1. DANIEL P. ZALESKI, JUSTIN L. NEILL, AND BROOKS H. PATE Department of Chemistry, University of Virginia, McCormick Rd., P.O. Box 400319, Charlottesville, VA 22904 EWA BIALKOWSKA-JAWORSKA AND ZBIGNIEW KISIEL Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warszawa, Poland. Structure Study of the Lactide Molecules By Chirped-Pulse FTMW Spectroscopy The Ohio State 66 th International Symposium on Molecular Spectroscopy, June 22 nd, 2011.

2. Terminology Referring to the chirality of the lactic acid monomers Not the chirality of the lactide unit

3. 3,6-Dimethyl-1,4-Dioxane-2,5-Dione Homo-Chiral Hetero-Chiral G. J. van Hummel, S. Harkema, F. E. Kohn, and J. Feijen. Acta. Cryst., B38, (1982), 1679-1681. Hetero lactic acid dimer has a small calculated dipole ~0.3 D (M052X/6-31+G(d,p) Lactide forms from 2 lactic acid molecules, loses 2 water molecules 6-member cyclic diester

4. Experimental Gordon G. Brown, Brian C. Dian, Kevin O. Douglass, Scott M. Geyer, Steven T. Shipman, and Brooks H. Pate. Rev. Sci. Instrum. 79, 053103, (2008). Originally assigned in a heated racemic lactic acid sample: 100 °C, 45 psi, neon Acquired chirally pure commercial lactide sample: 30 psi, 150 °C x3 24 Gs/s AWG

6. Heated lactide spectrum

7. Center of Symmetry – Doubled Isotope Intensities Intensities can determine equivalent positions Simulated isotopes going down are color-coded to left image Isotopes

10. Lactide-RR M052X/6-311++G(d,p) EXPMP2/6-31G(d,p) A (MHz)2202.53576(89)2201.0 B (MHz)1197.00335(31)1197.0 C (MHz)822.34942(46)822.3 ΔJK (kHz)0.137(28)0.0960 ΔK (kHz)0.119(25)0.1435 M052X/6-311++G(d,p): 1027 cm -1 barrier to internal rotation EXPMP2/6-31G(d,p) μ A (D)00 μ B (D)00 μ C (D)1.0*X2.83 Δ i (amu Å 2 )-37-38 70 lines 14 kHz rms

11. Lactide-RS EXPMP2/6-31G(d,p) A (MHz)2025.4060(11)2021.1 B (MHz)1246.64810(94)1236.2 C (MHz)903.0468(11)901.1 ΔJ (kHz)0.048(14)0.0568 ΔJK (kHz)-0.038(54)0.0684 ΔK (kHz)0.192(51)0.1231 δK (kHz)0.070(68)0.1579 M052X/6-311++G(d,p): 910 cm -1 (axial) and 1063 cm -1 (equatorial) barriers to internal rotation M052X/6-311++G(d,p) EXPMP2/6-31G(d,p) μ A (D)00.26 μ B (D)0.25*X0.58 μ C (D)1.0*X2.52 Δ i (amu Å 2 )-95-98 52 lines 14 kHz rms

12. Boat vs Chair Chair is not a minimum Boat is the detected structure M052X/6-311++G(d,p)

13. O-O- O+O+

14. Possible Lactide+Water Structures a b EXPab A (MHz)131115201366 B (MHz)946973958 C (MHz)684826699 Energy (cm -1 )-5370 M052X/6-311++G(d,p)

15. Lactide-RR+Water A(O + ) (MHz) A(O - ) (MHz) 1311.40787(40) 1311.43282(56) B(O + ) (MHz) B(O - ) (MHz) 946.86620(30) 946.87733(56) C(O + ) (MHz) C(O - ) (MHz) 684.99148(33) 684.99049(79) ΔJ(O + ) (kHz)0.3376(29) ΔJK(O + ) (kHz)-0.696(10) ΔK(O + ) (kHz)1.513(12) δJ(O + ) (kHz)0.1233(15) EXPM052X/6-311++G(d,p) μ A (D)1.0*X2.42 μ B (D)1.0*X2.36 μ C (D)1.25*X2.92 Δ i (amu Å 2 )-181-171 215 lines 9 kHz rms

16. Conclusions  Assigned unambiguously the homo- and hetero-chiral lactides Including a Kraitchman substitution structure for the homo-chiral lactide Electronic structure theory very accurately calculates these structures Autofitting routines, library-free detections  Assigned a potential homo-chiral lactide-water complex Future experiments include isotopically enriched H 2 18 O and D 2 O. A. L. Steber, J. L. Neill, M. T. Muckle, B. H Pate, and D. F. Plusquellic. Strategies for Complex Mixture Analysis in Broadband Microwave Spectroscopy. The Ohio State 65 th International Symposium on Molecular Spectroscopy. June 22, 2010.

17. Acknowledgments Award Number CHE-0960074