ALFRED R. BADERAND HENRYA. VOGEL
3992
Characterization of 2,4-Diphenylpyrimidine.-The
VIS-
cous distillate, n'% 1.6543, slowly crystallized t o a yelloh 5olid, 1ii.p. 58-,?9". .Inui. Calcd. for CilhHIPN. C , 82.8; H, 3.2; s, 12 0 ; iieut cquiv-., '33'3. ~ o u t l c l . C , x;{ (1; I € , 5 . 3 ; A-, 11.7; IlCLlt. q u i \ . , 249. I n comparing the ultraviolet spectrum of 2;Ldiphenylpyrimidine with the spectrd of the aliphatic pyrimidines, the former wa? found t o have .igreater absorption coefficient
[COYTRIBUrIOV FROM
THE
RESEARCH IdADORAToRIE'?OT'
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and the peak was shifted slightly t o the longer wave length. In another run, benzonitrile (125 9.) and potassium (2 g.) were treated with acetylene a t a gage pressure of 10-15 atmospheres for 14 hours, while the temperature was maintdinccl a t 180-200". There was recovered 25 g. of benzonitrile (b.p. 62-70' (7 mm. 1). The 2,4-diphenylpyrimidine distilled a t 19C-191" (3 mm.) (57 g., 51% yield). WILMINOTON, I)EI,AwARE
TIIE P A I V r D I V I S I O N O F TIIE PITTSBURGH PLATE
GLASSC O M P A S Y 1
11. Esters of Strong Organic Acids
Transesterification.
BY ALFREDR. BADERAND HENRY A. VOGEL RECEIVED FEBRUARY 22, 1952 The transesterification of P-keto esters has been compared with that of esters of other strong organic acids. Malonates and oxalates, like acetoacetates, are transesterified under mild conditions, and i t is suggested that the ease of transesterification of B-keto esters is due mainly t o special strurtural features inherent in these esters, while that of oxalates is due to the inductive effect of the neighboring group
In our first communication1 we reported on the because one would expect the acetoacetate to be transesterification of @-ketoesters which proceeds the more basic ester and its reaction might be the a t steam-bath temperatures in the absence of cata- only one catalyzed. lysts. We have now completed a qualitative study TABLE I of transesterifications of acids of strength similar Acid 105 KI a t 2 5 O Prodirctq and greater than that of acetoacetic acid to deter1.44" Sone mine whether this facile transesterification is due to Caprylic 1 . 5 0 ~ None the inductive effect of the acetyl group, to intermo- Butyric Sone 2.03" lecular catalysis by active hydrogen or to structural Crotonic .... . Kone features unique in @-ketoesters. Table I lists the Levulinic Benzoic 6 . 2 P S one acids investigated, their ionization constants and 13.9" Sone the products obtained after heating representative Lactic 2iid Acetoacetates primary and secondary alcohols with excess ester Acetoacetic ...... Berizoylacetates Benzoylacctic on the steam-bath without catalysts for 16 hours. 68' S one Furoic In any ester interchange one has the e q ~ i l i h r i : ~ Small amt. fumarates Fumaric 95, if C) .104' Sone Tartaric ,
I?-COORI
+- R20IT
R---(!--OR HOR?
-
t
R-COOR2
Sone Mixed and symm. ni alonat es Ethyl-n-hutylmalonic , , . , , , Sone Maleic 12001 None Oxalic 5900' Mixed and symm. oxalates C. G . Derrick, THIS JOURNAL, 33, 1152 (1911). J . F. J . Dippy, Chem. Recs., 25, 151 (1939). A. \Y, Martin and H. V. Tartar, THISJOURNAL, 59,2672 ( 1 9 3 L . E;. J . Pedersen, J . Phys. Chem., 38, 993 (1934). e W. I.. German, G. H. Jeffery and A. I . Vogel, J . Chem. Snc., 1604 (1937). f L . P. Hammett, "Physical Organic Chemistry," McGraw-Hill Book Co., Inc., S e w York, S. Y., 1940, p. 201. 0 I . Jones and F. G . Soper, J . Chem. SOC., 1836 (1934). W. J. Hamer, G. D. Pinching and S. F. Acree. J . Research Nail. Bur. Standards. 35. 539 (1945i: C.A ., 40, 3044 (1946). R . Gane and C . I-?. Ingold, J . Chcm. S o r . , 2153 (1931). Phthalic Malonic
It.-
4- R1OI-I
the equilibrium constants of which are probably not greatly different from le and the reason for the ease of transesterification of acetoacetates a t first considered most likely was the inductive effect of the acetyl group which removes electrons from the ester carbonyl, increases its electrophilic reactivity and thus the speed with which the equilibria are set up. A correlation is that acetoacetic acid is over ten times as strong an acid as acetic. Our qualitative data indicate, however, that the inductive effect can only be a mildly contributory factor in the ease of transesterification of @-ketoesters because esters of some stronger acids do not react under our experimental conditions. Nor does i t seem likely that the ease of transesterification of @-ketoesters is due to an active hydrogen catalysis because we have found that when alcohols are heated in unreactive esters such as ethyl butyrate containing ethyl acetoacetate in a molar ratio of 10 : 1,the higher acetoacetate is the sole reaction product. Such experiments are, however, not entirely conclusive i l ) .I K. Bader. I.. 0. CumrniIlg.; .in
