Phenyl electronically modified

Dimeric Cinchona-PTCs with Electronically Modified Phenyl Linker... 

Besides appHcation as heat-resistant molding powders for electronic and other appHcations, DAIP copolymers have been proposed for optical apphcations. Lenses of high impact resistance contain 50% DAIP, 20% benzyl methacrylate, and larger amounts of CR-39 (59). A lens of refractive index 71- = 1.569 andlow dispersion can be cast from phenyl methacrylate, DAIP, and isopropyl peroxide (60). Lenses of better impact properties can be obtained by modifying DAIP with aHyl benzoate (61). 

Riichardt originally made the assumption that substituents do not exert a noticeable electronic effect on the ground state of the radical precursor. He attributed the full electronic substituent power to the radical. On the basis of this presumption, the BDEs in [24] and [25] were interpreted in terms of radical stability. The original value for the BDE in [24] (Zamkanei et al., 1983) was later slightly modified (Birkhofer et al., 1987). The BDEs were compared with those where only one cyano- or one methoxyl group was incorporated. From Table 9 (Birkhofer et al., 1989) it can be derived that phenyl, cyano-, and methoxy-groups exert an additive substituent effect on... 

By the use of a model reaction (ionization of benzoic acids), die ability of a substituent to modify die electron-donating or electron-withdrawing ability of die phenyl group and tiius influence tiiat reaction can be defined quantitatively by the Hammett equation,... 

The best yields (51-89%) were for substrates with R1 =H and phenyl rings (R2 and/or R3), especially when containing an electron-donating group. This modified Hunsdiecker reaction was equally successful with DIB conventional methods for this transformation of a,/J-unsaturated acids gave poor results. DIB has also been used for the photochemical halodecarboxylation of acids (Section 4.8.1). 

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