Odd alternant structure

When eoating fullerenes with larger alkali metal atoms, the even-odd alternation is interrupted before reaeliing x = 21, so the structural sequence must be different for these. Nevertheless, we do suggest that the first 6 alkali metal atoms, having transferred their valence electron to the fullerene moleeule, will remain distributed over the surfaee of the fullerene, gather-... 

Demethylvasconine (85) (9-methoxy-5-methyl-phenanthridin-8-olate) presented in Scheme 31 was found in Crinum kirkii (95P1291) (Amaryllidaceae). Although published as cation, no information about the anion of this alkaloid is given. Its relationship to other alkaloids of this class, however, makes a betainic structure more than likely and this is confirmed by a comparison of the NMR data of 85 with the cationic and betainic alkaloids presented in Table III. This betaine is isoconjugate with the 2-methylphenanthrene anion and thus defined the alkaloid as a member of class 1 (odd alternant hydrocarbon anions). Whereas substitution of the isoconjugate phenanthridinium moiety at the 1-position with an anionic fragment results in zwitterions (cf. Section III.D), the phenanthridinium-2-olate is a mesomeric betaine. 

Benzo[c]phenanthridine alkaloids are widespread in Papaveraceae, Fumariaceae, and Rutaceae. Fagaridine (118), the structure of which had to be revised, is a derivative of the unknown 5-methyl-benzo[c]phenan-thridine-8-olate (119) which is isoconjugate with the 2-methyl-chrysene anion (Scheme 43). Thus, Fagaridine is a member of class 1 of conjugated heterocyclic mesomeric betaines, which are isoconjugate with odd alternant hydrocarbon anions. 

An alternative structure that has also been widely investigated both for high temperature piezoelectric, as well as for ferroelectric memory applications is the bismuth layer structure family as shown in Figure 1.14 for SrBi2Ta209 (sbt), e.g. [8], The structure consists of perovskite layers of different thicknesses, separated by Bi20 + layers. It has been shown that when the perovskite block is an even number of octahedra thick, the symmetry imposes a restriction on the polarization direction, confining it to the a-b plane. In contrast, when the perovskite block is an odd number of octahedra thick, it is possible to develop a component of the polarization along the c axis (nearly perpendicular to the layers). This could be used in... 

In the thermolysis of cyclohexanone virtually all of the products arise from the (8-cleaved structure 5.23) Jwo effects are important here. In the ion the a-cleavage structure is specifically stabilized (see below) and the jff-cleavage structure 9, would be specifically destabilized by the heteroatom which is at an active site in the odd alternant n system associated with the carbonyl. The primary photolysis products of cyclohexanone 24) are much more closely correlated to its mass spectrum than the thermolysis products are. This is because n- n excitation can be relaxed by an a-cleavage (Norrish type I) analogous to 7. The analogy for the photochemical reactions is, however, far from perfect because of the stabilizing effect of the oxygen atom on the even alternant even electron ions, e.g. 10. The photolysis of... 

The synthesis and liquid crystalline properties are presented of two classes of chiral (I-n) and prochiral (Il-m) thermotropic poly(ester 0-sulfide)s. The nematic mesophase behavior of the polymers I-n exhibits distinct even-odd alternations with chemical structure and is compared with that of closely related poly(ester 0-sulfide)s Ill-n and IV-m. 

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