Cyclic formulas

In 1887 (57) and 1889 (73) Andreasch confirmed the cyclic formula proposed by Liebermann and Lange (20). Freydl (74) obtained rhodaninic acid by condensing thioglycolic acid with thiocyanic acid. 

In 1891, Miolati (75) confirmed the cyclic formula of Liebermann and Lange by preparing the compound by three new pathways (1) reaction of CS2 on thiohydantoin, (2) condensation of ammonium dithiocarbamate with chloroacetic ester, (3) reaction of HjS on thiocyanoacetic acid. 

In 1910 Stobbe and Posnjak drew the conclusion that polystyrene is a colloidal body after noting that boiling point elevations of its solutions are negligible. They proposed cyclic formulas composed of four, five, or possibly more structural units, e.g. 

The views of Staudinger, on the one hand, and Meyer and Mark, on the other, actually were not so far apart as the tenor of their polemics might indicate. Their agreement on the essential macromolecular nature of high polymers appears to have contributed materially to the rejection of the simple cyclic formulas widely accepted up to that time. 

Similarly Stable and Posnjak (87) proposed cyclic formulas of four, five, or possibly more structural units for polystyrene. Lebedev (88) first assigned the cyclooctadiene structure to polybutadiene shown below before expanding the concept of the ring to include several isoprene units. 

Potassium ferrocyanidc was also given a cyclic formula by Friend, where iron is situated at the centre of the ring and is therefore not ionised in solution. The enclosing ring is made up of cyanogen radicles,... 

The last of these three examples is important, since it shows an explicit representation of a cyclic compound almost a decade before Kekule proposed his cyclic formula for benzene. This last formula is also important in showing that Couper did not explicitly represent double bonds between atoms in his stmctures. 

The historical aspects of Emil Fischer s fundamental conventions for writing stereoformulas in a plane have been thoroughly delineated.2 It may be mentioned that the perspective formulas generally attributed to W. N. Haworth were actually a revival of J. Bdeseken s cyclic formulas. ... 

Perkin (senior) determined the magnetic rotation1 of a few cyclopropane derivatives and tne values so obtained were used as an argument l or tne cyclic formula In the pioneer days of cyclopropane chemistry. 

Complete fundamental cyclic formulas showing all carbons and hydrocarbons are given only in Charts 1, 2, 4, 8, and 9 in the other charts, the conventional ter-pene skeletal formulas have been used. For those not familiar with these common terpene formulas of the monocyclic and bicyclic structures, Chart 2 is included to show the different forms of identical structures which appear in current chemical literature. Only saturated structures are given. The three-dimensional type of skeletal formulas shown for the bicyclic structures is being used currently more and more because they often permit much more to be expressed concerning the properties of a compound and its relations to a fundamental type than do the classical structural formulas. 

As shown in Chapter X., water is believed to be associated to a considerable extent to dihydrol (H2Q)2 and, at low temperatures even to trihydrol molecules, (H20 )3. Assuming the strictly monovalent nature of hydrogen, a higher valency than two is required for oxygen. Thus dihydrol may be written H2=0=0=H2, and to tnhydrol a cyclic formula may be given. 

Structure of Halonitrides.—On account of their stability towards heat and hydrolysing agents, as wrell as the requirements of valency, cyclic formulas have been assigned to the halonitrides in which the rings are composed either of >N—PC12 or of >N and >PC12 alternately.2 Thus the tri-compounds may be represented by... 

Etard and Bemont2 and Friedel3 suggested the cyclic formula -... 

The suggestion is therefore made that the salt is more correctly represented by the single formula, Na2[Fe(CN)5NO], than by the double formula 5 given above. In order to harmonise the double cyclic formula with this, it is merely necessary to assume that the double negative radicle [Fe(CN)5NO]2//,/ itself dissociates into two Fe(CN)5NO" ions in solution. 

Cyclic formula for Schardinger dextrins containing all maltose linkages... 

In the French version Arm, Chim. (3), 53, 489 (1858)) Coupcr adds the following cyclic formula for cyanuric acid, seven years before Kekule proposed the cyclic benzene formula ... 

Some historians, particularly John Wotiz, have recently argued that Kekul6 was "no genius," hut rather a "gifted opportunist," a "fraud," and a "cheat" who fabricated these anecdotes to create an irrefutable cover story—irrefutable because they were private mental events—in order to steal credit for cyclical benzene from those who he knew were really the first to write cyclical formulas, namely, Couper and Lo-schmidt. Having failed to publish before his rivals (Wotiz suggested), Kekule falsely claimed that he had had these ideas first, in dreams, before them. He was thus guilty of "misconduct." ... 

Thiele discovered nitro- and amino-guanidine and described a preparation of hydrazine from aminoguanidine, also of hydrazoic acid from hydrazine, ethyl nitrite, and alkali, and at first independently proposed and adopted the correct linear formula N. N NH, which had been given by Angeli, but later reverted to Curtius s cyclic formula on the basis of misleading parachor results. Thiele and A. Lachman discovered nitramide by way of nitrourethane, C2H50-C0-NH-N02. They formulated it both as the amide, NH2 N02, or imide, NH NO OH, of nitric acid. Thiele later preferred the second formula. 

The sugars are in effect reducing agents, the same as the aldehydes and ketones, but they do not restore the coloiu- to fuchsin bleached by SO Haworth s formulae are now generally accepted. They give a clearer idea of the relationship of the various groups than the ordinary cyclic formulae or the linear formulae, although any of the three may be met with. 

---