Credit: Yang H. Ku/C&EN/Shutterstock

In August 2017, attendees at the American Chemical Society national meeting in Washington, DC, crowded into a ballroom, buzzing with questions about the newest addition to the chemistry publishing world: preprint servers. Two online sites that would post scientific manuscripts for free prior to peer review had launched just weeks earlier. ChemRxiv was initially launched by ACS, with guidance from the Royal Society of Chemistry, the German Chemical Society, and other scientific organizations and publishers. And ChemRN was Elsevier’s latest offering in its sprawling SSRN repository.

The concept of a preprint server was well established in other scientific fields—the physics server arXiv was decades old, and the biology server bioRxiv was newer but rapidly growing—yet many chemists seemed uncertain about the new publishing tool.

At the meeting, skeptical researchers shared fears that disclosing their work in preprints would leave them vulnerable to being scooped by competitors. Journal editors expressed concern that preprints would lessen a paper’s novelty once it was eventually published. Still other critics argued that preprints were unnecessary, given chemistry journals’ relatively short publication times, and would introduce an additional content stream to an already flooded publishing landscape. Supporters argued for the benefits of preprints, like the ability to quickly and freely share results and receive feedback from peers, as well as enabling scientists in the developing world to access otherwise expensive literature to help them advance their work.

In the 17 months since that meeting, preprints have steadily gained popularity in the chemistry community. Researchers have begun experimenting with uploading their manuscripts, citing curiosity and speed among the reasons for giving it a try. Other societies have joined ACS, which also publishes C&EN, in ChemRxiv ownership. And chemistry journals that had refused to accept preprint papers—the Journal of the American Chemical Society is one notable example—loosened their restrictions. Skepticism still remains, to be sure, but it’s tempered by observations from scientists in other fields that preprints have not upended publishing practices in their communities.

Breaking down preprint submissions

About 2,300 chemistry preprints from many subdisciplines have collectively been posted to ChemRN and ChemRxiv. At ChemRN, materials science manuscripts represent the largest share of submissions, while computational chemistry papers make up the largest share on ChemRxiv.

Collectively, more than 2,300 preprints have been posted on ChemRxiv and ChemRN. Another server, called ECSarXiv, operated by the Electrochemical Society, slipped onto the scene in the spring of last year and currently hosts about 30 preprints.

Ellen M. Sletten, an organic chemist at the University of California, Los Angeles, was an early preprint adopter, posting a manuscript to ChemRxiv within weeks of its launch. As an assistant professor, Sletten was eager to preprint her work because she could show her lab’s progress before publication, which she says made a big difference in grant applications. “That was ultimately very successful for me,” she says. She adds that an extra benefit was the publicity the preprints got, particularly on Twitter because of ChemRxiv’s active presence on the site.

Many junior faculty at UCLA have embraced preprints, Sletten says, and have been educating the senior faculty on using ChemRxiv. “I think it’s very much on the path of being standard for the chemistry community,” she says, especially because preprints have already proved their worth in other fields.

“Chemists are pretty late to the party,” says Tim Gould of Griffith University. As a computational chemist, Gould has been posting preprints on the physics server arXiv for nearly two decades. Already, he has posted almost a dozen manuscripts on ChemRxiv, appreciating its sleek design and broad readership.

Chemistry preprints by the numbers 743 ChemRN 1,067 ChemRxiv Total number of preprints posted to these servers in their first 17 months. For comparison, bioRxiv had 1,385 preprints within its first 17 months. 59%

Percentage of ChemRxiv preprints that go on to be published in a peer-reviewed journal. ChemRN does not track publication data. For comparison, 67% of bioRxiv preprints go on to be published in a peer-reviewed journal.

Gould says he finds the debate among chemists over preprints perplexing. Work being scooped isn’t really an issue because preprints give you the ability to put a time stamp on your research, thereby establishing precedence, he says.

Christopher J. Cramer, a chemist at the University of Minnesota who has posted two preprints on ChemRxiv, recently experienced an unexpected benefit of sharing research before publication. An editor from the European Journal of Organic Chemistry saw one of Cramer’s manuscripts and asked him to consider submitting it to the journal. Such interactions could smooth the path to publication for scientists unsure of where to submit their work. Though flattered, Cramer turned the journal down because he had already submitted to the Journal of Organic Chemistry.

The most useful benefit of preprints is that they allow scientific research to be open access, says Jose Mendoza-Cortes, a theoretical chemist at Florida State University. “I sometimes don’t have access to my own papers,” he says, referring to the final, peer-reviewed versions of papers that typically get placed behind paywalls. And he’s met many researchers in other countries whose institutions can’t afford access to all the journals they need. At least with the preprint servers, he says, scientists can view the results of a new study, even if it’s an unpolished, non-peer-reviewed version. Access to these results can help them advance their science more quickly.

How fascinating... A solicitation from a (respectable) journal to submit our @ChemRxiv preprint for consideration. Had not anticipated the auction possibilities! pic.twitter.com/G83gwHCvu6 — Chris Cramer (@VPRCramer) December 18, 2018

Open access was also the main draw to preprinting for one assistant professor C&EN spoke with, though they weren’t clear on the rules for doing so. This chemist waited until their paper had been accepted and they had received galley proofs before uploading the manuscript to ChemRxiv. As posted on ChemRxiv’s website and confirmed by ChemRxiv publishing manager Marshall Brennan, this practice is against policy; preprints must not be accepted for publication at the time of submission. In contrast, ChemRN does allow manuscripts that have been accepted to a journal to be posted on its site. These manuscripts are labeled as part of the “Accepted Paper series,” and about half the manuscripts on ChemRN carry this label.

The assistant professor C&EN spoke with says they weren’t aware of the policy at the time of submission and won’t violate it in the future. They’ve asked to remain anonymous because of the possible consequences of the unintentional breach of policy. Still, the researcher says they’d prefer to post manuscripts that have undergone some peer review so that the work shared is as close to the final version as possible.

Neville Compton, editor in chief of Angewandte Chemie, says his journal has observed authors submitting their manuscripts to preprint servers at various times while they are under review at the journal and is working to set clear and uniform guidelines that will help authors understand the proper time to submit their preprints, which is ideally at the same time they submit to the journal.

Simultaneous uploading of preprints and submitting to journals is standard in physics, Griffith University’s Gould says, adding that physicists don’t seem to take advantage of the system and publish preprints after they’ve been accepted by journals.

Despite these small kinks in the system, Brennan says ChemRxiv’s growth has exceeded expectations. While the majority of uploads to the preprint server come from theoretical chemists, there’s also been growing participation from subdisciplines such as organic chemistry. Organic chemistry submissions made up 1 or 2% of submissions at launch but are now close to 10% of submissions, Brennan says. “It’s a good indication that this isn’t just a fad; this is something that’s going to continue to pick up with more and more chemists.”

Credit: XKCD

On ChemRN, organic chemistry preprints represent 15% of submissions. ChemRN is just one of more than 40 SSRN research networks and has been more popular than the organization expected, says Managing Director Gregory Gordon. The advantage of SSRN, he says, is that it exposes scientists to a wide range of research. When authors submit a preprint to SSRN, they can select up to a dozen research networks in which they’d like their paper to appear.

SSRN has also partnered with publishers like Cell Press and materials science consortium Acta Materialia Inc. to host manuscripts that are under review at their journals. The publisher has, for example, has preprinted more than 100 “First Look” manuscripts: Authors opt in to have these submissions shared on the materials science research network and ChemRN while they are under review at Acta Materialia journals. What opting in means, however, isn’t always clear to authors.

Kristie J. Koski, a materials chemist at the University of California, Davis, was surprised to find out that she had a preprint on ChemRN when C&EN contacted her for this story. Once informed of the manuscript title, she vaguely recalled ticking off a First Look check box but didn’t realize what it meant. Now she wonders what will happen if her preprinted manuscript isn’t accepted to the journal Acta Materialia. Christopher A. Schuh of the Massachusetts Institute of Technology, who is coordinating editor of the Acta Materialia family of journals, says that these manuscripts are treated the same as any other preprint, and authors are free to submit them elsewhere if they are no longer under consideration at an Acta journal. The manuscript will remain posted as a preprint on ChemRN regardless.

Chemists are pretty late to the party. Tim Gould, computational chemist, Griffith University

Koski hadn’t heard of ChemRN or ChemRxiv before C&EN contacted her and suspects that other chemists may not be aware of the preprint servers either.

Although the news of preprint servers hasn’t reached all corners of the chemistry community, publishers are making room for them. In March 2018, two other scientific societies, the Royal Society of Chemistry (RSC) and the German Chemical Society (GDCh), joined ACS as coowners of ChemRxiv.

Richard Kidd, RSC publisher and ChemRxiv Governing Board member, says the partnership seemed like a valuable opportunity to collaborate and felt that a society-led initiative for preprints could be effective. Because the rest of the scientific world had already embraced them, “preprints were always going to happen in chemistry eventually, and if it was to be done, it’s better that it’s done well,” he says.


The GDCh had long discussions about joining the endeavor because, in the beginning, there were “severe doubts whether the chemistry community is really in need of a preprint server,” says Wolfram Koch, GDCh’s executive director. But ultimately the society’s board members voted unanimously to join the experiment, he says. Once the decision was made, the editorial board of GDCh’s flagship journal, Angewandte Chemie, also voted to lift its ban on preprints. “Anything else would not have made sense,” Koch says.

A few months later, ACS’s flagship journal, the Journal of the American Chemical Society, followed suit. By year’s end, all ACS-owned primary research journals and GDCh journals accepted preprints. The RSC already had a blanket policy that its journals would accept preprints.

In December, ChemRxiv launched a one-click transfer feature that would allow researchers to submit preprints to ACS, RSC, or GDCh journals by simply selecting the journal from a list. A system that would enable users to comment on preprints—a feature offered by other preprint servers, like bioRxiv—has been put on hold. Market research by ChemRxiv revealed that the demand for a commenting system was less than initially thought, with some users expressly saying that such a system would drive them off the site.

Ultimately, it’s up to the community to decide what role preprint servers will fill for them, the RSC’s Kidd says. While some may find it useful, others may not. But he sees chemistry preprints as an experiment for publishers to be excited about, not feared.