Polarization inverse

The driving force of these reactions is the redox compensation of the involved Cl-species, which are inversely polarized, possessing Cl -character in CI2O and Cl -character in the metal chloride and POCI3 resp. (67). 

The various transitions of triafulvenes to pentafulvenes achieved by addition of electron-rich double bonds is complemented by the reaction of triafulvenes with ynamines and yndiamines299, which gives rise to 3-amino fulvenes 539. This penta-fulvene type deserves some interest for its merocyanine-like inverse polarization of the fulvene system and its formation is reasonably rationalized by (2 + 2) cycloaddition of the electron-rich triple bond to the triafulvene C /C2 bond (probably via the dipolar intermediate 538) ... 

Some thioketones are reported to give 1,3,2-dithiastannolanes in moderate to high yields in reactions with a stannylene Dis2Sn [Dis = CH(SiMc3)2] <930M4>. The key difference with the process discussed above is inversed polarization of intermediate ylide (380) which can exist in an equilibrium with a thiastannirane (381). 

Direct observation of inversely-polarized frozen nanodomains in fatigued FeCaps... 

In resonance Raman scattering (ga 0), it is possible to have pp >. For example, if ctxy — —ctyx and the remaining off-diagonal elements are zero, g° = gs = 0 and ga 0. Then, (1-49) gives pp —> oo. This is called anomalous (or inverse) polarization (abbreviated as ap or ip). As will be shown in Section 1.15, resonance Raman spectra of metallopophyrins exhibit polarized (Aig) and depolarized (B g and B ) vibrations as well as those of anomalous (or inverse) polarization () ... 

You have in fact met one example of each of the unnatural synthons with a2 and d1 reactivity. Such synthons are given the German name Umpolung, meaning inverse polarity because their natural reactivity is reversed, and umpolung reagents are the key to the synthesis of 1,2- and 1,4-difunc-tionalized compounds. 

In analogy to the chemistry of olefins, 1,2-elimination with suitable organyl phosphanes has proved valid. Those molecules with substituents showing inverse polarities may give thermodynamically favored leaving molecules XY [Eq. (2)]. The formation of XY is initiated thermally by bases or metals (12-21). 

This course of the reaction was examined and supports the assignment of an inverse polarization (-)Ge-H(+) of the bond in HGeCls as compared to the (+)Si-H(-) bond in trichlorosilane HSiCb, which is known to form a 1 2 adduct with pyridine instead. Dichlorogallane was found to form 1 1 coordination compounds (HGaCl2L), where L = pyridine, 4-dimethylaminopyridine, 4-cyanopyridine, and 3,5-dimethy Ipyridine. ... 

Inversely polarized (nontotaUy symmetric modes, normally Raman forbidden) Antisymmetric, a pa = —dap p =00... 

A-term (totally symmetric modes), B-term (nontotally symmetric modes), and C-term (first overtones and binary combinations of vibronically active modes) effective Anomalously polarized (ap) and inversely polarized (ip) bands attainable as well Overtones and combination bands common... 

If the donor were on the dienophile and the ewg on the diene (inverse polarity), the controlling interaction would be the filled Ji of the dienophile with the empty tp3 of the... 

Here the fragment pattern is the same as before but the condensation reaction is of inverse polarity. Oxazolium ions or zwitterionic munchnones contribute the CNCC chain and tris(trimethyl-silyl)phosphine/arsine contributes the fifth ring member. 

The synthetic value of homoenolates, in exact analogy to that of enolates, stems from their amphoteric nature (equations 1 and 2). In addition, homoenolates represent archetypal synthons in the concept of umpolung , acting as inverse polarity nucleophilic synthons of Michael acceptors. 

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