Benzenoids Wiswesser code

In the second book, we briefly mentioned Wiswesser coding system of benzenoids. This second book of ours was also dedicated to Bill Wiswesser, who died of heart problems in 1989. When NT talked to him in spring of 1988, Bill said he recently returned from hospital where he underwent yet another open-heart operation. Incidentally, a few years later NT had also open-heart surgery. 

Since the convention for constructing the Wiswesser codes for polyhexes is understood, one can easily produce the Wiswesser code of any benzenoid by inscribing the appropriate number in each hexagon of a properly oriented polyhex. In Figs. 9.4 and 9.5, we give as examples Wiswesser codes for two structures in which the starting numeral is not unity one representing perylenes, and the other circulenes. 

Fig. 9.6 Recovery of dibenzo[e,m]peropyrene from the corresponding (a) Wiswesser code 112123231, (b) Decoding Wiswesser code, (c) Construction of the corresponding benzenoid...

Fig. 9.10 The Wiswesser codes for cata-condesed polyhexes representing carbon skeletons of stable benzenoids with five six-membered rings C22H14...

Fig. 9.13 The Wiswesser code of the last memher of the set of polyhexes with five hexagons. This polyhex with three inner vertices represents the rather unstable benzenoid with five six-membered rings C19H11...

It should be noted that the numeric code is a linear code in which the codes for peri-condensed benzenoids are built in the same way as the Wiswesser codes. For example, the numeric code for the Kekule structure VI (see Fig. 9.17) is 45335. 

Fig. 9.21 The recovery of two Kekule structures of dibenzo[, op]naphthacene with identical numeric codes 552255, from their perimeter codes (a) Wiswesser code 3 1 2 3 4 2, (b) Numeric code 5 5 2 2 5 5, (c) Perimeter codes 2111212112121112121121, 1211212111212112121112, (d) Construction of the boundaries of benzenoids using the perimeter codes, (e) Filling up the interiors of the boundaries, (f) Construction of the corresponding Kekule structures...

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