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Proximity Effects. Kinetics, Mechanisms and Reactivity Correlations for the Acidic and Alkaline Hydrolysis of Ortho- Substituted-N-Methylbenzohydroxamic Acids

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Proximity Effects. Kinetics, Mechanisms and Reactivity Correlations for the Acidic and Alkaline Hydrolysis of Ortho- Substituted-N-Methylbenzohydroxamic Acids Western Michigan University ScholarWorks at WMU Dissertations Graduate College 8-1977 Proximity Effects. Kinetics, Mechanisms and Reactivity Correlations for the Acidic and Alkaline Hydrolysis of Ortho- Substituted-N-Methylbenzohydroxamic Acids Irl E. Ward Western Michigan University Follow this and additional works at: https://scholarworks.wmich.edu/dissertations Part of the Organic Chemistry Commons Recommended Citation Ward, Irl E., "Proximity Effects. Kinetics, Mechanisms and Reactivity Correlations for the Acidic and Alkaline Hydrolysis of Ortho-Substituted-N-Methylbenzohydroxamic Acids" (1977). Dissertations. 2789. https://scholarworks.wmich.edu/dissertations/2789 This Dissertation-Open Access is brought to you for free and open access by the Graduate College at ScholarWorks at WMU. It has been accepted for inclusion in Dissertations by an authorized administrator of ScholarWorks at WMU. For more information, please contact [email protected]. PROXIMITY EFFECTS. KINETICS, MECHANISMS AND REACTIVITY CORRELATIONS FOR THE ACIDIC AND ALKALINE HYDROLYSIS OF o r t h q - substituted -n -methylbenzohydroxamic ACIDS by Irl E. Ward A Dissertation Submitted to the Faculty of the Graduate College in partial fulfillment of the Degree of Doctor of Philosophy Western Michigan University Kalamazoo, Michigan August 1977 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. PROXIMITY EFFECTS. KINETICS, MECHANISMS AND REACTIVITY CORRELATIONS FOR THE ACIDIC AND ALKALINE HYDROLYSIS OF ORTHO-SUBSTITUTED-N-METHYLBENZOHYDROXAMIC ACIDS Irl E. Ward, Ph.D. Western Michigan University, 1977 The kinetics, mechanisms and correlations of observed rate data by the Taft-Pavelich equation were studied for the acidic and alkaline hydrolysis of ortho-substituted-N-methylbenzohydroxamic acids. The results of the mechanism study are interpreted in terms of a bi- molecular mechanism for acidic catalysis and as reaction of the hydrox- amic acid conjugate base with water or hydroxide ion for basic catalysis in the catalytic range investigated. Ionic strength effects and specific ion effects are also reported for both catalytic systems. Correlation of the log of the observed rate constants (i.e., log with the Taft substituent parameters a * and Eg was made for various ortho-substituents for both catalytic systems. Correlation of log for acidic hydrolysis was shown to be very good (R = 0.989). The F-test showed the correlation to be significant at the 1% level. For the alkaline hydrolysis, correlation of log kQbg with a* and Eg values was shown to be good (R = 0.928). The F-test showed this correlation to be significant nearly within the 5% level. For both hydrolysis systems, correlation with o* and Eg values together was always better than with o* and Eg values alone. These results lend support to the semi-empirical description of the "Ortho-Effect" proposed by Taft and Pavelich as a first approximation to a quantitative approach, which Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. is of the general form: log k = o * p* + 5Eg + log kQ The results support the descriptions of the steric effect of an ortho­ substituent by Taft and by McCoy and Riecke. Taft states that E s values are good measures of the actual steric effect of an ortho­ substituent, although for those substituents which exhibit direct resonance interaction with the reaction site, there is a resonance contribution to Eg. McCoy and Riecke separate Eg into independent contributions from primary and secondary steric and resonance effects only. The results of this work also support the qualitative conclusions of McCoy and Riecke that the susceptibility of a reaction system to steric effects by ortho-substituents varies with the structural skeleton of the system. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ACKNOWLEDGEMENTS I would like to thank Dr. Don Berndt for his valuable suggestions and assistance in the preparation of this work. I am also grateful to the chemistry department and graduate college of W.M.U. for the Graduate College Associateship appointment which allowed me to devote full time to the project and for my earlier appointment to a graduate teaching assistantship. My special thanks go to my wife, Sue, for her infinite patience and great help in the writing of this dissertation. Irl Eugene Ward ii Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. INFORMATION TO USERS This material was produced from a microfilm copy of the original document. While the most advanced technological means to photograph and reproduce this document have been used, the quality is heavily dependent upon the quality of the original submitted. The following explanation of techniques is provided to help you understand markings or patterns which may appear on this reproduction. 1.The sign or "target" for pages apparently lacking from the document photographed is "Missing Page(s)". If it was possible to obtain the missing page(s) or section, they are spliced into the film along with adjacent pages. This may have necessitated cutting thru an image and duplicating adjacent pages to insure you complete continuity. 2. When an image on the film is obliterated with a large round black mark, it is an indication that the photographer suspected that the copy may have moved during exposure and thus cause a blurred image. You will find a good image of the page in the adjacent frame. 3. When a map, drawing or chart, etc., was part of the material being photographed the photographer followed a definite method in "sectioning" the material. It is customary to begin photoing at the upper left hand corner of a large sheet and to continue photoing from left to right in equal sections with a small overlap. If necessary, sectioning is continued again - beginning below the first row and continuing on until complete. 4. The majority of users indicate that the textual content is of greatest value, however, a somewhat higher quality reproduction could be made from "photographs" if essential to the understanding of the dissertation. Silver prints of "photographs" may be ordered at additional charge by writing the Order Department, giving the catalog number, title, author and specific pages you wish reproduced. 5. PLEASE NOTE: Some pages may have indistinct print. Filmed as received. University Microfilms International 300 North Zeeb Road Ann Arbor, Michigan 48106 USA St. John’s Road, Tyler's Green High Wycombe, Bucks, England HP10 8HR Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. WARD, Irl E., Jr., 1949- PROXIMITY EFFECTS. KINETICS, MECHANISMS, AND REACTIVITY CORRELATIONS FOR THE ACIDIC AND ALKALINE HYDROLYSIS OF fiRTHfl-SUB- STITUTED-N.-METHYLBENZOHYDROXAMIC ACIDS. Western Michigan University, Ph.D., 1977 Chemistry, organic Xerox University Microfilms, Ann Arbor, Michigan 48io6 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. TABLE OF CONTENTS CHAPTER PAGE I INTRODUCTION............................................... 1 Substituent Constants and the Ortho-Effect .......... I Mechanism Background.................................... 20 Purp o s e .............................. 32 II EXPERIMENTAL METHOD, APPARATUS AND SYNTHESES.......... 35 Preparation of Ortho-Substituted Benzoyl Chlorides.. 35 Preparation of Ortho-Substituted-N-Methylbenzohy- droxamic Acids ........................................ 36 Preparation of Standard Hydrolysis Solvents......... 39 Preparation of Standard Ferric Chloride Solutions... 40 Preparation of Reaction Solutions and Kinetics Procedure.............................................. 41 The Constant Temperature Oil Bath ..................... 48 Determination of Rate Constants....................... 48 Reaction Product Analysis of Selected Hydroxamic ' Acids in Alkaline Solution .......................... 50 III RESULTS AND DISCUSSION.................................... 53 Acidic Hydrolysis Mechanism................ 53 Alkaline Hydrolysis Mechanism .................. 57 Proximity Effects for Acidic Hydrolysis............ 62 Proximity Effects for Alkaline Hydrolysis ..... 73 iy BIBLIOGRAPHY................................................ 80 V V I T A ........................... 83 iii Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. LIST OF TABLES TABLE PAGE I Yields of Prepared Ortho-Substituted Benzoyl Chlorides............................................. 36 II Yields of Prepared Ortho-Substituted-N-Methyl- benzohydroxamic Acids ............................... 38 III Elemental Analysis of Prepared Ortho-Substituted- N-Methylbenzohydroxamic Acids ..................... 39 IV Rate Constants for Base Catalyzed Hydrolysis ofQ 2-Chloro-N-Methylbenzohydroxamic Acid at 90.0 C 43 V Rate Constants for Acid Catalyzed Hydrolysis of 2-Methyl-N-Methylbenzohydroxamic Acid ........... 44 VI Rate Constants for Hydrolysis of Ortho-Substituted- N-Methylbenzohydroxamic Acids in 0.764M HC1 at 90.0°C............................................. 45 VII Rate Constants for Hydrolysis of Ortho-Substituted- N-Methylbenzohydroxamic Acids in 7.31M NaOH at 90.0°C ............................................. 46 VIII Rate Constants for Catalyzed and Uncatalyzed Hydrolysis of Ortho-Substituted-N-Methylbenzo- hydroxamic Acids at 90.0°C in the Presence of Salts.............................................
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