English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

In this paper we revisit coronoids, in particular multiple coronoids. Weconsider a mathematical formalisation of the theory of coronoid hydrocarbonsthat is solely based on incidence between hexagons of the infinite hexagonalgrid in the plane. In parallel, we consider perforated patches, whichgeneralise coronoids: in addition to hexagons, other polygons may also bepresent. Just as coronoids may be considered as benzenoids with holes,perforated patches are patches with holes. Both cases, coronoids and perforatedpatches, admit a generalisation of the altan operation that can be performed atseveral holes simultaneously. A formula for the number of Kekul\'e structuresof a generalised altan can be derived easily if the number of Kekul\'estructures is known for the original graph. Pauling Bond Orders for generalisedaltans are also easy to derive from those of the original graph.

Coronoids, Patches and Generalised Altans