Vol. 67
NOTES
3050
reaching from the end of a primary molecule to the undergoes a Michael condensation with unfirst cross-linkage aloeg its length are not perma- changed acetoacetic ester to form (111). nently distorted by a deformation of the sample. CH~COCHCOIC~H~ CHaCOCCOjC2Hj The latter, therefore, generally will not undergo 11 I crystallization, but rather will act like diluents CHzCl CHz dispersed in the oriented portion of the network T I1 Equation (6) can be deduced as a special case CH?COCHCO,C*H, of the more general dependence stated in italics I CH, above. If the concentration of cross-linkages 1 (degree of vulcanization) is fixed, the percentage CH~COCHCOGH~ of the rubber occurring in non-orienting terminal I11 chains will be inversely proportional to X , the The chloromethylation with boron trifluoride molecular weight of the priniary molecules (i. e., the molecular weight of the rubber molecules to form the C-alkyl derivative is in contrast to before vulcanization). Hence, in accordance with the reaction of chloromethyl, ether with sodium the above generalization, the tensile strength acetoacetic ester which forms mainly the 0varies linearly with l / M a t constant degree of methoxymethyl d e r i ~ a t i v eC, ~H ~ C = C H C O ~ C ~ H ~ . I cross-linking. OCHzOCHa This interpretation of the tensile strengthProcedure.-A mixture of one or one-half mole of molecular weight relationship cannot be applied chloromethyl ether and one-half mole of ethyl acetoacetate t o cellulose acetate which has no primary valence was saturated with boron trifluoride a t 0" as described network. It would appear that the similar de- previously' for alkylation with ordinary alcohols and pendence on molecular weight in this case is to be ethers. After the reaction mixture had come to room it was poured into aqueous sodium acetate. regarded as coincidental rather than as an indica- temperature, The mixtqre was extracted with ether and the dried ethereal tion of identical structural behavior when sub- extract distilled. There was obtained a 33% yield of jected to severe stresses. In this connection methylene-diacetoacetic ester, b. p. 192-210° a t 20 mm. giving, wjth ferric chloride solution, Spurlin3 has suggested that rupture originates a t with decomp~sition,~ deep purple enol test, and with alcoholic ammonia, ethyl the ends of molecules and, hence, that the ease of adihydrolutidinedicarboxylate, m. p, 174-176O.' A nonfailure (conversely the strength) should depend on distillable viscous residue (10-13 9.) remained in the disthe number of ends of molecules. This will ex- tilling flask. plain the explicit dependence of strength on the (3) Simonsen a n d Storey, J . Chem. Soc., 95, 2108 (1909). number average molecular weight; i t does not (4) Knoevenagel, Ann., 281, 94 (1894). seem to offer a satisfactory basis for linear de- DEPARTMENT OF CHEMISTRY DUKEUNIVERSITY pendence on 1 / M , or 1 / M n , however. (3) H. M. Spurlin, "Cellulose a n d Cellulose Derivatives," edited by Emil Ott, Interscience Puhlishers, Inc., New I'ork. K. Y.,lOi0, pp. L), 935-930.
DURHAM, X. C.
Determination of Pyrrole
RESEARCH LABORATORY GOODYEAR TIRE AND RUBBERCOMPAXY RECEIVED XLTGCST 28, 1945 AKRON,OHIO
Reaction of Chloromethyl Ether with Ethyl Acetoacetate in the Presence of Boron Trifluoride
RECEIVED SEPTEMBER 17, 1945
BY F. FROMM'
A photometric micromethod for the determination of pyrrole has been based on the blue color produced in the reaction between pyrrole and isaI
I
I
2.5
BY ROBERT LEVINE AND CHARLES R. HAUSER
I t has been shown in this Laboratory2 that, in the presence of boron trifluoride, certain ethers and alcohols alkylate acetoacetic ester to form the cdrresponding C-alkyl derivative. It has now been found that, under similar conditions, chloromethyl ether reacts with acetoacetic ester to form methylenediacetoacetic ester (111). The reaction involves presumably the chloromethylation of acetoacetic ester to form the C-alkyl derivative (I). This intermediate then either alkylates unchanged acetoacetic ester to form (111)or loses hydrogen chloride to form (11) which (1) Paper XXXl on "Condensations". 67. 1510 (1945).
paper X X S , TZIIS JOUR-
NAL.
(2) Adams, Abramovitch and Hauser, rbid., 65, 5.52 (1943).
2.3
slM
-
2.1 1.9
1.7
550
600 650 700 mw Fig. 1.-A, color reaction; 10.8 mg. pyrrole per liter: B, pyrrole blue B ; 5.3 mg. pyrrole per liter.
500
