close

Вход

Забыли?

вход по аккаунту

?

Fluorosulfonic Acid as a Reaction Medium and a Fluorinating Agent.

код для вставкиСкачать
Uniform polymers would be expected in ideal single crystals
from purest monomers if the mechanism were a biradical one.
Perhydrotriphenylene functions as host not only for small
molecules, but also for unbranched macromolecules, which
form highly stable, even fusable canal inclusion compounds
[4). This affords a method of separating branched molecules
even in the macromolecular range and provides a means of
shielding macromolecular substances in order to prevent
undesired reactions. Graft polymerization in canals has not
yet been observed. Radioactive host substances which can be
regenerated are economically important.
[Lecture at Clausthal (Germany), November l3th, 19641
[VB 8751179 IE]
dcrgo thermal decomposition to give either fluoride and SO3
ox mostly oxide and pyrosulfurylfl uoride (the anhydride of
fluorosulfonic acid).
Characteristic reactions oT fluorosulfonic acid are illustrated
by its reaction with telluric acid (in the form of BaH4TeO6)
which leads to new compounds containing the FeSTe group.
The most interesting product is undoubtedly FjTeOH, m.p.
40 "C, b. p. 60 " C , a strong acid which can be used to produce
salts with the anion FjTeO" and other derivatives with the
FjTe group.
[GDCh-Ortsverband Saar, Saarbrucken (Germany), Deceniber I Ith, 19641
[VB 8901192 IE]
German version. Ansew. Chem. 77, 3 5 7 (19651
German version: Angew. Chem. 77, 353 (1965)
Hydrolysis of Metal Alkoxides -~
a New Method for Studying Polyacids
Valence Tautomerism of Unsaturated
Ring Systems
K. F. Johr, Berlin (Germany)
R. Huisgen, F. Mietzsch, G. Boche, and H. Seidl,
Miinchen (Germany)
The same kinetic method [S] which was used to prove the presence of 0.01 % bicyclo[4,2,0]octa-2,4,7-trienein equilibrium
with cyclooctatetraene by valence tautomerism was applied in the cyclooctatriene series. Kinetic investigations of
the Diels-Alder additions of pure cycloocta-1,3,5-triene and
of bicyclo[4,2,0]octadiene afforded all the parameters of the
free-energy diagram; the free energy of tautomerism is 1 . S
kcal/mole, and the activation energy for conversion into the
bicyclic compound is 27.1 kcallmole.
With substituted cycloocta-l,3,5-trienes the equilibrium concentration of the bicyclic tautonier at 20 " C strongly depends
on the nature of the substituents: It is 0.0072 for 7,g-epoxycycloocta-1,3,5-triene, 5 P:for cycloocta-2,4,6-trien- I-one, 9
for cycloocta-1,3,5-triene, and lOOx for 7,s-dibromocycloocta-l,3,5-triene.
The kinetics of the Diels-Alder reaction also indicate a valence tautomerism between trans-l,2-diphenylbenzocyclobutene and trans,trans-5,6-dibenzylidenecyclohexadiene
(u$diphenyl-o-quinodimethane), activation energy : 20.6 kcdl/
mole. Analogous ring opening of cis-l,2-diphenylbenzocyclobutene at 50 "C to give frans,cis-S,6-dibenzylidenecyclohexadiene proceeds seventy times as slow.
[GDCh-Ortsverband Mainz (Germany), November 26th,
19641
[VB 8911193 IE]
If a n ester of a metallic acid, e. g. Nb(OC2H5)j or
WO(OCzH&, is hydrolysed i n an organic solvent with less
than the equivalent amount of water in the presence of a n
anhydro base, a polyanion is formed which precipitates as
the salt of the base. The degrees of condensation and protonation of the polyanion are determined mainly by the p K
of the base.
Advantages of this new method are:
Fluorosulfonic acid is probably the most strongly protondonating solvent. The conductivities observed for solutions
of sulfuric acid, perchlorid acid, and hydrogen fluoride in
fluorosulfonic acid can best be interpreted by assuming that
these substances behave as bases. Only a few fluorides (SbFj,
BF3, PtF4, TaFS, and AuF3) behave as Lewis acids in fluorosulfonic acid. Correspondingly, many salts, particularly salts
of oxyacids, are solvolysed completely in FS020H. I n most
cases fluorides are subsequently formed, sometimes immediately in strongly exothermic reactions ( e . ~ . FMnO-,,
F2Cr02, F3P0, and F5TeOH), sometimes only on prolonged
heating (e.g. FCIO3, FzSe02, AsFj, and AsF3). I n addition
to the fluorides, fluorosulfates or fluorosulfate-fluorides may
occur as more or less stable intermediates, which in turn un-
1. The products are pure salts of the polyacids, without any
water of crystallization [I]; in organic solvents, the water
only causes hydrolysis and not hydration. Any water contained in the salts is exclusively part of the molecular structure.
2. It is possible to estimate quantitatively the amounts of the
metallic acid ester and of the anhydro base which react with
a given amount of water to form the salt of a polyacid. The
reactions leading to the various anionic species of the polyacid cdii then be formulated precisely. In particular, the ratio
of oxygen to metal atoms ( e . g . Nb or W) can be determined
for each polyanion, a factor which is indispensible for
structure determination.
3. Salts of polyacids can be obtained which would becompletely hydrolysed in aqueous solution.
4. Salts can be obtained of polyacids which are intermediates
in the hydrolysis reaction but which cannot be isolated from
aqueous solutions. During the hydrolysis of WO(OC2H15)4in
ethanol, the ammonium salt of hexameric "paratungstic acid
A ' was isolated for the first time [2]. In contrast to the ammonium salt of dodecameric "paratungstic acid 2'' (the
ammonium paratungstate which crystallizes from aqueous
solution in a highly hydrated form) the new salt is readily
soluble in water and exhibits all reactions characteristic of
the paratungstate A ion, which was hitherto known only in
solution; these reactions serve to distinguish it from the
paralungstate Z ion.
Oxyacids which condense with metallic acids also react
with the e s t e r s of metallic acids to give heteropolyacids 131. Thus, acidolysis of t-butyl orthovanadate
VO(OC4H9)3 with phosphoric acid in anhydrous organic
solvents leads to linear chains of alkoxyvanadatophosin which the
phoric acids, H-(I-IP03--V02-OR)n-P04H2,
vanadate and phosphate groups alternate. The alkoxyl
groups are hydrolysed with a little water, giving short-chain
vanadatophosphoric acids H-(HPO~-HVO~),-PO~HZ ( I ) .
The solubilities of ( I ) i n organic solvents decrease as the
length of the chains increases, and hence the chain extension
ceases as soon as the solubility becomes zero. The greater
the hydrophilicity of the solvent, the higher is the solu-
[4] M . Farina, G . Allegra, and G. Natta, J. Amer. chern. Soc. 56,
516 (1964).
[ 5 ] R . Huisgen and F. Mietzsch, Angew. Chern. 76, 36 (1964);
Angew. Chem. internat. Edit. 3 , 83 (1964).
[I] K . F. Jnhr and J. Fucks, Chern. Ber. 96, 2457, 2460 (1963).
121 P. Witte, Ph. D. Thesis, Freie Universitat Berlin, 1964.
[3] U. Skumia, Ph. D. Thesis, Freie Universitat Berlin, 1964.
x
German version: Angew. Chem. 77, 353 (1965)
Fluorosulfonic Acid as a Reaction Medium and
a Fluorinating Agent
A . Engelbrecht, Innsbruck (Austria)
368
Angew. Chem. internat. Edit.
1 Vol. 4 (1965) / No. 4
Документ
Категория
Без категории
Просмотров
0
Размер файла
146 Кб
Теги
acid, reaction, agenti, fluorination, medium, fluorosulfonic
1/--страниц
Пожаловаться на содержимое документа