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Chemical Effects Associated with Nuclear Reactions and Radioactive Transformations.

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J . M y / (Pardubice, Czechoslovakia) discussed the stability of
supercooled liquids. Within the metastable zone, i. e. within
the range between saturation and supersaturation curves in
the solubility vs. temperature diagram, crystal seeds d o not
form spontaneously. The width of the metastable zone of
aqueous solutions increases with their purity and viscosity,
with the duration and degree of superheating, and with the
rate of saturation, i.e. with the increase in saturation per unit
time. This may be proportional to the rate of cooling. Complete degradation of the aggregates of water molecules may
be assumed to take place on prolonged and strong heating,
while their recombination is retarded on rapid cooling.
According to U. Steinicke (Berlin, Germany) aluminum hydroxide may be prepared by a channel process: the solutions
of aluminum salt and ammonia are mixed in a jet and directly
sprayed into the internal tube (a few cm in diameter) of a double-walled glass tube (the “channel”). The basic idea of this
continuous process is to mixtheoriginal solutions inthe absence
of a wall, with subsequent ageing of the precipitate in achannel
system. Ageing is controlled by the rate of flow (slope of the
channel), the pH-value and the temperature profile. The dried
and calcined final product has a high catalytic activity and a
sharp maximum in the particle size distribution curve (particle size can be varied from about 10 to 100 p).
M . J . Koslovski (Tiraspol, U.S.S.R.) examined the influence
of spark discharges o n the formation of seeds in aqueous electrolyte solutions. The rate of seed formation at the surface of
a supersaturated solution is proportional to the square of the
field strength and to the degree of supersaturation. The spark
flashes over from the electrode to the surface of the solution.
Seed formation largely depends on which pole of the power
supply the solution is connected to. In the case of KCI, spark
discharge with the solution as the negative pole produced a
marked crystallization, while crystallization was low with the
solution being the positive pole. The crystallization of halides,
sulfates, nitrates, phosphates, and carbonates of the alkali
metals and alkaline earths was investigated. The rate of seed
formation decreases with increasing viscosity and purity of
the solution.
According to H . J . Meyer (Bonn, Germany) vaterite (CaC03)
is preferentially formed during rapid precipitation from aqueous solutions, especially in the presence of electrolytes. The
proportion of the CaCO3-modifications (calcite, aragonite,
vaterite) at 50 “C and in the presence of uni-univalent electrolytes (e.g. NaCl, NH4N03) depends on the concentration and
nature of the latter. Other solutes present and high degrees of
supexsturation favor the formation of somatoids [*I.
As R. Boistefle and R. Kern (Nancy, France) showed, clumping of sodium chloride crystals can be prevented by spraying the crystalline powder, e . g . with K4[Fe(CN)6] solution.
On evaporation, the Kh[Fe(CN)6] forms small sharp points
on smooth sodium chloride surfaces. These probably prevent
a close fit of the crystal planes and, therefore, the clumping of
[“I Somatoids are small crystals with uneven planes, which,
depending on the conditions of precipitation, are spindle-shaped,
spherical, lenticular, sheaf-like, dumbbell-shaped or snowtextured.
the crystals. From a more than 23 %, supersaturated solution,
sodium chloride does not crystallize in cubes, but in octahedra.
Other solutes present (CdZ+, CO(NH2)2, Fe(CN):-, Fe(CN)i-)
lower the critical concentration and may lead to further
changes in form and habit (e.g. rhomboid dodecahedra and
dendrites are formed).
M . Hille (Berlin, Germany) prepared small NaCl and KCI
crystals of definite form and size for flotation studies. Cubes
of NaCl and KCI as well as octahedra of NaCl (size about 50
to 60 p) are formed by precipitation with methanol/ethanol/
acetone mixtures from aqueous solutions of these salts, saturated at 20°C. The organic solvents added must be miscible
with the solution. Formamide (20%) is required for precipitating octahedra of NaCl. Octahedra of KCl crystallize from
an aqueous solution of KCI, which is saturated at 50 “C, contains urea (50 %), and is supercooled down to 30 “C. The flotability of minerals may be improved or made at all possible by
a definite crystal form.
Ch. Jentsch (Berlin, Germany) carried out adsorption measurements on alkali halide crystals of different forms. The
crystals, 5 to 10 p in size, were obtained by precipitation with
methanol/ethanol/acetone mixtures. The crystal size varies
with the ratio of the organic solvents. The solution contained
PbClz for the precipitation of KCI octahedra, glycine for the
precipitation of NaCl rhomboid dodecahedra. N o adsorption
of the solutes affecting crystal form was noted, but water was
adsorbed in several layers.
M . Kahlweir (Gottingen, Germany) dealt with growth studies.
A temperature jump was used to produce super- or subsaturation in a saturated solution within about 10-5 sec. Growth
and dissolution of the crystals were traced by conductivity
measurements. It is concluded that growth is controlled by
surface reactions (e.g. dehydration) at lower degrees of supersaturation, and by diffusion at higher degrees of supersaturation (above 1
z).
H. Neels and S. Aslajan (Leipzig, Germany) studied the formation of spherolites of sodium hydrogen carbonate from an
aqueous solution by addition of methanol. The size of the
spherolites decreased from 8 to 4 p with increasing degree of
supersaturation (70-100 ”/,). The crystalline needles of the
spherolites showed a step-wise growth. H. Neels and A. Felbinger (Leipzig, Germany) observed that the rate of formation
of sodium hydrogen carbonate seeds on carbonization of an
ammoniacal sodium chloride solution, is related by a n exponential function to the degree of supersaturation. Todes
(U.S.S.R.) used the rate of seed formation to determine the
interfacial energy of CaS04 in aqueous solution as 12 erg/cm2,
and A . E. Nielsen (Copenhagen, Denmark) determined that
of Bas04 as 130- 10 ergjcmz. R . Piwonka, H . Orfmnnn, and
H . Hartmann (Liibenwalde, Germany) precipitated cadmium
sulfide, in the presence of halide ions, in the stable hexagonal
modification, while sulfate ions led to the metastable cubic
modification. St. Zagrodski and 2. Niedzielski (Lodz, Poland)
observed increased seed formation on ultrasonic irradiation
of supersaturated saccharose solutions, reaching a maximum
at a sound frequency of 7.2 kc.
[VB 881/212 IE]
German version: Angew. Chem. 77, 351 (1965)
Chemical Effects Associated with Nuclear Reactions and Radioactive
Transformations
About 130 scientists from 28 countries attended this symposium which was arranged by the International Atomic
Energy Agency and the I.U.P.A.C. Joint Commission on
Applied Radioactivity and was held in Vienna (Austria) on
December 7th-1 Ith, 1964. Some 60 papers, which are to be
published soon, were presented.
362
Investigations Using Mass Spectrometry
The chemical effects of internally converted isomeric transitions with subsequent Auger effect [l] could previously be
measured only with compounds of a few nuclides. Due to the
occurence of recoil the results were uncertain to an unknown
Angew. Chem. internat. Edit. I Vol. 4 (1965) 1 No. 4
extent. Molecular disintegrations following the Auger effect
were now brought about with non - radioactive molecules,
using X-rays to produce a n electron deficiency at one of the
atoms. The resultant positive charge is rapidly distributed
throughout the molecule, which then disintegrates due to internal Coulombic repulsion. The charges and kinetic energies of
the fragments were measured about 10-5 sec after the energy
absorption. After excitation of the L-shell, CH31 splits into
C2*, 3 H ! , a n d 15-, while HI decomposes into H + and 17’-, and
Xe yields Xeg-. Molecular ions and neutral fragments are not
formed. The recoil energy measured for the products of the
disintegration of CH3I corresponds to that calculated with the
assumption that C2IH ‘315; with the atomic parameters of
CH31 appears as an intermediate ( R . M . White, U.S.A.). For
the Wilzbach labelling of CH4, the Pratt-Wolfgang mechanism was confirmed by detection of the C2H4T+ ion. The
T2
-+P- T3He+
+ CHI
j
-3He
CH4T+*
+ CH
+ e-, -CHz
4 CzH4Tf --+
-H2
> 10-5 sec
-H2
-+
10 -11 sec
CH2T
CHzT’
+ CH4
-+
- ~ -
C H 3 T i CH3
radiochemical portion of the reaction, which is due to 9radiation, was determined separately by addition of D:! to
the C H ~ / T Zmixture; deuterated molecules can only be
formed in this way and not v i a T3He- ( S . W e d e r , U.S.A.).
Gases
Liquids
In organic halides a considerable proportion of activated
atoms is found incorporated into the starting material. This
is not due to retention, i.e. to lack of bond-breaking, ( J . E.
Willard, U.S.A.) but to substitution according to:
+ R*X i X
*X+RX
T o clarify the reaction mechanism, the following reactions
were carried out:
I . rneso- or ( )-2,3-dichlorobutane(n,.i)’sCI
3
dichlorobutanes
2.as I . but with the addition of Br2(n,y)8OmBr +
2-8omBr-3-Cl-butane
3 . 2-chlorobutane(n,:.38Cl
--f
dichlorobutanes.
The isomeric products were separated. It was shown that
the replacement of C1 by CI or Br proceeds partly with
retention of configuration and partly with racemization, and
that the time of reaction is comparable with the duration of
the radical transformation. The replacement of H by C1 is
mainly statistical; nevertheless differences due to the different
C-H bonds are perceptible. Radicals are not formed (F. S.
Rowland, U.S.A.). Although frequently investigated, the
chemical effects of the nuclear reaction 8lBr(n,y)82Br in liquids
and solids need further discussion, since it has recently become clear that the major part of the 36h-srBr in a strongly
internally converted isomeric transition originates from 6 min82mBr.
Radioactive carbon from the reaction 12C(y,n)llC reacts
mainly as such, or as methine after addition of a hydrogen
atom. 11C reacts with hydrocarbons to form CH-llCH,
and 11CH forms CH2=11CH2; oxygen reacts only with 11C
to yield 11CO. The formation of 11CO is six times more
probable than that of a labelled hydrocarbon (G. Stocklin,
Germany). The reaction of 11C with hydrocarbons proceeds
by insertion into a C-H bond. A primary C-H bond is
preferred t o a secondary by a factor of 1.26. I n hydrocarbon/
N2 mixtures, labelled hydrocarbons and H l l C N result, but
labelled amines are not observed. The ratio of the cross-sections in these mixtures with reference to the formation of
I1CO, C H r I l C H , and HllCN from energy-rich carbon
atoms, is 9:4.5: 1. Further informations on the reaction mechanisms are to be expected from investigations of the isotopic
effect ( A . P. Wolf, U.S.A.). Isotopic effects of hot T-atoms
from the reaction 3He(n,p)T are also being investigated.
Recently it has become possible to separate olefines in which
only one H is replaced by D. With CHjCD3 as starting
material, the reaction
yields CzHzDT and CzHDzT in the ratio I : 1.6. Correspondingly, replacement of H in the first stage of the reaction
I S preferred to the replacement of D by a Factor of about 1.3,
and disintegration of CH2TCD3* is more frequent than that
of CH3CD2T* by the same factor ( F . S . Rowland, U.S.A.).
The $-decay of T in CzH4T2 v i a C2H4T3HeLas an intermediate yields 1 1 X HT, 2.5 %, CH3T, 5.5 ”/, C2H3T, 1 %,
C3H7TI and 3-4 %, C4H9T ( F . Cacace, Italy). This result
agrees with mass-spectrometric observations of the ions
resulting from C2HqT3HeL. Calculations of bond conservation in tritiated alkanes and 14C02 during @-decay gave
values of ca. 1 and 80%,, respectively, in agreement with
experimental results ( A . A . Gordirs, U.S.A.).
[ I ] A n isomeric transition is called internally converted if the
energy of the -(-ray quantum is transferred to an inner-shell
electron which is then emitted. Filling of the vacancy by electrons from higher shells may result in further loss of electrons
by similar conversion of the X-ray quanta. The latter process
is termed the Auger effect and yields multiply positively charged
atoms.
Angew. Chem. internut. Edit.
/
Val. 4(1965) / No. 4
Solids
Products from the nuclear reaction 14N(n,p)l4C in carefully
purified NH4C1 were investigated. After dissolution the
CH3NH2, 8
radioactivity was found in the form of 75
gases (CO + CO:! + CH4), 3
HCOOH, 3 % HCHO, and
4 % CH3OH. While CH4 and CH3NH2 are probably present
immediately after irradiation, the oxygen-containing compounds apparently result from precursors o n dissolution in
water. Surprisingly, the distribution of products is unaltered
if, after irradiation, the substance is sublimed in vacuum, or
at 1 mm of H2 or NH3; thus the precursors survive destruction
of the lattice. Two possibly simultaneous mechanisms were
discussed in explanation: 1 . during sublimation the concentrations of NH3 and HCI are so small and the contact
times so brief, that the precursors d o not react; 2. the
precursors are less reactive or more stable in the lattice than
was so far assumed (P.E. Yankwich, U.S.A.). While i n
normal alkali-metal halides the nuclear reaction 3sCl(n,p)35S
yields 100 %, 35SO;- after dissolution, ca. 50 % of the activity
produced in vacuum-sublimed material or in single crystals
can be captured as 3 % - after dissolution in sulfide- or
sulfite-containing dilute alkali. The precursor may be atomic,
neutral sulfur SO, or perhaps S- or Sf. Its behavior depends
on the structure of its surroundings. From powdered CsCl,
3 5 s can be extracted with carbon disulfide. The lifetime of the
fragment in solution must be at least 10-6 sec, since, due to
the low sulfide concentration, only 1 in 106 collisions leads to
exchange according to
35SO + s23jS2- + SO
x
The numerical values varied within wide limits from experiment to experiment even when using different parts of the
same single crystal; they could also be considerably influenced
by doping (with Ca2’ or Cdzt), y-irradiation (before or after
activation), heating, optical bleaching, or crushing. In pure
solvents SO is oxidized by water mainly t o sulfate ( J . E. Willard, U.S.A. ; A . G. Maddock, England).
The change in proportion of the different recoil fragments,
caused by heating or irradiation, took up a considerable part
of the discussions. It was suggested that migrating electrons
363
transfer energy to the recoil atoms and t h i s activate the
process or that they alter the environment of the recoil atoms
50 that a lesser energy of activation is required. Moreover, these electrons interact with defects i n the crystal
matrix, which explains the complicated annealing behavior.
Electrons, ;IS well as defects, can be prodiiced by additional
-*,-irradiation. The structure of the surroundings of the recoil
atom is no longer regarded as controlling the course of
annealing ( K . E. Collins, U.S.A.). The importance of crystal
defects is seen from the different annealing behavior of
cobalt acetylacetonate/aluminum acetylacetonate mixed
crystals, which were prepared by two methods ( J . I. Vargtis,
Brazil). For neutron-activated potassium chromate, if
parallelism has been found between thernioluminescence,
electrical conductivity and isochronous thermal annealing.
All these properties or processes show maxima at 160, 250,
and 340°C. The product was found to be predominantly
51CrZ’. and not Cr3+ as pieviously assumed ( T . Andersen,
Denmark). The old theory by Libby, which explained the
recoil behavior of central atoms in complexes in terms of a
successive loss of ligands (CrO3, CrOz’, CrO4+, Cr6+) lvas
thcrcby finally disproved (G. Hnrbottle, U.S.A.). In cobalt
nitroammine complexes, annealing proceeds directly from
60CoZ+ to the end product with no intermediate stages. It is
not stereospecific ( A . Todesco, Brazil).
Recoil reactions are accomplished in a small area without
greater disturbance of the atomic arrangement and lead
t o specific changes. The triphosphate fraction isolated
from phosphates is preferentially labelled in the middle
(P-O-3ZP-O-P),
which can be explained in terms of the
insertion of a recoil atom between two PO4 etrahedra.
Triphosphate formed from diphosphates is preferentially
the triphosphate
labelled at the end (32P-O-P-O-P),
resulting from addition and not insertion (L. Lindner,
Netherlands). Analogous conclusions came from the nonstatistical distribution of ReCI,Br;:,
ions on activation
of KzReBr6-K2SnCl6 mixed crystals. Generalization of these
conclusions led to a “disorder model” for the mechanism of
recoil processes.The region in which the recoil atom originates
and in which its fate is decided, includes no more than 20
atoms ( H . Muller, Germany). Further evidence for the smdl
size of this region was obtained during investigation of alkylbromideibromine mixtures ( R . Ho/zne, U.S.A.) and from the
annealing behaviorofcompoLinds such as [Rh(N Hj)@mBr]Br2
after the nuclear isomeric transition XomBr + 8oBr (G. B.
Schmidt, Germany).
Considerable isotope effects are found with tctraphenylporphin complexes of Zn, Pd, and Pt ( H . E. Rosenbrrrg, U.S.A.).
Isotope effects of similar magnitude and retentions of less
than 17; were found with ruthenocene. In general, retention
seems to be mainly due to reformation (G. Hmi5oft/e, U.S.A.).
In contrast with earlier assumptions, reformation seems also
to be possible in complicated organic molecules. Thus, 35smethionine can be obtained directly from methionine by
neutron-irradiation ( B . G . Dzonriev, U.S.S.R.). Interesting
commercial applications can be expected.
Mossbauer Effect
1291 and 1311 disintegrate with (?-radktion into excited 129Xe
and 131Xe, respectively, which are converted to the ground
state after about 10-9sec. With the aid of the Mossbauer
effect information can be obtained about the chemical state
of the xenon at the instant of disintegration, i.e. 10-9 sec
after its formation. At this time all changes in the electron
shells are completed. The following chemical changes occur
due to $decay:
NaI
+ Xeo
~ a 1 0 ~ + XeO3
K104
+ Xe04
Na3H2106 i6 0 octahedrally around Xe, perhaps Xe0;12
+ Xeo, no Xed, no XeI
KICL4.H20 + XeCIq
KICI2 H2O + probably XeCIj
These experiments show that the hitherto unknown xenon
compounds XeOj, XeC14, and XeC12 are stable at least for a
short time ( G . Perlow, U.S.A.).
[VB 8921203 IE]
German ve;sion: Angew. Clieni. 77, 384 (1965)
Tenth Aniversary of the Institute for Organic Chemistry
of the German Academy of Sciences
The tenth anniversary of the Institut fur Organische Chernie
der Deutschen Akademie der Wissenschaften in BerlinAdlershof (Germany) was celebrated by a Colloquium on
November 26th, 1964. Three lectures were delivered: H. Bredereck (Stuttgart, Germany) reported on “Complexes of
Acid Amides with Acid Chlorides or Dialkyl Sulfates“,
J . Rudinger (Prague, Czechoslovakia) on “Oxytocin: Organic
Synthesis as a Means for Investigating the Effects of Hormones“, and H. A . Stnab (Heidelberg, Germany) on: “Investigations on New Aromatic Ring Systems”. During the
afternoon session, members of the Institute reviewed current
work of the Institute in the course of 10 short communications. Abstracts of some of these papers are given
below [I].
~.
~.
Ring Opening of Cyclic Diazo Compounds
E. Schmitz, R . Ohmc, D. Htibisch, S.Schrarnrn, A. Stnrk, and
Ch. Horig
Cyclic diazo compounds (f) split off nitrogen at temperatures
above 150 OC. Cyclopropanes (2) and olefines ( 3 ) are formed
vicr intermediary carbenes.
i 1)
i 2)
i 31
The formation of some of the olefines can only be explained
by the assumption that a linear diazo compound is formed
as an intermediate:
[ I ] Other papers, which havc in part already been published,
were the following: M . Schulz, Angew. Chem. 75, 918 (1963);
Angew. Chem. internat. Edit. 2, 623 (1963); 2. Naturforsch. 1915
263 (1964); M. Loren-, Mber. dtsch. Akad. Wiss. Berlin 6 , 578
(1964); H . Dorn, Angew. Chem. 76. 920 (1964); Angew. Chem.
internat. Edit. 2, 748 (1964).
3 64
Angew. Chem. internat. Edit. / VoI. 4 (1965)
1 No. 4
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