PHYSICAL A N D INORGANIC CHEMISTRY

DIVISION OF PHYSICAL AND INORGANIC CHEMISTRY

Quali tat ive Analysis Possible by Luminescence Spectroscopy

^ Use of ferf-butyl hypochlorite leads to new understanding of the Raschig synthesis of hydrazine

^ Atomic hydrogen and free radical effects on metallic surfaces measured by surface potential changes

χ UAIINESCENCE spectroscopy, presently -*-* the underdog when compared to ab­sorption spectroscopic techniques, may soon have an important advantage over those more popular methods—the ability to identify compounds in mixtures. This was the prediction made by Michael Kasha, Florida State University, when he reviewed luminescence spectroscopy of rigid glass solutions during a joint sympo­sium on modern tools for organic research sponsored by the Division of Physical and Inorganic Chemistry and the Divi­sion of Organic Chemistry.

Instruments for taking phosphorescent spectra, Dr. Kasha said, consist of the following: source of light energy, a slotted spinning disk, the sample, a second slotted spinning disk, and, finally, viewing and recording units. By appropriate ar­rangement of slots in the two disks, it is possible alternately to irradiate samples and not have incident light reach the viewing units and then to view the phos­phorescence and not have incident light reach the sample. Spectra can be studied for varying lengths of time as well as at varying periods after incident light is stopped. This is done by combining proper slot positions and disk rotation speeds. The time interval between excitation and viewing is called resolution time.

It should be possible, Dr. Kasha said, to identify compounds in mixtures because the time between the stopping of inci­dent light and the beginning of phospho­rescence plus the duration of phosphores­cence are characteristic of individual conn-pounds. He noted it will be possible to "select" the phosphorescence of each compound present by using a series oi different resolution times. Examination of separated spectra would then permit identi­fication of the compounds. The method is effective at low concentrations ( 10"3

molar), he reported. Work is currently under way to evolve the actual operating techniques which will make the scheme practical, thus adding another tool to those already possessed by organic chem­ists.

While luminescence spectroscopy may

have a potential use in qualitative analysis, one serious defect, Dr. Kasha pointed out, is slow recording—several minutes may be required for a single determination. An­other is the limited spectral region in which the method may be used. Best re­sults are obtained in the visible region with present equipment, but he noted that the most interesting compounds phos­phoresce in the near infrared. What is needed are photomultiplier tubes which would permit work in the near infrared.

Infrared Spectroscopy. In retrospect, organic chemistry might well have de­veloped differently had chemists recog­nized the significance of the infrared spectra published by Coblentz in 1903. R. Norman Jones, National Research Coun­cil of Canada, declared in his discussion of recent developments in infrared spec­trometry that 20 years elapsed before infrared spectra were again investigated systematically and that, therefore, a powerful tool was unduly delayed in being of help to chemists. Furthermore, it has been only in the past 10 years that prog­ress has been especially rapid.

He pointed out that physicists are now

able to calculate spectra of simple mole­cules, such as methane or ammonia, with high precision. They have not, however, extended this precise mathematical treat­ment to the more complex materials char­acteristic of organic chemistry.

The organic chemist, on the other hand, uses infrared spectrometry empirically for studying large molecules and does not be­come involved in the underlying theory.

Dr. Jones said he is now attempting in certain cases to predict spectra not pre­viously measured. This -ie does by mak­ing simplifying assumptions that vibra­tions are localized in individual bonds. He said that when infrared spectra of organic compounds in solution are meas­ured under sufficiently high resolution, spectra can be calculated in terms ot molecular extinction coefficients. For curves expressed in these units, it is possi­ble in certain cases to compute spectra of polyfunctional compounds by algebraically adding spectra of appropriate monofunc-tional compounds (see cut) .

For the future, Dr. Jones expects con­siderable improvement in Raman spectros­copy. Today's techniques are more com­plex than for infrared spectra, and much larger samples are needed, thus hindering the use of Raman spectra. Once the sample problem is overcome, however, he believes organic chemists will be able to get a great deal more information from comparisons of Raman and infrared spectra than they can now get from infra­red alone.

Reactor Monitor. Inexpensive, accurate, mobile, and rapid are some of the ad­vantages noted by Sheffield Gordon, Argonne National Laboratory, for the unit he has developed in cooperation with E. J. Hart for monitoring nuclear reactor power. The unit is based on the fact that water decomposes into hydrogen and oxygen when subjected to radiation. The volume of gases evolved has been cali­brated to show integrated gamma and thermal neutron fluxes.

First, ho said, a potassium iodide solu-This shows the close agreement R. N. Jones gets between observed spectra and spectra computed from the stereochemically appropriate systems of steroid ketone plus steroid alcohol minus steroid hydrocarbon. Work was done a t Research Council of Canada

AN DR OS TAN - 3 * - 0 L - 17-ONE COMPUTED

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ping it as teliurium-132, its parent compound form

124fh N A T I O N A L ACS MEETING

Small samples , rap id tube preparat ion, and virtually no chance of t ube explosions are advantages ci ted for this appara tus for phase studies above atmospheric pres­sure. Shown are H . W. Wright (left) and W. L. Marshal l , Oak Ridge Laboratory

M. Grief, Du Pont , and R. J . Orr, Polymer Corp. L td . , caugh t in a d e e p discussion of the kinet ics of reactions involving iron complexes of polyethylene polyamines

tion was exposed to neutron a n d gamma-ray bombardment in Argonne's CP-3 pile and the rate of gas evolution measured. An identical solution was then irradiated by a s tandard cobalt-60 source to cali­brate the unit for gamma a n d neutron radiation.

In a second series of experiments, boric-acid was added to the potassium iodide solution. Boron selectively absorbed neu­trons [ B , 0 ( n , a ) L P ] and the lithium recoils decomposed water into hydrogen and hydrogen peroxide, the latter further decomposing to oxygen and water . By subtracting the gas evolution r a t e obtained

Simon F r e e d and Kenneth Sancier study­ing the absorption spectra uf solutions of chlorophylls a t low tempera tures

in the first experiments from that in the second, intensity of the neutron beam was determined. Purpose of the potassium iodide is to prevent gamma radiation from causing recombination of hydrogen and hydrogen peroxide.

In addit ion to the advantages cited in the foregoing, Dr. Gordon also noted that the method is superior to foil activation because the solutions do not become highly radioactive.

• Raschig Synthesis

Clearer insight into the Raschig syn­thesis of hydrazine , a potential rocket fuel and an important in termedia te in the synthesis of a number of drugs, has been gained from work of Colton, Jones, and Audrieth at University of Illinois. As reported by Ervin Colton, tert-butyl hypochlorite was substi tuted for the usual Raschig .V-chlorinating agent , sodium hypochlorite, thus eliminating undesirable impurities always present in sodium hypo­chlorite and permit t ing them t o study t h e synthesis more precisely.

Dr. Colton and his coworkers s tudied the three most important variables in the Raschig synthesis—effect of mole ratio of ammonia to hypochlori te (yields , they found, approach 7 0 % using a ratio of 300 to 1 ) ; effect of t h e use of inhibitors, such as gelatin (wi thout gelatin, yield was about 3%; yield was markedly increased by the addition of only a few milligrams ) ; and, especially, the effect of the addi­tion of a pe rmanen t base, sodium hy­droxide.

T h e y have found the reaction to b e similar to the Hofmann reaction. T h e intermediate species is presumably NHCl" (since NH2C1 can be regarded as the N analog of hypochlorous a c i d ) , a n d t h e subsequent reaction with ammonia gives hydrazine plus chloride (possibly th rough formation of im ide ) .

A project is currently u n d e r way, D r . Colton said, to determine t h e possibility of producing anhydrous hydrazine directly by running the reaction ( us ing tert -butyl hypochlori te) in some solvent other than water. If successful, this w o u l d eliminate the cost now involved in producing an Anhydrous p roduc t when sodium hypo­chlorite is used.

Uniposi t ive Magnes ium. T h e first real, concrete evidence for the existence of

unipositive magnes ium has been the re­sult of work at t h e University of Kansas by R. L. Petty, A. W . Oavidson, and Jacob Kleinberg. Dr. Davidson said that elec­trolysis of a number o f different aqueous salt solutions in a d i v i d e d cell led to magnesium dissolving anodically wi th an initial mean valence considerably lower than two. Hydrogen is evolved at the anode in an amount e q u a l to the oxida­tion from the lower valence n u m b e r to the familiar M g * \ Mg* is stable for a limited period of tim-e in aqueous solu­tion as shown by t h i s anodic evolution of hydrogen and by the fact that the anolyte solution reduces a variety of oxidizing agents.

Borohydrides . Cont inuing interest in borohydrides as reducing agents for in­organic and organic materials was evi­denced in the s u m m a r y given by Sister M. Emilius Kramer, St. Louis University, of the reactions sod ium borohydride undergoes in aqueous solution with a r s en i c ( I I I ) , an t imony ( I I I ) , and bis­muth ( I I I ) . The meta l or metalbor ide and the t r ihydr ide w e r e found as reduc­tion products in all cases.

• I od ine -132

Medical science wil l soon have another radioactive tracer a n d therapeutic agent, now that workers at Brookhaven National Laboratory have evolved a s cheme for making iodine-132 avai lable for longer periods of time. To date, iodinje-131 is the compound used w h e r e therapy o r de­tection of abnormal b o d y condit ions re­quires its part icular combina t ion of prop­erties. Iodine-132 w o u l d actually have a number of advan tages over I131, b u t the short half-life of t h e 132-isomer—about 2.5 hours—has meant that it was avail­able only t o workers very near a source.

In order to give I1 3 2 a longer effective half-life, L. G. S tang , Jr., and coworkers a t B N L have taken advantage of the decay chain in w h i c h I132 is an inter­media te p roduc t :

U M fi*»ton|TeH, /* V Xe , !

77-hour 2.4-hour stable half-life half-life

The method consists of recovering and shipping t e l lu r ium-132 and le t t ing the usei separate I ia2, w h i c h is constantly being produced in t r i e radiotel lurium, as needed . Stang said a s imple appara tus has been developed w h i c h can b e operated easily by a hospital technician to separate a radioactive iodine s ample . T h e separa­tion process is rapid a n d may b e done in the shipping shield, tTius keeping worker-exposure to a m i n i m u m .

Phase S tudy A p p a r a t u s . Those who have had sealed glass tubes blow up in their faees while t ry ing to make phase studies at above-a tmospher ic pressures will wi-lroitu* ;< simple a n d inexpensive unit for semimicro experiments , which was described by W . L. ^Marshall, Oak Ridge National Laboratory.

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PHYSICAL AND INORGANIC CHEMISTRY

One-mill imeter inside diameter, :3-niin. outside diameter , borosilicate glass tubing is used for work up to 320" C ; for higher temperatures, silica tubing of slightly smaller bore is used. One end of such tubing is sealed, the tube filled with solu­tion, and then sealed at a predetermined point above the solution level. A second tube is joined to this sample tube for attaching to a vibrator. This vibrator im­parts a back-and-forth motion to the tube to agitate the contents (a rocking motion would not cause mixing in such small-bore tubes ) . Dr . Marshall said that tube prep­aration, Riling, and sealing required about two minutes.

T h e tube is then placed in a longitudinal hole in the heat ing block, the tube ex­tension protruding and being fastened to the vibrator. T h e heating block is cylin­drical and may be made of either alumi­num or graphi te . Resistance wire wrapped around its outside surface provides heating. A slot perpendicular to the sample tube hole permits viewing with a telescope.

Among the advantages h e pointed out are: rapid temperature change, tube in­sertion or removal at any temperature, and virtually n o tube explosions at pressures up to 3200 pounds per square inch.

T h e removal of minute port ions of metallic surfaces by the action of atomic hydrogen and free radicals may be meas­ured by surface potential changes. H . N. Alyea, Princeton University, working with Brian Meade, Jr., D u Pont, plated mirrors of ant imony, arsenic, or tin on a stationary platinum electrode so connected that their potentials could be measured with respect to a vibrating silver electrode. Hydrogen atoms and free methyl radicals were then used to bombard the surface, and the num­ber of effective collisions of the activated particles was calculated. The stud>, which was made within a temperature range of 25° to 60° C , indicated apparent energies of activation for hydrogen atoms with mirror surfaces of antimony to b e 17 kcal; with arsenic 20 kcal; with tin 14 kcal. Dr. Alyea predic ted that this method would find use as a means of investigating cata­lytic surfaces undergoing reaction.

A by-product of Dr. Alyea's study of the effect of hydrogen atoms on metallic surfaces is a new instrument for determin­ing the concentration of atomic hydrogen in the gaseous state. A copper plate oxi­dized in such manner as to acquire a coat­ing of cuprous oxide can be used as a photovoltaic cell. By first measuring the voltage produced by the cell when ex­posed to a carefully standardized light source, and then comparing this value to that obtained after exposure to t h e gas being tested, Dr . Alyea was able t o cal­culate the atomic hydrogen concentration. The activated hydrogen atoms reduce the cuprous oxide and thus lessen the output of the photovoltaic cells. After use, the i'«.»!]<; ran hp restored to approximately their original condition by hea t ing to 500" C in an atmosphere of nitrous oxide.

Reproducibility of this method is about

5</c. It is more sensitive to small concen­trations of atomic hydrogen than t h e tungsten filament recombination technique, and it is more accurate than the colori-metric m e t h o d based on the b lue color formed b y molybdenum trioxide, said Dr . Alyea.

Strontium Sulfate Crystals. Unlike many other salts, t he rate of dissolution of strontium sulfate is limited not by dif­fusion, b u t by the ra te of reaction of water molecules with the suiface. This conclu­sion was reached by Peter J. Lucchesi, New York University, from experimental ata obtained by using a new technique which allows dissolution rales to be meas­ured continuously without removing any material for sampling. Radioactive crys­tals of strontium sulfate are imbedded in the walls of a hollow plastic stirrer and the solution medium is circulated from the crystals to a dipping-type Geiger-Miiller counting tube and back. T h e rate of dis­solution of the crystals is followed by recording the increase in radioactivity of the solution.

Isonicotinic Acid Hydrazide. From measurements made using Cu Ka radia­tion, L. H . Jensen has plotted the crystal structure of isonicotinic acid hydrazine. T h e compound is of interest currently be ­cause of its application in the treatment of tuberculosis. The length of the bond b e ­tween t h e carbonyl carbon atom and the r ing carbon was considerably less than tha t of a C—C single bond. T h e N—N bond w a s 1.40 A. in length, 0.06 A. shorter t h a n the N—N bond in hydrazine, said Dr. Jensen.

Radical Isomerization. Both n-propyl and isobutyl radicals undergo isomerization when the i r iodides are subjected to photol­ysis by light of wave length 2587 A. ( t he mercury resonance l ine) . T h e discovery tha t these radicals are converted to iso­propyl and tert-huty\ radicals was an­nounced by C. E. McCauley, Notre Dame University. Iodides of the radicals were labeled with I1S1 and subjected to photol­ysis. Suitable carrier iodides had to be added before the small samples were separated by fractional distillation. Ra­dioactivity measurements were used to de­termine the relative concentrations of the two fractions of photolyzed material. In this investigation Dr. McCauley and his colleagues found that the reverse isomeri­zation, ferr-butyl to isobutyl, and isopropyl to n-propyl, takes place only in negligible amounts . Oxygen almost entirely inhibits the isomerization.

Chloramine to Hydroxylamine. It has long been suspected that the decomposi­tion of chloramine by hydroxyl ions should give rise to hydroxylamine, but efforts to isolate hydroxylamine have been fruitless. T h e difficulty lies in the fact that hydroxyl­amine is immediately at tacked by the chloramine which remains and is itself decomposed, said Robert E . McCoy, Dow Chemical Co. By carrying out the de­composition in the cold and in the pres­ence of cyclohexanone, Dr. McCoy was

able to identify cyclohexanone oxime in the reaction mixture. Th i s indicates that at least one of the paths of t h e decomposi­tion reaction involves the formation of hydroxylamine. W h e t h e r this is t he most important path or not, D r . McCoy said he did not know.

Halogen Fluorides. The solubility of a number of metal fluorides has been de­termined by Irving Sheft and his co­workers, H . H. Hyman and J . J. Katz, all of Argonne National Laboratory. T h e ability of a fluoride to donate or accept fluoride ions is related t o the metal 's posi­tion in the periodic table. O n this basis, Dr. Sheft was able to correlate the solu­bilities he found with solubilities in water and hydrogen fluoride. Of the metals studied, cesium was the most soluble, 18.8 grams per 100 grams of saturated solution at 25° C. Following, in order of decreas­ing solubility, were niobium, potassium, bar ium, silver, and lithium; t h e solubility of the last was 0.125 grams p e r 100 grams of saturated solution. Nickel, copper, cal­cium, aluminum, lanthanum, zirconium, and thorium were all less soluble than lithium.

Dielectric constants for liquid chlorine trifluoride and iodine pentafluoride have been measured by H. Bradford Thompson and his associates at Michigan State Col­lege. The experimental data for chlorine trifluoride fits the equation:

€t - 4.754 - 0.0817 t For iodine pentafluoride the equation be­comes:

t ( =: 46.22 — 0.388 t A cell composed of two concentric nickel cylinders insulated with teflon was used in these measurements.

Chlorophyll Solvation. Chlorophyll b as well as the related compound, pheo-phytin b apparently undergo solvation in hydrocarbon solution according to Ken­neth M. Sancier, Brookhaven National Laboratory. The spectra of t h e two com­pounds show similar changes thus indi­cating that if solvation in chlorophyll b takes place at the magnesium atom, as is believed, the solution of pheophytin /; must take place at the corresponding hy­drogen atoms.

Even at as low a temperature as 75° K., the solvation is quite rapid. Under differ­ent conditions two different solvate forms seem to exist. One is a n equilibrium mix­ture of zero- and monosolvate while the other is a mixture of mono- and clisolvate.

Liquid Metal Mixtures. A new theor> to explain the nonideal thermodynamic behavior of metallic mixtures has been advanced by Peter L . Auer, California Research and Development Co. Dr. Auer is of the opinion that compound formation takes place thus complicating the nature of the mixtures. It is possible that some­thing similar to polymerization occurs. This supposed polymerization would in­volve the metals themselves as well as compounds which might be formed.

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