1. David Wilcox Purdue University Department of Chemistry 560 Oval Dr. West Lafayette, IN 47907-2084

2. Product of isoprene oxidationProduct of isoprene oxidation Correlated with biogenic isoprene*Correlated with biogenic isoprene* Generates destructive carbonyls that contributes to ozone destruction**Generates destructive carbonyls that contributes to ozone destruction** Methyl Vinyl Ketone *D. Pierotti, S.C. Wofsy, D. Jacob, J. Geophys. Res. 95 (1990) 1871. **E.C. Tuazon, R. Atkinson, Int. J. Chem. Kinet. 21 (1989) 1141.

3. Infrared data: enthalpy +2.36 kJ/mol (Bowles et al.)Infrared data: enthalpy +2.36 kJ/mol (Bowles et al.) Ab initio calculationsAb initio calculations Discharge spectrum of isoprene (unpublished results)Discharge spectrum of isoprene (unpublished results) Foster et al. (7 to 33 GHz)Foster et al. (7 to 33 GHz) Fantoni et al. (26.4 to 40 GHz)Fantoni et al. (26.4 to 40 GHz) P.D. Foster, V.M. Rao, R.F. Curl, Jr., J. Chem. Phys. 43 (1965) 1064. A.C. Fantoni, W. Caminati, R. Meyer, Chem. Phys. Lett. 133 (1987) 27. A.J. Bowles, W.O. George, W.F. Maddams, J. Chem. Soc. B (1969) 810.

4. 20 μs FID ~20 kHz resolution, interpolated to 5 kHz 20 μs FID ~20 kHz resolution, interpolated to 5 kHz

5. ~100,000 time domain averages S/N 10,000:1 S/N 10,000:1

6. A-state effective Hamiltonian: E-state effective Hamiltonian: with Reduced barrier parameter (F R fixed to 5.3 cm -1 ) R. Lavrich, D. Plusquellic, R. Suenram, G. Fraser, A. Walker, M. Tubergen, J. Chem. Phys. 118 (2003) 1253.

7. Propagation of error from cross-terms (F R fixed to 5.3 cm -1 ) P.D. Foster, V.M. Rao, R.F. Curl, Jr., J. Chem. Phys. 43 (1965) 1064. A.C. Fantoni, W. Caminati, R. Meyer, Chem. Phys. Lett. 133 (1987) 27. *Includes transitions from refs: *

8. H. Hartwig, H. Dreizler, Z. Naturforsch 51a (1996) 923. Rotational Hamiltonian in principal axis frame Torsional Hamiltonian in Rho-axis frame -Eliminates 2/3 torsion-rotation cross terms.

9. P.D. Foster, V.M. Rao, R.F. Curl, Jr., J. Chem. Phys. 43 (1965) 1064. A.C. Fantoni, W. Caminati, R. Meyer, Chem. Phys. Lett. 133 (1987) 27. *Includes transitions from refs: * fixed

10. HF* DFT** JB95 XIAM HF* DFT** JB95 XIAM A (MHz) 9056.92 8912.33 8941.552(1) 8941.547(1) B(MHz) 4311.38 4258.51 4274.4144(4) 4274.3593(9) C(MHz) 2974.36 2936.50 2945.3365(5) 2945.2903(9) V 3 (cm -1 ) 397.5 258.7 433(4) 433.8(1) θ a ( o ) 80.72 81.63 78.5(7) 78.21(2) ap-MVK HF* DFT** JB95 XIAM HF* DFT** JB95 XIAM A (MHz) 10481.39 10229.70 10238.657(4) 10238.610(1) B(MHz) 4012.61 3979.18 3991.507(9) 3991.6814(6) C(MHz) 2954.22 2916.42 2925.652(1) 2925.4885(1) V 3 (cm -1 ) 375.2 290.3 375(5) 376.6(2) θ a ( o ) 32.78 32.71 36(5) 29.71(3) sp-MVK *6-311++G(d,p) **B3LYP/ 6-311++G(d,p)

11. P.D. Foster, V.M. Rao, R.F. Curl, Jr., J. Chem. Phys. 43 (1965) 1064. A.C. Fantoni, W. Caminati, R. Meyer, Chem. Phys. Lett. 133 (1987) 27. I. Foster et al. V 3 = 437(7) cm -1V 3 = 437(7) cm -1 Fixed parameter: F R = 5.33 cm -1 F R = 5.33 cm -1 II. Fantoni et al. V 3 = 424(7) cm -1V 3 = 424(7) cm -1 Fixed parameter: F = 5.38 cm -1 F = 5.38 cm -1 This study V 3 = 433.8(1) cm -1 (XIAM)V 3 = 433.8(1) cm -1 (XIAM) = 433(4) cm -1 (JB95) = 433(4) cm -1 (JB95) Fixed parameter: F R = 5.30 cm -1 F R = 5.30 cm -1

12. 1.504(9) Å 1.475(9) Å 1.333(7) Å C3C4 C1 C2 C1 C2 C3 C4 a b C2: 0.06 Å from a-axisC2: 0.06 Å from a-axis C4: 0.1 Å from a-axisC4: 0.1 Å from a-axis

13. C1 C2 C3 C4 a b 1.48(2) Å 1.492(8) Å 1.340(6) Å C3 C4 C1 C2 1.24(1) Å C2: 0.06 Å from a-axisC2: 0.06 Å from a-axis C4: 0.08 Å from a-axisC4: 0.08 Å from a-axis

14. CP-FTMW spectrometer: sp-MVK unambiguously detected with high S/NCP-FTMW spectrometer: sp-MVK unambiguously detected with high S/N V 3 barrier precision and experimental resolution: JB95 and XIAMV 3 barrier precision and experimental resolution: JB95 and XIAM Efficient structural analysis with CP-FTMW spectrometerEfficient structural analysis with CP-FTMW spectrometer Revisit spectra of related moleculesRevisit spectra of related molecules

15. Purdue University Camille and Henry Dreyfus Foundation Amanda Shirar Owen Williams Brian Dian David Plusquellic Isabelle Kleiner

17. A) Improved accuracy for isotopic rotational constant predictions: I) Calculated us – Experimental us = Δ us II) Calculated s – Δ us → Predictions within 100 kHz to 1 MHz of experimentally determined rotational constants B) Isotope ν A - ν E splitting consistent with unsubstituted splitting. C) 13 C identified in both ap- and sp-MVK 18 O lines for the A-state of ap-MVK. 18 O lines for the A-state of ap-MVK.

18. Approximate rigid rotor constants in the absence of internal rotationApproximate rigid rotor constants in the absence of internal rotation 18 O A-states within 10% of the rigid rotor constants. 18 O A-states within 10% of the rigid rotor constants. J. Demaison, L. Margulès, I. Kleiner, A. Császár, J. Mol. Spec. 259 (2010) 70.