NOTES
1372
and A / V ratio indicated that the two substances were produced by a single reaction. Empirical Equation and Range of Application.The data discussed above may be summarized in the form of the following empirical equation at a constant temperature of 25.8' -d[II,Ozl =
4.21 X 10-3[02]*/2[HzOz]'/2 X
dt
1.97 X lo-'
A
7 [HaO+]
+ [KaO+]
Now over the range of experimental conditions employed the molar ratio of cupric ion to hydrogen peroxide was constant at the value two, or
Vol. 66
d [Cu + +I -=
dt
d [HiOzl
2XdtP
ELECTRIC MOMENTS FROM EXTRAPOLATED MIXED SOLVENT DATA. IV. AMIDES AND THIOAMIDES'V' BY GEORGEK. ESTOK AND SATYAP. SOOD Chemical Laboratories of The Men's College, University of San Diego, San Diego, CaEif. Received January IO, IS89
This work represents the final part in the titled ~ e ries.~.~ 5.95 x 10-3[02]1~~[C~++]*/~[H80+] x4 V Because simple amides are known to associate 1.97 X 10-2 + [H,O+] strongly in benzene solution, this work was done to At a constant acid concentration of 0.2 M the equa- determine reliable moments for such compounds tion above takes the form of the equation found by in this solvent. Previous work686 on carboxylic acid amides has indicated considerable abnormal Lu and Graydon.' solvent effect (>0.15 D.) between moments obd [HzOz] d [CU+ $1 A tained from benzene and dioxane solutions. How2 x --&= -&= 5.44 x 10-3[OzJ'/~[Cu++]'/r ever the known association in benzene solution puts A = 5.7-14.3 cm.* considerable doubt on the reliability of extrapolaV 0.500-0.800 1. tion intercepts at infinite dilution. [OZ] 0.53 X 10-4-12.35 X lo-' M KOprevious work has been noted on moments of [ c u + + ] = 0-10 x 1 0 - 4 ~ thioamides in benzene solution, although some [HZOZ] = 0-5 X lo-' M values in dioxane and CCb solution have been T = 29823°K. reported (Table I). [H30+] = 0.009-0.41 M Experimental The value of the rate constant was actually 5.44 Preparation and Purification of Compounds.-Benzene and dioxane were purified by standard methods.* for 31 runs. X lo-$ rt 0.48 X Recrystallization details and melting points of Eastman Proposed Mechanism-The following reaction Kodak Co. roducts were: Propionamide, thrize from benscheme, which is consistent with the constant zene, and &ied in a vacuum desiccator: 80 . n-Butyrmolar ratio of cupric ion to hydrogen peroxide of amide, from CC4-petroleum ether; l14-115°. Acetanilide, two and the empirical dependence of the hydrogen twice from water; 114'. Thioacetanilide, from water, Thiobenzanilide, in a vacuum desiccator; 75-76'. peroxide rate on the variables examined, is sug- dried four times from methanol a t Dry Ice temperature; 101.5gested 102.0'. Thiourea was purified as indicated in earlier work7;
v
i=
i=
Cui+
+ Os
Jcl
CU+,
k-
..
On
1
+ HsO+ +Cui++ + OH + HzO OH + OH +HzOz K' Cui++ + Cu 2Cui+ (equilibrium) kl
CU+... 0.
Jc3
K" Ozi
20, (equilibrium)
The symbol Cu+ ... 0, was meant to represent some transitory combination of quprous ion and oxygen at the solution-metal interface which comes rapidly to a stationary concentration as does the hydroxyl free radical OH. The subscripts i and s refer to interface and surface, respectively, and the letters IC and K refer to rate constants and equilibrium constants, respectively. Also [Cu++] = [CU++]i 1 0 2 1 = [Ozli
These assumptions combined with the reaction scheme given above result in equations of the same form as the empirically developed ones
m.p. 180". Benzmilide, prepared in a standard manner, was recrystallized twice from methanol; m. . 163'. Thioacetamide, a Matheson Coleman and Be! product, was recrystallized four times from benzene and stored over PzO~; m.p. 112-113". Measurements and Calculations.-These were made 88 reported earlier.3~4 Figures 1 and 2 are plots of data where mixed solvent w m required to obtain satisfactory intercepts a t infinite dilution for benzene solution. The satisfactory solubility and non-cyclic association of the aromatic comounds obviated the need for mixed solvent work. Table I ists moments and related data.
P
Discussion of Results A significant observation made possible by mixed solvent work is that the simple non-substituted carboxylic acid amides, whether aliphatic or aromatic, do not show any abnormal solvent effects in passing from benzene solution to dioxane solution. Table I indicates a difference of less than 0.15 D. (1) This work was supported mostly by a Frederick Gardner Cottrell Grant from Research Corporation, New York, N. Y. (2) Presented a t the Pacifia Southwest Regional Meeting of the American Chemical Society, San Diego, CaIif., Dec. 1-2, 1961. (3) G. K. Estok, S. P. h o d , and C. H. Stembridge, J . Phys. Chem., 62,1464 (1958). ( 4 ) G. K. Estok and S. P. Sood, ibid., 61, 1445 (1957). (5) W. W. Bates and M. E. Hobbs, J . Am. Cham. So&, 78, 2151 (1951). (6) J. E. Worsham and M. E. Nobbs, i&X, 76,206 (1954).
(7) W. D.Kumler and G . M. Fohlen, ibid., 64, 1944 (1942).
1373
NOTES
July, 1962
TABLE I (Benzene: el Solute
Propionamide
ELECTRIC MOMENTS AND RELATED DATA(25")a = 2.2730, v1 E 1.145;Dioxane: €1 = 2.206,V I = 0.973)
MRD
Vfb
Pz m
P
19.55
1.002e
Benzene
20.7
306
3.73
1.037"
Dioxane Benzene
25.5 17.9
328 320
3.87 3.78
0.9068
Dioxane Benzene
21.20 10.8
330 311
3.85 3.62
0.860"
Dioxane Benzene
14.85 7.70
366 336
3.97 3.66
0.869'
Dioxane Benzene
10.15 30.3
379 448
3.94 4.53
Bolvent
a m
AP
wlit.
3.3030"~ (0.14)
n-Butyramide
24.1b
3,853006 3,483006 (0.07)
408
Acetanilide
3.86300~ 4.01: 3.5CCl49 (0 35)
Benzanilide
48.4d
4.02lO 3.38~00' (0.28)
Thioacetamide
25.5'
3.83f
....... (0.27)
Thioacetanilide
47* gd
0.846"
Dioxane Benzene
39.55 13.65
509 426
4.80 4.28
0.832'
Dioxane Benzene
18.22 9.03
491 415
4.64 4.10
0. 6527
Dioxane Benzene'
12.53 36
492 534
4.53 5.0
4.7 7 3 6 0 h 4.5Cc14' (0.36)
Thiobenzanilide
67.4d
(0.43) Thiourea
24.07
.......
.......
....... .......
(0.1) 552 5.07 42.8 4. Dioxane a Data at 25" unless otherwise indicated. * G. K. Estok, J . Phys. Chem., 60, 1336 (1956). Extra olated from melt data A. Kotera, From atomic refractions. e Based on solution gnsities. in J. Timmermane "Physicochemical Constants." S. SoundararaS. Shibata, and K. Sone, J . Am. Chem. floc., 77, 6183 (1955). From solution refraction measurements. jan, ! h n $ .Fumdug floc., 53, 159 (1957). * Hypothetical benzene solution.
for propioriamide and n-butyramide. This also is true for benzamjde (3.77, 3.88), reported previously.4 These results are in contrast to larger effects indicated b,y other earlier workSI6in benzene and dioxane solutions only. The strong cyclic association in benzene solutions leads to unreliable extrapolation to infinite dilution in such cases. Moments in dioxane solution in Table I, however, are in good agreement with other work in dioxane solution. Because of steric effects it is generally agreed that amides with aromatic groups on CO and on N exist essentially in the s-trans conformation, for which resonance structures may be written as
8
Ar
/ \N/
Ar
8'
0-
I H
I
b+
/ \N/
Ar
I
Ar
Ar
B
?+ B
I1 0
Ar
/ \ / I11
0-
IV v Since the moment for benzamide in benzene (3.77) is consistent with those for simple aliphatic amides (ca. 3.7-3.8) it is concluded that V contributes little to the over-all moment. It is gener-
ally conceded, however, that I, 11, and I11 contribute significantly. The role of IV serves to reduce the over-all moment a little by reducing the contribution of 111. Thus acetanilide (3.62) and benzanilide (3.66) have lower moments than the simple amides. The moment of acetanilide was redetermined because previously reported valuessps were not consistent. The value of 3.97 obtained in dioxane solution, however, is in satisfactory agreement with 4.02 reported earlier.lo There is a definite solvent effect with acetanilide and with benzanilide which may be attributed to hydrogen-bonding between dioxane and the aniline residue, a marked effect observed earlier with aniline itself, and with various substituted anilines.1lIl2 The behavior of the thioamides is somewhat comparable to that of the amides in that moments for thiobenzanilide (4.10) and thioacetanilide (4.28) are lower than for thioacetamide itself (4.53). However the latter does show some abnormal solvent effect. The low solubility of thiourea in benzene and dioxane makes the moment values of 5.0 in benzene and 5.07 in dioxane too uncertain for a judgment (8) C. G . LeFevre and R. J. W. LeFevre, J . Chem. Soc., 1130 (1936)' (9) I. Suzuki, M. Tsuboi, T. Shimanouohi, and 8. Misushima, Speetrochim. Acta, 16, 471 (1960). (10) 6. Nakakura and A. Kuboyamtt, Chem. Abstr., 46, 1315f (1952). (11) A. V. Few and J. W. Smith, J . Chen. Soc., 753 (1949). (12) C . Curran and Q. Isfor thiourea also indicates complex associations, probably both mutually and with the dioxane solvent. The data plots for propionamide, n-butyramide, and thioacetamide, in benzene solutions, show considerable cyclic association of the solutes into dimers of zero moment. This association Tor thioacetamide is interesting because it represents a case of hydrogen-bonding involving sulfur (N-H . . . S). Evidently two such bonds are strong
u
Fig. 2.--Plots
0.1 0.2 0.3 0.4 0.5 Wt. % solute. (analogous t o Fig. 1) for thiourea and thioacetamide.
enough to yield a discrete cyclic dimer. The weaker nature of these bonds relative to N-H . 0 bonds, however, is evidenced by their disappearance in solyent with 25% I dioxane, ivhereas amides still show some association at 50% dioxane. The s-trans conformation of N-phenylated amides and thioamides prevents cyclic association. The rise in a with concentration for acetanilide (not plotted) indicates that some liiiear association occurs in benzene solution in the range 0.17 to 1.2 wt. % solute. However, thioacetanilide does not show any evidence of such linear association in benzene in the concentration range 0.05 to 0.30 wt. S bond is not o/c. Evidently a single N-H strong enough to promote appreciable linear association. 9
a
- -
COMMUNICATIONS TO THE EDITOR THE STRUCTURE OF ACTIVE CENTERS dislocations, respectively. As the coiicentratioli of lattice defects increases with the degree of coldIN KICKEL CATALYST working, strong interactions among them lowers Sir: TD, resulting in unavoidable overlapping of Tv and * ~ the other hand, TD is elevated remarkOn annealing cold-worked nickel, release of the T D . ~ On %tored energy and changes of the physical proper- ably by the existence of non-metallic impurities; ties take place in two temperature ranges, L e . , hence the difference among specimens is consider200-300° (Tv) and -400-700* (TD).’ They axe able.3 One of us (1.U.) and his co-workers4estabattributed to the disappearance of vacancies and ( 2 ) D. RIitehell and F. D. Haig, Phd. Mag., 2, 15 (1557). (1) (a) L. AI. Cbarebrough, &I. E, Hargreaves, and G. W. West, Proc. Roy. Soc., A233, 252 (1565); Phzl. Mag., 1, 528 (1556); (b) W. Eoas, “Defects in Crystalline Solids,” The Phyaical Society, 1555, P. 212.
(3) L. M. Clarebrough, &I. E. I-Iargreaves, 11.€1. Loretto, and G. W. %Test, S c t n M e t . , 8 , 757 (1980)
(1) 1. Uhasa, S Yanagsrnoto, I< Tani, a n d G. Adaclii, Katuie. 19!4, 867 (1962).
