SYNTHESIS, STABILITY AND ENERGETICS OF CYCLOBUTADIENE A THESIS Presented to The Faculty of the Graduate Division bY Ping Hung Li In Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the School of Chemical Engineering Georgia Institute of Technology October, 1969 SYNTHESIS, STABILITY AND ENERGETICS OF CYCLOBUTADIENE A THESIS Presented to The Faculty of the Graduate Division bY Ping Hung Li In Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the School of Chemical Engineering Georgia Institute of Technology October, 1969 SYNTHESIS, STABILITY AND ENERGETICS OF CYCLOBUTADIENE Approved: Chairman Date approved by Chairman: ii ACKNOWLEDGMENTS I am grateful to Dr. H. A. McGee, Jr. for the suggestion of this research problem and for his advice, encouragement, and assistance during the progress of the research work. I am thankful to Dr. J. A. Knight, Jr. for his suggestions and willing assistance in the chemical preparations, as well as in the gas chromatographic and infrared analyses carried out in this research work and for his suggestions while serving on the reading committee. I also wish to thank Dr. W. T. Ziegler for his interest and suggestions while reading this thesis. Deep appreciation is due to the National Aeronautics and Space NQL 1 1-002-005 Administration for its support through grant NsG-337dl I also wish to thank Badische Anilin and Soda Fabrik A. G. for the gift of cyclooctatetrene and General Aniline and Film Corporation for furnishing the iron pentacarbonyl. The many hours spent by Mr. G. B. Oglesby in correcting the English are deeply appreciated. I also wish to extend my thanks to Mrs. L. P. Gordon for her calculations of theoretical ionization potential and heat of formation and to Mrs. Claudine Taylor for her excellent typing. The understanding, encouragement, and assistance of my wife, Grace, my parents, Mre and Mrs. L. S. Li and my other relatives are gratefully acknowledged. TABLE OF CONTENTS LIST OF TABLES, ..e ..e e.. V Chapter I. INTRODUCTION. e . e I) e . e e e . e e e e 1 Definition of the Problem Purpose of this Research Review of the Literature of Attempted Synthesis of Cyclobutadiene Electron Ground State of Cyclobutadiene Chemistry of Cyclobutadiene 11. APPARATUS AND EXPERIMENTAL PROCEDURES e e . e 23 Instruments Coaxial Furnace Inlet System Cryogenic Inlet System Low Temperature Reaction System Chemic a1 Preparations Energy Measurements EI. RESULTSANDDISCUSSION e e . e e a . e e . 47 Reaction of Cyclobutadieneirontricarbonyl with Ceric Ion Dehalogenation of Cis- 3,4-dichlorocyclobutene Attempted Dehalogzation of -Cis- 3,4-dichlorocyclobutene at Low Temperature Radio Frequency Discharge of _ICis-3,4-dichlorocyclobutene Pyrolysis of Cyclobutadieneirontricarbonyl Copyrolysis of Cyclobutadieneirontricarbonyl and Dienophiles C opyr oly sis of Cyclobutadieneir ontricarbonyl and Oxygen iv TABLE OF CONTENTS (Continued) Chapter Page III. (Continued) Pyrolysis and Quenching Experiment with Cyclobutadieneirontricarbonyl Reaction of Dimethyl Acetylenedicarboxylate with Quenched C H Produced by Pyrolysis of Cyclobutadieneirontricarbonyl 44 Unsuccessful Copyr oly si s with Cyclobutadieneiron- tricarbonyl Mechanism of the Pyrolysis of Cyclobutadieneiron- tricarbonyl Ionization Potential of Cyclobutadiene Derived Heat of Formation of Cyclobutadiene IV. CONCLUSIONSANDRECOMMENDATIONS. * 4 e e e 0 * 0 0 * e 85 A PPENDTCE S A. MASS SPECTRUM AND IONIZATION POTENTIAL OF CYCLOBUTADIENETIRONTRICARBONYL e e . e . e 90 B. MISCELLANEOUSSPECTROMETRICDATA . e e e . e e . 95 C. DERIVATION OF HEAT OF FORMATION OF CYCLOBUTADIENE FROMENERGETIC STUDY . e . e e 130 D. THEORETICAL IONIZATION POTENTIALS AND HEATS OFATOMIZATIONOFC H ISOMERS. e . e . a . ., . 137 44 . V LIST OF TABLES Table Page 1. Products of rf Discharge of -Cis-3, 4-dichlorocyclo- butene and their Appearance Temperatures a (I e e e . e . 52 2. Mass Spectra of C H from rf Discharge of C4H4C12 andC H Isomers4at%OeV e e a e 54 44 . 3. Mass Spectrum of the Products at 70 eV from the Pyrolysis 0 of Cyclobutadieneirontricarbonyl at 380. a e . e . e . 57 4. Products of Copyrolysis of Cyclobutadieneirontricarbonyl hth Oxygen and Their Appearance Temperatures . ~ ~ ~ . 64 5 e Pyrolysis Products of Cyclobutadieneirontricarbonyl and their Appearance Temperatures ~ , . ~ ~ . ~ . 68 Mass Spectra of C4H4 Isomers and C H from 6. 44 PyrolYsisofCIT. e . e e . a 0 . e 0 I) e . D e 0 70 7. Ionization Potential and Heat of Formation of c H Isomers. 0. * e.. a e. * . 0 . 82 44 . 8. Relative Abundances of the Principal Positive Ions from Cyclobutadieneirontricarbonyl at 70 eV e e . e 93 0 9. Mass Spectrum of Furan at -105 at 70 eV from the Copyrolysis of Cyclobutadieneirontricarbonyl with Oxygen e . e 96 10. Relative Abundance of the Principal Positive Ions from Cyclooctatetraene (C H ) at 70 eV e e e e 97 88 . 11. Relative Abundance of the Principal Positive Ions from -Syn Cyclobutadiene Dimer at 70 eV e e . e e e 99 12. Relative Abundances of the Principal Positive Ions from -Cis-3,4-dichlorocyclobutene at 70 eV . e . ~ ~ e . ~ 100 13. Mass Spectrum of the Products at 70 eV from the 0 Copyrolysis of CIT withMethy1 Propiolate at 380 e e e 103 vi LIST OF TABLES (Continued) Table Page 14. Heat of Formation of Cyclobutadiene DerivedfromEnergetic Study. e . e e e . a . e 135 15. Theoretical Ionization Potential and Heat ofAtomization of C H Isomers ., . e e . 139 44 . vii LIST OF ILLUSTRATIONS Figure Page 1. Coaxial Furnace Inlet System e . a e . e . e . e a 25 2. Pyrex Furnace Tube . e . e . e . e e e e e . e a 26 3. Cold Reactor Attached to Cryogenic Inlet System A ., . e . a 28 4. Radio Frequency Discharge Tube & Cryogenic Inlet SystemB. e.. e.. e.. e *.. a 31 5. Low Temperature Reaction Arrangement . e e . a . e e . 33 6. Ionization Efficiency Curves of Water and C4H4 fromthe Pyrolysis of CIT. ., . e . ’. e . e . 45 7. Ionization Efficiency Data for C H from the 0 44 Pyrolysis of CIT at 380 (I). e a . e a . e . e . 79 8. Ionization Efficiency Data for C4H4 from the Pyrolysis of CIT at 380°(11) e . e a . e . a e , e 80 9. Ionization Efficiency Data for Cyclobutadiene- irontricarbonyl (I e . e . * a . e 92 10. Mass Spectrum of HC1 and C H at -155’ from the rf Discharge of Cis-3,4-dich~orocyclobutene2 - 0 Followed by Quenching at -196. e . e . e . 104 0 11. Mass Spectrum of C H , C H Cf and NCl at -140 from the rf Discharte 5f _L_C&-3d 4-dichlorocyclobutene Followed by Quenching at -196. e . e e . e . e 105 0 12. Mass Spectrum of C H and C4H2 at -120 from the rf Discharge of -Cis-%, 4-dichlorocyclobutene0 Followed by Quenching at -196. e e . e . e . e . e 106 13. Mass Spectrum of C4H2, C H C1 and CZH2Cl at -90’ from the rf Discharge of C1s-3~.4 4-dichlorocyc~obutene Followed by Quenching at -196, ~ e e ~ . ~ e . ~ 107 viii LIST OF ILLUSTRA TIONS (Continued) Figure Page 14. Mass Spectrum of C4H3C1 and C H C1 at -80' from the rf Discharge of Cis-3, &&h?oro- - 0 cyclobutene Followed by Quenching at -196 . e . - 0 e e e 108 15. Mass Spectrum of the Products of Co2 yrolysis of CIT with Methyl Propiolate at 380. e . e a . .. 109 16. Mass Spectrum of the Products of Copyrolysis of0 CIT with Dimethyl Acetylenedicarboxylate at 380 e . e . e . e 110 0 17. Mass Spectrum of C H 0 at -100 from the Copyrolysis of CI; &it%Oxygen Followed by Quenchingto-196 . e . a . e . a e e e e . e 111 18. Mass Spctrum of C4H402 and Unpyrolyzed CIT at -60 from the Copyrolysis of CIT with Oxygen 112 Followed by Quenching at -196' . e . e . a . e . 0 19. Mass Spectrum of C02 at -140 fromo~ePyrolysis of CIT Followed by Quenching at -196 . e . ,, . 113 0 20. Mass Spectrum of C H6 and C H4 at -115 fromothe Pyrolysis of CIT Fofiowed by $uenching at -196 e e . e e e . 114 21. Mass Spectrum of C H C H and C4H at -100' from the Pyrolysis c!f &I'#ol?owed by duenching 0 at-196.. *. e *. e.. -.. D.. e (I 115 22. Mass Spectrum of C H at -90' from the Pyrolysis 6 of CIT Followed by duenching at -196' e . e . e . e . 116 23, Mass Spectrum of C H8 and C H6 at -80' from bhe Pyrolysis of CIT Fohowed by buenching at -196. e . 117 24. Ionization Efficiency Data for Cis-3,4-dichlorocyclo-- butene.... ..... ....O......O......ll$ 25. Ionization Efficiency Data for Butatriene e . e e . a . e e e 119 26. Ionization Efficiency Data for Vinylacetylene e e . a e e e 120 ix LIST OF ILLUSTRATION§ (Continued) Figure Page 27. Ionization Efficiency Data for Condensed 0 C H at-100 fromPyrolysisof CIT. 121 44 ............. 28. Ionization Efficiency Data for Condensed 0 C H at -70 fromPyrolysis of CIT e e e e e e e 122 88 . + 29. Ionization+ Efficiency Data for C H and C H from Cis-3,4-dichlorocyc o utene 123 22 - 4% ............ + IoniTation Efficiency Data for C H and 30. 4 C H from 124 42 Cis-3,4-dichlorocyclo&utene- ............ 31. hfrared Spectrum of the Reaction Mixture of Dimethyl Acetylenedicarboxylate and Condensed C H from the Pyrolysis of CIT 125 44 ........... 32. Infrared Spectrum of the Mixture of CIT and Dimethyl Acetylenedicarboxylate after 1/2 hr of Heatingat 900 .................... 126 33. Infrared Spectrum of Authentic Dimethyl 1,2-Benzenedicarboxylate. ..................127 34. Infrared Spectrum of Cyclobutadiene- irontricarbonyl. ....................... 128 35. Infrared Spectrum of -Cis-3,4- dichlorocyclobutene. .................... 129 X SUMMARY Cyclobutadiene is the simplest conjugated cyclic polyene which has still eluded the researcher in all attempts at unequivocal synthesis.