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Influence of Solvent on Free Radical Reactions Dale Glenn Hendry Iowa State University

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Influence of Solvent on Free Radical Reactions Dale Glenn Hendry Iowa State University Iowa State University Capstones, Theses and Retrospective Theses and Dissertations Dissertations 1962 Influence of solvent on free radical reactions Dale Glenn Hendry Iowa State University Follow this and additional works at: https://lib.dr.iastate.edu/rtd Part of the Organic Chemistry Commons Recommended Citation Hendry, Dale Glenn, "Influence of solvent on free radical reactions " (1962). Retrospective Theses and Dissertations. 2050. https://lib.dr.iastate.edu/rtd/2050 This Dissertation is brought to you for free and open access by the Iowa State University Capstones, Theses and Dissertations at Iowa State University Digital Repository. It has been accepted for inclusion in Retrospective Theses and Dissertations by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. This dissertation has been 62—4152 microfilmed exactly as received HENDRY, Dale Glenn, 1936- INFLUENCE OF SOLVENT ON FREE RADICAL REACTIONS. Iowa State University of Science and Technology Ph.D., 1962 Chemistry, organic University Microfilms, Inc., Ann Arbor, Michigan INFLUENCE OF SOLVENT ON FREE RADICAL REACTIONS by Dale Glenn Hendry A Dissertation Submitted to the Graduate Faculty in Partial Fulfillment of The Requirements for the Degree of DOCTOR OF PHILOSOPHY Major Subject: Organic Chemistry Approved: Signature was redacted for privacy. Signature was redacted for privacy. Signature was redacted for privacy. Dean f Graduate College Iowa State University Of Science and Technology Ames, Iowa 1962 ii TABLE OF CONTENTS Page GENERAL INTRODUCTION ' 1 PHDTOCHLQRIMTION OF ARALKYL HYDROCARBONS 5 Introduction 5 Results and Discussion 11 Relative reactivity of alpha- and beta-hydrogen atoms 11 Reactivity of alpha- and beta-hydrogen atoms relative to cyclohexane 17 Experimental 33 ^paratus and procedure 33 Analysis procedure 3li Reagents 35 METHYLATION OF HYDROCARBONS 36 Introduction 36 Results and Discussion 39 Experimental Ui Apparatus and procedures for methylation reactions UU Analys is k5 Reagents U6 OXIDATION OF HYDROCARBONS kl Introduction 1+7 Results and Discussion $1 Oxidation kinetics of cyclohexene $1 Study of rate of initiation in various solvents 55 Solvent effect on oxidation of hydrocarbons 61 Relative reactivity of cyclic hydrocarbons toward the peroxy radical 8l Experimental 86 Oxidation procedure 86 Reagents 8? iii Page OXIDATION OF HYDROCARBONS IN THE PRESENCE OF TRIPHENYLMETHANE AND SIMILAR TYPE COMPOUNDS 89 Introduction 89 Results and Discussion 91 Experimental 119 Procedure 119 Reagents 119 SUMMARY 120 REFERENCES CITED 122 ACKNOWLEDGMENTS 130 XV LIST OF TABLES Table Page 1 Photochlor inat i on of aralkyl hydrocarbons at U0° 12 2 Competitive photochlorination of cyclohexane and aralkyl hydrocarbons at U0° 18 3 Reactivities of some carbon-hydrogen bonds toward chlorine atoms at U0° 22 U Relative reactivities of some aralkyl hydrocarbons . toward various radicals 27 5 Methylation of 2,3-dime tlylbutane in the presence of benzene at 25° UO 6 Methylation of benzene with diazomethane Ul 7 Oxidation of cyclohexene at 60° in the presence of AJBN $2 8 Inhibited oxidation of cyclohexene and cumene at 60° in the presence of inhibitor and 0.0970 M AJBN 56 9 Stability of cyclohexerryl hydroperoxide in nitro- methane at 60° 59 10 Effect of hydrocarbon concentration on inhibited oxidation at 60° in nitromethane and in the presence of 0.002 M inhibitor and 0.0970 M AIBN 60 11 Oxidation of 2.0 M cyclohexene at 60° in various solvents and in the presence of 0.0501; M AIBN; effect of solvent on overall rate and on k^/kz 63 12 Oxidation of 2.0 M cyclohexene at 60° in various solvents and in the presence of 0.050lt M AIBN; correlation between rate and dielectric constant of solvent 6U 13 Oxidation of 2.0 M cyclohexene in mixed solvents at 60° in the presence of 0.050U M AIBN 72 lh Oxidation of 2.0 M cumene at 60° in various solvents and in the presence of 0.050U 22 AJBN 76 15 Oxidation of 2.0 M hydrocarbon in chlorobenzene and ni trome thane solution at 60° and in the presence of 0.050k M AIBN 77 V Table Page 16 Relative reactivity per hydrogen atom of some cyclic hydrocarbons toward a peroxy radical and a methyl radical 82 17 Oxidation of cyc 1 ohexene-triphenylmethane mixtures in chlorobenzene solution and in presence of O.O^OU M AIBN at 60° ~ 92 18 Oxidation of 2.0 M cyclohexene at 60° with various added hydrocarbons in chlorobenzene solution and in the presence of O.O^Olt M AIBN 9k 19 Oxidation of eye1ohexene-f1uorene mixtures at various pressures at 60° in chlorobenzene solution and in the presence of 0.050U M AJBN; total hydrocarbon concentrations = 2.0 M 100 20 Effect of tri pheny lme thane on the oxidation of 2.0 M cumene at 60° and 90° in bromobenzene solution ~~ 107 21 Effect of tripheny lme thane and cobalt salts on the oxidation of 2.0 M cumene at 60° in acetic acid solution and in the presence of 0.050U M AIBN 113 vi LIST OF FIGURES Figure Page 1 Effect of the concentration of cumene on the relative reactivity of the alpha- and. beta-hydrogen atoms of cumene at U0° 13 2a Effect of the concentration of indan on the relative reactivity of the alpha- and beta-hydrogen atoms of indan at U0° in nitrobenzene solution 15 2b Effect of the concentration of tetralin on the relative reactivity of the alpha- and beta-hydrogen atoms of tetralin at U0° in nitrobenzene and cyclohexane solutions 15 3 Effect of concentration of cumene on the reactivity of the "alpha-hydrogen atom of cumene compared to the reactivity of a hydrogen atom of cyclohexane at U0° 19 ii Effect of aromatic concentration on the reactivities of an alpha-hydrog en atom of indan and tetralin rela­ tive to a hydrogen atom of cyclohexane 20 5 Oxidation of 9.L M cyclohexene as a function of the one-half power of""AIBN concentration 53 6 Rate of oxidation as a function of cyclohexene con­ centration 5U 7 Correlation of oxidation of 2.0 M cyclohexene at 60° in various solvents and in the presence of 0.050U H AIBN with Kirkwood-Onsanger parameter according to"" Laidler and Eyring 67 8 Correlation of oxidation of 2.0 M cyclohexene at 60° in various solvents and in the presence of 0.050U H with Kirkwood-Ons anger parameter according to the — method of Fowling and Bernstein 70 9 Oxidation of 2.0 M cyclohexene at 60° in mixtures of two solvents and Tn the presence of 0.0501; M AJBN 7b 10 Effect of tr ipheny lme thane on the oxidation of cyclo­ hexene at 60° in the presence of 0.050li M AJBN 93 11 Effect of various hydrocarbons on the oxidation of 2.0 M cyclohexene at 60° in the presence of 0.0501; M AJBN 95 vii Figure Page 12 Effect of pressure on the rate of competitive oxi­ dation of cyclohexene and fluorene 101 13 Effect of oxygen pressure on the oxidation of fluorene-cyclohexene mixtures in the presence of 0.050U M at 60° 103 lU Drawing showing hydrogen-hydrogen interactions in the 1-naphthyldiphenylmethyl radical 105 15 Effect of tripheny lme thane on the oxidation of 2.0 M cumene in bromobenzene solution ~ 108 16 Effect of 0.1 M tripheny lme thane and 0.02 M cobalt (II) bromoacetate on the oxidation of 2.0 TR cumene at 60° in the presence of 0.050U M AIBN ™* Ilk 17 Effect of 0.5 M tripheny lme thane and 0.02 M bromide ion on the oxidation of 2.0 M cumene at 60® in the presence of 0.050ii. M AIBN and 0.02 M cobalt (II) ion 115 1 GENERAL INTRODUCTION The capability of the reaction media to influence the course or rate of free radical reactions has not been realized until recently (la, p. 237; lb, p. 35)» The failure to acknowledge the possible importance of the solvent in these reactions -rests on the fact that free radical inter­ mediates do not usually have any positive or negative charge and there­ fore, should not be affected by such properties as the ionizing power of the solvent. There are cases where the solvent does appear to have only an insignificant effect on rate (2), and in a number of cases where there is a small variation in rate with change in solvent, relatively large but compensating changes in the entropy and enthalpy of activation have been reported (3). However, these latter effects have been seriously ques­ tioned, and they appear to be more a consequence of experimental error than actual phenomena (it). One of the earliest indications that radical reactions could exhibit a polar nature was found in a study of the copolymerization of vinyl com­ pounds (lb, p. 97). To explain the great tendency for alternation of the two monomer units in the polymer structure, it has been necessary to assume a polar transition state. If there were a highly polar transition state in these reactions, the solvent should be able to contribute to the stability of the transition state in accord with its polar nature. Thus a pronounced dependence of the reactivity of monomer on the dielectric constant of the solution would be expected. However, experimentation did not show such a dependence (2b, e). Apparently, the nature of the tran­ sition state is such that the lines of force between the charged portions 2 of the transition state do not radiate appreciably into the solvent. Therefore, the solvent.can contribute little in stabilization of the charges in the transition state. Other properties besides the ionizing power of the solvent can be important in influencing radical reactions.
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