ELINOR ADMAN
1480
AND
T. N. MARGULIB
Crystal and Molecular Structure of cis-1,3-CyclobutanedicarboxylicAcid by Eliior Adman Department of Chemistry, Brandeis Uniaersity, Waltham, Massachusetts
02154
and T. N. Margulisl Department of Chemistry, University of Massachusetts, Boston, Massachusetts
0.211 6
(Received October 1 5 , 1 9 6 8 )
The crystal structure of cis-lJ3-cyclobutanedicarboxylicacid, CIHe(COOH)I, has been determined by threedimensional X-ray analysis. Full-matrix least-squares refinement gives an R of 0.057 for 427 reflections measured by counter techniques. The crystals are monoclinic, space group P21/n, with a = 6.439 A, b = 13.268 A, c = 8.036 A, p = 92.84", and four molecules per cell; Pobsd = 1.36 and Poslod = 1.39 g/cms. The cyclobutane ring is puckered with a dihedral angle of 149 =t 3" and an average C-C single bond length of 1.554 f 0.01 A. The molecules are connected by hydrogen bonds in infinite chains.
Introduction Cyclobutanes exist in both puckered and planar conformations.2 Infrared and Raman studiesa indicate a barrier of the order of 1 kcal/mol with the puckered form predominating. We have recently shown that the conformation of a cyclobutane ring may depend not only upon the nature of the molecule but upon the environment in which it is found. In crystals of pure trans-l,3-cyclobutanedicarboxylic acid (I), the cyclobutane ring is planarS4 In crystals of a sodium salt of
I,trans 11, cis
I, shown to be Na&4Ha(C00-)2*2C4H~(COOH)2, I has a puckered ring while its dianion has a planar ring.2 It is thus clear that solid-state forces play an important role in determining the structure of a given cyclobutane. Continuing this work we now report the detailed structure6 of cis-l,3-cyclobutanedicarboxylic acid (11). Experimental Section Markownjkoff and Krestownikoff reportede the synthesis of I and 11,C4Ha(COOH)z,in 1881. Deutsch and Buchman showed' that the early synthesis was incorrect and noted a successful synthesis. A detailed synthesis has been reporteds by Allinger. Authentic crystals of I1 (mp 134") prepared by Buchman were given to us by Professor K. N. Trueblood. The crystal used for all X-ray work was a prism of approximate dimensions 0.08 X 0.08 X 0.2 mm, mounted on a glass fiber with the long axis ( a ) parallel to the fiber axis. Cell dimensions and intensities were measured a t 21' on a Picker manual full-circle diffractometer with scintillation counter and pulse-height analyzer. Nickelfilter Cu K a radiation (A 1.5418A) was used for all work. The cell dimensions were obtained by measuring The Journal of Physical Chemistry
28 values of some carefully centered reflections. The errors in the cell dimensions were estimated by examination of the range of computed values. Intensities were measured by symmetrical 28 scans of 1.4', at a scan rate of 2"/min, with takeoff angle 1.5', receiving slit 2 X 2 mm and crystal to receiving slit distance of 23cm. Background was measured by offsetting o 1.25" and scanning again. A total of 427 nonzero independent reflections were measured up to 28 = 129'. Within this range there were 564 weak reflections considered to be zero intensity. The intensities were converted to structure factors, scaled by Wilson's method, and converted to normalized structure factorse for use in the phase determination. For Cu Ka X-rays the linear absorption coefficient is 10.3 cm-' which considering the geometry of the crystal could cause errors in relative intensities of as much as 12%. No absorption corrections were made.
Crystal Data The crystals are monoclinic with a = G.439 f 0.006A, b = 13.268 f O.OIOA, c = 8.036 z~=0.007 A, and p = 92.84 f 0.2". The space group assigned from systematic absences (OkO, k = 2n, and h01, h 1 = 2n) is P21/n. This choice is confirmed by the successful structure determination. All atoms are in the general positions: x, y, z; -2, -y, - 2 ; 3 - x, y, 3 - a, & x, 3 - y, 3 z. The density calculated assuming
+
+
+
+
(1) Author to whom correspondence should be addressed. (2) E. Adman and T. N. Margulis, J. Amer. Chem. SOC.,90, 4517 (1968).
(3) W. D. Rathjens, Jr., N. K. Freeman, W. D. Gwinn, and K. S~ Pitzer, ibtd., 75, 5634 (1953). (4) T. N. Margulis and M. Fischer, ibid., 89, 223 (1967). (5) Prelimfnary report: E. Adman and T . N . Margulis, Chem. Commun., 641 (1967). (6) W. Markownikoff and A. Krestownikoff, Ann., 208, 333 (1881). (7) D . H. Deutsch and E. R . Buchman, Ezperientia, 6, 462 (1950). (8) N. L. Allinger and L. A. Tushaus. J. Org. Chem., 3 0 , 1945 (1965). (9) J. Karle and I. L. Karle, Acta Cryst., 21, 849 (1966).
Cis-1 ,3-cYCLOBUTANEDICARBOXYLIC ACID
1481
four molecules per unit cell is 1.39 g/cm*; the density measured by flotation is 1.36 f 0.03 g/cma. b r e * @
Determination of the Structure A trial structure was obtained directly from the normalized structure factors using the computer program of Long.’O Input to the calculation consists of the 128 reflections with E larger than 1.5. The signs of three reflections with large E were chosen as positive to determine the origin. Four more reflections with large E of undetermined sign were chosen to complete the starting set. The program was then used to solve the Z2 relationshipg for all 16 possible combinations of the four undetermined reflections. One solution stood out as the most consistent.” The E map calculated from this solution showed the structure clearly. The sign of each of the 128 reflections used in calculating the E map was the same at the end of the refinement as it had been at the start of the refinement. The coordinates of the carbon and oxygen atoms,
Table I: Observed (FOBS) and Calculated (FCAL) Structure Factors ( X 10) foes
L
K
..I. 2 b
I IO
n
m
0
120 102
5:
-1
131
201 89
-4
317
-4
JYl Z”3
-b -b -b
111 lbb 2b5
lb7
.I
o
-I
I2 -3
a
-(I
::
-5 1 -5 -I -5 b -I I -I 1 -b 8 -6 b -b 7 -b 1 -7 3 -7 b -1 B -1 I -9 b S
n I
I 1 9
*I
0 0
0 0 0
;! i
0
0
1 1
S
I
I 8
b S
b
T I
I
1
1
I
I I
’. 1 1
3
115
-6
I1
8 8
19b 106
257
;:
81
IY
IO
2V
7b 175 Ib 54
(10
17b 61
b2 Vl
P4
11 *I I O b7 111 152 34 Yl 97 v2 55 7* b5 a5 51 41
.
I
I 9
a a a
b 7
io
11 0 1 2 3 4
5 b 7 10 11 1 2
I
.a.
rcii
3V 114 1Yb
50 119 110
95
101
3 3
1 I 3 3 3 b b b b
4 ’b
I I 5
I
7 O
5 5 5
.2
120 125 I03
859 4b 70 201 2bO Ibb 2Ib 114 110 309 309 92 V(
I22 121 bo I9
18
bb v2
I1
I25 320
197 106
177 145 llb
L
5 -b 7 -b 0 -7 2 -7 4
-7
791 b03 395
797 b21
Ilb
b
1
0 0 0
3
1 :: I V V 20s 181 I 7 8
31
111
lbl
155
101
208
Y7
41 45 b9 71
53 b7 100 Ib 7b
W b 112
70
7)
511
bO
irn 152
I b 7
1
a 5 b 7
I P
10 0 1 2
3
0 0
0
1 I
1
1
2 2 2
6
2
5 0
b b
05 bl
5 b 7 I
2
63 P7
I
6
-1 1 -1 2 -1 I -1 4 -1 5 -1 b -1 7 -1 0
n -I 9
-1
12‘ -1 I -2 2 -2 3 -2 I -2 6 -2 7 0
-2
-2 -2 -2 -3 1 -3 1 -3 I -1 b -3
11 12 0
a -I
-3 I -3 9 -3 10 -3 11 -3
12 -3
11
b2 21
9 10
58
b0 18b 01 b1 257
6
6 b b
12 16
5 b
#‘
I21
7 0 9 10 1 2 1 b 0 7
I2 171 bO
250
51 I O
lnb
ao*
62 150 10
1+5 52 31
15 32 48
141 41
II* YbS
11
171 I3 109
2b2 I3 I4 205
-L’
-6
1Yb 17 lob be
-I b -I 1 .I 1 -b 2 -b I -b I -5
b
-I
n
3 I 3
(7
lb7 b0 39 ZbV 16
bI 100 b2 b9
SI
YM 54
1.1 b9 1.1 I9
15 7n
66
7 141 1V 169
I40 81 170 I5 101 201 86 5s 207
139 73
101 bl a7 1b1 b0 7s 25b a7 53
101 I V I O
el Sb
2 I
3 I
b
4
6 7
1
v
lo
12
I -> I -3
5
1bI
-a
->
b -3
9Y
52 148
bb 7b bI 9b 151
bI 61
SI
I1 I5
I -2 3 -2 4 -2 b -2 7 -2 1 -2 9 -2 11 -2 b
bP 180 1%
5
-1
1 2 3 5
2;;
91 3V 1Ul 169
100
1
I
Yb 356 06 90
70
1b1
0
a
lb0 111
152
b
5 5 b b 7 8 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -2
91 I O
69
b b
5
1bZ
101
110 112
in*
1
2
I5 *I bo 151
15b
3 3
1
b
127 105 165
IOb 172 166 2bl Zbb
; .;
V
2
29)
111
117 llb 51 3bl PI 93 2;
218
-b
I
15
hbl
2 2
215
3
6 b I -6 10 -b 11 -i) 0 -9
76 76
YP2 * I 9 663
1
2
5b 150 117
2
IYL PI
v2 29b 120 97 1b1
151
2
1Yb IO
3Y7
1
119
1113
135 100
35 57 66
I L
Y92
bO1 b20 101 I11
1
211
115
8b
0 0 0.
$6
7 9 Y
41
0 1 2 1
22b 115
7
I11
160
300 11.
L
7
b1 .bo Y21 b5 7b 72
b 6
1 3
rcii
.S7 bb
SO
?5 115 lbb
1 3 b 0
loris
102 122
248 243 in2 i i v
ll*
I
1 .I 5 -I
2 I I I
. Hi -.
LbI 176 lbl 17b 2b5 155
131
1YI
I
b
I02 311
117 134 711
b
v
100s
2
2
3
140
L
I
81
bb0 *YO 202 187 bb 51 Ilb 131 127 127 41 in *I 62 92 77 9b 10s 22) 222 52 34 51 b5
-3
b
I&? 250
:: ::: ::: -I
I:
4 7 9 0 1
15
40 lb3 11b
-3 10 -3
10 1:
5:
10 7b 00 Ob 2b7 23II 101 ins 128 127 262 231 1 3 5 222 571 557
7 -3
b 7 9
106
b79 448 ,b4b
9
b
132
96 502
2 -9 I -1
2 I
411
121 120
I -1 9 -1 10 -1 0 -2 I -2 a -2 I -2 b -2 5 -a b -2 T -2 I -2
5
e91 lbb
7 -1
b
I9
1 1 1 LO1
0
: ::
1;
..*I
102
0
0 0 lb 0 1 -1 I -1 1 -1 b
o
FCLL
03
05
PI *I I2
I1
%I
50 7)
07 bV 104
OS 91 5. 722 b . 3 114
PO
711 lb7 111 a27 3b
h33 $0
a2 bl
1P 3b
iw
IZ b5
$7
7I
%I
(1 252 2P
260 11
bb 32 176
70
fans r c i i
I
L
f o w mi
Figure 1. One molecule viewed along a.
obtained from the E map, were refined by full-matrix, least-squares calculations. The program of Gantzel, Sparks, and Trueblood was used with scattering factors for neutral atoms obtained from the “International Tables for X-Ray Crystallography”.12 The function minimized was Z w ( F , - F J 2 with the weights, w , assigned according to the procedure given by Evans.la With isotropic temperature factors for all atoms R = Z I( F, I - I F , 11/2 I F , I fell to 0.15. Further refinement with anisotropic temperature factors reduced R to 0.09. A difference electron density map revealed the coordinates of the hydrogen atoms. Refinement with isotropic temperature factors for hydrogen resulted in an R of 0.060. During this refinement the temperature factors of the acidic hydrogen atoms increased to over 16 Az. For this reason a difference map was calculated based on the carbon, oxygen, and six nonacidic hydrogen atoms. This map revealed six peaks of about the same magnitude. Two were in positions expected for the acidic hydrogens while four fell between oxygens in different hydrogen-bonded chains. An interpretation of these four anomalous peaks is given below. The six peaks were added to the refinement as # hydrogen atoms and the refinement was continued to a final R of 0.057. The results given below correspond to this last refinement but the 0.060 refinement gave the
bb
217 2 l P
bI Ill 101 lb2 1 0
L
Ot4)
I1
3bl
V I
I
H cc n/)
b7
.
100 42 170
bI 111
VI
lbb 115 bI
(10) R. E. Long, Ph.D. Dissertation, University of California, Los Angeles, Calif., 1965. (11) For further details on the use of Long’s program see: T . F. Koetzle, F. E. Scarborough, and W. N. Libscomb, Inorg. Cham., 7, 1076 (1968). (12) “International Tables for X-Ray Crystallography,” Vol. 111, The Kynoch Press, Birmingham, England, 1962, p 202. (13) € T. I . Evans, Jr.. Acta Cryst., 14, 689 (1961). Volume 73,Number 6 May 1988
ELINORADMANAND T. N. MARGULIS Table I1 : Positional and Isotropic Thermal ParametersaJ Atom
E,
X
J!
I
0.0819 (10) -0.0060 (10) 0.0790 (9) 0.0138 (10) 0.0606 (13) 0.0720 (14) 0.1135 (14) 0.2547 (15) 0.1059 (14) -0.0646 (16) 0.175 (14) 0.162 (10) 0.238 (12) 0.430 (14) -0.171 (12) -0.156 (15) 0.003 (29) -0.079 (30) 0.203 0.265 -0.139 0.155
0.0884 (4) 0.1052 (4) 0.3883 (4) -0.4696 (4) 0.1408 (6) 0.4365 (7) 0.3891 (6) 0.2944 (6) 0.2525 (6) 0 3246 (7) 0.273 (6) 0.440 (4) 0.260 (6) 0.308 (5) 0.293 (5) 0.350 (7) -0.423 (14) 0.019 (17) 0.419 0.406 0.405 0.021
-0.3598 (7) 0.3696 (8) 0.0802 (7) 0.2128 (7) -0.4891 (15) 0.2110 (12) 0.3766 (11) 0.3923 (12) -0.4796 (11) 0.4428 (11) -0.343 (13) 0.458 (8) 0.282 (11) 0.413 (9) 0.348 (10) -0.470 (13) 0.085 (27) 0.341 (22) -0.152 0.047 0.076 0.279
I
A8
Standard deviations are given in parentheses as deviations in the last significant figures. Little physical meaning can be attached to the hydrogen atom thermal parameters since the atom scattering factors used are for the free atom: L. H. Jensen and M. Sundaralingam, Science, 145, 1185 (1964). Acidic hydrogen atoms with weight. Peak between hydrogen-bond chains assumed to be 4 hydrogen.
+
Table 111: Anistropio Thermal Parametersa in the Form Exp[-((Pllh2
0 0394 (23) 0.0510 (27) 0.0414 (24) 0.0490 (27) 0.0241 (32) 0.0276 (33) 0.0351 (35) 0.0253 (38) 0.0367 (36) 0.0282 (31) I
0
0.0048 (4) 0.0050 (4) 0.0056 (4) 0.0043 (4) 0.0049 (6) 0.0047 (7) 0.0039 (6) 0.0059 (6) 0.0042 (6) 0.0063 (6)
0.0133 (11) 0.0157 (13) 0.0113 (11) 0.0145 (11) 0.0189 (21) 0.0175 (21) 0.0136 (16) 0.0170 (20) 0.0125 (16) 0.0096 (15)
+ p22k2 + pSsP + plzhk + PlshZ + @28k2)] 0.0006 (14) -0.0040 (17) 0.0054 (15) 0.0012 (16) 0.0014 (20) -0.0025 (20) -0.0007 (25) 0.0009 (24) -0.0009 (21) 0.0027 (25)
-0.0054 (23) -0.O006 (28) 0.0045 (24) -0.0076 (24) 0.0019 (40) 0.0070 (37) -0.0040 (37) -0.0036 (40) -0.0027 (39) 0.0006 (39)
0.0030 (12) -0.0004 (12) 0.0021 (11) 0.0011 (11) 0.0000 (21) 0.0035 (20) 0.0020 (18) 0.0080 (20) 0.0023 (16) 0,0035 (16)
Standard deviations are given in parentheses as deviations in the last significant figures.
same bond lengths and angles within 1.5 standard deviations. Table I Iists the observed and calculated structure factors. Final atomic coordinates and temperature factors are listed in Tables I1 and 111,respectively. The standard deviations given in these tables are from the least-squares calculations and assume random errors in the structure factors. Tables IV-VI give interatomic distances and angles. The standard deviations given should be considered lower limits. Corrections to bond lengths for thermal motion were made using the Busing and Levy "riding" m0de1.l~ Although this model may not be appropriate, it is probably better than no correction at all. The structure is illustrated in Figures 1 and 2. The Journal of Physical Chemistry
Discussion The four-membered ring in cis-l,3-cyclobutanedicarboxylic acid is puckered with a dihedral angle of 149 f 3", defined as the angle between the normals to tlie planes of C(4), ( C 5 ) , C(6) and C(4), C(3), C(6). This value is consistent with values found in other compounds which range from 145" in cyclobutane16to 160" in chlorocyclobutane.16 The carboxyl groups occupy positions analogous to the equatorial positions (14) W. R. Busing and H. A. Levy, Acta Cryst., 17, 142 (1964).
(16) 9. Meiboom and L. U. Snyder, J . Amer. Chem. Soc., 89, 1038 (1967). (16) H. Kim and W. D. Owinn, J . Chem. Phys., 44, 866 (1966).
Cis-1 ,3-cYCLOBUTANEDICARBOXYLIC ACID
1483
Table IV: Bond Lengths and Bond Angles0 Atoms
C(1)-0(1) C(1)-0(2) C(2)-0(3) C(2)-0(4) C(l)-C(5) C(2)-C(3) C(4)-C(5) C(6)-C(5) C(4)-C(3) C(6)-C(3) Q
-Bond length, AObsd Tempcor
1.251 1.284 1.233 1.301 1.511 1.484 1.545 1.563 1.552 1.547
1.265 1.305 1.246 1.316 1.513 1.487 1.549 1.563 1.555 1.648
Atoms
Angle, d~
O(l)-C(l)-0(2) 0(3)-C(2)-0(4) O(l)-C(l)-C(5) 0(3)-C(2)-C(3) 0(2)-C(l)-C(5) 0 (4)-C (2)-C (3) C(5)-C (4)-C(3) C (5)-C (6)-C (3) C(4)-C(5)-C(8) C(4.)-C(3)-C(6)
123.2 121.9 119.3 122.2 117.4 115.8 88.0 87.6 87.7 88.0
Estimated standard deviations are 0.012
A for bond lengths and
0.6"for bond angles.
Table V: Intermolecular Close Approaches Atoms
0(1)-0(2) 0(3)-0(4) 0(3)-0(1) O(3)-O(1')
Dist,
2.616 2.631 3.26 3.27
Atoms
0(3)-0 (2) o(4)-0 (1) c(1)-0(3) C(2)-0(1)
Dist,
A
3.23 3.22 3.20 3.20
Figure 2.
The cryshal structure viewed along a.
this plane. Within the ring the C-C bonds average 1.552 A without correction for thermal motion and Table VI: Bond Lengths Involving Hydrogen" 1.554 A with correction. Both values are somewhat longer than the usual value of 1.537 A for a C-C single Atoms Dist, Atoms Dist, A bonds2' This is in agreement with previous work where reasonably precise measurernents2l give C-C C(5)-H(I) 1.2 C(6)-€€(6) 1 .o C(3)-H(2) 1.0 0(4)-~(7) 1.2 bonds over l.56A. The C-H bonds average 1.07.k C(4)-W3) 1.0 0(3)-H(7) 1.5 in good agreement with expected values. C(4)-H(4) 1.1 0(2)-H(8) 1.1 Each molecule is hydrogen bonded to two others to C(6)-H(5) 1.1 0(1)-H(8) 1.6 form infinite chains. The hydrogen bonding occurs Estimated standard deviations are 0.08 A. Distances are not across centers of symmetry in a manner typical of corrected for thermal motion. carboxylic acids, with O...O distances of 2.616 and 2.631 The chains cross one another so that crystallographically independent pairs of hydrogen bonds lie of cyclohexane. The puckered conformation is to be above one another, with the centers of the planes expected since planar rings have only been found in separated by +a = 3.22 and tipped 10" to one another. those molecules with a centrosymmetric arrangement The principal interaction holding the chains together of s~bstituents.'~Thus, pura Irans-1,3-cyclobutanedicarboxylic acid, cis,trans,cis-1,2,3,4-tetraphenylcyclo- thus occurs in the region of hydrogen bonding. We butane,l8Jgoctahydroxycyclobutane120and cis,trans,cis(17) We exclude from consideration molecules with endo- or exocyclic 1,2,3,4-tetracyanocyelob~tane~~ have planar rings, while unsaturation and molecules in which the cyclobutane ring is part of Ibromocyclobutane, chlorocyclobutane,16 anemonin,22 a condensed poiycyclic system. (18) J. D. Dunitz, Acta Cryst., 2 , 1 (1949). cis-l,2-cyclobutanedicarboxylic and cis- and (19) T. N. Margulis, i b i d . , 19, 857 (1965). trans 1,2 dibromo - 1,2 - dicarbomethoxycyclobutane24 (20) 0.M.Bock, J. Amer. Chem. Soc.. 0 0 , 2748 (1968). have puckered rings. However, a centrosymmetric (21) B. Greenberg and B. Post, Acta Cryst., B24, 918 (1968). arrangement in itself is not sufficient to assure a planar (22) I. L. Karle and J. Karle, ( b i d . , 20, 555 (1966). ring since, for example, octachlorocyclobutane,1~~2~(23) D. van der Helm, J. J. Sims, and D. S, Seigler, Abstracts o f the Summer Meeting o f the American Crystallographic Association, c y c l ~ b u t a n e and , ~ ~ ~trans-1,3-cyclobutanedicarboxylic ~~ Minneapolis, Minn., 1967. acid in a sodium salt2 have puckered rings. Also, it (24) I. L. Karle, J. Karle, and K. Britts, J . Amer. Chem. SOC.,8 8 , 2918 (1966). must be stressed that proof of conformation in the solid (25) T. B. Owen and 3. L. Hoard, Acta Cryst., 4, 172 (1951). state does not indicate conformation in any other phase. (26) A. Almenningen, 0. Bastiansen, and P. N. Skancke, Acta Chem. The carboxyl groups are arranged so that 0(1), Scand., 15, 771 (1961). (27) L. E. Sutton, "Tables o f Interatomic Distances and Conflgura0(2), C(1),C ( 5 ) , C(3), and C(2) lie in a plane, and tion in Molecules and Ions." Supplement 1956-1959, The Chemical the plane of 0(3), 0(4),and C(2) is twisted 28" from Society, London, 1965.
A.
A
- -
Volume 75,Number 6 May 1089
LYNDENJ. STRYKER AND EGONMATIJEVIE
1484 find peaks in the difference map corresponding to electron density between the chains as well as peaks corresponding to the expected positions of the acidic hydrogen atoms in asymmetric hydrogen bonds. This could mean statistically disorderedhydrogen atoms with weak hydrogen bonds holding the chains together. These would be very long hydrogen bonds, since the shortest 0-H- -0 distance is 3.22 A, but this value is no longer than the O H - * o O distance found in some bifurcated hydrogen bonds.28 The six peaks (two in the conventional hydrogen bonds and four between planes) were each refined as 4 hydrogen. They are found 1.3-1.7 A from the nearest oxygen atom and point approximately toward oxygen atoms in the chains above and below. The extra peaks may be just noise in the difference
map due to errors in the data or lack of proper accounting for thermal motion, absorption, or extinction. The fact that the C=O and C-0 bond lengths are longer and shorter, respectively, than the expected values is also consistent with disorder in the hydrogen bonding. In any case the results (bond lengths and angles) for the heavy atoms are the same for the refinement with the disordered hydrogens and the refinement with only ordered acidic hydrogens. Acknowledgment. This work was supported by the National Science Foundation. We thank Professor K. N. Trueblood for providing the crystals. (28) W.0. Hamilton and J. A. Ibers, “Hydrogen Bonding in Solids,’’ W. A. Benjamin, Inc., New York. N. Y., 1968. p 261.
Counterion Complexing and Sol Stability. 11. Coagulation Effects of Aluminum Sulfate in Acidic Solutionsl+2 by Lynden J. Stryker3and Egon Matijevik Institute of Colloid and Surface Science and Department of Chemistry. Clarkson College of Technology, Potsdam, New York 13676 (Received October 1 6 , 1 9 6 8 )
Coagulation of a silver iodide sol by aluminum sulfate in solutions acidified with sulfuric acid showed an increase in the critical coagulation concentration (ccc) with a decrease in the pH (4) sulfate ions act as “penetrators” replacing some hydroxyl groups in the hydrolyzed aluminum complex ion. Coagulation and reversal of charge results’ led to the formulation of a species having the composition [A&(OH) lo (SO4),I4++.In acidic solutions (pH
