BORAX TO BORANES A collection of papers comprising the Sym• posium—From Borax to Boranes, presented before the Division of Inorganic Chemistry at the 133rd National Meeting of the American Chemical Society, San Francisco, Calif., April 1958, together with three papers from the 135th ACS Meeting in Boston, Mass., April 1959. Publication Date: June 1, 1961 | doi: 10.1021/ba-1961-0032.fw001 Number 32 ADVANCES IN CHEMISTRY SERIES American Chemical Society Washington, D.C. 1961 A. C. S. Editorial Library In BORAX TO BORANES; Advances in Chemistry; American Chemical Society: Washington, DC, 1961. Copyright © 1961 AMERICAN CHEMICAL SOCIETY All Rights Reserved Publication Date: June 1, 1961 | doi: 10.1021/ba-1961-0032.fw001 Library of Congress Catalog No. 61-15059 PRINTED IN THE UNITED STATES OF AMERICA In BORAX TO BORANES; Advances in Chemistry; American Chemical Society: Washington, DC, 1961. ADVANCES IN CHEMISTRY SERIES Robert F. Gould, Editor AMERICAN CHEMICAL SOCIETY APPLIED PUBLICATIONS ADVISORY BOARD Allen L. Alexander Calvin L. Stevens Walter C. McCrone, Jr. Glenn E. Ullyot Wyndham D. Miles Calvin A. VanderWerf William J. Sparks George W. Watt Albert C. Zettlemoyer Publication Date: June 1, 1961 | doi: 10.1021/ba-1961-0032.fw001 In BORAX TO BORANES; Advances in Chemistry; American Chemical Society: Washington, DC, 1961. Preface Over the past decade boron has been accorded a treatment of which most of the other elements might well be envious. Acting on more or less qualitative indications that certain boron compounds held considerable promise as "superfuels" for jet craft and rockets, the Government of the United States invested many millions of dollars in a program of research and development which encompassed almost all aspects of boron chemistry. A not insignificant segment of American scientific manpower re• sponded to the need for personnel, and, by 1955, boron was enjoying a level of popu• larity in university and industrial research that it could not have aspired to ten years earlier. Although prior contributions had been made largely by inorganic chemists, active investigations in the field were now also being conducted by workers in all of the other branches. The industrial effort was concentrated largely in two firms (the Callery Chemical Co. and the Olin Mathieson Chemical Corp.) but quite a few companies were engaged in the program on a smaller scale. On the academic side, there were few major chemistry departments which did not number among their staff members at least one person engaged in work on boron compounds. Interest became so general that, in 1957, the ACS Division of Inorganic Chemistry established a Boron Committee to handle the steadily increasing flow of boron papers that were being submitted for presentation at national meetings. Now, in 1961, the Boron Committee has been discharged and government support of the industrial program has dwindled to a small fraction of its former level. The boron "superfuels," while not discredited, now appear less spectacularly promising than they once did. Factors such as lower-than-expected performance, high cost, and high toxicity have combined to dampen enthusiasm for the program. Yet, disappoint• ing though this showing may be, we cannot help but be encouraged by the resulting tremendous progress in the fundamental chemistry of boron—progress which might have required several decades had it not been for the great concentration of effort that the boron program provided. Our understanding of the nature and behavior of boron compounds has grown immeasurably during the past ten years, and the Publication Date: June 1, 1961 | doi: 10.1021/ba-1961-0032.pr001 unique character of many of these substances is certain to lead to applications unfore• seen when the program got under way. Finally, interest in the high-energy aspects of boron compounds is far from dead. Work is continuing, and boranes or their derivatives may yet emerge triumphant in the area of chemical fuels. Perhaps the year of peak interest in boron chemistry came in 1958, when the symposium "From Borax to Boranes" was presented at the 133rd ACS Meeting in San Francisco. This volume is composed of papers presented at that meeting and was to have been edited by the late Professor George W. Schaeffer who organized still another symposium on boron at the Boston ACS Meeting in 1959. Professor Schaeffer's untimely death, in 1959, represented a serious loss to boron chemistry. He had been one of the most active workers in the field and had made many impor• tant contributions. It is to Professor Schaeffer's memory that this volume is dedi• cated. THOMAS WARTIK Pennsylvania State University University Park, Pa. In BORAX TO BORANES; Advances in Chemistry; American Chemical Society: Washington, DC, 1961. Introduction DONALD R. MARTIN1 Olin Mathieson Chemical Corp., Niagara Falls, N. Y. As a consequence of events which occurred in the closing years of World War II, the need for an aircraft fuel containing more energy was recognized. Military opera• tions were requiring greater efficiencies from their air-borne weapons in terms of either a greater distance or a larger pay load per unit of fuel. The high energy available in boron compounds was known and the British in 1947 evaluated some of these compounds for use as ramjet fuels. The United States Department of Defense, seeking a better fuel, initiated Project ZIP in 1952. The objective of ZIP was to develop a fuel having properties similar to JP-4 (a hydrocarbon jet fuel) but having a higher density, a faster flame speed, a lower vapor pressure, and more energy per pound. Project ZIP was large and had as its two prime contractors the Callery Chemical Co. and the Olin Mathieson Chemical Corp. Many universities, research institutes, government laboratories, and private companies were subcontractors on the project. After a careful evaluation of the high energy-containing, light weight elements, it was decided that the fuel objective of Project ZIP should contain a borane or a modified borane. Consequently, research in boron chemistry was pursued feverishly by the many scientists working on the project. To facilitate the exchange of experimental results obtained on these programs and to stimulate interest among those not on the project, the Division of Inorganic Chemistry of the American Chemical Society appointed a Committee on Boron Chem• istry in 1957. This committee [composed of G. W. Schaeffer, St. Louis University Publication Date: June 1, 1961 | doi: 10.1021/ba-1961-0032.ch001 (deceased), R. W. Parry, University of Michigan, and D. R. Martin, Olin Mathieson Chemical Corp., Chairman] sponsored a number of programs on boron chemistry at the national meetings of the American Chemical Society. Symposia were held at two of these meetings at which the papers in this book were presented: "From Borax to Boranes" in April 1958 in San Francisco, and "Boron and Binary Boron Compounds" in April 1959 in Boston. The relationship of these papers to the prob• able steps in making a High Energy Fuel (HEF) is self-evident in the following description of a composite of possible processes for going "From Borax (an ore) to Boranes (a fuel)." The three most common and stable boranes known at the inception of the project were diborane, pentaborane(9), and decaborane. Under ambient conditions, diborane is a gas, decaborane is a solid, and pentaborane(9) is a liquid possessing certain objectionable properties. It is pyrophoric and toxic, has a low density and a comparatively high vapor pressure. However, the heat of combustion (Table I) of each of these boranes was attractive and a logical procedure would be to attempt to modify these molecules sufficiently to give the desired properties without sacrificing the greatly desired high heat of combustion. 1 Present address, 2714 Drummond Road, Toledo 6, Ohio. 1 In BORAX TO BORANES; Advances in Chemistry; American Chemical Society: Washington, DC, 1961. 1 ADVANCES IN CHEMISTRY SERIES Table I. Heat of Combustion of Fuels Fuel B.t.u./Lb. Hydrogen 51,571 Diborane 31,078 Pentaborane(9) 29,070 Decaborane 27,850 Methyldiborane 26,420 JP-4 18,400 After inspection of Table I, it is obvious that most of the heating value of a fuel comes from the captive hydrogen. Therefore, a high energy fuel should contain boron, as much hydrogen as possible, and a third element to modify its properties. The modifying element selected was carbon, inasmuch as it? was a component of hydro• carbon fuels and inasmuch as the materials, reactions, and techniques of organic chemistry could be utilized. The process of modifying the boranes would not be easy, as can be seen from Table I. For example, the replacement of one hydrogen atom in a diborane molecule by the smallest organic radical, the methyl group, results in a diminution of the heat of combustion by at least 15% (compare diborane with methyldiborane). Because of the sensitivity of the heat of combustion of a borane molecule to the replacement of hydrogen by hydrocarbon groups, the ternary diagram (Figure 1) for boron, hydrogen, and carbon was constructed to serve as a guide for research. 5/jS7l ©TU./LB. Publication Date: June 1, 1961 | doi: 10.1021/ba-1961-0032.ch001 Figure 1. Ternary diagram for boron, hydrogen, and carbon In the ternary diagram, the heats of combustion for known hydrocarbons and boranes were indicated on the appropriate axes. Recalling that the fuel should con• tain as much hydrogen as possible, and leaving one of the four sp3 "bonds of boron and of carbon for bonding, a tie line was drawn on the diagram from a point repre• senting the composition of BH8 on the borane axis to a point representing the com• position of CH8 on the hydrocarbon axis. Obviously, this line represents the maximum amount of hydrogen that the resulting fuel molecule can have.