NOTES
3645
from the values of 1 and 2, respectively. Therefore, the large discrepancy between steady shear and dynamic mechanical data may not be surprising. However, closer inspection of Figure 4 reveals that the gap between the curves of - b p / b In r and 2G‘ and that between ulz and G” become smaller and smaller as the rate of shear (or the angular frequency) is decreased. It is conceivable that they would coincide at the limit of very small rate of shear. From the experimental results obtained above, we 2rI is come to the conclusion that the value of \/3 much smaller than that of 1/31 or 171. Therefore, from eq. 2, we conclude also that uz2 - u33 is much smaller than cr11 - uz2 in their absolute values. By taking possible experimental error into account, we would say that the former is no more than 10% of the latter except for the system PMMA-DEP. At the moment, we hesitate to draw any conclusion about the observed discrepancy in the system of PMMA-DEP. It might be due to the contribution of the u22 - 433 term in the range of higher shear rate or to the contribution of higher order terms in ull - uZ2and 2G‘than the second order of K and w. The problem of the relation between three components of the normal stresses has attracted much attention since the earliest days of research, and some controversies have been found among the results of various investigators.‘j- Most recent and thorough investigations on thc: problem were given by MarkovitzlO and by Adams and Lodge.11 They have drawn conclusions mostly from the comparison between the pressure distribution observed in a cone-plate (CP) system and that in a parallel-plate (PP) system. With the present notations, the difference between two pressure distributions is
+
( - d p / b In T)PP - ( - b p / b In r)cp = [b(Qz - U33)/bln K ] - (uzz - U33) = @
+ 2Y)K2
(10)
On the basis of the observed difference, they concluded that the value of u22 - a33 is quite large although they did not mention specifically how large it was. Our present conclusion differs somewhat from theirs. In principle, the use of relation 10 is a better procedure for the evaluation of uz2 - u~~ because the second line of eq. 10 should be valid for any value of K, and the method is straightforward. However, the procedure employed in this paper also has certain advantages, we believe, if its application is restricted to the range of sufficiently small rate of shear (again assuming the prediction of the second-order viscoelasticity theory is valid in general). The reasons are first, as is seen in eq. 9 and 10, the difference between ( - d p / b In T)PP and 2G’ is larger than that between
( - b p / b In r)pp and ( - b p / b In T)CP by a factor of 3, and, secondly, the present method does not involve the measurement with the cone-plate system, in which the machinery set-up is much more diffcult than it is in the parallel-plate system. Therefore, we would prefer our conclusion, at the moment, that uZ2- u33 is, if not zero, no larger than 10% of ull - uz2. ~~~~~~
(6) J. E. Roberts, Proc. Intern. Congr. Rheology, 2 4 , Oxford, 1969, 91 (1954). (7) H. Markovita, Trans. SOC.Rheol., 1, 37 (1957). (8) T. Kotaka, M. Kurata, and S. Onogi, Progr. Theoret. Phys. (Kyoto), Suppl., 10, 101 (1959). (9) W. Philippoff, Trans. SOC.Rheol., 5 , 163 (1961). (10) H. Markovitz, Proc. Intern. Congr. Rheology, 4th, Providence, R. I., 2963, in press. (11) N. Adams and A. S. Lodge, Proc. Roy. SOC.(London), A256, 149 (1964).
The Nuclear Magnetic Resonance Spectra
of Some N-Monosubstituted Methylamines
by Morris Freifelder, Richard W. Mattoon, and Russell Kriese Organic and Physical Chemistry Departments, Research Division, Abbott Laboratories, North Chicago, Illinois (Received April 6 , 1966)
The scarcity of information on splitting of the methyl proton signal of N-monosubstituted methylamines by the proton on nitrogen‘ prompted us to examine the n.m.r. spectra of a number of these compounds in order to group the types where splitting of the N-methyl signal is observed. I n the course of some other work the spectrum of 2methylaminop yridine NHCHS I
was examined.2 The methyl signal was seen as a (1) For example, only four such compounds are listed: “High Resolution NMR Spectra Catalog,” Vol. 1, Varian Associates, Palo Alto, Calif., 1962; Spectrum 85, ethyl N-methylcarbamate, shows a doublet for the N-methyl protons; Spectrum 319, another N-methylcarbamate, shows a doublet; Vol. 2,1963, Spectrum 489, N - m e t h y l 4 nitroaniline, shows a single peak for the methyl signal; Spectrum 652, l,Pbis(methylamino)-9,1&anthraquinone, shows a doublet, due perhaps t o hydrogen bonding. I n the Formula Index to “ N M R Literature Data,” Vol. 1, M. G. Howell, A. S. Kende, J. S. Webb, Ed., Plenum Press, New York, N. Y . , 1965, only N-methylformamide and N-methyltrifluoromethyhulfonamide are reported t o show doublets for the N-methyl protons. (2) M. Freifelder, R. W. Mattoon, and Y . H. Ng, J. Org. Chem., 29, 3730 (1964).
vo~unte69, Number 10
October 1966
NOTES
3646
Table I: Data for R(C=X)NHCHa r
X
Solventd
NHd
0 0
A A A A A A
460-500 347' 446-476 410-430 440-470 450-480
VI1
0
B
VTII
0
IX
0 0
XI
XI1 XI11 XIV XV XTn" XVII XVIII"
161.5 169.5 151 162.5 162 167
9, h
185, 189.5
188
B
9
168, 172.5'
169.5
0 0 0 0 0 0 0
B A
B
180, 184.5
S N(CH3) NH NH NH
B B B B B B B
191.5O 163 157.5 171.5 170 168 171 189 195 196 187 188 182 185
NH
B
C A
B B
B
S
S
xlrsc
xxa'c XXI XXII
(3
XXIIIC
DNCHs
161.5, 166 166.5, 171.5 149, 154 160.5, 165.5 161, 165.5 164.5, 169
0 0
Xb
Peaks, c.p.8. HNCHi
330-380 346-374' 360-420 9 9 9 9
9 9 9 9 9 9
160.5, 165.5 151.5, 156 169.5, 173. 5k 167, 172 166.5, 171 167.5, 172 186, 190.5 192, 196' 191.5, 196.5 191, 195'" 186, 190.5 180.5, 184 n 199.5
'
Samples were generously supplied by Dr. Peter de Benneville of the Rohm and Haas Co., Bristol, Pa. Reported in ref. 1. ' HyA = carbon tetrachloride; B = pyridine; C = deuterated dimethyl sulfoxide. e I n most instances a broad area drochloride salt. W&S seen. The signal was a sharp peak for OH and NH (integration, 2). The signal was lost in the solvent region. No peak was observed beyond 500 to 1000 C.P.S. to indicate hydrogen bonding. Integration, 6H, for two Signal for NH2 wm seen at 336 C.P.S. A sharp strong peak was also seen at 193.5 C.P.S. for N(CH3)2. No splitting was observed in aqueous solution. methyl groups. I n water the signal was a singlet at 199.5 C.P.S. The area Upon addition of DzO, the doublet and singlet merged to a single peak. was a broad ragged one suggestive of splitting, centered at 186 C.P.S. (integration, 3). The N(CH3)zsignal (integration, 6) was seen at 173.5 C.P.S. (169.5 C.P.S. after DzO); the NCH, signal (integration, 3) was a singlet a t 204 C.P.S. (198 C.P.S. after DzO). ' When the spectrum was run in DZO, the signal was a singlet at 192.5 C.P.S.
'
'
doublet (J =: 4 4 . 5 c.P.s.) in carbon tetrachloride and deuteriochloroform. Addition of DzO converted the signal to a single peak. N-Methylacetamide (I) and N-methylurea (XI) also showed splitting with J values of 4.5 and 5 c.P.s., respectively. The three compounds had a common structural relationship, adjacency of the NHCHJ group to a carbon atom double bonded to a heteroatom [H&NH-C f 1. This suggested examination of such compounds as were available with this structure. The spectra of monosubstituted N-methylated aryl-, aralkyl-, and cyclic amines were also studied as well as a few N-methylsulfonamides [RSOZNHCHS, R = alkyl, substituted aryl, or a cyclic structure]. The J
O U T of ~
Physical Chemktry
'
Experimental Section The spectra were run on a Varian A-60 spectrometer a t 60 Mc./sec. at a sweep width of 500 C.P.S. at 33" in 10-20% concentrations (weight, volume) in solvents listed in Tables 1-111 with tetramethylsilane as the internal standard. I n general, the entire spectrum was recorded and integrated, but only those signals which have a bearing on this study are noted in the tables. The positions of other methyl signals are found in the superscripted portions of the tables. The chemical shift is given to the nearest half-cycle per second. The compounds used in this study were either commercially available or generously supplied by colleagues
NOTES
3647
~
Table 11: Data for RSOZNHCHI" -Peaks, c.p.0.-
No.
XXIV
xxv
XXVI XXVII
R
HNCH:
DNCHa
CsHii 4CH&ONHCsH4 ~-CHIOCEI& CsHii
170.5,175.5 163,168 162,167 170.5,175.5
173.5 165 164 173.5
The spectrum of the hydrochloride salt in water showed a singlet for the methyl group a t 207 C.P.S. In pyridine it was still a singlet a t 200 C.P.S. (We had previously reported on the failure of 2-methylamino-3,4,5,6tetrahydropyridine, a cyclic amidine, to show splitting.2) The single signal is probably due to interchange of the tautomeric forms RC=NH
"The solvent used in this group was pyridine. The NH signal wm lost in the solvent area.
Table III: Data for RNHCH8" Peak, c.P.E.,
No.
XXVIII XXIX
xxx
HNCHa
R
C& 2-HOOCCsH' 4-HsCCsI4
XXXI XXXII XXXIII XXXIV
15gb 174c 132d 167
CsH6CHt 2-HsCOCsHdCH2 CaHii
13ge 140 141'
" The solvent used in this group was carbon tetrachloride. No change in deuterated dimethyl sulfoxide solution (DMSO). Deuterated DMSO. 143 C.P.S. in deuterated DMSO. e 137 C.P.S. in deuterated DMSO. Neat; 137 C.P.S. in deuterated DMSO.
'
of this and other laboratories. They were generally of high purity or were purified by appropriate means. I n particular, the N-methylsulfonamides (Table 11) were prepared by Mr. Bruce W. Horrom, who treated the substituted sulfonyl chlorides with excess methylamine. Compound XXXIII was prepared by Dr. William B. Martin and Miss Carol Christensen by treating the substituted benzaldehyde with methylamine. After isolation and characterization of the intermediate imine, it was hydrogenated by M. F. The preparation of these compounds will be reported in greater detail a t a later date by Mr. Horrom and Dr. Martin.
Results and Discussion The amides, ureas, biurets, guanidines, thioureas, and thioamides which were examined showed splitting of the N-methyl signal when a suitable solvent was found3; see Table I, compounds I-XXII. Only one amidine (XXIII)was examined
OH @=" NHCH3
I
NHCHa
E RCNHz
II
NCH8
or other proton transfers which occur too rapidly for the spectrometer to record the one which might give a split signal. Among this group of compounds the spectrum of VI is worth noting. It showed that the vinyl protons
[E>c=c
