Exploration of the chemical space and its three historical regimes

Abstract

Chemical research unveils the structure of chemical space, spanned by all chemical species, as documented in more than 200 y of scientific literature, now available in electronic databases. Very little is known, however, about the large-scale patterns of this exploration. Here we show, by analyzing millions of reactions stored in the Reaxys database, that chemists have reported new compounds in an exponential fashion from 1800 to 2015 with a stable 4.4% annual growth rate, in the long run neither affected by World Wars nor affected by the introduction of new theories. Contrary to general belief, synthesis has been the means to provide new compounds since the early 19th century, well before Wöhler's synthesis of urea. The exploration of chemical space has followed three statistically distinguishable regimes. The first one included uncertain year-to-year output of organic and inorganic compounds and ended about 1860, when structural theory gave way to a century of more regular and guided production, the organic regime. The current organometallic regime is the most regular one. Analyzing the details of the synthesis process, we found that chemists have had preferences in the selection of substrates and we identified the workings of such a selection. Regarding reaction products, the discovery of new compounds has been dominated by very few elemental compositions. We anticipate that the present work serves as a starting point for more sophisticated and detailed studies of the history of chemistry.history of chemistry | chemical space | chemical reactions | World War | structural theory

Does repeat synthesis in materials chemistry obey a power law?

“…The CoRE MOF database and related collections of MOF materials (14,15) clearly demonstrate that tens of thousands of distinct MOFs have been made, but not even the most optimistic proponents of the versatility of these materials would claim that millions or billions of different materials have been made. For comparison, it has been estimated that worldwide, around 6 × 10 5 new chemical species per year are reported (26).…”

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“…By 1869 there were a bit more than ten thousand known substances; a large proportion of which were O‐, H‐, C‐ and N‐based . This dramatic concentration of compounds based on light elements has not changed with the discovery of heavier elements . Most of the new compounds keep being synthesized in wet‐labs at the level of stuffs, the reactivity and physical properties of which are then analysed.…”

“…Further tests of the systems involve, for example, to pinpoint the conditions of the space at which the known systems fade away. We wonder what the shape of the system would be if chemistry evolution change drastically its conservative way of extending the chemical space …”

“…Would it show that chemistry needs an ew icon?S hould it be something similar to the 1860s system,t his could correspond to the "law" Mendeleev was after.N ot an algebraic expression, but an invariance of the structure through the evolution of the chemical space.I ti s not, after all, any "law" an invariant of the field explored?F urther tests of the systemsi nvolve, for example, to pinpoint the conditions of the space at whicht he known systems fade away.W ew onder what the shape of the system would be if chemistry evolutionc hange drastically its conservative wayo f extending the chemicalspace. [19] Whatever the result of considering the current size of the chemicals pace is, periodic systems, either historically stable or unstable, are the sought depiction of chemistry,t he map including all gathered chemical knowledge over the history of chemistry.S uch am ap must be explored and analysed on a regularb asis to keep track of the expansiono ft he chemical space.…”

Bioactivity descriptors for uncharacterized compounds

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