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7




Summary

The specific gravity of fibers of polyacrylonitrile and chlorinated poly vinyl chloride (64% Cl) subjected to stretching and thermore-laxation has been determined by the flotation method. The results have been interpreted in terms of changes in the molecular packing density which has been shown to depend on both orientation and ther-morelaxation. A theoretical calculation has been made of the specific gravity of a number of polymers.

1 . Present Perfect Tense , , , . Indefinite.

150. Present Perfect - l(b ) . (. 149), Present Perfect , , , .

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Introduction

Ever since the discovery by Szilard and Chalmers, in 1934 that chemical reactions can result from the consequences of nuclear processes, the attempted elucidation of the chemical consequences of radiative neutron capture has been the object of much experimental effort. A mechanistic approach to hot atom chemistry has appeared comparatively recently. No generalization has yet appeared which provides a unifying rationale of all currently available data. Several models, for example physical impact, epithermal reactions, random bond fragmentation and the displacement spike, which emphasize physical considerations, have been suggested. Models stressing the importance of chemical environment have also appeared.

Introduction

Although several previous investigations have led to the conclusion that pure benzene is unaffected by ultraviolet radiation in the range of quartz transmission, a number of workers have observed a change when benzene in an organic glass is irradiated at the boiling point of nitrogen. Ingram, Hodgson, Parker, and Rees, using a paramagnetic resonance technique, found evidence for the formation of trapped free radicals in similar unmelted glasses. Leach and his co-workers have also investigated these effects.

151. Present Perfect , .

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It is already well known that in many reactions of this type, relatively high yields can be obtained especially, for example, where the steric requirements for the reaction are favourable, as in Pschorr's phenanthrene synthesis. A study has therefore been'made of the electrolysis of a series of o-benzoylbenzoic acids in order to find out if the o-benzoyloxy-radical will give rise to an o-ben-zoylphenyl radical, which can then undergo intramolecular cyc-lisation with loss of a hydrogen atom to form a fluorenone. The formation of fluorenones by means of o-benzoylphenyl radicals (and the o-benzoylphenyl cation), prepared from the diazonium salts of 2-aminobenzophenones, has already been reported, but attempts to prepare the peroxide of o-benzoylbenzoic acid as an alternative source oj the o-benzoylphenyl radical have failed. The present work should provide such an alternative source.

152. , PresentPerfect Indefinite. :


Abstract

Nuclear magnetic relaxation of a two-spin system is discussed using Redfield's semiclassical formulation of the relaxation processes. An expression for the nuclear signal is given, from which the expected shape of multiplet lines and their behaviour upon various origins of the relaxation are discussed in detail. The discussion leads to the conclusion that the mechanism of nuclear relaxation can he determined by carefully analyzing the spin multiplet lines on the basis of the theory. Finally, it is shown that there is a possibility of finding the absolute sign of the spin-spin coupling constant in a two-spin system using the multiple resonance method.

Summary

The thermodynamic description of inhomogeneous systems is adapted to a determination of the pair correlation function. The method is most effective for describing the correlation behaviour near a critical point. The critical-point behavior is investigated for a simple model fluid of the van der Waal's type. A novel optical scattering phenomenon is predicted for the interface between two equilibrium phases for temperatures below but very near to the critical temperature. The effect of inclusion on critical point phenomena is noted.

Abstract

Equations are obtained which express the decay of motion of fluids between concentric cylinders, parallel plates, and in tubes. Numerical examples are given which indicate that the time required for the flow to decay may not always be short compared to the streaming birefringence relaxation times.

153. Past Perfect. , : , . :

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The temperature had been raised by 20 before the explosion occurred.

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. They had been through with their series of experiments by the end of the year.

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, , -, , . It was surprising to find that andros-terone is an alcohol of the epitype, for such substances had not been known to occur in nature.

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1934 . , , , , . In 1934 Danielli and Adam pointed out that the area occupied in the surface by an crgosterol molecule was decidedly unfavorable for the hydroxyl gvoup,'ashadbecn suggested in the same year by Rosenheim and King.

154. Future Perfect , : , .

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, 80 90000 . Before the Exhibition closes 80 to 90,000 people will have attended it.

. if, when, after, before, until, unless, as soon as . . Future Perfect Present Perfect (. 117). :

, . If the operation has been performed properly, the material will give a negative test for unsaturation.

, , . When the two hydrogen atoms of the amino group of amiline have been replaced by alkyl radicals the compounds will react, losing hydrogen from the para position of the ring.

, - ' . The blue colour will occur at a half-way stage in the oxidation when each benzidine molecule has lost one electron.


, 70. .4s soon as the carbon disulfide has all reacted, the temperature will be raised to 70.

, , 1 2 . After the gel has solidified, the cell will be turned upright and enough pure mercury is added to the reference electrode compartment to give a layer a centimeter or two deep.

, 25 .

Alternate filling and distilling will be continued until 25 ml of condensate has been collected.

155. Present Perfect Continuous. : to have + been + . Perfect Continuous Continuous , . Perfect Present Perfect Continuous .

() () 10 . I have been living in Moscow for 10 years.

() () 30 . I have been studying English for 30 years.

. Evidence for the association of Grignard reagents in solution has been accumulating for a long time.

5000 . The South African industry has been running at a uranium oxide output of about 5,000 tons per annum for the last few years.

156. Present Perfect Present Perfect Continuous. , , , Present Perfect, since ( ) for ( , ).

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. Methods for the preparation of diazomethane have steadily improved.

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. Ever since Taylor first proposed "the active point" concept to account for the extreme sensitivity of catalytic surfaces to poisons, the structural nature of these points has been under discussion.

. We have dealt with these problems for many years.

157. . (Past Indefinite), , . . (Present) (Past), (Future in the Past, Future Relative).

Future Relative: should (would) + to. .

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, . It ivas said in the article that our age was the age of specialization.

, . The ancient Greek philosophers reasoned that matter was made up of infinitely small particles.

, . Aristotle considered that this theory would best agree with his general views on nature.

, . It was noticed that some water distilled at the beginning of the distillation.

1869 . , . As early as 1869, Gore reported that filter paper was readily attacked by liquid hydrofluoric acid.

, , , , --, - . They also demonstrated that under a given set of conditions the hydrochloric acid-catalyzed reaction yielded the same ratio of orto p-chloroacetanilide as did the reaction of acetanilide with chlorine.

, . Reppe found that carbonyl iron and electrolytic iron were very suitable catalysts for partial hydrogenation

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, . Berzel-lius reported that water, especially if hot, dissolved the acidic component of calcium fluoborate and left a residue of a basic salt containing an excess of calcium fluoride.

158. . , :

, 1. After Copernicus and Galileo everybody could Jmow that the earth turns round the sun.

, *. Cavendish discovered that water consists of a definite proportion of hydrogen and oxygen.

, , , , - , Present Indefinite Future Indefinite, , Past Indefinite Future in the Past (Future Relative), .

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, . // teas found that ultraviolet-activated pliages cause marked alterations of cell structure.

, . Kelner discovered that visible light has the remarkable ability of restoring viability.

, - -. Nagel showed that active a-benzylpropiinamide gives optically pure a-benzylethylamine.

, , , , . The improbability of hydroxylamine being an intermediate at all was demonstrated by Goldschmidt when he found that the action of copper on plenyldichloramine also gives azobenzene and phenyF quinonedi-imine.

f,' , -, , 8 10%- .

1 . . . . , , . 2- ., .> 1962, . 94.


King and Hibbert found that methanol sprice Hgnin and primary lignin are both stable, even when heated with 810% sodium hydroxide.

159. , , , , : to believe, to assume, to suggest, to express the view, to maintain, to state initially, to claim, , .

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, . They believed that, on treatment of beechwood lignocellulose with ozone the latter reacts with the cyclohexanone group.

, - . Klason believed thatlignin is built up of coni-feryl aldehyde complexes.

, . Schuz assumed that in protolignin this hydroxyl group is acetylated.

, ( ) . established the formula of the alcohol and suggested that saponification of the ester (uder rather drastic conditions) proceeds as follows.

, . It was sug gested that hydrate formation plays a part in the aqueous polymeri zation.

, 2- . Kurschner suggested that the main valency chains of lignin are built up by a repeating 2-ring system.

, , , . Lapworth expressed the view that it is to electrolytic dissociation that the majority of changes in organic compounds may be most probably assigned.

, . maintained that chemical reactivity


in a constant thermodynamic environment is determined by three different factors.

, , . Doisy initially stated that these and related degradation products possess several times the estrogenic potency of pure estrone.

, II . The author claimed that formula II is in good agreement with the following experimental results.

160. . . . : , , . : Pasteur discovered that sodium ammonium racemate crystallized in two hemihedral forms, , 1848 ., , , . : Pasteur discovered that sodium ammonium tar-trate crystallises in two hemihedral forms1.

, . . . , , , . , . , . , , to show , , .

Interest in organic free radicals was revived in 1900 by Gomberg's chance discovery of triphenylmethyl. He showed by chemical and physical means that hexaphenylethane dissociated into triphenylmethyl in solution. In a few years many heavily substituted methyl radicals were prepared. During the next decade numerous workers showed that free radicals are involved in many commonplace

1 L. and M. Fieser. Op. cit., p. 14. 172


chemical systems. Rice and Herzfeld (1934) showed how the results obtained in the study of the thermal decompositions of hydrocarbons and other simple molecules could be explained in terms of chain mechanism involving free radicals. At the same time it was shown that the combination of hydrogen with bromine is also an atomic reaction1'

.

Holmberg assumed that a transacetalization takes place and believed that thio compounds would react more readily. Burg reported that boron trifluoride reacts quantitatively with zinc methyl to yield boron trimethyl and zinc fluoride. Kraus and Brown found that boron trifluoride reacted with lithium methyl in liquid ethylamine to give lithium fluoride, hydrogen, and boron triethylimine.

Barltrop and Jeffreys pointed out furthermore that the weak ferric chloride test for their base resembled that of isochondrodendri-ne but was much less intense that of curine and chondrocurine. They ascribed this more intense reaction to the presence of group (IV), and deduced that their base does not contain a phenolic nucleus bearing only two oxygen atoms.

Craig pointed out that the dimensions and energies of the phosphorus d-orbitals will be affected by the adjacent li-gands. Craig believed that the resulting changes in Coulomb and resonance integrals are such as to make interactions of the adjacent nitrogen atoms much more important. This assumption seemed to us unjustified. Since we also felt that the experimental evidence did not support the idea of aromatic resonance in the phosphonitrilic chlorides, we suspected that the prediction of such resonance by Craig's treatment was an artefact, due to neglect of the dU2-inter-actions; and that when these were included the it-electron system would be seen not to be continuous around the ring.

161. ' . . , , , . , , :

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, , , , . Doisy thought that an ethylenic double bond was indicated by the ready reaction of oestrone with bromine, but Marrian soon showed that the substance formed is not an addition product but simply a product substitution in the phenolic ring.

162. : to be + ( ).

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: Our aim is to oxidise this compound. to be + , : , , , , , , , , , , , , , .

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, . The object of Strecker's research was to find a method for synthesizing lactic acid.

, , . In the quantitative determination, however, the goal is to obtain the lignin, not only in the purest possible state, but also quantitatively.

. A simpler method is to render the aqueous solution more acidic.

, , . The procedure traditional at Gottingen had been to allow the ultraviolet light source to heat the solution of ergosterol.

, , . The mode of the action of the


catalyst is often described as being to find a "pass" through the energy barrier.

. The general scheme of such a method will be to take an ammo-acid.

Another possibility was to utilise hecogenin.

. The aim of the present investigation is to acquire new data on the chemistry of isoxazoles.

- . The purpose of the present work was to investigate the electron exchange between the various substituent groups of the organosilicon radicals chosen.

163. : to be + ( ) , , , ( , . 143).

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, , , , , , . It is to be noted that according to classical ideas the reaction under consideration would be expected to follow the complete path of the potential energy curve, the various stages taking place in turn.

, - . It is to be pointed out that both series of derivatives fail to isomerise in acids.

. This compound is rarely to be found free in nature.

, . <iWe are to find these starting compounds to carry out a new experiment.

, . , . Sulfuric acid is generally preferred if the butyl alcohol procedure is to be followed or the bases are to be isolated. Hydrochloric acid is preferable when the monoamino acids are to be determined.





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