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Determination of the Magnetic Susceptibility of Organic Compounds from Proton Resonance.

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were added after the end of the reaction, After 3 days the
mixture was worked up in the usual way [3] and treated in
addition with NH3 for 10 hours at 25 'C. By chromatography
on DEAE-cellulose, polythymidylic acid (56), n = 1-10, was
obtained in the same yield and purity as in the procedure with
acetic anhydride/pyridine [3].
(1)
(a) R ' =
ment with the theoretical value 2r/3 = 2.094. Corresponding
measurements in paramagnetic media (solutions of diphenylpicrylhydrazyl) yielded c = 2.07 - 0.1.
The method [ 5 ] was applied to the determination of the
magnetic susceptibilities and spin densities of novel radicals
[6] recently prepared by Hiinig (cf. Table). We measured the
H
L
Received, February 28th, 1964
[Z715/540 IE]
German version: Angew. Chem. 76, 439 (1964)
[I] H . Schaller and H . G . Khorana, J. Amer. chem. SOC.85, 3828
(1963).
[2] H . G . Khorana: Some Recent Developments in the Chemistry
of Phosphate Esters of Biological Interest. Wiley, New York
1961. Chapter 5.
[3] H . G . Khorana, J . P . I'iszolyi, and R. K . Ralph, J. Amer. chem.
SOC.84, 414 (1962).
Determination of the Magnetic Susceptibility of
Organic Compounds from Proton Resonance
By Dr. H. J. Friedrich
Chemisches Institut der Universitit Wiirzburg (Germany)
The magnetic susceptibility effect observed in proton resonance in small cyclindrical tubes causes a shift of the resonance signal, relative to a n external standard, which is
proportional to the volume susceptibility of the medium [l]:
AH/H = cAXv
Previous c-values taken from the literature (e.g. 2.60 [2];
2.79 [3]; 1.57 141) have usually been vitiated by influences of
the medium, such as magnetic anisotropy effects, van der
W a d s interaction, and electrical polarization effects.
Our determinations o n tetramethylsilane in 35 diamagnetic
media yielded the value 2.09 i 0.1 for c, which is in agreespinslg
x 10-21
R = N-ethylquinol-2-yl
X=N,Y=C104
j
1021
j
-250
i
1271
1.3
R = N-ethylbenz1.3
thiazol-2-yl
X = N, Y = BF4
R = N,N-diethylbenzimidazol-2-yl
shift o f the 1H-signal of acetonitrile (10 ?() in nitromethane,
after the addition of about 5 mg radical/ml, at 2OoC, by
means of a Varian-A60-NMR-spectrometer. The observed
paramagnetism corresponds to that for monomeric radicals
with a s i n g l e unpaired electron (xP,theor. = 1280.: 10-9.
_
_-
~
Received, March 11th. 1964
[Z 720/551 IE]
German venion: Angew. Chem. 76, 496 (1964)
[ I ] Cf. C. A . ReiNy, Analytic. Chem. 30, 842 (1958).
[2) A . A . Bofhner-By and R. E. Glick, J. chem. Physics 26, 1647
(1957).
[3] D. F. Evans, Proc. chem. SOC.(London) 1958, 115.
14) H . P. Fritz and K. E. Schwarzhans, J. organometallic Chem.
1, 208 (1964).
[5] H . J . Friedrich, Z. Naturforsch., in the press. See this paper
for further literature references.
[6] S. Hiinig et al., Liebigs Ann. Chem., in the press; Tetrahedron
Letters 1964, 181.
Photolysis of Bicyclo[4,2,0]octa-2,4-diene,
Cycloocta-1,3,5-triene and Cycloocta-1,3,6-triene
By Dr. W. R. Roth and Dipl.-Chem. B. Peltzer
Institut fur Organische Chemie
der Universitat Koln (Germany)
Bicyclo[4,2,0Jocta-2,4-diene
( l ) , cycloocta-1,3,5-triene (2),
and cycloocta-1,3,6-triene (3), which are in equilibrium at
200 'C [11, were photolysed (high-pressure mercury lamp,
quartz apparatus) at room temperature in methanol solution
and in the gas phase. Compound (1) was thereby isomerized
to (2) in 4 0 % yield, the remainder was decomposed into
benzene and ethylene. Compound (2) formed 6 8 % of bicyclo[4,2,0]octa-2,7-diene (4) [2] and 32
of tricyclo[3,2,1,0*.8]-3-octene (5). All-trans-octatetraene (6) was
formed as an intermediary product and reacted further to
produce (4) and (5) presumably with re-formation of (2).
1.3
X=N,Y=BF4
1.7
R = N-ethylpyrid-2-yl
X = N, Y = ' 2 1 0 4
R = 2.3-dimethylindolizin- I-yl
X = CH, Y = C 1 0 4
R = 1,2-dimethylindolizin-3-yl
X = CH, Y =- C104
440
1010
-240
-240
1.4
I .4
The structures of (4) and ( 5 ) were deduced from the infrared
and NMR-spectra, from the products of hydrogenation, viz.
bicyclo[4,2,0]octane and bicyclo[3,2,l]octane, and from
thermal reactions: (4) was converted at 200°C into an
Angew. Chern. internat. Edit.
1 Vol. 3 (1964) 1 No. 6
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compounds, organiz, magnetic, determination, proto, resonance, susceptibility
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