121st NATIONAL ACS MEETING—BUFFALO DIVISION O F PHYSICAL A N D I N O R G A N I C CHEMISTRY
Phosphorus Provides N e w Family of Compounds for Industry, Theory • Nomenclature system proposed to integrate organic and inorganic usage • Radiotracers, electron emission give new insight into character of surfaces • Geochemistry leads to better understanding of origin and evolution of planets • Nuclide studies amplify orbital concept, recommend atomic weight revisions XVN AIR of enthusiasm surrounded the meetings of the symposium on phosphorus chemistry; it suggested that some of the more optimistic investigators were beginning to suspect that the phosphorus compounds might evolve into a family rivaling the silicones in importance. Their hopes are based on the multiple bonding potentials of phosphorus and its well-known ability to form long polymer chains. They received encouragement from reports that told of the important role already played by phosphorus compounds in lubrication, fireproofmg, agricultural chemicals, and physiological processes. Films from Phosphorus Polymers. One of the most interesting properties of the phosphorus compounds is their ability to form high molecular weight polymers. The glassy form of some of the alkali phosphates has long been known to have a cross-linked polymer structure, but the extreme brittleness of these compounds has discouraged any practical applications of this property. However, R. K. Her told the meeting that a research group at the Du Pont Experimental Station had found that relatively strong, flexible films could be formed by substituting organic cations for the alkali ions. Films were formed from polymers containing 130 metaphosphate groups, and 1000-unit polymers were easily formed. The backbone of the polymer chain was assumed to be a phosphorus-oxygen-phosphorus linkage. Cross-linking is provided by ionic attraction of the cations lying between the chains. Quaternary ammonium compounds proved to be excellent cations for the purpose, particularly when mixed with minor percentages of metal ions, usually sodium, potassium, or magnesium. The organic cations act as integral plasticizers while the metal ions add stiffness and stability. Tetramethylammonium polymetaphosphate was the film most extensively investigated although other films were made of cetyltrimethylammonium polymetaphosphate, dimethyldi-n-octadecylammonium polymetaphosphate, lauryl1386
pyridinium polymetaphosphate, and other materials. In general, as the organic cations used became larger the film became less water soluble but more waxy in texture. Her said that his group has not yet developed any uses for this new material, but he predicted that any applications would be dependent on the chemical properties of the polymers. The best films produced have had a tensile strength of 3000400 pounds per square inch but they are extremely water soluble. He suggested that the rather unusual ionic nature of the polymers suggests possible applications as ion exchange resins, but he insisted that much more investigation must be done on the properties of the materials before their field of ultimate utility will even be indicated. Phosphorus in Insecticides, Fireproofing. In addition to their new promise, the phosphorus compounds already enjoy a solid record of accomplishment in many fields. Their use in agricultural poisons is well established although all the phosphorus compounds now used for this purpose are toxic to warm-blooded animals. Arthur Toy of Victor Chemical reminded the meeting that the ideal insecticide is toxic to most insects and harmless to all warm-blooded animals. Although there is no immediate promise of attaining this ideal with a phosphorus compound, Toy said that tetrapropyldithionopyrophosphate had proved to be only slightly toxic to white mice and quite toxic to some insects. Phosphorous compounds, particularly the inorganic phosphates were some of the first materials used for the fireproofing of fabrics. Recently several techniques have been suggested for a treatment in which the phosphorus compound reacts directly with the cellulose chain in cotton, usually to form an ester. This kind of treatment gives good fire protection but tends to weaken the cloth by as much as 50%. A new type of chemical treatment described by James M. Church, Columbia University, in which the phosphorus group CHEMICAL
is attached to the cellulose through an amino-ether linkage is designed t o overcome this disadvantage. The treatment involves animation of the cellulose, phosphorylation of the amino cellulose, and then the amination of any free phosphoric acid groups. • Phosphorus Nomenclature Developing As the study of phosphorus compounds has expanded rapidly and from both the organic and inorganic branches of chemistry, it has experienced t h e inevitable growing pain—nomenclature trouble. The irregularity of phosphorus nomenclature became apparent as long ago as 1948 when the Organic Phosphorus Nomenclature Advisory Committee was formed by the ACS Committee on Organic Nomenclature. After four years of study of the numerous nomenclature systems in current use, this committee has now synthesized a comprehensive and self-consistent system which it recommends for general use. The committee's report has been approved by the Organic Nomenclature Committee and will ultimately be submitted to the Nomenclature Committee of the International Union of Pure and Applied Chemistry for issuance as Tentative Rule 34. Representatives of the Chemical Society of London have already approved the system. However, as Robert Fox of the Naval Research Laboratory who read the report said, final approval of the system can ultimately come only from t h e men who will work with it. The system applies directly only to phosphorus compounds containing organic groups, but because of the special position of the phosphorus compounds on the borderline between organic and inorganic chemistry it has been necessary to consider some inorganic compounds in establishing the rationale of the system. The general principles follow t h e usage of Chemical Abstracts but with some important innovations. Compounds which contain only one phosphorus atom are named as derivatives of parent acid compounds. Thus PhPO(OH) 2 becomes phenylphosphonic acid and EtPSCL2 is ethylphosphonothioic dichloride. Polyphosphorus compounds are named as aggregates of a hypothetical "phosphane" radical more-or-less following the "silane" of the silicon compounds. The sponsors of the system claim that it will provide an unambiguous name for any monophosphorus structure while providing a separate system by which polyphosphorus compounds can be named without confusion. Both of the types of nomenclature have been carefully developed to ensure that all phosphorus compounds will b e indexed under "P." Ê> Electrons Give Closer View of Surfaces Since all chemical reactions involving solids must take place on a solid surface, the properties and configurations of these AND
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PHYSICAL A N D INORGANIC CHEMISTRY surfaces are of constant and profound interest to a large variety of chemists and physicists. Attendants at the Buffalo meeting heard about a new technique which would give them a more intimate look at such surfaces than they have ever had before. J. A. Becker of the Bell Telephone Laboratories told them that by using a small needle of the solid as the emitting cathode of a cathode ray tube they could get a fluoroscopic reproduction of the surface of the needle with a magnification of 10e and a resolution of 20 X lO^8 cm. The modified cathode ray tube in which these experiments are conducted is called a field emission microscope. The device operates on the principle that the electron emission of a surface in fields of 50 million volts per centimeter or more will vary with the energy conditions of the surface which in turn will reflect the structure of that surface. Becker worked "with tungsten and barium and found that the edges of the crystal planes seem to be in violent motion at even moderate temperatures. He also determined that surface atoms are mobile at temperatures as low as one third the melting point of the metal. The speaker said that it is possible that a similar technique giving even greater resolution would be possible by adsorbing hydrogen on the surface of the needle and then causing it to emit hydrogen ions or protons to activate the fluorescent screen. Tracers, in Surface Studies. Radioactive tracer techniques, because they make possible the measurement of extremely small quantities of matter, have also proved valuable in following changes in the first few molecular layers of a solid surface, particularly in matters involving the sorption or evaporation of materials from the surface. An indirect method for studying surfaces with the use of radioisotopes was discussed by D. E. Beischer of the U. S. Naval School of Aviation Radiotracers can give much data of surface phenomena according to J. E. Willard of the University of Wisconsin
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Medicine. Beischer deposited monolayers of stearic acid tagged with carbon-14 on the surfaces he desired to study by the method perfected by Katherine Blodgett of General Electric. As laid down these films were of molecularly uniform thickness and gave equal radiation at all points. However, heating released the molecules from their two-dimensional order and allowed them to migrate to points of greatest attraction. The relative concentrations of the tagged stearic acid could be easily determined by autoradiography. The acid molecules were retained or concentrated at points of chemisorbtion but were usually evaporated off where they were only physically adsorbed. Even the difference in attraction of different faces of the same crystal could be detected by this technique, according to Dr. Beischer, which makes possible the detection of any cracks, faults, or stresses in the structure of the surface. Reactions between a surface and its environment can also be studied by tagging the environment with radioactive tracers and seeing how they end up on the surface by radioautograph. John Willard tried a number of variations of this technique at the University of Wisconsin and found them very informative. He worked primarily with glass and sodium and found that he could measure among other things the rate of solution of glass in water, the exchange of sodium ions on a glass surface, and the effects of various pretreatments, including mild and strong naming, on the sorbtion of sodium ions by a glass surface. It was suggested from the floor, however, following his presentation that his results may have rather specific significance because of the unusual spongy nature of the surface of glass. Irreversible Systems Stir Practical Interest. The thermodynamics of irreversible systems are a favorite study of theoretical physical chemists but have generally been considered a fairly "longhaired" pursuit. Recently engineers and applied scientists have begun to suspect that some of these esoteric formulae might have some utility in practical problems which after all are mostly concerned with nonequilibrium conditions. Problems in diffusion, thermal conductivity, thermal effects on electrical and elastic properties, and various stress and strain relationships have been mentioned as possible beneficiaries of these theories. One symposium at the Buffalo meeting was devoted to these systems, not so much to present new data but to consider the statement of practical problems in terms of the thermodynamic equations. However, apparently there are still some questions about basic theories to be resolved. During one of the lively and prolonged discussion periods that characterized all of the sessions of the Physical and Inorganic Division this year, there was an extended but inconclusive consideration of the applicability of the basic Boltzman equation to nonequilib» APRIL
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A. W. Francis, Socony-Vacuum Oil Co., holds an opalescent cell before projector to produce characteristic color on screen rium, irreversible systems. The crux of the matter seemed to lie in whether or not it was permissible to treat changing systems near the equilibrium point instantaneously or whether it is necessary to use a time average. The principle participants were Harold Grad of New York University and John Kirkwood of Yale. • Planetary Evolution Probed Just as a better understanding of the properties of matter has led to a more complete knowledge of atomic structure without our directly visiting the interiors of atoms themselves, we now have a better understanding of many aspects of the origin of the solar system without having been there when it happened, according to Harrison Brown, California Institute of Technology. Dr. Brown explained the chemical aspects of trie origin and evolution of planets in a medal address before this division after having been presented the ACS Award in Pure Chemisty at the general meeting, and from the large crowds in attendance, which extended into the hallways, many people were intrigued by the tour beginning three thousand million years ago and leading up to most recently established chemical knowledge having a relation to planet' formation. Omitting the purely physical facts which have been widely discussed for many decades, including the regularities of motion, spacing of orbits, and regularities and irregularities of statellite systems, Dr. Brown confined his discussion to those features which give us some indication of the chemical composition and structure, such as density, atmospheric composition, and, in the case of the earth, crustal composition. He divided the planets into two groups. The inner planets, Mercury, Venus, Earth, and Mars, possess relatively small masses (ranging from 0.0543 for Mercury to 1 for Earth) and high spe1387
121st NATIONAL ACS MEETING—BUFFALO cine gravities, ranging from 4.18 to 5.52. Contrasting are t h e outer planets (Jupi ter, Saturn, Uranus, and N e p t u n e ) with large masses and low specific gravities, the range values of the two properties being 1 4 . 6 - 3 1 8 a n d 0 . 7 1 - 2 . 2 . H e ex plained t h a t carbon is highly oxidized o n the inner planets, giving an atmosphere containing carbon dioxide, whereas it is highly reduced on t h e outer planets, where the atmospheres contain substantial quan tities of methane a n d ammonia. Prof. Brown stated that these differ ences in size and composition are explained in a general way o n the basis of an origin through condensation and accretion, the philosophy of which has developed dur ing t h e last decade. H e explained that it is clear that the process of planet for mation involved initially condensation at low temperatures, b u t that there is strong evidence that a subsequent high tempera ture stage was involved as well. But h e added that numerous details are yet to be explored and that it will take the chem ist; t h e geologist, t h e astronomer, and t h e physicist, working closely together, before the process by which our solar system was formed can b e successfully reconstructed. (Dr. Brown's address will be published in full in t h e April 21 issue of C&EN).
fc-The Nucleus Has Orbits, Too Recent developments in nuclear science points to a much more sharply defined chemistry of the atomic nucleus than has been recognized previously, R. A. Brightsen, Westinghouse Atomic Power Division, reported in a paper under his joint author ship with Charles D. Coryell, Massachu setts Institute of Technology. Brightsen stated that protons and neu trons take their place in regular orbits and show effects of closed shells in a matter analogous to the atomic electrons that form the basis of atomic and molecular structure. These shell effects are neces sary to explain t h e quantitative aspects of radioactive decay, and, in the p r - -»t early state of nuclear theory, the e~r mental results from the field of radioac tive decay serve as the most reliable guide for the magnitude of the energy effects associated with t h e formation of nuclear shells. Too, they provide a sensitive method of search for smaller energy ef fects that may be associated with subshell structure in the nucleus. T h e speaker pointed out that nuclear shells (independent ones for protons and neutrons) are filled at particle numbers 2, 8, 20, 28, 50, 8 2 , and 126, correspond ing t o the unusual stabilities of the nuclei of helium, oxygen, and calcium, and for protons of nickel, tin, and lead. T h e 126neutron shell is apparent in the great stability of the nuclei of lead-208 and bismuth-209, the stable end members of long series of radioactive decay. He also stated that the shell numbers have an effect on the spin energies of unpaired isotopes or neutrons which are directly responsible for t h e absence of stable iso
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topes of t h e two missing elements, tech netium and promethium; that shell effects seem to regulate pattern of occurrence of nuclear fission, leading t o pronounced asymmetry of fission process. Translead Nuclide Masses. Some of the officially accepted values of atomic weights will necessarily have t o be changed as a result of more correct values possible tlii'OTjgh use of data that have been "accunixilated on t h e energy of radioactive decay associated with the nuclides above lead, Glenn T. Seaborg, University of California, predicted. The Radiation Laboratory at U C has been engaged for several years in t h e accumulation of data in t h i s field, and, using t h e relation be tween mass and energy and t h e known mass of t h e alpha particle, it is possible to convert this radioactive decay energy in each case to a relative mass value based on t h e mass of o n e of the four end prod.ids—Pb^, Pb207, Pb 3 *\ or Bi209. Using a mass of 208.04340 for Pb 208 as determined b y t h e mass spectrographic doidblct method, together with known neutron binding energies and neutron mass of 1.00897, the mass for Pb 206 is calculated to b e 206.04057; for Pb 207 , 207.04235; and for Pb 200 , 209.04820. Using these figures as base values together with radioactive decay energies and 4.00387 for the mass of He 4 , the masses of the heavy nuclides have been calculated. Atomic weights on the chemical scale have been calculated from the mass values based on t h e physical scale described above. A comparison of t h e values with tliose of the Commission on Atomic AVeights of the International Union of Chemistry are as follows: Mass Int. Data Union 207.21 207.19 208.99 209.00 226.04 226.05 282.05 232.12 238.03 238.07 Mass values based on energy of radio active decay is n o t in error by more than 0.01 atomic weight unit. D r . Seaborg reported even more strik ing discrepancies in calculated atomic weights based on mass spectrometer and nuclear transmutation studies and ac cepted values for some of the other ele ments. These are shown below: Data Int. Mass Union 101.04 101.7 106.55 106.7 168.94 169.4 192.22 193.1 196.99 197.2 158.93 159.2 Color Emulsions. It was observed some years ago that emulsions of colorless liquids of equal refractive indices but different dispersions show brilliant colors by transmitted light with a light barrier, but the phenomenon was not understood. Alfred W . Francis, Socony-Vacuum, ex plained work which shows t h a t where direct light is blocked by a barrier, the
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only light passing t h r o u g h such an emul sion is that reflected from surfaces of drop lets. This reflected light lacks t h e color for which t h e refractive indices of t h e phases are identical since such a color cannot b e reflected, and i t appears as t h e complementary color of that eliminated. A single emulsion shows yellow, amber, brick red, magenta, lilac, purple, indigo, a n d light blue as its temperature changes over 10° to 3 0 ° . The phenomenon has scientific uses in observations of refractive indices of con densed gases under pressures such as chlo rine, hydrogen sulfide, a n d butanes, or of other liquids above their boiling points. A possible technical use is in t h e analysis of glycerol and similar substances. M e t a l C a r b o n y l Studies. A straight line relationship b e t w e e n t h e estimated C—Ο bond order a n d wave length of ab sorption of metal carbonyls substantiates assumptions that metal-carbon double bonds are n e e d e d to m a k e the metal neu tral in carbonyl complexes, according to studies reported by E. O. Brimm and M. A. Lynch, Jr., L i n d e Air Products. Chromium carbonyl, C r ( C O ) 0 , was given as an example. The electronega tivity of transition metals are said to b e about 1.5 on Pauling's scale, and, on this basis t h e chromium-carbon b o n d would b e 8 0 % covalent. The formation of a chromium-carbon single bond would give t h e chromium a charge of —0.8 while t h e formation of a chromium-carbon double bond would give t h e chromium a charge of -{-0.4. Thus t h e n u m b e r of each type of bond to give chromium a charge of zero in chromium carbonyl is calculated to b e four double bonds a n d t w o single. H o w ever, only three " d " electron pairs are available for double b o n d formation and four double bonds could not b e formed. Another attack is to estimate t h e n u m b e r of double b o n d s from t h e types of derivatives of chromium carbonyl and from this estimât to calculate the covalent character of i.ie metal-carbon bond, a n d hence, the electronegativity of t h e metal. Experiments have shown that it is possible to replace not more than three carbon monoxides b y amines. If there were three metal-carbon double bonds in chromium triamine-tricarbonyl, the electronegativity of chromium would b e 1.12 a n d 3.35 chromium-carbon double bonds would be needed in chromium carbonyl b u t this is not possible. If four carbon monoxides could be displaced by amines a n d t h e remaining two carbon monoxides were doubly bonded, the electronegativity of chromium would b e 0.6 and chromium carbonyl would have 2 . 5 double bonds. T h e speakers concluded that chromium carbonyl has close t o three chromium-carb o n double bonds, -which gives t h e chromium-carbon bond 2 / 3 covalent character a n d gives chromium an electronegativity of about 0.9. On this basis t h e carbonoxygen bond in chromium carbonyl would b e 5 0 % double bonded and 5 0 % triple b o n d e d or have a bond order of 2.5.
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