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Mechanism of Indirect Nuclear Spin Coupling.

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Biochemistry of Phosphatides Containing Vinyl
Ethers (Plasmalogens)
By Hildegurd Debuch L “1
Plasmalogens [Z-acyl-1-(l-alkenyl) -sn-glycero- 3 -phosphoryl
compounds [**I] occur, usually as choline or 2-aminoethyl
esters, in almost all animal cells and tissues. By mild acid
hydrolysis the aldehyde that is bound like a vinyl ether is
liberated and a corresponding @-lysophosphatide is formed,
whereas o n mild alkaline hydrolysis a lysoplasma~ogenis
obtained. An “ether phosphatide” is obtained o n catalytic
hydrogenation. (Such compounds often occur in small
amounts also in Nature.)
Plasmalogens are, specifically, components of the lipid
mixtures that are obtained from myelin sheaths of nerve fibers
(occurring there almost exclusively as 2-aminoethyl esters)
and from the phosphatide fractions of heart muscle (here
usually cholineplasmalogens). Correspondence in chain
length and degree of hydrogenation can often be found when
studying the =-groups of glycerophosphatides that are always
derived from fatty acids, fatty aldehydes, or fatty alcohols.
In vitro experiments with tissue homogenates or cell fractions
from brain contributed little to the nature of biosynthesis of
plasmalogens, so that in vivo experiments must be carried out
t o clarify such problems. Results to date do not provide unambiguous evidence whether the enoi-ether-like linkage of
the aldehyde in plasmalogens arises through oxidation of an
ether group or through reduction of a n ester linkage; in any
case, “Clabeled aldehydes are not direct precursors of
plasmalogens in the brain in vivo.
Lecture at Hamburg (Germany) o n December 1 5 , 1967
IVB 133 IE]
German version: Angew. Chem. 80, 321 (1968)
[ * ] Prof. Dr. Hildegard Debuch
Physiologisch-Chemisches Institut der Universitlt
5 Koln-Lindenthal, Joseph-Stelzmann-Str. 52 (Germany)
[**I
“sn” denotes “stereospecific numbering”; for nomenclature
see IUPAC Information Bull. 30, 21 (1967).
Fluorides and Perfluoroorgano-substituted
Compounds of 11+ and 13+
By M . Schmeisser [ *I
iodine monofluoride is accessible in good yields as a pale
gray solid of decomposition point 0 ° C by reaction of
iodine with the stoichiometric amount of fluorine, by reduction of iodine trifluoride with iodine in presence of traces of
pyridine, and by metathetical reaction of iodine chloride
with nitrosyl fluoride, in all cases in CC13F at temperatures
from -40 t o -5OOC:
I2+
F2
+ 21F
Izf IF3 CSH%
ICI+NOF
3 IF
+ IF+NOCl
Compounds C S H ~ N . I ( O ~ C Rwhere
),
R = CF3 o r C6F5, are
obtained by the action of iodine on silver salts of the corresponding perfluorocarboxylic acids in pyridine/benzene and
can be considered as further derivatives o f Il+.
Pale yellow, solid iodine trifluoride, decomposition point
-28 “C, is formed on treatment of iodine with a n excess of
fluorine at -45 O C in presence of catalytic amounts of IF3
or pyridine a n d can be stabilized as 1:l adducts with organic
nitrogen bases. The compounds IFzCI, CF3IF2, C6F51F2.
and IFzN03, which can be considered as derivatives of IF3,
are formed o n low-temperature fluorination of ICI, CF31, and
C6F51, or in the case of IF2NO3 by reaction of IFzCl with
chlorine nitrate.
Angew. Chem. internat. Edit. / Vol. 7 (1968) 1 No. 4
The covalently constituted iodine tris(perfluoroacylates) ( 1 1
I(OzCR)3, where R -- CF3, C2F5, C3F7, or C6F5, can be
obtained in almost quantitative yields (a) by oxidation of
iodine with fuming nitric acid i n presence of the corresponding perfluorocarboxylic anhydride, (b) by treatment of iodine
trichloride with silver perfluoroacylates, or (c) in the case of
iodine tris(trifluor0acetate) by the action of peroxotrifluoroacetic acid and trifluoroacetic anhydride o n elemental
iodine; they can be isolated in pure form by fractional
vacuum sublimation:
(a)
I2
(c)
12
+ 6 HNO, + 6 (CF3CO)20
3
2 I(02CCF3)3
+ 6 NO2
+ 6CF3C02H
(CFjC0)20
(b) IC13 + 3 AgOzCCF3
3 I(OzCCF3)3 + 3 AgCl
CCI )F
+ 3 CF3C03H + 3 (CF3C0)20 ---+
2 I(OzCCF3)3 +
-15°C
3 CF3CO2H
When method (c) is used an intermediate, iodyl trifluoroacetate 102(02CCF3), can be isolated in 95 % yield.
Analogously t o the preparation of iodine trisfperfluoroacylates) methods (a) and (c) can be used for preparation,
also in almost quantitative yield, of pentafluorophenyliodine bis(perfluoroacy1ates) C ~ F S I ( O ~ C Rwhere
) ~ , R = CF3,
C2F5, C3F7, or C6F5. Treating these compounds with
NaHC03, leads to formation of dimeric pentafluoroiodosobenzene (C6F510)2, as does hydrolysis of CsFsIF2. This
dimer reacts with perfluorocarboxylic anhydrides in the
reverse reaction, regenerating the corresponding pentafluorophenyIiodine bis(perfluoroacy1ates).
Lecture at FrankfurtiM. (Germany) o n January 11, 1968 [VB 134 IE]
German version: Angew. Chem. 80, 321 (1968)
[*I Prof. Dr. M. Schmeisser
Institut fur Anorganische Chemie und Etektrochemie
der Technischen Hochschule
51 Aachen, Templergraben 55 (Germany)
[I1 M . Schmeisser, k-.Dahmen, and P . Sartori, Chem. Ber. 100,
1633 (1967).
Mechanism of Indirect Nuclear Spin Coupling
By H. Dreeskamp [*I
Scalar “indirect” spin coupling of nuclei of a molecule causes
splitting of N M R signals owing t o interaction of the magnetic
field of the outer shell electrons and the magnetic dipole that
is associated with the nuclear spin. The coupling constants J
and their appropriate signs can be determined by analysis
of the spectrum or by double resonance experiments and
thus can be traced back to the coupling constant of directly
bound C and H atoms. This constant is known to be positive
(with the implication that a positive J denotes decrease in
energy owing t o antiparallel spin) from measurements on
partially oriented molecules.
For tetramethyl derivatives and hydrides of elements of the
fourth main group ’the normalized coupling constants J’
(defined as the constants referred to a gyromagnetic ratio
of i 1) of two nuclei linked by one bond have positive signs
and are, within a good approximation, proportional to the
product of the valence electron densities at the site of the
coupling nuclei. It is thence concluded that the Fermi contact
term makes a preponderant contribution to coupling of
nucleus and electrons.
In a paper concerned with an MO approach t o coupling
constants calculated from peturbation energies and considering only the Fermi contact term, Pople and Sanfry [ ’ ]
predict for J’ a progression from positive values for the C-H
and the C-C bond t o negative values for the C-F and H-F
bond. The analogous constants for Se and T e compounds
confirm this theory, since J’ for Se-C and Te-C is small
309
and negative but for Se-H is small and positive (each
referred to data for compounds of the fourth main group).
Finally, for hydrides of elements of the fourth main group,
the geminal H-H coupling constant shows a progressive
change from -12.4 H z for CH4 to t15.3 for SnH4, which
can be interpeted by a simple MO theory.
These examples can be used to show that values and absolute
signs of coupling constants can, in principle, always be
determined and that even relatively simple approximations
yield useful interpretation of these data. Thus investigation
of indirect nuclear spin coupling can enrich o u r conceptions
of the electron shell of molecules.
Lecture at Berlin (Germany) on January 19, 1968
IVB 136 IE]
German version: Angew. Chem. 80. 320 (1968)
[*I Doz. Dr. H. Dreeskamp
Institut fur Physikalische Chemie der Universitat
7 Stuttgart N, Wiederholdstr. 15 (Germany)
[I] J. A. Pople and D. P . Sanrry, Molecular Physics 8, 1 (1964).
Abnormal Reaction in Alkylation of Silicon and
Germanium Tetrahalides
By J. Valade [*I
It is known that alkylation of silicon and germanium tetrahalides by Grignard compounds can be used for preparation
of C-Si and C-Ge bonds. Abnormal reactions (formation
of H-Si or H-Ge bonds) have been occasionally noted. We
have shown that for SiHal4 and GeHal4 these can become the
main reactions.
The Grignard compound decomposes at 160 “C first into the
unstable magnesium hydride which forms compounds having
H-Si or H-Ge bonds ; on silicon two, but on G e only one
halogen atom is replaced by hydrogen. At 4 ° C halogenhydrogen exchange also occurs, but this differs from exchange at higher temperatures.
In the case of silicon the reaction at 4 OC proceeds through
C13SiH to yield R2SiHCI. GeIv, however, is first converted
into GeII, which is reoxidized to a germylated Grignard
compound containing Gelv. The presence of this intermediate can be demonstrated best by hydrolysis.
Adsorption Calorimetry
By S. &rnp [*I
The bond dissociation energy is the measure of the strength
of bonding of adsorbed particles to solid surfaces. Experimental determination of the bonding energy is, however, difficult
and thus it is usually the adsorption energy, i.e., the heat of
adsorption, that is measured. Although the relation between
bond energy and adsorption energy is close, it is not quite
simple since the total energy effect consists, not only of the
dissociation energies of the forming and breaking bonds, but
also of the changes in degree of freedom of the system, and
in particular, the final regrouping of the surface atoms of the
adsorbent.
The value of the heat of adsorption and its dependence on
occupation of the surface is extremely important for a study
of chemisorption and heterogeneous catalysis. Nevertheless,
there are few reliable data for heats of adsorption, o n the one
hand because the crystallographic state of the surface is
usually inadequately defined and there is insufficient information about surface contamination, and on the other
hand because of shortcomings in the measuring technique for
the heat of adsorption itself.
Heats of adsorption can be measured indirectly or directly.
Indirect methods utilize either equilibrium data (adsorption
isosteres, retention times in gas chromatography) or kinetic
data (thermal desorption, field emission microscopy). Direct,
i.e., calorimetric, determinations of heats of adsorption are
carried out in calorimeters that operate adiabatically, isothermally, or diathermally; the first two of these types can be
used only for powder adsorbents, but the diathermal calorimeter can be used also for films and threads.
For small temperature differences the heat transport (by
conduction or radiation) between the calorimeter and the
outer covering is described by Newton’s law. The simple
Tian formula is approximately valid for all diathermally
operating calorimeters. If the explicit equation for the
kinetics of the adsorption process is available, an expression
can be set up for variation in the measured quantity with
time. This expression affords the heat of adsorption and also
provides a model of the calorimetric curves for use in an
analog computer. Setting up the analog model provides
valuable information about the role of individual parameters
of the calorimeter and the kinetic parameters of the adsorption process.
Lecture at Giessen (Germany) on January 16, 1968
[VB 135 IEJ
German version: Angew. Chem. 80, 321 (1968)
Lecture at Hamburg (Germany) on November 17, 1967
[VB 130 IEI
German version: Angew. Chem. 80,290 (1968)
[*I Prof. Dr. J. Valade
[*] Dr. S . Cern9
Laboratoire de Chimie Organique, Faculte des Sciences
Universite de Bordeaux
F-33 Talence (France)
Institute for Physical Chemistry of the
Czechoslovakian Academy of Sciences
Praha 2, Machova 7 (CSSR)
SELECTED ABSTRACTS
Reactions of organocopper compounds with halogenoolefins
have been studied by J . Burdon, P. L. Coe, C . R. Marsh, and
J . C. Tatlow. Copper acetylides suspended in DMF or pyridine react readily with halogenoolefins at 40-100 OC to give
ethynylolefins, e.g.
C~HS-C_CCU+ ICH=CHCl
-+ C&-C=C-CH=CHCI.
The yields are between 40 and 90%. The ease with which the
halogens are replaced decreases in the order I > Br > C1;
fluorine is not replaced. Perfluoroalkyl iodides react when
heated with halogenoolefins and copper bronze in pyridine
or D M F to give perfluoroalkylolefins, e.g.
3 10
The reaction very probably proceeds via perfluoroalkylcopper compounds (yield 50-96 %). / Chem. Commun. 1967.
1259 J -Ma.
[Rd 816 IE]
“Self assembly” of the fr-phage from the subunits of the coat
protein and the phage RNA has been observed by T. Hohn.
The isohedral protein coat of the fr-phage consists of more
than 180 protein subunits having a sedimentation constant of
4 S. Since the shape of the coat can be achieved only with
distortion of the surface arrangement of the subunits, the
positions of the subunits are,not equivalent. The subunits do
not associate in 0.5 M tris-acetate buffer, even in the presence
of the phage RNA. In 0.15 M tris-acetate buffer, on the other
hand, about 80% of the material aggregates into particles
Angew. Chem. internat. Edit.
Vol. 7 (1968) / No. 4
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