford the corresponding ortho-quinone imines. Thus, for the reaction of DHBQ with diamines, exact predictions of the regioselectivity, and the resulting product structure, can be made on the basis of simple computations of bond spacings and product geometries.

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