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The crystal structure of tetra-acetylethane by neutron diffraction
INORG.
NUCL.
CHEM.
LETTERS
Vol. 8,
pp.
313--315,
1972.
Pergamon
Press.
Printed in Great Britain.
THE CRYSTAL STRUCTURE OF TETRA-ACETYLETHANE BY NEUTRON DIFFRACTION L.F. Power and K.E. Turner James Cook University of North Queensland, Townsville, Australia. F.H. Moore Australian Institute for Nuclear Science and Engineering, Lucas Heights, Australia. (Received 14 December 1971)
An X-ray study of tetra-acetylethane has been reported by Schaefer and Wheatley
(i).
Hydrogen atom positions were not obtained but it was suggested
that the compound exists in the dienolic form.
It was further suggested that
the hydrogen atoms of this dienolic form might be synm~trically located with respect to the corresponding oxygen atoms.
The neutron structure analysis has
therefore been undertaken to ascertain the position of the enolic hydrogen atom. This is part of a continuing project
(2-4) to elucidate the nature of the
hydrogen bonding in bis-(S-diketones) . Crystal data are as follows: a = 9.114; b = 9.372; c = 11.897;
tetra-acetylethane;
CIOH1404; Pbcn (No. 60);
(based on A = 0.981 ~ from a KCl crystal
assuming a of KCI = 6.2931 ~); z = 4; ~ for neutrons = 1.90 + 0.05 cm -I Two sets of equivalent neutron reflections were collected on the Australian Atomic Energy Commission computer controlled automatic neutron diffractometer at Lucas Heights using th~ w-20 scan technique. The atomic coordinates of Schaefer and Wheatley were used as initial input in the block diagonal least squares programme.
A Fourier map based on these
initial coordinates yielded an unambiguous position for the enolic hydrogen and less well defined positions for four of the six methyl hydrogens.
Subsequent
least squares cycles and a Fourier map allowed the location of the remaining hydrogens.
A further series of least squares cycles, based on 748 reflections,
313
314
NEUTRON DIFFRACTION
Vol. 8, No. 4
using anisotropic thermal parameters for all atoms reduced the R factor to its present value of 9.15%. The data has been corrected for absorption.
It is obvious from the present
structure factors that correction has to be made for extinction effects. Accordingly extinction corrections will be applied using the procedure of Zachariasen H = -0.372
(5).
Neutron scattering lengths used were C = 0.665;
O = 0.577;
(6).
Present atomic coordinates agree well with those of Schaefer and Wheatley, and are tabulated in Table i. Bond lengths and angles for tetra-acetylethane
are shown in the diagram.
The dienolic nature of the compound is verified and the position of the enolic hydrogen is clearly asymmetric.
The values obtained for the OI-HOO and O2-HOO
bond lengths compare favourably with those found by Power and Jones the related bis- (8-diketone)
3,3 '-trithiobis- (2,4-pentanedione).
One of us (K.E.T.) acknowledges
the tenure of an Australian
Nuclear Science and Engineering Postgraduate this work.
Institute of
Studentship during the course of
The provision of the A.A.E.C. diffractometer
is the financial
(2) for
is acknowledged,
as
support by the Australian Institute for Nuclear Science and
Engineering to L.F.P.
References i.
J.P. SCHAEFER and P.J. WHEATLEY, J. Chem. Soc.
(A), 1966, 528.
2.
L.F. POWER and R.D.G. JONES, Acta Cryst.,
3.
L.F. POWER and R.D.G. JONES,
4.
L.F. POWER and R.D.G. JONES, Inorg. Nucl. Chem. Letts., 1971, 7, 887.
5.
W.H. ZACHARIASEN, Acta Cryst.,
6.
G.E. BACON, Acta Cryst.,
1971, B27, 181.
Inorg. Nucl. Chem. Letts.,
1967, 23, 558.
1969, A25, 71.
1971, 7, 35.
Vol. 8. No. 4
NEUTRON DIFFRACTION
H32 ~
H31
315
H33
%)
e o 1.286(5;
~'/ 1 ~y
116.1 (41 ,
Cl
122.2(3) C 1
~
Ol
120.4(
-~<,>021.286(6)~'7" "2 ~
i00.9(7)
,,,~2.~.4(4)
0/~03.9(8)
122.9(4)#C 2 -
~.~
/ 1 5 . 7 (4)
C4
C4
~'I~ I~.~
"/ H41
~I-~\ H42
H43 Fi~
1
Bond Lengths and An@les TABLE 1 - ATOMIC COORDINATES FOR TETRA-ACETYLETHANE Atom
x/a
y/b
z/c
C1
0. 3627 (4)
0. 2533 (4)
0. 3486 (3)
C2
0. 3222 (4)
0. 4321(4)
0.2054 (3)
C3
0. 4590 (5)
0.1603 (5)
0.4191 (3)
C4
0.3708(5)
0.5370(6)
0.1188(4)
C5
0.4197(3)
0.3428(4)
0.2629(3)
01
0.2246(4)
0.2486(7)
0.3707(4)
02
0.1835(5)
0.4286(7)
0.2248(5)
HOO
0.1719(i0)
0.3460(16)
0.2958(11)
H31
0.3994(17)
0.1139(23)
0.4846(15)
H32
0.5505(20)
0.2122(18)
0.4547(13)
H33
0.5158(20)
0.0912(20)
0.3688(13)
H41
0.3426(28)
0.5006(33)
0.0405(11)
H42
0.3083(27)
0.6235(25)
0.1181(26)
H43
0.4853(17)
0.5484(20)
0.1154(15)
NUCL.
CHEM.
LETTERS
Vol. 8,
pp.
313--315,
1972.
Pergamon
Press.
Printed in Great Britain.
THE CRYSTAL STRUCTURE OF TETRA-ACETYLETHANE BY NEUTRON DIFFRACTION L.F. Power and K.E. Turner James Cook University of North Queensland, Townsville, Australia. F.H. Moore Australian Institute for Nuclear Science and Engineering, Lucas Heights, Australia. (Received 14 December 1971)
An X-ray study of tetra-acetylethane has been reported by Schaefer and Wheatley
(i).
Hydrogen atom positions were not obtained but it was suggested
that the compound exists in the dienolic form.
It was further suggested that
the hydrogen atoms of this dienolic form might be synm~trically located with respect to the corresponding oxygen atoms.
The neutron structure analysis has
therefore been undertaken to ascertain the position of the enolic hydrogen atom. This is part of a continuing project
(2-4) to elucidate the nature of the
hydrogen bonding in bis-(S-diketones) . Crystal data are as follows: a = 9.114; b = 9.372; c = 11.897;
tetra-acetylethane;
CIOH1404; Pbcn (No. 60);
(based on A = 0.981 ~ from a KCl crystal
assuming a of KCI = 6.2931 ~); z = 4; ~ for neutrons = 1.90 + 0.05 cm -I Two sets of equivalent neutron reflections were collected on the Australian Atomic Energy Commission computer controlled automatic neutron diffractometer at Lucas Heights using th~ w-20 scan technique. The atomic coordinates of Schaefer and Wheatley were used as initial input in the block diagonal least squares programme.
A Fourier map based on these
initial coordinates yielded an unambiguous position for the enolic hydrogen and less well defined positions for four of the six methyl hydrogens.
Subsequent
least squares cycles and a Fourier map allowed the location of the remaining hydrogens.
A further series of least squares cycles, based on 748 reflections,
313
314
NEUTRON DIFFRACTION
Vol. 8, No. 4
using anisotropic thermal parameters for all atoms reduced the R factor to its present value of 9.15%. The data has been corrected for absorption.
It is obvious from the present
structure factors that correction has to be made for extinction effects. Accordingly extinction corrections will be applied using the procedure of Zachariasen H = -0.372
(5).
Neutron scattering lengths used were C = 0.665;
O = 0.577;
(6).
Present atomic coordinates agree well with those of Schaefer and Wheatley, and are tabulated in Table i. Bond lengths and angles for tetra-acetylethane
are shown in the diagram.
The dienolic nature of the compound is verified and the position of the enolic hydrogen is clearly asymmetric.
The values obtained for the OI-HOO and O2-HOO
bond lengths compare favourably with those found by Power and Jones the related bis- (8-diketone)
3,3 '-trithiobis- (2,4-pentanedione).
One of us (K.E.T.) acknowledges
the tenure of an Australian
Nuclear Science and Engineering Postgraduate this work.
Institute of
Studentship during the course of
The provision of the A.A.E.C. diffractometer
is the financial
(2) for
is acknowledged,
as
support by the Australian Institute for Nuclear Science and
Engineering to L.F.P.
References i.
J.P. SCHAEFER and P.J. WHEATLEY, J. Chem. Soc.
(A), 1966, 528.
2.
L.F. POWER and R.D.G. JONES, Acta Cryst.,
3.
L.F. POWER and R.D.G. JONES,
4.
L.F. POWER and R.D.G. JONES, Inorg. Nucl. Chem. Letts., 1971, 7, 887.
5.
W.H. ZACHARIASEN, Acta Cryst.,
6.
G.E. BACON, Acta Cryst.,
1971, B27, 181.
Inorg. Nucl. Chem. Letts.,
1967, 23, 558.
1969, A25, 71.
1971, 7, 35.
Vol. 8. No. 4
NEUTRON DIFFRACTION
H32 ~
H31
315
H33
%)
e o 1.286(5;
~'/ 1 ~y
116.1 (41 ,
Cl
122.2(3) C 1
~
Ol
120.4(
-~<,>021.286(6)~'7" "2 ~
i00.9(7)
,,,~2.~.4(4)
0/~03.9(8)
122.9(4)#C 2 -
~.~
/ 1 5 . 7 (4)
C4
C4
~'I~ I~.~
"/ H41
~I-~\ H42
H43 Fi~
1
Bond Lengths and An@les TABLE 1 - ATOMIC COORDINATES FOR TETRA-ACETYLETHANE Atom
x/a
y/b
z/c
C1
0. 3627 (4)
0. 2533 (4)
0. 3486 (3)
C2
0. 3222 (4)
0. 4321(4)
0.2054 (3)
C3
0. 4590 (5)
0.1603 (5)
0.4191 (3)
C4
0.3708(5)
0.5370(6)
0.1188(4)
C5
0.4197(3)
0.3428(4)
0.2629(3)
01
0.2246(4)
0.2486(7)
0.3707(4)
02
0.1835(5)
0.4286(7)
0.2248(5)
HOO
0.1719(i0)
0.3460(16)
0.2958(11)
H31
0.3994(17)
0.1139(23)
0.4846(15)
H32
0.5505(20)
0.2122(18)
0.4547(13)
H33
0.5158(20)
0.0912(20)
0.3688(13)
H41
0.3426(28)
0.5006(33)
0.0405(11)
H42
0.3083(27)
0.6235(25)
0.1181(26)
H43
0.4853(17)
0.5484(20)
0.1154(15)