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Страница 64.

Theoretical studies of this model have, however, not been taken far enough to establish whether it provides an explanation of the behaviour of the quasi-spherical polyatomic molecules described in the present paper. They are generally in good agreement, however, with the results from the densimetric and X-ray methods within the limits of experimental error.
All these features suggest aromatic character. The ring differs, however, from that in benzene in that the formation of я-bonds requires the use of a d-orbital at the phosphorus atom.
В «Style Book», составленной О. Горчаковым (Москва, 1957), отмечается, что however следует ставить после первой значимой единицы, что, в основном, соответствует приведённым выше примерам. • -: Наряду с этим нельзя не обратить внимание на многочисленные случаи употребления however в начале предложения. Возможно, что в таком случае however имеет более категорическое значение «однако»,;в то время как находясь в середине предложения,
1 L. and М. Г i e s e r. Op. cit. , p. 23. 8 А. Л. Пумпянский
however скорее приближается к значению «тем не менее». Например:
Neither preparation had a significant effect on the production of maltose from amylopectin-p-amylase or Floridean starch-p-amylase systems; by this criterion gross contamination with-a-amy-lase could be ruled out. However, when amylose, amylose (3-dextrin, or amylopectin p-dextrin was used as substrate, and assay was by iodine-staining and reducing power or viscosity, the presence of a trace of oc-amylase was established.
Although the tendency of trans-l,3-0-benzylideneglycerol to isomerise in the presence of acid has not been studied the cis-isomer is known to be sensitive to acid and to be rapidly and predominantly converted into 1,2-0-benzylideneglycerol. However, treatment of cis- and trans-l-3-O-benzylideneglycerol with pyridine-benzene-hydrogen chloride at 30° for 24 hr. had little effect.
From Table 2 it is obvious that the behaviour of the remaining three tervalent vanadium complexes we have studied is very similar to that of the alum. However, in view of the Weiss constant of 14°, not too much significance can be placed on the result for the malonate.
All of the points obtained fell on a plateau, and the form of the isotherm at lower pressures can only be supposed to be similar to that for untreated firebrick. However, it is clear from the diagrams that saturation of the treated firebrick is reached at about one tenth of the equilibrium pressure for saturated untreated firebrick.
In principle the estimation of relative nucleophilicities in this system should not be difficult because the reactions are effectively irreversible, and so product yields should be directly proportional to the individual rates of reaction. However, other factors complicate such an analysis. The comparison of hydroxide and etho-xide ions, for example, is impracticable because of the base-catalysed exchange of OH by OEt with the hydroxy-compound (I) in ethanol. However, it can be shown that ethoxide ion is a stronger nucleophile towards the N-cyanoquinolinium ion than is the t-bu-tyl hydroperoxide ion, for only the ethoxy-compound (II) can be recovered from an equimolar solution with sodium t-butyl peroxide and sodium ethoxide in ethanol.
Таким образом, можно предположить, что в тех случаях, когда между двумя предложениями дается четкое противопоставление, вводное слово however ставится в начале предложения.
Например:
Когда производилась работа при температуре ниже оптимальной, то присутствовали непревращенный антрацен и некоторые количества сильно окрашенных примесей. Однако при работе с температурами, равными или выше оптимальной, был легко получен антрахянон с чистотой выше 99%. «When operating below the optimum temperature, unconverted antheracene and some highly
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colored impurities were present.

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