Abnormal Reactions of Fürfuryl Chloride And

ABNORMAL REACTIONS OF FÜRFURYL CHLORIDE AND RELATED COMPOUNDS DISSERTATION Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of the Ohio State University By Calvin J. Benning, B.Sc. The Ohio State University 1953 Approved by: ' "Adviser ACKNOWLEDGEMENT The author wishes to express his deepest thank.s to Dr. Christopher L.Wilson for the continuous help and en couragement he has given throughout the entire course of this investigation. The author is also indebted to the Cincinnati! Chem ical Co. for the fellowship grant which was available during the completion of the major portion of this work. The author also wishes to thank the Quaker Oats Co. for their fellowship grant, which was essential to the final completion of this work. il TABLE OF CONTENTS Page Introduction 1 Statement of Problem 3 Discussion of Results 3 Experimental: Preparation of Furfuryl Chloride 8 Reaction of Furfuryl Chloride with Sodium Me- thoxide in Anhydrous Methanol 10 Attempted Separation of Furfuryl Chloride/So dium Methoxide Reaction Products 11 Preparation of W-6 Raney Nickel 12 Reduction and Separation of the Products from Furfuryl Chloride/Sodium Methoxide Reaction 13 Index of Refraction Method of Analyzing Pro ducts of W-6 Reduction and Distillation 15 Beckman Infrared Absorption Method of Analysis of Mixture 16 Reduction of Furfuryl Alcohol with W-6 Catalyst 17 Preparation of Tetrahydrofurfuryl Methyl Ether 18 Preparation of Furfuryl Methyl Ether 20 W-6 Reduction of Furfuryl Methyl Ether 21 Preparation of N-Dimethyl Levulinamide 22 LiAlH^ Reduction of N-Dimethyl Levulinamide 23 Preparation of 5-methoxy-2methyltetrahydrofuran 25 Preparation of Derivative of 5 methoxy-2 methyl- 26 tetrahydrofuran Molecular Weight Determination of 5-methoxy-2meth- yltetrehydrofuran 26 ill TABLE OF CONTENTS(cont»d) Page OzonaLysis of Furfuryl Chloride/Sodium Methoxide Reaction Product Mixture 27 Iodoform Reaction of Furfuryl Chloride/Sodium Methoxide Reaction Product îUxture 29 Infrared Spectrograms of Pure Furfuryl Methyl Ether and Abnormal Product 29 Ultra-Violet Absorption Curves of Furfuryl Meth yl Ether, 2-methylfuran & Reaction Product Mixture 30 Derivatives Obtained from Methanolic HCl Solution of 2,4 dinitrophenylhydrazine 30 Attempted Synthesis of 5-methoxy-2-methylfuran gg Reaction of Anhydrous Methanolic HCl Solution with Furfuryl Chloride/Sodium Methoxide Products 31 Summary 39 Appendix 40 Bibliography 57 Autobiography 59 1 ABNORMAL REACTIONS OF FURFURYL CHLORIDE AND RELATED COMPOUNDS Introduction Furfuryl chloride is a very unstable compound and its reactions have not been extensively stuaied. Among the first to attempt the preparation of furfuryl chloride were Von Braun and Kohler. These authors attempted^^ the Von Braun reaction of the benzoyl derivative of furfuryl meth yl amine with phosphorous pentachloride. This resulted in complete résinification of the entire reaction mixture. Later, Gilman and Vernon^l attempted to prepare furfuryl chloride by treatment of an ethereal solution of furfuryl alcohol with thionyl chloride at low temperature and also by passing dry hydrogen chloride into an ethereal solution containing calcium carbide as a dehydrating agent. The chloride v/as never isolated. If, however, the ethereal so lution was treated with sodium ethoxide Gilman claimed the formation of 5-10% ether. W.R.Kirner^ was reallythe first to isolate furfuryl chloride in fair yields (63%). His method consisted of reacting furfuryl alcohol with thionyl chloride in the presence of excess pyridine. All flasks used in the distillation, were previously washed with so dium hydroxide solution. T.Reichstein^ improved this pre paration further by using a pentane ether mixture for the solvent and running the reaction at the boiling point of ether. The yield rose to about 75%. The method used in this work is a variation of the Kirner and Reichstein method. The«abnormal» or «anomalous» reactions of furfuryl 2 chloride were first studied by Reichstein . He obtained mostly 5-methyl furoic acid and a small amount of furyl- acetic acid by hydrolysis of the reaction products ob tained by the reaction of furfuryl chloride and strong a- queous sodium cyanide. Reichstein explains the reaction according to Figure 2. Further work by hirn^^ and his co-workers confirmed this proposal but they did not es tablish the existance of Figure 2-IV, For example, 1-fur- ylethyl chloride VII under similar circumstances also gave the «abnormal acid» VIII. k c n H-zO *CH NlTRtUE.6 \CH% ---5ZEL 7 V lit Scott and Johnson' studied the mechanism of the re action, They reported that the hydrogen in the 5 position was essential to rearrangement because 5-methyl-2-furfuryl- chloride gave no «abnormal» product. About the same time Reichstein^^ reported identical findings, Scott and Johnson^^ synthesized 5-chloro-2-metiiylfuran which is isomeric with furfuryl chloride, A study of the properties showed that rearrangement prior to metathesis was impossible. 3 This reaction of furfuryl chloride appears to be an example of a bimolecular type displacement reaction with rearrangement (Winstein^^ et.al,). Only two other such cases are established. One is V/instein and Young demon stration that cx methyl and cx ethyl-allyl chloride react with sodioraalonic ester to give 10 and 22% respectively "abnormal" product. The other is Hughes, de la Mare, and Vernon^® claim allylidene chloride reacts abnormally, A kinetic study (Wilson and Eland-English'^ of the furfuryl chloride-cyanide reaction failed, owing to the non-homoge neity of the reactants. Instead the reaction with sodium methoxide was studied. The results showed strictly second order kinetics, first order with respect to methoxide ion and first order in fur furyl chloride concentration. The ratio of abnormal ether to furfuryl methyl ether, determined by precipitation of derivatives was 40;60 and nearly independent of temperature between 0°C and 40°C, Statement of Problem The present work v/as concerned mainly with an estab lishment of the structure of the reaction products of the furfuryl chloride/ sodium methoxide reaction and an eluci dation of the mechanism of the formation of levulinic acid derivatives. Discussion of Results (Figure 1) The reaction of furfuryl chloride with sodium meth oxide yielded a mixture of products B.P, 134-126^C.(IR 2,5j the infrared spectrograms are in the Appendix). Attempts to resolve the above mixture by distillation, crystalliza tion at lovf temperatures and formation of maleic anhydride adducts were unsuccessful. Analysis of the mixture showed the mixture to have the formula C^^EgOg, and to absorb two moles of hydrogen per mole of mixture. The reduced mix ture yielded the expected tetrahydro-furfuryl metlQ''l ether and theabnormal acetal, (IR 4,5). The reduced mixture was analysed by infrared absorption spectra and index of refraction curves. The calibration data were obtained on mixtures of the pure compounds synthesized by reliable meth ods. The methods showed there was approximately 31-36 per cent abnormal product and 64-69 percent normal. The Structure of the Normal Ether (Figure 1,11) The identity of furfuryl mettiyl ether was established tlirough its tetrahydro derivative. The reaction product, tetrahydro furfuryl methyl ether was identified by two inde pendent synthesis; (1) by catalytic reduction of pure fur furyl methyl ether with Yf-6 Raney nickel, (2) by converting the tetrahydro furfuryl alcohol to its ether with dimethyl sulfate. The saturated reaction product gave the same boil ing point, index of refraction, density, carbon and hydrogen analysis and identical infrared spectrograms (IR 5,6) as the authentic tetrahydrofurfuryl methyl ether. The Structure of the Abnormal Product (Figure 1,111) The structure of the abnormal acetal, obtained from the catalytic reduction of the original reaction mixture, was established by tv/o methods. First, the abnormal ace tal gave a yellow DWPH which gave no melting point depres sion with the DHPH of authentic ^-hydroxyvaleraldehyde thereby indicating the structure to be 5-methoxy-2-metliy 1 - tetrahydrofuran. The X-ray powder photographs of the tv/o DNPH’s were compared and they proved to be identical. The structure of the saturated abnormal product was further es tablished by synthesizing 5-methoxy -2-me tliy It etrahy dr of ur an from authentic Y-hydroxyvaleraldehyde. The boiling point, index of refraction, dinitrophenylhydrazone derivatives, and infrared spectrograms (IR 4,7) være the same. The abnormal ether must therefore be one of the follow ing. H^CO A b c Structure A is the most likely for the following reasons; 1. The infrared spectra of the reaction mixture shows absorption in the conjugated carbon double bond region (IR 2,3,8) while the ultraviolet spectra indicates a non-fur an conjugation at 2,450A (UY 1). 6 2. The reaction between 5-iodo-2-metliylfiiran and sodium methoxide at elevated temperature gave traces of 5-methoxy-2-methylfuran detected by a DNPH derivative. The only derivative obtained was that of metiiyl levulinate which would be expected from structure B. The react ion product mixture gave three derivatives, of v/hich a small proportion was methyl levulinate. Structure B and G would be expected to give only the derivative of methyl levul- ina.te. Therefore, from the derivatives obtained, struc ture A is again favored. 5. The reaction product mixture gave an iodoform test, while pure furfuryl mettiyl ether, and 2-metliylfuran did not. This is an indication of structure A or C but not B. The mechanism of iodoform formation may be pic tured as happening according to the mechanism in Figure 4. 4. Structure A is also favored since pure furfuryl methyl ether gave the three derivatives in the same pro portion but slower than the reaction product mixture. 2,5- Dlmethoxy-2,5-dihydro-2-methylfuran gave the same deriva tive also in the same proportions but at a slightly faster rate than the reaction mixture. This can be explained by rearrangement' of the furfuryl carbonium ion,(Figure 5).

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