Ring condensation index

The value of ring condensation index (3), ring compactness (7), and the extent of condensation of unsubstituted aromatic clusters (4) all indicate a skeleton of a peri-condensed system in the aromatic portion of this asphaltene. 

The nature of cyclical structures (e.g., ring condensation index, aromaticity, heteroatoms)... 

Quinophthalone (6.229) and its derivatives [86] also fall into the methine category, although they appear in the Colour Index under quinoline colouring matters. The parent compound was discovered in 1882 by Jacobsen, who condensed 2-methylquinoline (quinaldine) with phthalic anhydride. The product, quinoline yellow, is used as a solvent dye (Cl Solvent Yellow 33). The light fastness is improved by the presence of a hydroxy group in the quinoline ring system. Derivatives of this type provide greenish yellow disperse dyes for polyester. The moderate sublimation fastness of Cl Disperse Yellow 54 (6.230 R = H) is improved by the introduction of an adjacent bromine atom in Cl Disperse Yellow 64 (6.230 R = Br). 

The lability of thieno[3,4-6]thiophene (3) and other iso-annelated systems, such as benzo[c]thiophene and benzole] furan, may be due to the strain effect (Mills-Nixon effect see also Zwanenburg et alP and references therein) in the condensed five-membered ring. The stability of the iso-annelated dithienothiophenes 7—9 is noteworthy. Simple LCAO MO method calculations on benzo[c]thiophene indicate that its instability is due to low specific delocalization energy and high free valence index at position 1. 

What Zhou and Parr found was that the smaller the activation hardness is, the faster is the reaction." Thus is a reactivity index. Table 3.18 shows the results for the amounts of ortho-, para- and weZ -substitution in the nitration of substituted benzenes. Similar good results were found for the site selectivity in a large number of condensed-ring hydrocarbons and heterocyclic molecules. 

Volume 70 of Advances in Heterocyclic Chemistry consists of three chapters together with the Subject Index for Volumes 61 through 70. The first contribution by Dr. Istvan Hermecz (Chinoin, Hungary) continues with Part II of his set of three chapters on condensed pyridines. Part I, in Volume 69, covered pyrido[l,2-ft][l,2]oxazines, -thiazines, and -pyridazines, and the present chapter deals with [l,2-c]-fused 1,3-oxanes, 1,2-thiazines, and -pyrimidines. The third part will appear in a subsequent volume of our series and will deal with 1,4-oxazines and 1,4-thiazines, fused pyridine rings. 

Critical examination of the data plotted in Figs. 16-3 and 16-4 reveals that aromatic content is not the only constituent which influences the viscosity index. Table 16-12 shows data taken from these graphs for the structural type content of various oil fractions at three different levels of viscosity index. It is obvious that the rise in the viscosity index from 100 to 140 for saturated oils as plotted in Fig. 16-3b cannot be ascribed to decrease in aromatic content. The decrease in the content of condensed-ring naphthenes from 34% to 18% and... 

This chapter summarizes the syntheses of various tetracyclic and pentacyclic condensed thiophene systems that are reported in Chemical Abstracts, Index of Ring Systems for the period from 1952 through December 31, 1980 (i.e., through Volume 93). Previous syntheses are reported in the monograph... 

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