ChemRxiv is a free online submission, distribution, and archival service for unpublished preprints in chemistry and related areas.
ChemRxiv is now available in a fully functioning Beta version for use and feedback by researchers. Find out more from this ACS press release: https://www.acs.org/content/acs/en/pressroom/newsreleases/2017/august/chemrxiv-beta-open-for-submissions-and-powered-by-figshare.html?hootPostID=c5c5e00bed4e6b0db448b1ba9bc18551.
ChemRxiv itself can be found here.