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Chemical Shifts of NMR Signals of the Acetyl Protons of -Penta-O-acetylglucose.

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band (cf. Table 2). This result is not intelligible within the
framework of the H M O theory.
Received: August 4th, 1967
[Z 607 lE]
G e r m a n version: Angew. Chen;. 79, 931 (1967)
[*I Priv.-Doz. Dr. H. Fischer and
W. D. Hell
Max-Planck-Institut ftir hledizinische Forschung,
Institut fur Chemie
Jahnstr. 29
69 Heidelberg (Germany)
[ l ] Part I1 of Interaction of Orthogonal jr-Electron Systems of
Cumulenes. - Part I: H . Fisclier and H. Fischer, Chem. Ber. 100,
755 (1967).
[2] H. Fischrr in S. Patai: The Chemistry o f the Alkenes. Wiley,
London 1964.
[3] R. Kuhn and H. Krauch, Chem. Ber. 88. 309 (1955); cf. also
F. Bohlmann and K. Kieslich, ibid. 88. 1211 (1955).
!4] D.Y.Curtin, r7. C. Tuires, and D . H. Dybvig, J . org. Chemistry
25, 1 5 5 (1960).
[ 5 ] G. E. Coafvs and I.. E. Surton, J. chem. SOL (London) 1942,
567.
[6] M . Sintonetto and S. Carra, Tetrahedron 19, pp. 2,467 (1962).
Chemical Shifts of NMR Signals of the Acetyl
Protons of 6-Penta-0-acetylglucose
By K. Heyns, W.-P.Trautweiii, and F. Garrido Espinow[*l
The N M R signals of the acetoxyl groups of acetylated carbohydrates are often used for configurational and conformational analysis[il, a use that depends on the fact that the
methyl protons of equatorial acetoxyl groups in general
absorb at higher field than do such axial groups. Whereas
this rule has proved its value for countless partially or
completely acetylated pyranoses [21, halogeno sugars 131,
amino hexoses 141, and inositols 151, there are only a few, and
partially contradictory, indications as to how to assign the
individual signals within each of these groups. It is sometimes
assumed that acetoxyl groups on the primary C atom 6 of
hexopyranoses absorb at highest field [L ,61 and that acetoxyl
groups above the plane of the ring are less shielded than those
under the pyranose ring[7,81.
We have studied, by N M R spectroscopy, 2,3,4,6-, 1,3,4,6-,
1,2,3,6-, and 1,2,3,4-tetra-O-acetyl-~-~-glucopyranose
that
have been acetylated on the unsubstituted O H group by
hexadeuterioacetic anhydride in pyridine. Whereas the N MR
spectrum of unlabeled 8-penta-0-acetylglucose shows four
Fig. 1. IH-NMR s p e c t r u m of 1,2,3,4-penta-U-acetyl-::-u-glucose at
100 M H z in CDCI,.
signals for the acetyl protons (one of these signals has double
intensity), the spectra of all the labeled compounds lack one
line, namely, that of the trideuterioacetyl group (Fig. 1). By
Angew. Chem. internat. Edit.
1 Vol. 6 /I9671 1 No. I I
selective labeling of individual acetyl groups it is possible to
assign each line in the spectrum to a definite acetyl group. It
was thus shown that the two signals at lowest field refer t o
groups o n C - l and C-6, whereas the line of relative intensity 2
is caused by the groups on C-2 and C-4; the signal a t highest
field was present in all the spectra and thus is to be ascribed
t o the group on C-3.
Received: August 4th, 1967
[Z 608 IE]
G e r m a n version: Angew. C h e m . 79, 937 (1967)
[*I Prof. Dr. K. Heyns, Dr. W.-P. TrdutWeln, and
Dr. F. Gariido Espinosa
Chemisches Staatsinstitut,
Institut fur Organische Chemie der Universitiit
Papendamm 6
2 Hamburg 1 3 (Germany)
111 L . D. Hall, Advances Carbohydrate Chem. 19. 51 (1964)
Bernsfein, and W. G.
[2] R. U . Lemierrx, R . K. Kiillnig, H. .I.
Schneider, 1. Arner. chem. SOC.80, 6098 (1958).
[3] D. Horfon and W. N . Turner, J . org. Chemistry 30, 3387
(1965); Chem. Commun. 1965, 113.
[4]D.Horton, W. E . Most, and K. D. Philips, J . org. Chemistry
32, 1471 (1967).
[ 5 ] F. W. Lichtenthnler, Chem. Ber. 96, 2047 (1963).
[6] f. C. Sowden, C. H. Bowers, I.. Hough, and S. H. Sliufe,
Chem. and lnd. 1962, 1827.
[73 K. Onodera, S. Hiram, F. M o ~ u d a and
,
N . Kashitviwa, J . org.
Chemistry 31, 2403 (1966).
[8] L. D . tIaN and I-. Hougli, Proc. chem. SOC.(London) 1962,
352.
Occurrence of Cyclododecasulfur in Sulfur Melts
B y M. Schniidt and H.-D. Block I*]
The physical properties of liquid sulfur have long been the
subject of studytll, but it was only the theoretical propositions by Powell and E y i n g [*], Gee [31, and in particular
Tobolskp and Eisenberg (41 that made it possible to interpret
satisfactorily its unusual behavior over the whole liquid
range. Fundamental to the theory that is currently recognized is the assumption of temperature-dependent equilibria
between cyclooctasulfur and catenaoctasulfur as “monomers” and of polycatenaoctasulfur as “polymer”.
We now report experiments which throw doubt on this
principle and at least necessitate refinement of, i f not a
change in, the theoretical interpretation. Working up sulfur
that has been melted at 120”C, 140”C, 165OC, 19OoC,
220°C, 29OoC, 340”C, 3SOoC, or 370°C and then brought
quickly to the solid state by cooling in air, cold water, or
liquid air leads in each case, reproducibly, t o crystalline
cyclododecasulfur~~l,
S12, even if only in a “yield” of cu.
0.1 ”/,. The sulfur used as starting material was free from
S12, as also from S6 and s g that are formed by chainbuilding on decomposition of thiosulfate by acid [ b l . Slow
cooling of the melt (during 10 hours) leads, however, to pure
s8. This result shows that in sulfur melts there are also Slz
rings in the equilibrium mixture alongside sg, and it is
certain that only a small part of the ,512 rings survive transition, on cooling, into the Ss rings that constitute the only
thermodynamically stable form. It is, however, also probable
that other, hitherto unisolated, rings S, ( x < 1 2 and in
particular x > 12 - perhaps even x 2- 12) are present in the
equilibrium of the melt, as previously postulated by Krebs 171.
It remains an open question to what extent the S12 content,
already shown to be present slightly above the melting
point, is responsible for the decrease of the “ideal” to the
“natural” melting point.
Experimental Example: 20 g of sulfur is heated at 200 “C for
10 min. The vessel is cooled with tap water and the sulfur is
divided as finely as possible and stirred for 1 2 hours with
955
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protons, chemical, nmr, signali, acetylglucose, acetyl, shifts, pentax
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