CO~IXLJNICATIONS TO THE EDITOR
4742
Vol. 82
7.53), and the enantiomer, (R)-VI11 (Y = CHOH), m.p. 77-79" (fd.: C, 85.94; H, 7.48) by LiAlH4 reduction of (S)-XIV respectively (R)-XIV; (S)-X (Y = CHz), m.p. 63-64' (fd.: C, 92.05; H, 8.38), by modified Clemmensen reduction of (S)-XIV; (R)-XI1 (2 = C(COOEt)2), m.p. 165-167' (fd.: C, 61.75; H, 5.07; C1, 17.29), from (+)-6,6'dichloro-2,2'-bis-(bromomethyl)-biphenyland malonic ester.
Using ionic catalysts, we have prepared two new types of crystalline dimethylketene polymers of regular chemical structure. Dimethylketene in toluene solution was polymerized a t -60' in the presence of aluminum tribromide (moles monomer/ moles catalyst approximately 1500); the fraction, which was not extractable with boiling toluene, had an intrinsic viscosity of 0.7 in nitrobenzene a t 135' ; m.p. 250-255' (determined with a polarizing microscope). (9) Support by t h e Alfred P. Sloan Foundation is gratefully acknowledged. The high crystallinity (see Fig. 1) of this fraction (10) Trubek Fellow. 1958-1959; N S F Cooperative Fellow, lY3Q- (polymer I) indicates that i t is made up of micro1960. molecules having a regular structure. The strong (11) Trubek Fellow, 1937-1958. absorption in the infrared spectrum (Fig. 2 ) near (12) Supported by t h e Sational Cancer Institute (by grant ,'\lo. CRTY-3OGl) and the National Science Foundation. Rotatory disper5.9 I* indicates the presence of carbonyl groups, sion measurements were performed by l f r s . T. Nakano and Rlrs. R u t h a conclusion which is confirmed by the ultraviolet Record with an automatically recording Rudolph spectropolarimeter. spectrum The two bands around 7.25 p are in KCRTMI SLOW^ accord with the presence of one type only of gem L)EPARTMENT O F CHEMISTRY M, A. LV. GLASS SEW YORKUNIVERSITY ROBERT E. O'BRIEN'O methyl groups. SEW YORK5 3 , N.Y. PHILIPRUT KIN^^ DAVIDH. STEINBERG
OF CHEMISTRY DEPARTMEXT STASFORD UNIVERSITY C.4RL STANFORD, CALIF. RECEIVED JULY 18, 1960
I)JERASSI"
CRYSTALLINE POLYMERS O F DIMETHYLKETENE
Sir: I t is known that dimethylketene dimerizes readily Higher polyto tetramethyl-1,3-~yclobutanedione.~ mers were obtained by Staudinge? using aliphatic or aromatic amines as catalysts. These amorphous products can be considered as derived from the irregular copolymerization of the two monomeric
I
CHI
I, -c-o-
(a)
(8)
units formed, respectively, by the opening of the ethylenic or of the carbonyl double bond.
L 20 25 28. Fig. 1.-X-Ray Geiger registration (CUKCY) of the two crystalline poly-dimethylketenes: -polymer I , --------polymer 11. 3
10
15
(1) H. Staudinger, H. Schneider, P. Schotz and P. hl. Strong; Helv. Chim. A d a . 6, 291 (1923). (2) H. Staudinger, i b i d . , 8 , 306 ( 1 9 2 3 .
01
I
3
5
7
b
'
,
11
,
,r
13
Fig. 2.-Infrared spectra of the two crystalline polydirnethylketenes, mulls in Xujol and C4Cl8: -polymer I, --------- polymer 11.
From the chemical properties of polymer I we conclude that i t consists of macromolecules formed by the regular head-to-tail enchainment of monomeric units of type (a). In fact, polymer I behaves chemically like a p-diketone; treatment of I suspended in tetrahydrofuran with excess ethyl alcohol and a small quantity of sodium ethoxide, for a long time (100 hours) a t 200-26O0, yielded ethyl isobutyrate and di-isopropyl ketone in addition to the unchanged polymer. The structure assigned to polymer 1 has been confirmed by the results of reduction of the carbonyl groups with LiAIHt. Treatment of I suspended i n tetrahydrofuran with LiAlH4 gave a white, airiorphous polymer (90% yield) which was insoluble in ether and acetone, but soluble in acetic acid and ethyl alcohol. The infrarcd spectrum shows that only traces of carbonyl groups remain, whereas there is strong absorption a t 3.02 p which is attributable to associated hydroxyl groups. This reduction product, therefore, is an atactic polymer of polydimethylvinyl alcohol Polymerization of dimethylketene under the conditions previously mentioned with triethylaluminum as the catalyst, gave a polymerizate, 70yo of which can be extracted with boiling benzene, but not with boiling acetone. This fraction (polymer 11) has an intrinsic viscosity of 0.4 (in tetralin a t 135') and a regular structure as indicated by its high crystallinity (see Fig. 1). The two bands a t 5.71 and 5.75, (only the 5.75, band occurs in solution) indicate the presence of ester groups. That only traces of carbonyl groups are present is demonstrated by the weak absorption bands a t 295 mp in the ultraviolet.
Sept. 5, 1960
COMMUNICATIONS TO THE EDITOR
When polymer I1 dissolved in tetrahydrofuran was treated with LiAlH4, we obtained 2,2,4-trimethyl-1-pentanol-3-one (80yoyield). This result agrees with a structure of the polyester type: AH3 0
/ I I/
/I
C,H31,CH3 C CH3O
I/
-C---~-~--c-C-~--~-C-\
I
I1
c@CIt
+
I1
701
4743
\
LiAlH4+
I
‘
CH3
\CH:
dlute
2 iI-(LiAl)~~O-C---CH,O--!Li*~~,_ II
H2S0,
I CH3 C e ,CH3 C CH:. /I I 2!iHO-C-C-CH20H~
I
C&
c? 2n
,CHs CH CHj I
CO-&-CH,OH
I
CH3
Furthermore, ozonolysis of I1 gave a good yield of acetone. The chemical behavior of polymer I1 enables us to conclude that i t consists of macromolecules derived from the regular, alternate polymerization of the two monomeric units ( a ) and
PHOTOOXIDATION TIME IN M I N U T E S
Fig. 1.-Loss
of methionine on photooxidation of phosphoglucomutase.
and “all-or-none” assays. Aliquots of the enzyme were removed a t various time intervals durGIULIONATTA ing photooxidation, hydrolyzed and assayed on the DI CHIMICA IKDUSTRIALE GIORCIOMAZZAKTI automatic amino acid analyzer of Spackmann, ISTITUTO POLITECXICO DI MILANO GIANFRANCO PRECACLIA Since acid hydrolysis is known MILANO,ITALY MARCO BINAGHI Stein and MARIOPERALDO to destroy tryptophan and was found to cause regeneration of methionine from methionine sulf oxide, these residues were determined after barium EVIDENCE FOR INVOLVEMENT OF A METHIONINE hydroxide hydrolysis of the photooxidized protein. RESIDUE IN T H E ENZYMATIC ACTION OF Other residues were determined after acid hydrolysis PHOSPHOGLUCOMUTASE AND CHYMOTRYPSIN except for cysteine which was determined by the Sir : p-chloromercuribenzoate reaction. I n studies to clarify the role of histidine in The fraction of methionine remaining as a funcphosphoglucomutase action it was found’ that loss tion of photooxidation time is shown in Fig. 1. of enzyme activity on photooxidation could be This biphasic curve can be analyzed as described explained on the basis of the model shown in equa- previously3 giving oxidation constants of 0.37 tion l. Here the various enzyme species are indi- min.-’ for the accessible methionines and 0.051 inin.-‘ for the inaccessible residues. The constants kx Esy --+ EY obtained for other amino acids were cysteine, 0.07 min.-’, tryptophan, about 0.01 min.-’, and tyrosine, about 0.01 min.-l. No other residues were detectably affected. X can therefore be identified as an accessible methionine residue. Since cated by subscripts which identify intact amino photooxidation of this residue produces enzyme acid residues. Thus, EXYrefers to original enzyme which is nert in the “all-or-none” assay, methionine with X and Y unchanged, Ex refers to enzyme in oxidation decreases enzyme activity by a factor which X is intact but Y has been oxidized, etc. of more than 200. I t is of interest in this regard Ex has an activity equal to about 87, of theorigi- that Gundlach, Stein and Moore have found that nal activity, while Ey and E are inactive in the carboxymethylation of methionine also reduces present assay systems.’ Since Y has been identi- ribonuclease activity. fied as histidine, i t was clearly of interest to identify Since a similarity in the bond-breaking or X which is apparently even more important t o “catalytic” residues a t the active sites of phosenzyme activity. phoglucomutase and chymotrypsin had been indiTo allow such an identification, the rate con- cated in previous work,3 i t was of interest to perstants for oxidation of the susceptible residues of (2) D. H. Spackmann, W. H. Stein and S. Moore, Anal. Chem., the protein were obtained for comparison with the 3 0 , 1190 (1968). (9) D. E. Koshland, Jr., W. J. Ray, Jr., and hl. J. Erwin, Fedevolion value of 0.38 min.-’ attributed to X by both rate
(P) *
(1) W.J. Ray, Jr., J. J. Ruscica and D. E. Koshland, Jr., THIS J O U R N A L , sa, 4739 (1960).
Proc., 17, 1145 (1958). (4) H. G. Gundlach, W. H. Stein and S. Moore, J. Biol. C h e m . , 234, 1754 (1959).
