70 - 14,004 DAUERNHEIM, Lauren William, 1938- SYNTHESIS OF ALKYLATED BENZENES AND LITHIUM ALUMINUM HYDRIDE REDUCTION OF 1,3-DIHALIDES. The Ohio State University, Ph.D. , 1969 Chemistry, organic University Microfilms, Inc., Ann Arbor, Michigan THIS DISSERTATION HAS BEEN MICROFILMED EXACTLY AS RECEIVED SYNTHESIS OP ALKYLATED BENZENES AND LITHIUM ALUMINUM HYDRIDE REDUCTION OF 1,3-DIHALIDES DISSERTATION Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University By Lauren William Dauernheim, B.A., M.A ****** The Ohio State University 1969 Approved by Adviser Department of Chemistry ACKNOWLEDGMENT I am thankful for having had the opportunity to work under Dr. Melvin S. Newman. His guidance and support made fulfillment of this research possible. ii VITA February 16, 1938 , ....... Born, St. Louis, Missouri 1960 ...................... A.B., Washington University St. Louis, Missouri 1963 M.A., University of Arizona Tucson, Arizona iii TABLE OF CONTENTS Page ACKNOWLEDGMENTS ................................... ii VITA ............................................. iii LIST OF TABLES.................................... v LIST OF FIGURES ................................... vi LIST OF C H A R T S ......... vii PART I. SYNTHETIC ROUTES TO CERTAIN ALKYLATED BENZENES INTRODUCTION ................................ 1 SYNTHETIC ROUTES TO ALKYLATED NEOPENTYLBENZENES . 12 SYNTHETIC ROUTES TO ALKYLATED ETHYLBENZENES ........ 20 PART II. SYNTHESIS AND LITHIUM ALUMINUM HYDRIDE REDUCTION OF CERTAIN 1,3-DIHALOPROPANES INTRODUCTION ..................................... 23 SYNTHESIS OF 2-BENZYL-2-METHYL-1,3-DIHALOPROPANES . 25 SYNTHESIS OF 2-BENZYL-l,3-DIHALOPROPANES .......... 27 DISCUSSION OF THE NMR SPECTRA OF 2-BENZYL-l,3- DIHALOPROPANES ................................. 29 RESULTS AND CONCLUSIONS FROM THE LITHIUM ALUMINUM HYDRIDE REDUCTION OF CERTAIN 1,3-DIHALOPROPANES . 33 EXPERIMENTAL OF PART I ............... 43 EXPERIMENTAL OF PART I I ............................ 63 iv LIST OF TABLES Table Page I,. Reduction of Certain 2-Benzyl-l,3-dihalides with Lithium Aluminum Hydride .............. 79 II. Product Distribution from LAH Reduction of 2-Benzyl-2-methyl-l,3-dichloropropane .... 83 III. Product Distribution from LAH Reduction of ! 2-benzyl-2-methyl-l,3-dibromopropane .... 84 IV. Product Distribution from Competitive Reduction of 2-Benzyl-2-methyl-l,3- diiodopropane and 2-Benzyl-2-methyl-l- iodopropane................................ 86 V. Product Distribution on Reduction of 2-Benzyl- 1,3-diiodopropane .......................... 87 VI. Product Distribution on Competitive Reduction of 2-Benzyl-2-methyl-l,3-diiodopropane and 2-Benzyl-l,3-diiodopropane ................ 89 v LIST OF FIGURES Figures Page 1. Structures of Silver and Halogen IT -Complexes............................... 2 2. Partially Hindered Faces in O-Dineopentyl- tetramethylbenzene . ...................... 5 3. View of Angular Dependence on Hyperconjuga­ tion ............................. 9 4. Some Possible Rotomers in Alkyl Benzenes . 10 5. Possible Rotomers of 2-Benzyl-l,3- dihalopropanes ........................... 30 6. Partial NMR Spectrum of 2-benzyl-l,3- dibromopropane ............. 30 7. Partial NMR Spectrum of 2-benzyl-l,3- dibromopropane at 90° C ........... 31 8. Partial NMR Spectrum of 2-benzyl-l,3- dichloropropane ............................ 31 9. Partial NMR Spectrum of 2-benzyl-l,3- dichloropropane at 100° C .................. 32 10. Partial NMR Spectrum of 2-benzyl-l,3- diiodopropane .............................. 32 11. Partial NMR Spectrum of Benzylcyclopropane . 76 12. Partial NMR Spectrum of 2-Benzyl-l- iodopropane ......... .............. 77 vi LIST OF CHARTS Chart Page I. Synthesis of 1,3,5-Trimethyl-2,4- dineopentylbenzene......... , . 13 II. Synthesis of 1,2,4,5-Tetramethyl-3- neopentylbenzene .......................... 16 III. Synthesis of l,2,3,5-Tetrarnethyl-4- neopentylbenzene....................... 18 IV. Attempted Synthesis of 1,2,5-Trimethyl-3,4- dineopentylbenzene ........................ 19 V. Partial Synthesis of Ethyl-2,3,4,6- tetramethylbenzene ................ .... 21 VI. Synthesis of 2-Benzyl-2-methyl-l,3- dihalopropanes ..... ........ ..... 26 VII. Synthesis of 2-Benzyl-l,3-dihalopropanes . 28 VIII. Reaction Pathways in LAH Reduction of Certain 1,3 Dihalides .................... 33 vii LIST OF CHARTS Chart Page I. Synthesis of l,3,5-Trimethyl-2,4- dineopentylbenzene......... 13 II. Synthesis of l,2,4,5-Tetramethyl-3- neopentylbenzene .......................... 16 III. Synthesis of l,2,3,5-Tetramethyl-4- neopentylbenzene .......................... 18 IV. Attempted Synthesis of l,2,5-Trimethyl-3,4- dineopentylbenzene ........................ 19 V. Partial Synthesis of Ethyl-2,3,4,6- tetramethylbenzene ........................ 21 VI. Synthesis of 2-Benzyl-2-methyl-l,3- dihalopropanes ........................... 26 VII.Synthesis of 2-Benzyl-l,3-dihalopropanes . 28 VIII. Reaction Pathways in LAH Reduction of Certain 1,3 Dihalides .................... 33 vii PART I ^Synthetic Routes to Certain Alkylated Benzenes -I. Introduction Statement of Problem Synthetic routes to 1,3,5-trimethyl-2,4-dineopentyl- benzene and l,2,5-trimethyl-3,4-dineopentylbenzene were explored. These compounds might give information on the participation of hypothetical Tf-complexes in certain aromatic nitration and bromination reactions. The synthesis of l,2,4,5-tetramethyl-3-neopentylbenzene, l,2,3,5-tetramethyl-4-neopentylbenzene, and the partial syn­ thesis of l,2,4,5-tetramethyl-3-ethylbenzene and 1,2,3,5- tetramethyl-4-ethylbenzene was undertaken. In future studies, these compounds might yield information on the importance of steric restrictions on alkyl hyperconjugation in aromatic bromination. Discussion of TT-Complexes in Aromatic Substitution The geometries of the TT-complexes between the silver ion and benzene and the bromine molecule and benzene have been determined by X-ray methods. Infrared and Raman absorption, dipole moment, and charge transfer absorption data also relate to the geometry of halogen TT-complexes with benzene. Studies of the X-ray crystal structure of the TT-complex between silver perchlorate and benzene showed the silver ion associated with four carbon atoms but not with the six-fold axis of symmetry in benzene. ' The 1. R. E. Rundle and J. H. Goring, J. Am. Chem. Soc., 72, 5337 (1950) . 2. H. G. Smith and R. E. Rundle, J. Am. Chem. Soc., 80, 5075 (1958). silver ion is associated with two carbon atoms on a benzene ring above it and with two carbon atoms on a ring below it as shown in figure 1. In a theoretical treatment the same structure was concluded for the silver complex with benzene.^ 3. R. S. Mulliken, J. Am. Chem. Soc., 74, 881 (1952). Figure 1 Structures of Silver and Halogen Tf-Complexes X-ray studies on crystalline 1:1 adducts of benzene with bromine and chlorine show that the components of the 4 5 TT -complex have the axial model geometry (figure 1). ' An 4 . O. Hassel and K. O. Stromme, Acta Chem. Scand.r 12, 1146 (1958). 5. O. Hassel and K. 0. Stromme, Acta Chem. Scand., 13, 1781 (1959). “ analysis of infrared and Raman active bands in the benzene- bromine complex and benzene-iodine Tf-complex supports an axial model which places the bromine and iodine molecules coincident with the benzene six-fold axis.® A study of the 6. E. E. Ferguson, J. Chem. Phys., 25, 577 (1956). infrared spectrum of the hexadeuterobenzene-iodine complex leads to the same conclusion. A dipole moment study and 7. E. E. Ferguson, Spectrochim. Acta, 1£, 123 (1957). calculations corresponding to the charge-transfer absorption maximum for the benzene - iodine complex are also in agree­ ment with the axial model,® 8. K. Fukui, A, Inamura, T. Yonezawa, and C. Nagata, Bull. Chem. Soc. Japan, 35, 33 (1962). Theoretical calculations support a less symmetrical Q model for the iodine - benzene complex. This possibility 9« R. S. Mulliken, J. Chem. Phys., 23^, 397 (1955). can not be completely ruled out in solutions, although experimental evidence favors the axial model. Work in this laboratory has shown that hindrance near the six-fold axis of symmetry of the pTT orbitals of o-dineopentyltetramethylbenzene can effect the equilibrium constant of the tetracyanoethylene Tf-complex.*® The ortho, 10. M. S. Newman, J. R. Le Blanc, H. A. Karnes, and G. Axelrad, J. Am. Chem. Soc., ££, 868 (1964). meta, and para isomers of tetramethyldineopentylbenzene were prepared. Molecular models indicated that only o-dineopentyl- tetramethylbenzene had a steric hindrance near the six-fold axis of symmetry of the pTT orbitals on both sides of the aromatic plane. This hindrance is evident by the lack of TT-complex formation in the ortho isomer with tetracyano­ ethylene, while the corresponding meta and para isomers form deep colored complexes with this reagent.*® Figure 2 Partially Hindered Faces in O-Dineopentyl- tetramethylbenzene The order of IT donor strength of these three isomeric tetramethyldineopentylbenzenes with respect to iodine was found to be p> m> o. The contrast between the ortho and the meta and para isomers in TT-complex formation with iodine was not dramatic as with tetracyanoethylene.*^ 11. R. E, Lovins, L. J. Andrews, and R. M. Keefer, J. Phys. Chem., 68, 2553 (1964). The preparation of the similar l,2,5-trimethyl-3,4- dineopentylbenzene and l,3,5-trimethyl-2,4-dineopentylbenzene was undertaken to gain information on U-complexes in certain aromatic nitration and bromination reactions. A major