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The conformation of trimethylene sulphite
Tetrahedron LettersNo.37,PP. 4433-4436, 1966. PergsuonPressLtd. Printedin GreatBritain.
TEE COWPO~TIOW
OF TPIMDTByLDWE SDLPHITS
Gordon Wood and PI.Miskow Department of Chemistry, University of Windsor, Windsor, Ontario, Canada. (Received 3 June 1966)
Benzene as an @DIP solvent has been shown to exert a fairly specific influence on the chemical shifts observed for protons located near a carbonyl group in six-membered ring compounds.1,233 In general the observed results are consistent with the formation of a complex between the benzene and the positive contra of the polar group.lp4
The axial groups generally lie within the region
of shielding while the equatorial groups are less shielded or even deshielded. We now wish to report that the proton spectrum of trimethylene sulphite (I) is shifted by benzene in a manner not expected from the conformational assignment made for this compound.
Hellier5
adduced some evidence that (I) exists in a single conformation and chose the chair form with S-O axial (Ia).
Xowever, the
measured dipole moment for this molecule (3.5-3.6 D) does not agree with that calculated for form (Ia) (1.8 D).
Further, the
WWR spectrum was not assigned in detail and was anomolous in that the assignments made placed the equatorial protons at higher field than the axial.
6
4433
No.37
SIactra were raaured at 6OMcm on a JSOLJlW-C-60 spectroxmtir with the remits &own in the Table. Table Solvent Bffects on the NMR Spectrux of TrixethyleneSulphite proton assignmenta
C2(eg) C2(=)
Cl,C3(eg) Cl,C3(=)
cDC13 ( lO$ w/V)b
8.38=
7.47
6.13
5.05
benzene (infinitedilution)d
9.6
8.5
7.0
5.6
A(benzene-CDCl3)
1.2
1.0
0.9
0.6
A(20$ henrene-CC14)
1.1
0.0
0.6
0.4
0.6~
0.4h
A(20$ beaueue-CC14)for (II)' a.
As proposed in ref.
@.951f
5.
b. These chexical shifts do not differ appreciablyfrom thsse found in CC14 or in the neat liquid. Chexical shifts are quoted in tau units from tetramthyleilane C. for the rid-point of each maltGet. d. Extrapolatedfrom points at 30. 20, 10, aud 5s w/v. 0. wso-Pentane-2,4-diol cyclic sulphite (isomer B, ref.10). reported for proton6 at C2. f. cmultiplet g. Value for CE group. h. Value for CJ group. It can be seen that the protons are shielded by benzene to a considerableextent and those protons labelled equatorial5are shielded more than those labelled axial. At least for the protons at Cl and C3 this result ie opposite to that expected. The shielding at C2 could depend in part on which side of the molecule the benzene 8pproaches. This appears to be the case with the 1,3-dioxanastudied by Anderson." PIafound that the C4 and C6
No.37
w3
axial protons ware lhiftd
0.3 pm
upfield while the
corre8-
pending equatorial proton8 were shifted only 0.2 ppa by ben*.ne. The equatorial proton at C5 was shifted mubstantially mre
than
the axial one (0.6 vr 0.3 ppm); thio result is consistent with the approach of the benaene molecule froa
the
side opposite to
this axial proton. When thi8 anomolou8 effect of the lmnrene solvent is added to the considerable difficulties in interpretation of dipole moment, RHR, and (in our handa) IR data8 for (I) it would aeex to cast 8erious doubt on the a88ignmant of conformation (Ia). Considering all the data presented up to now, the moat likely conformation for trimethylene sulphfte appear8 to be the flexible form (Ib).
Waver,
more evidence i8 needed before the earlier
suggestion9 of a chair-chair eguilibriux can be coxpletely ruled out.
(Ia)
It i8 intereating to note that one of the diol cyclic sulphites (II)" form shows,
for (I).
which has been a88igued the flexible
in benzene, behavior strikingly 8ixilar to that ob8erved
The last two lines of the Table 8how A value8 for theme
molecules under comparable condition8.
The clo8e agreement is
4436
NO.J7 other
probebly fortuitoua end dependa, mng correlation c.
3
of
the
iao
thinga, on arbitrary
multipleta repreaenting proton8 at Cl and
Eowever, the other two ieomeric pentane-2,4-diol cyclic
aulphitea whose spectral propertiea are in good agreemant with thoae anticipated for a chair conformation ahow benzene solvent shifts two to five timaa smaller then (I)." The authors wiah to thank the Wational Research Council of Canada for financial aupport of thia work.
1. KS.
Bhacca and D.H. Williema, Applications of BWR Suectroacopy
in Orqenic Chemistry, Chapter 7, Bolden-Day, San Francisco, 1964. 2. B.S. Bhacca and D.A. Williams, Tetrahedron Lettera, 3127, (1964).
3. D.H. Williama, e., 4. J.D. Co~olly
2305, (1965).
end R. McCrindle, Chem. end Ind., 379, (1965).
5. D.G. Bellier, J.G. Tillett, *.,
H.F.
VanWoerden, and R.FIW. White,
1956, (1963).
6. For en attempt to interpret the WMR spectrum aee Yu. Yu. Samitov, Dokladv Akademii Wauk SSSR, 164, 347, (1965).
7. J.E. Anderson, Tetrahedron Letters, 4713, (1965). 0. We have found that the IR spectrum of (I) in the region 1300-1 1150 an is sensitive tc solvent changes. For example, aubatitution of chloroform for carbon tetrachloride increases the -1 intensity of the 1230 cm band from about 12$ (relative to the main band at 1190) to about 35s. Acetonitrile has a similar effect.
9. B.A. Arbouzov, Bull. aoc. them. France, z, -
1311, (1960).
10. ~.C..Lauterbur, J.G. Pritchard, and R.L. Vollmer, J. Chem. Sot., 5307, (1963).
See alao C.G. Overberger, T.
S. Yaroaiavaky, J. Org. Chem., 2,
-
Kurtz,
and
4363, (1965).
11. These measurements on (I) were made in 50$ benzene solutions for comparison with the data of ref. 10.
TEE COWPO~TIOW
OF TPIMDTByLDWE SDLPHITS
Gordon Wood and PI.Miskow Department of Chemistry, University of Windsor, Windsor, Ontario, Canada. (Received 3 June 1966)
Benzene as an @DIP solvent has been shown to exert a fairly specific influence on the chemical shifts observed for protons located near a carbonyl group in six-membered ring compounds.1,233 In general the observed results are consistent with the formation of a complex between the benzene and the positive contra of the polar group.lp4
The axial groups generally lie within the region
of shielding while the equatorial groups are less shielded or even deshielded. We now wish to report that the proton spectrum of trimethylene sulphite (I) is shifted by benzene in a manner not expected from the conformational assignment made for this compound.
Hellier5
adduced some evidence that (I) exists in a single conformation and chose the chair form with S-O axial (Ia).
Xowever, the
measured dipole moment for this molecule (3.5-3.6 D) does not agree with that calculated for form (Ia) (1.8 D).
Further, the
WWR spectrum was not assigned in detail and was anomolous in that the assignments made placed the equatorial protons at higher field than the axial.
6
4433
No.37
SIactra were raaured at 6OMcm on a JSOLJlW-C-60 spectroxmtir with the remits &own in the Table. Table Solvent Bffects on the NMR Spectrux of TrixethyleneSulphite proton assignmenta
C2(eg) C2(=)
Cl,C3(eg) Cl,C3(=)
cDC13 ( lO$ w/V)b
8.38=
7.47
6.13
5.05
benzene (infinitedilution)d
9.6
8.5
7.0
5.6
A(benzene-CDCl3)
1.2
1.0
0.9
0.6
A(20$ henrene-CC14)
1.1
0.0
0.6
0.4
0.6~
0.4h
A(20$ beaueue-CC14)for (II)' a.
As proposed in ref.
@.951f
5.
b. These chexical shifts do not differ appreciablyfrom thsse found in CC14 or in the neat liquid. Chexical shifts are quoted in tau units from tetramthyleilane C. for the rid-point of each maltGet. d. Extrapolatedfrom points at 30. 20, 10, aud 5s w/v. 0. wso-Pentane-2,4-diol cyclic sulphite (isomer B, ref.10). reported for proton6 at C2. f. cmultiplet g. Value for CE group. h. Value for CJ group. It can be seen that the protons are shielded by benzene to a considerableextent and those protons labelled equatorial5are shielded more than those labelled axial. At least for the protons at Cl and C3 this result ie opposite to that expected. The shielding at C2 could depend in part on which side of the molecule the benzene 8pproaches. This appears to be the case with the 1,3-dioxanastudied by Anderson." PIafound that the C4 and C6
No.37
w3
axial protons ware lhiftd
0.3 pm
upfield while the
corre8-
pending equatorial proton8 were shifted only 0.2 ppa by ben*.ne. The equatorial proton at C5 was shifted mubstantially mre
than
the axial one (0.6 vr 0.3 ppm); thio result is consistent with the approach of the benaene molecule froa
the
side opposite to
this axial proton. When thi8 anomolou8 effect of the lmnrene solvent is added to the considerable difficulties in interpretation of dipole moment, RHR, and (in our handa) IR data8 for (I) it would aeex to cast 8erious doubt on the a88ignmant of conformation (Ia). Considering all the data presented up to now, the moat likely conformation for trimethylene sulphfte appear8 to be the flexible form (Ib).
Waver,
more evidence i8 needed before the earlier
suggestion9 of a chair-chair eguilibriux can be coxpletely ruled out.
(Ia)
It i8 intereating to note that one of the diol cyclic sulphites (II)" form shows,
for (I).
which has been a88igued the flexible
in benzene, behavior strikingly 8ixilar to that ob8erved
The last two lines of the Table 8how A value8 for theme
molecules under comparable condition8.
The clo8e agreement is
4436
NO.J7 other
probebly fortuitoua end dependa, mng correlation c.
3
of
the
iao
thinga, on arbitrary
multipleta repreaenting proton8 at Cl and
Eowever, the other two ieomeric pentane-2,4-diol cyclic
aulphitea whose spectral propertiea are in good agreemant with thoae anticipated for a chair conformation ahow benzene solvent shifts two to five timaa smaller then (I)." The authors wiah to thank the Wational Research Council of Canada for financial aupport of thia work.
1. KS.
Bhacca and D.H. Williema, Applications of BWR Suectroacopy
in Orqenic Chemistry, Chapter 7, Bolden-Day, San Francisco, 1964. 2. B.S. Bhacca and D.A. Williams, Tetrahedron Lettera, 3127, (1964).
3. D.H. Williama, e., 4. J.D. Co~olly
2305, (1965).
end R. McCrindle, Chem. end Ind., 379, (1965).
5. D.G. Bellier, J.G. Tillett, *.,
H.F.
VanWoerden, and R.FIW. White,
1956, (1963).
6. For en attempt to interpret the WMR spectrum aee Yu. Yu. Samitov, Dokladv Akademii Wauk SSSR, 164, 347, (1965).
7. J.E. Anderson, Tetrahedron Letters, 4713, (1965). 0. We have found that the IR spectrum of (I) in the region 1300-1 1150 an is sensitive tc solvent changes. For example, aubatitution of chloroform for carbon tetrachloride increases the -1 intensity of the 1230 cm band from about 12$ (relative to the main band at 1190) to about 35s. Acetonitrile has a similar effect.
9. B.A. Arbouzov, Bull. aoc. them. France, z, -
1311, (1960).
10. ~.C..Lauterbur, J.G. Pritchard, and R.L. Vollmer, J. Chem. Sot., 5307, (1963).
See alao C.G. Overberger, T.
S. Yaroaiavaky, J. Org. Chem., 2,
-
Kurtz,
and
4363, (1965).
11. These measurements on (I) were made in 50$ benzene solutions for comparison with the data of ref. 10.