A method of synthesizing trimethylene carbonate, which includes the steps of reacting 1,3-propanediol and phosgene in vapor form, providing a combination of temperature and pressure at which trimethylene carbonate is in its vapor phase, providing a residence time sufficient to react 1,3-propanediol and phosgene to trimethylene carbonate, condensing the trimethylene carbonate vapors, and isolating the condensed trimethylene carbonate. The present method advantageously does not require the use of catalysts and the associated expense of recovering and/or recycling or disposing of catalyst residues.