In this issue, which contains articles dedicated to Nobel Laureate Roald Hoffmann on his 80th birthday, G. Bertrand et al. review recent developments in the field of cyclic (alkyl)(amino)carbenes. M. Bickelhaupt and K. N. Houk discuss reaction rates with the distortion/interaction-activation strain model in a further Review. D. J. Tantillo contributes a Minireview on inherent substrate reactivity in enzyme-promoted carbocation cyclization/rearrangements. In Essays, B. Kahr et al. write on the abuse of Rachel Carson and the misuse of DDT science in the context of environmental deregulation, and K. A. Jørgensen et al. wonder why it is so challenging to move from six to ten electrons in cycloaddition reactions.

In the Communications section, A. Ghosh et al. describe the stabilization and structure of the cis tautomer of a free-base porphyrin (see picture). J. R. Long et al. found a trinuclear radical-bridged lanthanide single-molecule magnet, and B. Kahr et al. investigated DDT polymorphism and the lethality of crystal forms.

And finally, N. W. Ashcroft asks what constitutes an atom, and J. I. Seeman paints the picture of R. B. Woodward as a larger-than-life chemistry rock star.

• Angewandte Chemie 34/2017: Going in Circles,
  Angew. Chem. Int. Ed. 2017, 56 (34).