KOHEIHOSETINO AND
4816
hf.4SAMOTO br:ATANABE
Acknowledgments.-We are indebted to G. A41derton for lanthionine and the C,HI4N2O4S compound and for tests for cystine, to 11. K. Mecham for the periodiate oxidation test for serine and threonine, to H. Fraenkel-Conrat for colorimetric tests for acid and basic groups, tyrosine and
' ~ O N l R I B TIC)?' I P R O V AMI1 4 \
1701.
73
histidine, to H. S. Olcott for the preliminary isolation of glutamic acid, to J. B. Stark for aid with ion exchange columns, and to P. A. Thompson and F. (2. Marsh for technical assistance with the microbiological assays. ALBASY,CALIF,
r)EPAKrMFNT,
RECEIVED MAY31, 1951
TO\ 0 RAYOYC O M P A \ Y ,
SACOVA1
Studies on Synthetic Polyamides. XVIIL1 On Hydrolysis of Polycapramide BY KOHEIHosriwo AXD ?dASAMOTO nT.4TANARE Assuming that the molecular weight distribution of polycapramide is a F l a y equilibrium distribution, the hydrolysis mechanism of polycapramide in 50% sulfuric acid was studied by viscosity measurement data using Montroll depolymerization equation. The Staudinger viscosity equation is not applicable t o polycapramide, and the Sakurada-Houwink general viscosity equation holds; the following result was obtained.
171
+ :)I[In p (1 - ,);and
= ( M o / K ) .(a j
the first
order velocity c o n ~ t a i i,t 30" 1)
Introduction The theoretical treatment of depolymerization of the linear condensation polymer was solved previously by Montroll and Siniha,2 and in a simpler fashion, by Sakurada and 0 k a m ~ u - a . ~ Matthes4 measured the rate of hydrolysis of polycapramide in 4oy0 sulfuric acid a t 50". The degree of polymerization decreases in accordance with a first-order splitting of amide linkage over the entire range investigated from Z, = 220 to 6. But Montroll and Simha,2S a k ~ r a d aand , ~ Matthes*assumed that all bonds connecting monomeric units in the homogeneous system of the same molecular weight have the same probability of being broken regardless of their position in a given polymer in which they are found. Such a homogeneous system is difficult to prepare, so one must often be satisfied with more or less heterogeneous mixtures. Montrolls obtained the theoretical equation of depolymerization in a polydisperse system of long chain molecules. Mre used this Montroll depolymerization equation, and the hydrolysis mechanism of polycapramide in 50yosulfuric acid at 30°, 40" and 50' was studied kinetically. The aim of this paper is to establish the general law of degradation of high polymers in a polydisperse system taking polycapramide as an example. Experimental and Results The material for measurement was cold-drawn fiber spun from the melt of polycapramide which had been prepared by polyamidation of e-caprolactam. Its number-average degree of polymerization was 113. The polymer was fractionated into (1) K. Hoshino a n d H Yiimoto, Paper X V I I J Chew Soc J a p a n . 70, 104 (1949) ( 2 ) E Montroll a n d R. Simha, J Chem Phys., 8 , 721 (1940) (3) I Sakurada and S Okamura Z ghysrk C h o n , 8187, 289 (1840) (4) A Mntthes, J prakt Lhem , 163, 245 (1943) ( 3 ) IS Montroll, THISJ O U R N A I , 63, 1235 (1941); Montroll leates o u t a a i d n,+i, a t t h e riglit vtlr 111 '13a) a n d ( I ? b ) , re,pecti\rly A n d the term of ( 1 3 d ) i b Y 5 i
40'
4 9s
50"
8 I5 29
4
6 cuts in a phenol-water, two-liquid phase system at Viscosity of the fractionated materials in 50% sulfuric acid was measured in Ostwald viscometers. Generally, number-average molecular weight and intrinsic viscosity [Q] are related by the Sakurada-Houwink equation of the form
un
11?, = Kjs]" where K and a are constants. Data shown in Table I are the results of the viscosity measurement in 50'& sulfuric acid. TABLE I MEASUREMENT I N 5070 SULFURIC ACID
RESL-LTSO F THE
Intrinsic viscosity in 50% sulfuric acid :io0 40' 500
Sample Vraciioii
.if%&
1 2
3,793 4,471 7,067 8,165 9,704 10,700
:j
1 > ri
0.222 .:3 R3 .392 .133 ,441 .63 1
0.307 .343 .378 .353 ,417
...
0,275 ,304 ,396 .417 .421
...
k,, in Table 1 were determined from equation (1) ' in m-cresol -
ATn = 10,400
[q]'.61
Constants k' and a in equation (1) in 5070 sulfuric acid were calculated by the least square method from the data shown in Table I. Its result is given in Table 11. .Is an example of the depolymerization reaction, hydrolysis in 50% sulfuric acid a t 30°,40' and 50" was followed by viscosity measurements. Relative viscosity was measured by Ostwald viscometers ( 6 ) K. Hoshino and M. Watanabe, J . Chem. Soc. Japan, 70, 24 (I94!C) ( 7 ) T h e reciprocal of a corresponds to a' in [VI = K'E;'. Accordingly it is not surprising t h a t values of a in Table I are greater than unity. An equation of t h e form of (1) is only generally applicable w h e n the viscosity average molecular weight is employed, but we regard i? eqii:il " t o 2" for sharp fractions.
HYDROLYSIS OF POLYCAPRAMIDE
Oct., 1951 TABLE I1 VALUES OF
K
AND a I N THE SAKURADA-HOUWINK
(1) I N 50%
ao K
0
SULFURIC 40 O
x monomer units, N is the total number of molecules EQUATIONand p is the extent of reaction, ;.e., the fraction of 60'
22,500 1.25
19,200 1.10
a
ACID
25,800 1.38
and specific viscosity extrapolated to c = 0 from graphs constructed from the formula =
%P/C
hl
+ kI712c
(2)
where k is 0.31, 0.33 and 0.34 a t 30, 40 and 50°, respectively. The results are shown in Table 111. TABLE I11 THERESULTOF
VISCOSITY MEASUREMENTS
RADATION CONSTANTS CALCULATED FROM
At 30' 1,
hr.
[? 1
0 10 14 21 27 38 47 53 62 71 83
0.644 .36 .311 ,331 ,296 ,275 .257 ,246 ,222 ,219 .197
0 5 8 20 32 48 56 66 72 80 90
0 2 4 6 9 13 21 26 29
I - a
- h i 5
P - 1( 1 - P )
- p(l - a)p[p(l -
a)]y-l
(4)
and [q] =
( J l f o / K ) 1 / 2v1'a 5
(6)
A!!" = 2"MO
therefore [q] =
( ~ ~ ! O / O / K ) ~ ' ~ ( Z N ~ , ) ~Z1Vxx) +'/"/(
(6')
The total number of molecules before hydrolysis N is given by N = ZxN, if the molecular distribution of polycapramide is a Flory equilibrium distribution (3)
- p)'ZpZ-l xl.5 = ,V(1 - p)zp-lJmxl+a
ZN,x'+: = N ( 1
... 11.90 11.30 9.29 7.96 7.71 7.13 7.00 6.65 6.47 6.09 8.15
e-(-lnP)t
dx
From (S'), the viscosity before hydrolysis is expressed by the equation
Similarly the viscosity after hydrolysis niay be expressed by the equation
... therefore
34.7 31.8 33.9 31.8 29.9 23.4 25.2 24.9 29.4
1
[l11*/hlo
= [In P / l n
P(1
-
(8)
As the extent of reaction p is 0.9904, the number of unbroken bonds (1 - a) divided by the total number of bonds in the undegraded system, is calculated by (8). To express the time dependence of a , we shall assume that the rate of depolymerization is proportional to the number of unbroken bonds
(3)
where N , is the number of molecules composed of (8) P. J. Flory, THISJOURNAL, SS, 1877 (1936).
Ny(ol) = N[1
I
7.88 5.89 5 12 4.17 3.77 3.64 3.62 3.25 3.24 4.98
Equations on Depolymerizations.-It has been shown from statistical consideration of condensation polymerization that the molecular size distribution in linear condensation polymers containing equal numbers of the two eo-reacting functional groups (e.g., NH, and COOH) is given bys x -
the functional groups which have condensed. Montrolls calculated the molecular weight distribution in the case where the bonds of all chains in the mixture a t any given time are equally accessible to reaction independent of both their position in a chain and the length of their parent chains. If x is the degree of polymerization before hydrolysis, y is the degree of polymerization after hydrolysis, and (Y is the degree of depolymerization, the Montroll equation reduces to
When the Staudinger viscosity equation is generAND THE DEG- ally applicable, viscosity average molecular weight (8) AND (10) M -v is equal to weight average molecular weight M,. But if the Sakurada-Houwink general equax x 10' tion (1) is applicable ... 1P" = ( ~ ~ , ~ ~ , I + ( l / a ) / ~ ~ ~ r , ~ ~ f , (5) ) ) a 9.27
1 0,9908 .9890 ,9877 .9862 ,9843 .9824 .9811 .9777 .9772 .9735 Average At 40" 0.597 1 .392 0.9941 .310 .9887 .9816 .245 .9748 .204 ,9636 ,164 .151 .9605 .9548 .I41 ,9532 ,138 ,9501 ,131 .9465 ,125 Average At 50' 0.570 1 .385 0.9931 .310 ,9873 .250 .9797 .208 .9718 .174 .9618 .153 .9519 .128 .9365 .121 .9303 Average
A7
4817
d B / d t = -AB
(9)
where B is the number of unbroken bonds a t time t and X is the degradation constant. Integration of (9) gives X = - 111 ( 1 - U j , , t
(10)
The degradation constants calculated from (8) and (10) using the experimental results are given in the 4th column in Table 111. These degradation constants are apt to decrease as the hydrolysis
Vol. 73
J. B. CULUEKTSON
4818
and introduce (lo), we get
+ lnp
i t = A/[q]*"
This equation should give a straight line by plotting 1/ [?I*" against t. The experimental data for the relation between t and 1/ plotted in Fig. 1, show a linear relationship within the experimental error. The values of A were calculated from (11) by use of the experimental values of K and a. A / h was calculated from the slope of the straight line inaFig. 1. The values of X from these relations, as is shown in Table IV, almost agree with the values of X in the 4th column in Table 111.
5 ti0
r
w
e
.e
$*
( 12)
40
3
20
TABLE IV 'krill>
,
'C.
3 J
8
4 Fig. 1.-Plot
of l / [ q ] "
12
16
1/[?11". DS. t: -4-4-1, 30"; -X-X-X, 40"; -0-0-0, 50".
progresses, but they are nearly constant. Momover if we put in (7)
40 50
A
A/h
0 0115 ,00957 .00827
25.70 8.50 2.29
x x IO' 4.47 11 28
36.18
Acknowledgment.-The authors wish t o express their appreciation to Professor I. Sakurada for many illuminating discussions which were extremely helpful during the course of this investigation. SAGOYA, JAPAN
RECEIVED NOVEMBER G , 193J
[CUNTRIBUTION FROM THE DEPARTMENT OF CHEhlISTRY UF CORNELL COLLEGE]
Factors Affecting the Rate of Hydrolysis of Ketimines BY J. €3. CULBERTSON Earlier work on the preparation of ketimines (references 1, 2 and 4) has indicated wide variation in the ease of their hydrolysis to the corresponding ketones. Certain structural relations have appeared to be connected with this variation in rate of hydrolysis. It has been the purpose of this study to investigate some of these structural influences. To this end variously substituted diphenyl ketimine hydrochlorides have been prepared-their rates of hydrolysis, ultraviolet absorption spectra and ionization of the free ketimines as bases determined. Two types of substituent effects have appeared t o be established; (1) a tautomerism and/or resonance, and ( 2 ) steric hindrance. Two other intramolecular factors suggested from earlier work on ketimines, and analogous compounds, have been considered. They are: (1) the relative negativity of the radicals attached to the carbimino group, and (2) strength of the free ketimines as bases. From the data of this report there is only meager evidence for the operation of any such factors.
This report represents an investigation of the rates of hydrolysis of variously substituted diphenyl ketimines-as hydrochloride salts in dilute aqueous solution-to their corresponding ketones. +C1The general reaction is: [R-C(=NH~)-RI] HOH+R-CO-Rl+ NHd+Cl-. A number of reports has indicated wide variation in the rate of this hydrolysis with structural differences. The early work of Moureu and Mignonac' pointed out that diary1 ketimines were more stable toward hydrolysis than the alkyl aryl ketimines. They were unable to prepare dialkyl ketimines. Later work2 revealed striking effects of other structural difference^.^ Especially the
+
(1) C. Moureu and G Mlgnonar C o i n p i r e n d , 156, 1801 ( 1 9 I 3 ) , 169, 237 (1919). 170,936 (1920), .4nn Chrm , [YI 14, 322 (1920) (2) P Rruylaets, Bull V I arad roy B r l g , L5l 8, 7 (1922) Bull SOL chrm f M g , 39, 307 (1923), I. Hary, ; b i d , 31, 397 (1922), D e Boosere, rbrd , 84, 26 (19231, R Breckpot, ~ b r d, 81, 386 (1923) and M Jaspers rbrd , 34, 182 (1925) (3) T h e extrdordlnarlly stable ethyl cyclopropyl ketiminc hydro chloride reported b y DeBoosere wds shown by Cloke lo be the isoni~ric 1 ethylpyrroline salt (J €3 Cloke, Tms J O U R N A L , 61, 1174 (1929))
work of Hoesch4 on the preparation of polyhydroxy diphenyl ketones by way of intermediate ketimines has suggested the latter as much more stable toward hydrolysis than the unsubstituted diphenyl ketimine. To gain some idea of the structural relations involved, measurements have been made on the rates of hydrolysis and ionization constants as bases of a selected group of substituted diphenyl ketimines. Table I lists these data. Large variations in rates of hydrolysis are evident. Two factors have appeared t o play significant roles in affecting this sensitiveness of ketimines tow:ird hydrolysis : (1) a ketimine-enamine tautomerism and/or resonance, ( 2 ) steric hindrance (ortho-effect). (1) The imine-enamine tautomerism has been suggested by the early work of Collie5 and of Best (4) K Hoesch, Be? ,48, 1122 (1915); K Hoesch aud T V Zarzecki r b t d , 60, 462 (1917) ( 6 ) 1 Y Culhi J Clirru . ~ O L 71, 2(VJ J l l (18'J71
