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Chemistry of Quinonemethides and Quinodimethanes.

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The Influence of the Solvent on
Coordination-Chemical Reactions
V. Gurninnn [*I
Solvents can be classified as donor or acceptor solvents. Interaction of a covalent acceptor molecule and a donor solvent
molecule (D) can be measured calorimetrically. The values
of - A H (not AHO) for the reaction
SbCIs (soh.) -t D (soln.)
:-Q
D.SbClS (soln.)
are termed donor numbers, DN(SbCl5). They are proportional to the equilibrium constants K1 and the - A H values
of the corresponding reactions of the solvent with other
acceptors, such as SbC13, SbBr3, (CH&SnCI, 12, and phenol.
Formation of a chloro complex on addition of chloride ions
is considered as a ligand exchange:
D.SbC15 (soln.)
+ C1- +
[SbC16]-
+ D (soh.)
The equilibrium constant is inversely proportional to the
donor number of the solvent:
DN (SbC15) log K2
- const.
The donor number of a solvent determines its ability to
dissolve ionic as well as covalent compounds, also the
ionization of dissolved substances, the occurrence of autocomplex formation, and the tendency to formation of
coordination compounds with other ligands (competing
ligands).
The larger DN(SbC15) is, the better is the dissolving power
and the greater the ionization. Competing ligands give
complexes if they are stronger complexing agents than the
solvent. The smaller the donor number, the smaller is the
dissolving power and the ionization; thus solvents with
relatively small DN(SbCI5) must be used for reactions with
weakly competing ligands. Autocomplex formation is to be
expected when the coordination-chemical properties of the
donor solvent and competing ligands are similar.
The dielectric constant is important only for ionic dissociation
and thus for the electrochemical behavior of solutions.
Steric factors have more effect the higher the coordination
number, the smaller the central ion, and the more bulky the
solvent molecule.
Numerous examples in, particularly, acetonitrile (DN 19,
propylene carbonate (DN 15), trimethyl phosphate ( D N 23),
and dimethyl sulfoxide (DN 30) are used to show that the
donor number can be used to explain the varied behavior of
one system, e.g. Fe3+ Cl-, in different solvents. Whereas in
acetonitriie all the C1--coordination forms can be obtained,
FeC13 undergoes autocomplex formation in trimethyl phosphate, and ionization occurs in dimethyl sulfoxide even in the
presence of large concentrations of C1-:
+
FeCI3
where m’ = the reduced monomer unit rotation; the constants were calculated electronically: A0 = 201 mp, A1 =
225 mp, A2 = 163 mp, for CHCI3 a0 = -641 ; bo = 311 ; A1 =
212; A2 = -1402.
Copolymers of r-lactide with or-lactide, glycollide, 6-hexanolactone, 3,3-bis(chloromethyl)oxetane, 3-propiolactone, epichlorohydrin, and 1,2-epoxy-?-vinylcyclohexanehave been
prepared and the influence of composition on the rotatory
dispersion has been studied.
Racemisation of atropisomeric groups is much slower when
they are present in polymer molecules than when they are
present in model compounds of lower molecular weight [21;
but the viscosity of the medium has no influence on the rate
of racemisation. Optically active polyamides ( I ) and polyUreaS (2) have been prepared from (+)-1,I,-binaphthalene2,T-diamine.
+ 6 DMSO +
[Fe(DMSO]#+
+ 3 CI-.
[VB 33 IE]
Lecture at Brunswick (Germany) on November 7th, 1966
German version: Angew. Chem. 79, 279 (1967)
-20.4
-2330
On the basis of the helix structure assumed by Freudenbergr31
the familiar blue iodine-starch complex should show an
induced Cotton effect; in fact, a maximum in the O R D curve
occurs at 585 m p ; the circular dichroism is positive, with a
maximum at 545 mp. With a molar ratio 12:glucose unit =
1:6, [m];i0 = +4000 (calc. per C6H1005). I n contrast to the
extinction (A,,,
= 565 mp), the rotation is approximately
doubled in 40 hours. Factors that destroy the helix structure
(heating, addition of urea or detergents) decrease the rotatory
power. Addition of solvents (methanol, dimethyl sulfoxide,
hexafluoroacetone hydrate) also alter the absorption and
rotatory dispersion curves.
Lecture at Giessen (Germany) on December 6th, 1966
IVB 38 IE]
German version: Angew. Chem. 79, 280 (1967)
[*I Dr. R. C. Schulz
Organisch-chemisches Institut der Universitat
65 Mainz (Germany)
[I] R. C. Schulr and J . Schwanb, Makromolekulare Chem. 87,90
(1965).
121 R . C. Scltulz and R. H . Jung, Makromekulare Chem. 96, 295
(1966).
[ 3 ] K . Freudeiiber-g et al. Naturwissenschaften 27, 850 (1939);
F. Cramer and W . Herbst, ibid. 39, 256 (1952).
[*I Dr. V. Gutmann
Institut fur Anorganische und Allgemeine
Chernie der Technischen Hochschule
Getreidemarkt
Vienna VI (Austria)
Chemistry of Quinonemethides and
Quinodimethanes
By R. Gompper[*l
Recent Studies of Optically Active Polymers
R . C. Schulz[*l
The rotatory dispersion of poly-L-lactide can be described
by the Moffit-Yang equation (a) or by the modified two-term
Drude equation (b).
Angew. Chem. internat. Edit. J Vol. 6 (1967) 1 No. 3
w,w-Bis(alky1thio)quinomethides “1 (In) and related compounds ( I b ) are ambifunctional nucleophiles and electrophiles.
Typical reactions of (Za) with electrophiles include those
with PCls o r SOC12, whereby, for instance, 4-chloroaryl
1,3-dithiolanium salts are formed. 0-and p-Quinodimethides
271
differ in their reactions with diphenylketene: whereas the
para-compounds give diphenylquinodimethanes, dihydrocoumarins are formed from the ortho-isomers.
Reaction of (la) with nucleophiles normally leads to removal
of RSH, addition of amines gives, for instance, the product
(16) with R = R = NR2. The CO group is attacked only on
interaction of Grignard compounds with compounds of type
(la) in the anthracene series; this yields p-quinodimethanes
(2) that are characterized by halochromism(vio1et coloration).
Synthesis of other p-quinodimethanes can be achieved (i)
by heating phenylmalonodinitrile or related compounds
with, e.g., l-methyl-2-methylthio-1,3-dithiolaniummethyl
sulfate121 or (ii) by removal of H X from N,N-disubstituted
p-cyanomethylthiobenzimidic ester salts. The color of quinodimethanes is strongly dependent on the extent of annelation.
Some 2-aryl-l,3-dithiolanium salts of related structure
were prepared by dehydration of the corresponding aldehyde
mercaptals, to serve as models for study of the relation
between color and constitution.
Method (ii) was used in the first synthesis of a n o-quinodimethane (3) that was stable at -40 to -20 OC, and in which
valence isomerisation to the substituted bicyclo[4.2loctatetraene is apparently hindered. Compound (3) dimerises
rapidly at room temperature to give a dibenzocyclooctate-
CN
CN
traene and reacts with acetylenedicarboxylic ester to give a
naphthalene derivative. Heterocycles of o-quinodimethane
structure, e.g. ( 4 ) , are obtained on treatment of (3) with
diphenylcarbodiimide, phenyl isocyanate, phenyl isothiocyanate, or carbon disulfide. Substitution of (3) by l-fluoro2,4-dinitrobenzene affords an o-quinodimethane that is stable
even at room temperature.
[VB 40 IEI
German version: Angew. Chem. 79, 279 (1967)
Lecture in Wiirzburg on November 18th. 1966
[*I Prof. Dr. R. Gompper
S
U
Institut fur Organische Chemie der Universitat
8 Miinchen (Germany)
[l] R . Gompper, R . R. Schmidt, and E. Kutter, Liebigs Ann.
Chem. 684, 37 (1965); Chem. Ber. 98, 1374 (1965).
[21 R. Gompper, E. Kutter, and H.-U. Wagner, Angew. Chem.
78, 545 (1966); Angew. Chem. internat. Edit. 3, 517 (1966).
SELECTED AB STRACTS
Tetrangomycin and tetrangulol, the first benz[u]anthraquinone
derivatives obtained from natural sources, have been isolated
by M. P. Kunstmann and L. A . Mitscher from Streptomyces
rimosus cultures. 363 mg of tetrangomycin ( I ) , [a]::= 41.8 i
3.5 O (chloroform), yellow crystals, m.p. 182-184 OC, and
2.41 g of tetrangulol (2), purple needles having m.p. 189 to
200 "C, were obtained from a 3000 1 fermentation. Hydrocarbons with this ring system can act as carcinogens. / J. org.
[Rd 605 IE]
Chemistry 31, 2920 (1966) / -De.
1,ZAzaboretidme (I) has been synthesized by S. AkerfeIdt
and M. Hellstrom by the reaction of aziridine with sodium
tetrahydridoborate in moist tetrahydrofuran, or in dry tetrahydrofuran with the addition of glacial acetic acid [ ( I ) , m.p.
47-4SoC, yield 70 or 7373. The compound is relatively
toxic. Its structure was established from the NMR and IR
spectra. ' Acta. chem. scand. 20, 1418 (1966) / -WG.
[Rd 606 IE]
An Arbusov-type rearrangement of a >P-0-N grouping has
been postulated for the first time by B. J . W. F. Hibberd and
B. L. Tonge. For example, N,P, P-triphenyl-O-phosphinohydroxylamine (I), which is prepared from equimolar
amounts of chlorodiphenylphosphine and phenylhydroxyl-
272
amine in benzene in the presence of triethylamine or pyridine
at 5 "C, rearranges spontaneously and quantitativcly to give
N, P,P,-triphenylphosphinamide(Z), probably by a six-center
synchronous mechanism.
However, only compounds of the type (R0)zP-0-N
< have
so far been isolated, and not compounds of the type (I). 1
Chem. and Ind. 1966,1599 / -Jg.
[Rd 607 IE]
The separation of zirconium and hafnium with o-phenylenebis(dimethy1arsine) in a single operation has been achieved
by R. J . H. Clark, W. Errington, J. Lewis, and R. S .
Nyholm. The rates of precipitation of the complexes
[ M X ~ . ~ ~ - C ~ H ~ ( A S ( C( M
H ~=)Zr,
Z ) ~Hf;
] X = C1, Br) differ
considerably. These complexes (coordination number 8,
symmetry class D2d) are obtained from the anhydrous tetrachlorides in anhydrous THF. Corresponding complexes can
also be prepared with Tic14 and TiBr4; with TiF4 and TiI4,
however, the coordination number 8 is evidently n o longer
reached. The first fraction in the fractional precipitation of a
mixture of zirconium and hafnium halides contains 35 % of
the zirconium used, but no hafnium. A disadvantage of the
separation process is probably the need for complete exclusion of air and moisture. / J. chem. SOC.(London) A 1966,
989 / -Bu.
[Rd 617 IE]
Angew. Chem. internat. Edit. / Vol. 6 (1967)
No. 3
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