University of Windsor Scholarship at UWindsor Electronic Theses and Dissertations Theses, Dissertations, and Major Papers 1-1-1964 A study of the decomposition of some aromatic diazonium hexafluorophosphate salts. William A. Redmond University of Windsor Follow this and additional works at: https://scholar.uwindsor.ca/etd Recommended Citation Redmond, William A., "A study of the decomposition of some aromatic diazonium hexafluorophosphate salts." (1964). Electronic Theses and Dissertations. 6038. https://scholar.uwindsor.ca/etd/6038 This online database contains the full-text of PhD dissertations and Masters’ theses of University of Windsor students from 1954 forward. These documents are made available for personal study and research purposes only, in accordance with the Canadian Copyright Act and the Creative Commons license—CC BY-NC-ND (Attribution, Non-Commercial, No Derivative Works). Under this license, works must always be attributed to the copyright holder (original author), cannot be used for any commercial purposes, and may not be altered. Any other use would require the permission of the copyright holder. Students may inquire about withdrawing their dissertation and/or thesis from this database. For additional inquiries, please contact the repository administrator via email ([email protected]) or by telephone at 519-253-3000ext. 3208. A STUDY OF THE DECOMPOSITION OF SOME AROMATIC DIAZONIUM HEXAFLUOROPHOSPHATE SALTS BY WILLIAM A. REDMOND A Thesis Submitted to the Faculty of Graduate Studies through' the Department of Chemistry in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy at the University of Windsor Windsor, Ontario 1964 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. UMI Number: DC52601 INFORMATION TO USERS The quality of this reproduction is dependent upon the quality of the copy submitted. Broken or indistinct print, colored or poor quality illustrations and photographs, print bleed-through, substandard margins, and improper alignment can adversely affect reproduction. In the unlikely event that the author did not send a complete manuscript and there are missing pages, these will be noted. Also, if unauthorized copyright material had to be removed, a note will indicate the deletion. UMI ® UMI Microform DC52601 Copyright 2008 by ProQuest LLC. All rights reserved. This microform edition is protected against unauthorized copying under Title 17, United States Code. ProQuest LLC 789 E. Eisenhower Parkway PO Box 1346 Ann Arbor, Ml 48106-1346 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Approved 8 0 9 9 ? Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ABSTRACT In order to open new routes to tlie synthesis of arom­ atic fluorides many modifications based on the classical Schiemann Reaction have appeared in the literature in the last fifteen years. These methods are discussed and a new modification is presented in this work. The substitution of hexafluorophosphoric acid for fluoboric acid in the Schiemann Reaction was found to lead in almost every case to increased yields of fluoroaromatic. A quite marked im­ provement was noted in the preparation of ortho and para- fluorobenzoic acids and in the synthesis of o-bromofluoro- benzene. A comparison of the yields obtained by the hexa- fluorophosphate method to those obtained via the normal Schiemann Reaction is included. In the course of work on the preparation of arylfluo- rides a new method for the reduction of diazonium compounds was discovered. Tetramethylurea was found to reduce these compounds. Its use has several advantages over the standard methods. The reaction is spontaneous, simple to perform, and one of the few reductions of diazonium compounds that can be carried out in non-aqueous media. Greatly increased yields of reduction product are obtained from ortho and para-aminobenzoic acids over the usual deamination proce­ dures by this method. ii Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. iii A new compound, o-methylphenoxytetramethylamidinium hexafluorophosphate, was isolated from the attempted reduc­ tion of o-toluenediazonium hexafluorophosphate in tetra- methylurea. The structure of this compound was proved by elemental analysis and hydrolysis to o-cresol and dimethyl- amine. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ACKNOY/LEDGEMENTS I wish to acknowledge, with thanks, the direction and encouragement given me by Dr. K.G. Rutherford during the course of this work. Thanks are also due the Ozark-Mahoning Co. of Tulsa, Oklahoma for generous supplies of hexafluorophosphoric acid and other chemicals. Special thanks are accorded Dr. R.J. Thibert for. his generous assistance in the writing of this thesis and for his helpful advice over the years. iv Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. TABLE OF CONTENTS Page ABSTRACT .......... ii ACKNOWLEDGEMENTS .............. ........ iv Chapter 1. INTRODUCTION . ............ 1 Replacement of an Aromatic Amino Group with Fluorine ....................... 1 Replacememt of an Aromatic Amino Group with Hydrogen ................ 33 II. DISCUSSION OP EXPERIMENTAL RESULTS .... 41 The Preparation of Arylfluorides ... 41 The Reduction of Diazonium Hexafluoro­ phosphate s in Tetramethylurea .... 50 III. EXPERIMENTAL * . ■................ 64 The Preparation of Aryldiazonium Hexafluorophosphates .... ........ 64 The Preparation of Arylfluorides . 73 The Reduction of Aryl am i n e s ........ 82 BIBLIOGRAPHY.............. 90 VITA AUCTORIS .............. 96 v Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. LIST OP TABLES Table Page 1. A Comparison of the Use of Pluosilicate versus Pluoborate in the Schiemann Reaction ..... 12 2. The Decomposition of Diazonium Hexafluorophos- phates in the Schiemann Reaction . ...... 14 3. Yields of Diazonium Pluoborates and Arylfluor­ ides .............. 19 4* Hexafluorophosphoric acid versus Pluoboric Acid in the Schiemann Reaction.............. 47 5. A Comparison of Yields of Reduction Product via Common Deamination Procedures .......... 53 vi Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. LIST OP ILLUSTRATIONS Pigure Page 1. The Schiemann Reaction ..................... 3 2. Mechanisms of Decompositions of Aryldiazonium Pluoborates ...... ..................... 6 3* Selective Deamination of an Aromatic Amino Group . • • ........ .............. .. 36 4. Relative Amounts of Protonated Porms of p- Aminobenzylamine ..... ............ .. 38 5. Preparation of 4-Trimethylammonium-2,6-di- chlorobenzenediazonium Pluoborate Chloride . 40 6. Preparation of Arylfluorides via the Diazon­ ium Hexafluorophosphate Method ....... 42 7. Reaction of 2,4,6-Trichlorobenzenediazonium Pluoborate with 2-Phenyl-l,3-di::~elare . 52 8.. Reduction of 4-Trimethylammonium-2,6-dichlor- obenzenediazonium Pluoborate Chloride with Substituted Dioxolanes ..................... 55 9. Free Radical Reduction of 4-Trimethylammonium- 2 ,6-dichlorobenzenediazonium Pluoborate Chlor­ ide ...................... 57 10. Abstraction of a Proton from the Solvent . 58 11. Formation of a Salt with the Solvent .... 58 12. Reaction with Hexafluorophosphate Anion . 59 13* Reduction of 4-Trimethylammonium-2,6-dichloro- benzenediazonium Pluoborate Chloride with Tri- methyl amine .......................... 59 14. o-Methylphenoxytetramethylamidinium Hexafluo­ rophosphate .................. 61 15. Free Radical Breakdown of Aryldiazonium Hexa­ fluorophosphate .......... 62 16. Tetramethylthiouronium Pluoborate .......... 63 vii Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. A Study of the Decomposition of Some Aromatic Diazonium Hexafluorophosphate Salts CHAPTER I IITRODUCTION 1* The Replacement of an Aromatic Amino Group by Fluorine. Aryldiazonium salts are useful intermediates in the preparation of several classes of organic compounds. Such salts are precursors in the following synthetic procedures: a) The preparation of phenols by the hydrolysis of a diazonium salt. b) The preparation of aryliodides, bromides, chlorides, nitriles and thiocyanates by the Sandmeyer Reaction. c) The replacement of the diazonium group by -SH, and -SCH2C00H, 1 2 d) The preparation of nitroaromatics. ’ e) The introduction of arsonic or stibonic acid groups by the Bart Reaction. f) The preparation of fluoroaromatics by the Schiemann Reaction. 1 E.B. Starkey, J. Am. Chem. Soc., 5 9 , 1479 (1937). 2 H.H. Hodgson and E. Marsden, J. Chem. Soc., 22 (1944). 1 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 2 g) The preparation of arylphosphonic or diarylphos- 3 phinic acids. h) The preparation of aromatic compounds of mercury,^ *5 6 7 8 tin, lead, bismuth, and antimony. i) The replacement of the diazonium group by hydrogen 5) Aryl coupling reactions - the Bachmann-Gomberg Reaction. k) Arylation reactions - Meerwein Arylation. 1) The preparation of azo compounds by coupling with phenols and aromatic amines. q m) The preparation of anilides. n) The preparation of organo-thallium compounds. 3 G.Q. Doak and L.D. Preedman, J. Am. Chem. Soc., 73. 5658 (1951). 4 A.N.•Nesmeyanov, Ber., 62, 1010