Dipole copper

Mills calculated the enhancement of dynamic dipole moments for a dipole moment on a smooth silver or copper surface with a silver tip above it, which... 

The author believes that dipoles cause deformation hardening because this is consistent with direct observations of the behavior of dislocations in LiF crystals (Gilman and Johnston, 1960). However, most authors associate deformation hardening with checkerboard arrays of dislocations originally proposed by G. I. Taylor (1934), and which leads the flow stress being proportional to the square root of the dislocation density instead of the linear proportionality expected for the dipole theory and observed for LiF crystals. The experimental discrepancy may well derive from the relative instability of a deformed metal crystal compared with LiF. For example, the structure in Cu is not stable at room temperature. Since the measurements of dislocation densities for copper are not in situ measurements, they may not be representative of the state of a metal during deformation (Livingston, 1962). 

The redox potential of blue copper oxidases varies from species to species. The high redox potential of around 700 mV in fungal laccase is primarily attributed to nonaxial methionine ligand, a geometry that stabilizes the reduced state. Other factors such as solvent accessibility, dipole orientation, and hydrogen bonding also play an important role. ... 

As indicated in Section ni.B, deprotonation of a carbamate affords a dipole-stabilized a-amino-organolithium that can be transmetalated with copper salts to form cuprates, thereby expanding the versatility of the organolithium. Suitable electrophiles include enones, alkenyl, alkynyl, allenyl and dienyl carboxylic acid derivatives, nitriles and sulfoxides. Dieter and coworkers have shown that the same process can be accomplished via transmetalation of a stannane (Scheme 36). The procedure is particularly... 

Photolysis as well as thermolysis (150°C, copper-catalyzed) of (79) results in quantitative loss of CO2 (Scheme 29). The 1,3-dipole (80) cyclizes to the benzimidazole (81) or is intercepted by dipolarophiles like benzonitrile or by an alcohol (Scheme 29) <68TL325>. Other oxadiazolones of type (79) fragment to CO2, a nitrile, a nitrene, and a carbene finally leading to a host of products <79JCS(P1)483>. 

Two recent publications feature metal vinylidenes functioning as 1,3-dipole equivalents, as in the Cu-catalyzed Huisgen cyclization (Section 9.4.5). Fiirstner and coworkers described intramolecular Diels-Alder reactions of unactivated die-nynes catalyzed via a proposed [4+3]-diene/copper vinylidene cycloaddition [59]. 

The reaction of a-diazocarbonyl compounds with nitriles produces 1,3-oxazoles under thermal (362,363) and photochemical (363) conditions. Catalysis by Lewis acids (364,365), or copper salts (366), and rhodium complexes (367) is usually much more effective. This latter transformation can be regarded as a formal [3 + 2] cycloaddition of the ketocarbene dipole across the C=N bond. More than likely, the reaction occurs in a stepwise manner. A nitrilium ylide (319) (Scheme 8.79) that undergoes 1,5-cyclization to form the 1,3-oxazole ring has been proposed as the key intermediate. 

The dipole moments of bis(2-pyrrolylmethyleneimine)copper(II) complexes have been measured and the results correlated with square planar and tetrahedral configurations.273... 

Oxa-l -silabicyclo[ . 1,0 alkanes (n = 3 111 n = 4 113) were the only products isolated from the photochemical, thermal or transition-metal catalyzed decomposition of (alkenyloxysilyl)diazoacetates 110 and 112, respectively (equation 28)62. The results indicate that intramolecular cyclopropanation is possible via both a carbene and a carbenoid pathway. The efficiency of this transformation depends on the particular system and on the mode of decomposition, but the copper triflate catalyzed reaction is always more efficient than the photochemical route. For the thermally induced cyclopropanation 112 —> 113, a two-step noncarbene pathway at the high reaction temperature appears as an alternative, namely intramolecular cycloaddition of the diazo dipole to the olefinic bond followed by extrusion of N2 from the pyrazoline intermediate. A direct hint to this reaction mode is the formation of 3-methoxycarbonyl-4-methyl-l-oxa-2-sila-3-cyclopentenes instead of cyclopropanes 111 in the thermolysis of 110. 

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