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The Kinetics and Mechanism of the Reaction of Hydrazoic Acid With This dissertation has been 62-2123 microfilmed exactly as received BEKNDT, Donald Carl, 1935- THE KINETICS AND MECHANISM OF THE REAC­ TION OF HYDRAZOIC ACID WITH SUBSTITUTED NAPHTHOIC ACIDS. The Ohio State University, Ph.D., 1961 Chemistry, organic University Microfilms, Inc., Ann Arbor, Michigan THE KINETICS AND MECHANISM OF THE REACTION' OF HYDRAZOIC ACID WITH SUBSTITUTED NAPHTHOIC ACIDS DISSERTATION Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University By Donald Carl Berndt, B. Sc. ****** The Ohio State University 1961 Approved by idviser Department of Chemistry ' ACKNOWLEDGMENTS The author wishes to thank Professor Harold Shechter for his suggestion of this investigation, for his encour­ agement and guidance during the course of this study, and for his aid in the preparation of the manuscript. The author is grateful to the Mershon fellowship fund and the Chemistry Department of The Ohio State University and to the National Science Foundation for fellowship funds. He is also grateful to the members of the staff and fellow graduate students for informa­ tion and for the use of chemicals and apparatus. i i CONTENTS P^ge I, Introduction ............................................................................ 1 Statement of Problem ...................................................... 1 Historical Aspects ........................................................... 3 II. Discussion of Results . ...................................... 12 Kinetic Order of the Schmidt Reaction . 12 Proximity Effects . ..................................................... 12 Electrical Effects ........................................................... l6 In terp retatio n of Reaction Mechanism . 19 Relationship between Schmidt and Gurtius R eactions .......................... 24- III. Experimental ..................................... 27 Syntheses of Naphthoic Acids ................................. 27 Reaction of Naphthoic Acids with Hydrazoic A cid .............................................................. 35 Solvents for Kinetic Determinations . 42 Stability of Naphthoic Acids in Sulfuric A cid .............................................................. 4-2 Kinetic Rrocedure ........................................................... 44 Calculations ........................................................................... 46 Determination of DissociationConstants . 53 IV. A ppendix ............................................................................... 55 Autobiography ............................................................................... 60 i i i Illustrations Table Page 1. Relative Rates of Schmidt Reactions of Substituted Benzoic àcids in Excess 95.8% Sulfuric A cid ........................................................... 6 2. Average Rate Constants for Reaction of Naphthoic Acids with Hydrazoic Acid . 13 3. Relative Rates of Reaction at 0° of Substituted Naphthoic and Benzoic Acids with Hydrazoic Acid ......... 15 4. Dissociation Constants of Conjugate Acids, and Free Energies of Activation of 1-Naphthoic and 8-Chloro-l-naphthoic A c i d s ......................................................................................................22 5. S ta b ility Data for 1-Naphthoic and 2-M ethyl-l-naphthoic Acids in Sulfuric A cid .................................................................................43 6. Analytical Wave Lengths for Kinetic Determinations . 45 7. Rate Constants and Activation Para­ meters for Schmidt Reactions of Naphthoic Acids .......................................•.............................48 8. Spectrophotometric Data for Determination of pKgH+ .............................................. 54 9-17. Typical Kinetic Data for the Schmidt Reaction of Naphthoic A c i d s ...................................' .....................................................55-59 Figure 1. Graph of Kinetic Data for Schmidt Reaction of 1-Naphthoic Acid ...... 50 2. Graph of Kinetic Data for Schmidt Reaction of 9-Chloro-l-naphthoic A c i d .......................................... 51 3. Activation Energy Plots ................................................ 52 iv I. Introduction Statement of Problem Reaction of a carboxylic acid with hydrazoic acid (the Schmidt reaction) in the presence of sulfuric acid yields the corresponding amine, nitrogen and carbon dioxide (Equation 1). RCOOH + HN3 > RNHg + CO2 + Ng (1) Schmidt reactions in concentrated sulfuric acid of ^-substituted phthallc acids (l), ^-substituted isophtha- ■ (1 ) H. R. Barkemeyer, M. Sc. thesis, The Ohio State University, 1952. lie acids (2 ), 2 -substituted terephthalic acids ( 2 ), and (2 ) T. Moritsugu, Ph.D. d issertatio n . The Ohio State University, 1954. 2 , 6-disubstituted terephthalic acids ( 2 , 3 ) occur exclus- (3 ) M. S. Newman and H. L. Gildenhorn, J. Am. Chera. 8 0 c., 10, 317 (1 9 4 8). ively at the sterically hindered carboxyl group to give the corresponding amino acids. 3-Araino-phthalic, anthra- nilic and jg-aminobenzoic acids do not react with hydrazoic acid however in concentrated sulfuric acid (l). 2 Presumably the electrical effect of the ammonium group is responsible for this result. 1,2- and 1,6-Naphthalic acids (2) yield amino acids derived from exclusive reac­ tion of the 1-carboxyl group (Equation 2). HOOC—ks * « 3 HOOcJ O U * * "2 The kinetics of Schmidt reactions of substituted benzoic acids in excess 95.8% sulfuric acid are first order with respect to the benzoic acid and to hydrazoic acid (4 ). Electronegative or electropositive substitu­ er) M. E. D. Hillman, Ph.D. d isse rta tio n . The Ohio State U niversity, 1958. ents (with the exception of fluoro and carboxyl) in the ortho position increase the rate of reaction.with respect to benzoic acid. & study of the Schmidt reaction of toluic acid in sulfuric acid over a concentration range of 7 4 .3 - 98% indicates that the activity of water in the rate-controlling transition state is low ( 4 ). k kinetic study of reactions of hydrazoic acid with 1-naphthoic acid and its 2- and 8-substituted derivatives, 4-bromo-'l-naphthoic acid, and 2-naphthoic acid was undertaken in order to determine the relative electrical and steric effects of ortho and oeri substituents on the Schmidt reaction and to provide data on the relative re­ activity of naphthalene and benzenoid systems. 3 The predominant form of a carboxylic acid dissolved in concentrated sulfuric acid is usually the dihydroxy- cerbonium ion (5), RCfOH)^. In order to determine the (5) H. Stewart and K. Yates, J. Am. Chem. Soc., 8g, 4059 (I960). effect of different extents of protonation of the carboxy- lic acids on the rates of Schmidt reactions^ dissociation + constants of the species RCOgHg in sulfuric acid were de­ termined . Historical aspects The reactions of hydrazoic acid with carbonyl com­ pounds in the presence of strong mineral acids as catalysts have been named Schmidt reactions. kldehydea give nitriles and formyl derivatives of amines, and ketones give amides. Carboxylic acids yield amines with one less carbon atom, carbon dioxide, and nitrogen; an isocyanate, subsequently hydrolyzed, is presumed to be an intermediate (Equation 3). RCOOH + HN^ ----- Hg + RHGO RNH2 + COg (3) Caronna obtained 3 -n itro isa to ic anhydride (l) from the Schmidt reaction of 3-nitrophthalic acid (6). 4-Pb8nan- do )0 NOg “ I (6) G. Caronna, Gazz. chira. i t a l . , 21, 475 (1941); C. A., 21, 118 (1943) . 4 thryl isocyanate was isolated (7) from a Schmidt reaction (7 ) K, F. Rutherford and M. S. Newman, J. Am. Chera. Soc., 22, 213 (1957). of 4-phenanthrenecarboxylic acid with a mixture of tri- -ijf' fluoroacetic acid anhydride and trifluoroacetic acid as solvent and ca ta ly st. Wolff has reviewed the scope of the Schmidt reaction (8). Hillman has summarized in (8) H. Wolff in Adams Organic R eactions, Vol. I l l , John Wiley & Sons, Inc., New York, N. Y., 1946, pp. 307- 336. d e ta il the mechanisms proposed for Schmidt reactions of carboxylic acids ( 4 )• Perhaps the most striking aspect of the Schmidt re­ action of substituted aromatic dicarboxylic acids is that the reaction occurs exclusively at the more "sterically hindered" carboxyl group (1-4) • Newman and Gildenhorn (3 ) found that 2,6-dimethylterephthalic acid reacted with one equivalent of hydrazoic acid exclusively at the hin­ dered carboxyl group (Equation 4 ). On the basis of the GOGH IÜI2 ^3°|rS^^3 + HN 3 ^3°|fj~^^3 + Ng + GO2 ( 4 ) GOOH COOH similarity of this reaction to the estérification of mesi- toic acid in sulfuric acid they proposed the following mechanism for the Schmidt reaction of hindered acids (Equations 5-7): RCOOH RC(0H)2 hC = 0 + HgO (5) jj) R&=0 + HN- -------> EGN-N5N (6 ) 3 H 0 RGN-NSN ------> RNC=0 + ----RHH^ + GOg (7) The function of the sulfuric acid is to convert the hindered carboxyl group to an oxocarbonium ion. Loss of nitrogen from the protonated acyl azide produces an unstable imino derivative which undergoes rearrangement and subsequent hydrolysis. The authors also pointed out that dihydroxycarbonium ions may react in a similar manner (Equations 8,9): OH HgSOv . HN-3 ' + RCOOH RC(0H)2 — HO-y-y-H=M (8 ) R H HO-Ç-]jI-N=N ------> RNh5(0H) + N2 KNH3 + GO2 (9) R H Because of the accelerative influences of proximal groups in Schmidt reactions, Hillman ( 4 ) studied the rates of Schmidt reactions of ortho- . meta-, and oara- substituted benzoic acids. Table 1 contains the relative rates determined in excess 95.8% sulfuric acid. The kinetics are
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