Interactions of limonene with the water dimer

The interactions of two molecules of water with the terpene limonene are characterised by chirped-pulse Fourier transform microwave spectroscopy. Seven isomers of limonene-(H 2 O) 2 have been observed, and identified from the comparison of their experimental spectroscopic parameters with those predicted by computational methods. In all isomers a distorted water dimer binds to limonene through O-H π and C-H O interactions, and shows a strong preference for interacting with equatorial conformations of limonene. O-H π hydrogen bonds to both endocyclic and exocyclic double bonds of limonene are established. In one of the isomers the water dimer forms a bridge between the endocyclic and exocyclic double bonds of limonene. Our results help advance our understanding of the interactions of water with atmospheric compounds. The interactions of limonene with the water dimer have been characterised through the identification of seven different isomers.