THE SYNTHESIS OF SOME 1,2-Dn!ETHYL-3-;JZYlEENZQ;ES Aim l,2,3-TRIMirrHYL-li-ALKYLBENZENES FROM 2-ALKÏLFURAKS AND 2-METHYL-5-AIi'DfLFURANS DISSERTATION Presented in Partial Fulfillment of the Requirements lo: the Degree of Doctor of Philosophy in the Graduate School of The Ohio State University By EARL PHILLIP MOORE, JR., B. S., W. S. The Ohio State University 1S?57 Approved by: Adviser Department r.f Chemistrj' ACKNOWLEDGiaæNT The author wishes to express his sincere appreciation to Professor Cecil E. Boord for his advice and counsel* Gratitude also is expressed to Dr. Kenneth W. Greenlee for his continued interest and guidance. Acknowledgement is made to Professor Boord and Dr. Greenlee for their cooperation in making available to the writer the equipment, materials and facilities of the American Petroleum Institute Research Project h$» The financial support of this work by the General Motors Corporation, E.I. du Pont de Nemours and Company, and the American Petroleum Institute Research Project LS is gratefully acknowledged. Table of Contents Page I. Introduction, 1 II. Literature Survey.......... ..... ..................... 3 A. l,2,3"Triinethylbenzene (Heraimellitene ) and l|2,3jl4“ Tetramethylbenzene (Prehnitene) from Natural Resources.............................................3 B. 1,2,3“Trimethylbenzene (Hemimellitene) from De­ gradations of Natural Products and their Derivatives & C. 1,2,3jh-Tetramethylbenzene (Prehnitene) from De­ gradations of Natural Products and their Derivatives I4 D. Syntheses of 1,2,3“Trimethylbenzene (Heraimellitene) and l,2,3,U“Tetramethylbenzene (Prehnitene).......... 5 E. The Synthesis of l,2-Diraethyl-3-8thylbenzene .... 10 III. Discussion............ ................................ 11 A. General Scope . 1 1 B. The Production of 2-Alky Ifurans and 2-Methyl- 5-alkylfurans ...... ........................Hi 1. 2-Methylfuran...................................... lU 2. 2-Ethylfuran...................................... Hi 3 « 2-n-Propylfuran.................................. 1 6 U. 2 j ^-Dirae thylfur an « I6 5 » 2-Methyl-^- etbylfuran..............................17 6 . 2-Methyl-^-n-propylfuran ........ .. .... 18 7. 2-Isopropylfuran ................................. 19 8. 2-tert-Butylfuran.............. .......22 C. The Production of 2-FuryIcycloalkanes ........23 1. 2-Furylcyclopropane* ........................23 2. 2-FuryIcyclopentane and 2-FuiyIcyclohexane .... 25 D« The Production of Miscellaneous 2-Substituted Furans 28 1. Furfurylidene Diacetate and Furfuryl Acetate . 28 2. 2-Broraofuran...................................... 28 3 . Tetramethylfuran...................... 29 E. Production of Diels-Alder Adducts of 2-Alkyl- and 2-Methy 1-5-alkylfuran3 ndth Maleic Anhydride......... 29 1, Stereochemical Considerations......................29 2. Preparation of A dducts ............................32 F. The Production of 3-Alkylphthalic Anhydrides and 3-Methy 1-6-alkyIphthalic Anhydrides ............... 3 7 1. General Background........... 37 H i Table of Contents (Continucd) 2. îlydrogen Bromide M e t h o d .........................35 3. Sulfuric Acid Method h2 , ' G. Reduction of 3-Alkyl- and 3-Methy1-6-alkyIphthalic Anliydrideo to Hydrocarbons . ................ 1. General Background . .................. 35 2. Copper Chromite Method ................ 3» Reduction of Anhydrides to Hydrocarbons........ 62 ij. Reduction of Diesters to Hydrocarbons.......... 63 5* Reduction of Esters by Sodium and Methanol in Liquid Ammonia ........ .6^ 6. Preparation of Esters ........... .6& 7, Conclusion .................................... 63 IV* Experimental .....................................6? A* Determination of Physical Properties and Purities cf %rdrooarbon Products .6? 1* Gryoscopie Determinations , , .................. 67 2. Boiling Points .................. ..............cd 3* Refractive Indices .65 li* Densities .......... 69 B. Special Apparatus ...... .................... 69 C. Production of 2-Alkylfurans and 2-Methyl-3-alkyl- furans ............................................. 70 1* 2-Methylfuran ................ 70 2. 2-Ethylfuran...................................71 3* 2-n-Propylfuran ............. .80 ll* 2, B^-Dime thylfur an .............. ..............31 3 . 2-Methyl-3-ethylfursn ................ 32 6. 2-Methyl-3-n-propylfuran .............. SL 7. 2-Isopropylfuran .................. 66 8. 2-tert-Butvlfuran.............................. 95 D. Production of 2-Furylcycloalkanes................... 97 1. 2-Furylcyclopropane * ........................ 97 2. 2-Furylcyclopentane.............. 102 3 . 2-Furylcyc loh ex a n e ............. 109 E. Production of Miscellaneous 2-Substituted Furans. .113 1. Furfurylidene Diacetate........................ 113 2. Furfuryl Acetate ...................... HU 3 . 2-Bromofuran 115 L. Tetramethylfuran ............................ 116 iv Table of Contents (Continued) Page F. Production of Diels-Aider Adducts of 2-Alkyl- furane and 2-Ueth7l-5-alkylfurans 'with Maleic Anhydride 118 G. Production of 3-AlkyIphthalic Anhydrides and 3-Methyl-6-alkylphthaHc Anhydrides.................126 1. Hydrogen Bromide Method .......... « 126 2, Sulfuric Acid Method* 127 3* Other Aromatization Experiments ............ 132 H. Reduction of 3-Alkyl- and 3-Methyl-6-alkylphthalio Anhydrides to Hydrocarbons* •••••••••••• 133 1. Preparation of Phthalate Esters .•••*.•« 133 2« Copper Ghrmiite Method* **** *** *** 136 3* Reaction of Phthallc Anhydrides to Hydrocarbons 139 1;* Reduction of Phthalate Esters to Hydrocarbons * 1U2 V. Summary................................................. IL? VI. Autobiography........ ................................ Index to Tables Table No. Page I Syntheses of 1,2,3“Trimethylbenzene (Hemimellitene) 6 II Syntheses of 1^ 2, 3,li-Tetramethylbenzene ( Prehmitene ) 8 III Physical Properties of Hydrocarbons 9 IV Classes of Substituted Furan-Maleic Anhydride Adducts 35 V Hydrogen Bromide Aromatization Experiments ijl VI Sulfuric Acid Aromatization Experiments hS VII Aromatization Experiments with Various Substituted Furan-Maleic Anhydride Adducts {96% Sulfuric Acid at -15* to -10®) L8 VIII Other Aromatization Experiments 52 IX Elemental Analyses of New Diels-Alder Adducts 1 2 k X Melting Points of Diels-Alder Adducts 125 XI Alkylbenzoic Acids from Aromatization Experimentsl25 XII Elemental Analyses of New Phthalic Anhydrides I30 X m Melting Points of Phthalic Anhydrides I3I XIV Physical Properties of phthalate Esters 136 XV Elanental Analyses of Phthalate Esters I36 XVI Elemental Analyses of Diols 21x3 XVII Physical Properties of Diols lijli XVIII Elemental Analyses of New Hydrocarbons 2lx$ XIX Physical Properties of hydrocarbons 1L6 vi INTRODUCTION In the latter part of the nineteenth century, much interest in pvorslble synthetic routes to 1,2,3"trimethylbenzene (hemiaellitene ) and 1,2,3,h-tetramethylbenzene (prehnitene) was actuated by absorp­ tion spectra studies of the isomeric tri- and tetramethylbenzenes. The above tiro aromatic structures were the last of these isomers to succumb to the efforts of early investigators and indeed, to the present time, continued interest in synthetic approaches to heni- melütene and prehnitene have occupied investigators in the field of organic chemistry. It was not until the advent of World War II, when S.F. Birch and his co-TTorkers began studies of the ultra-violet spectra of the iso­ meric dimethylethylbenzenes, that another l,2-dimethyl-3-alkylbenzene was prepared; their work was published in 191^9. Since then the synthesis of no other member of this class of vicinally substituted baizenes or of the 1,2,3-trimethyl-f4-alkylbenzene class has been re­ ported in the chemical literature. From information obtained from this source regarding the transformation of Diels-Alder adducts of substituted furans and maleic anhydride into aromatic anhydrides through the agency of acid catalysts, possible isomer-free routes to the above aromatic types materialized. The main effort of this research program therefore was in­ vested in determining the best method of aromatizing a number of 2—alkyl- and 2-methyl-^—alkylfuran-maleic anhydride addends and - 1- -2" converting the resulting 3-alkyl- and 3-methyl-6-alkylphthalic anhydrides into hydrocarbons, I'bcistlng procedures for the preparation of the required furan precursors were tailored to enlarged-scale work and new ones were devised when necessary. Also included In this work were nhe preparations of three 2-furyIcycloalkanes (two of them new} and several miscellaneous 2-3ubstituted furans, and the application of the best aromatization method to tlieir adducts* The physical properties of those hydrocarbons which were syn­ thesized were determined in order to aid in future identifications of them. LITERATl'RE SIjJÎV?T 1.2.3-Triinethylbf^nsftno (ngri-Lv.eUi tone ) .ind 1.2,3.^~TetrôJicfchyl- benzene ( Prehnitene ) from Natural ilesources Although both hemimelliter.t; and prehnitene were first prepared in the l800^s, it was not suspected for a good many years afterward that these compounds occurred in the gasoline or naphtha fraction of petroleum and in the low temperature oils removed from coal tar during its destructive distillation. The reason for this oversight can be attributed to the presence of only very small amounts of these vicinally substituted aromatics relative to the quantities of close- boiling isomers, for in X 9 2 h Kruber^ reported that very carefully repeated fractionations of low temperature tar oils ( 190300"F. ) reve"al6d the presence of a compound which