Unusual ring systems in organic chemistry

On molecular identification numbers

“…In order to be objective as possible in trying to include different cases and not exclude potential problem structures, we decided to examine all structures that have been mentioned in a brief review on unusual ring systems in organic chemistry. 42 In Table XI and Figure 6 At first look, the two compounds appear less similar, but they correspond to a butane-isopropane kind of variation if attention is focused on the C3 rings. Thus, even if compounds may not at first glance look alike, similar I.D.…”

Compact molecular codes

“…In both cases it is not difficult to locate the two vertices that, when excised, produce the subspanning tree on which the compact code is based. We obtain the following codes: for chrysene 211111111111100348 16 3711 15 for benzophenanthrene 15 16 The long strings of l's can be contracted with a superscript, subscript, or other typographical sign. For example, we can write for the two codes Here 1**13 and 1**6 indicate repetitive occurrences of the digit 1 13 and 6 times.…”

Kinetic stabilization allows structural analysis of a benzoborirene

“…Strain is among the fundamental concepts of chemistry. 1–3 Deviations from ideal bonding arrangements result in an increased energy content compared to a hypothetical unstrained reference. The high energy content not only makes strained compounds highly reactive and thus valuable for chemical transformations, 4–11 but strain can also result in unusual structures that allow testing the limits of the theory of chemical bonding.…”