Hydrogen isotopic exchange in biphenylene and the preparation of biphenylene-d₈

Abstract

The hydrogen isotopic exchange with basic and acidic agents has been widely investigated with the aim of preparing fully deuterated biphenylene. It has been noted that the very strong base KOD completely decomposes the hydrocarbon, while the strong base NaOD leads to random exchange, and the medium strength base Ca(OD)2 gives preferential exchange in a-position. Since the stability of biphenylene is less in acid mixtures than in basic ones, only acids of medium strength, which give preferential exchange in P-position, can be used.Good results in preparing fully deuterated biphenylene are obtained from two methods. The first of these consists of two exchanges which occur successively; one with an acid mixture and the other with a base. Both agents are of medium strength. The second method entails repeated exchanges with the strong base NaOD supported on Ca(OD)2. The latter method gives the highest isotopic purity and the best yield, as well as being much easier to carry out.Canadian Journal of Chemistry, 46, 391 (1968) The study of the vibrational spectrum of biphenylene (BPH), which is in progress in this laboratory,2 has required the availability of the corresponding fully deuterated compound (BPH-d8). Since the reported syntheses of BPH, which give reasonable yields (1-3), did not appear to be conveniently adaptable3 to the preparation of BPH-ds, the hydrogen isotopic exchange method was chosen, since it gives good results with aromatic compounds (5,6).The reactivity of the hydrogen atoms of BPH has been the object of both theoretical and experimental research (7-1 1). Kinetic data for hydrogen isotopic exchange in trifluoroacetic acid and trifluoroacetic acid -70 % HC104 are also available (12,13) and the /?-position has been shown to be more reactive than the a one, which has almost the same reactivity as the /?-position in naphthalene (13). Since each of the hydrogen atoms of naphthalene exchange with 50% D2SO4 (14), the first exchange experiments attempted were wit11 30-70 % D2SO4 (runs 1-3, Table I). In these reaction mixtures, the D / H atom ratio was 10:l and therefore BPH with 90% deuterium content could be expected if a random distribution of hydrogen isotopes were obtained. The results (Table I) show that an increase of acid concentration results in an lThis investigation was supported by the National Research Council of Italy, Chemistry Committee.2C. Pecile and B. Lunelli. J. Chem. Phys. In preparation.3A new method, which may be adaptable, was reported briefly (4) when the present work was in an advanced stage.increase in deuterium content of the product but a poorer yield of recovered BPH is obtained. The 60% D2SO4 gives an acceptable yield but the percentage of deuterium is too far below 90 %; the 70 % D2SO4 (5 h at 110 "C) produces nearly complete decomposition.Results obtained with other acids were not useful. Gaseous DCl(15) bubbled through a 5 % solution of BPH in benzene or in carbon disulfide in the presence of AlC13 gave unexchanged BPH and 30 % decomposition products. Liquid anhydrous ...

Perchlorylation of Benzene and Synthesis of Perchlorylbenzene-d5

“…Although the preparation of PBD should give no problem using an automatic H/D exchange apparatus previously de-signed (Lunelli and Pecile, 1968) and extensively used by us (Lunelli and Giorgini, 1976;, it was tempting to get it in a single operation, analogously to P B (Inman et al, 1958(Inman et al, , 1963Scott and Oesterling, 1960;Inman et al, 1964;Khuthoretskii et al, 1967), by simply replacing benzene with benzene-d6. However, the very large excess of benzene-d6 required and the low yield implied if the method of synthesis of P B is directly carried over to the synthesis of PBD made it desirable to investigate the perchlorylation of benzene-a reaction rather scantily discussed in the literature (Inman et al, 1958(Inman et al, , 1964Scott and Oesterling, 1960;Olah, 1973a)-in order to get the chemical information essential to a satisfactory preparation of PBD.…”