Group bivalent

The hypothesis that two chlorine atoms can form a bivalent group (either —C1=C1— or —Cl—Cl—), was used to explain the constitution of chloroplatinic acid by S. M. Jorgensen (1877), and by J. W. Mallet (1881) to explain the formation of the double fluorides and by J. F. Heyes to explain the structure of the double halides. In 1889, Ira Remsen showed that the structure of most of the double halides can be explained on the hypothesis that the halogen atom has the power to unite with itself to form a bivalent group which can take the place of one oxygen atom in the oxygen salts. 

A Catalog of the (bivalent) group contributions or group increments is given in the comprehensive Table IX of Part VII. 

TABLE 4.2 Group increments of mass and Van der Waals volume (bivalent groups)... 

For other groups, the contributions mentioned by different authors show larger variations. This appears from Table 4.5 where published values of the contributions for a number of groups are compared. All the results are expressed in the form of bivalent groups. This has been done because a number of authors did not make a clear distinction between the contributions of monovalent end groups and the above-mentioned residual volume. 

M. F. Lappert, The Coordination Chemistry of Bivalent Group IV Donors Nucleophilic-Carbene and Dialkylstannylene Complexes, J. Organomet. Chem. 100, 139-159 (1975). 

N(side chain) s defined [7] as the "extra effect of side chain, per -CH2- or other bivalent group". Since the of any polymer is a constant whose value is exactly determined from the structure of the repeat unit, the only remaining task is to develop a correlation for HTlsum. The total value of can be calculated by adding B, . to B. ... 

Each of these elements forms two series of compounds. One contains compounds of the bivalent group II )1 or(HgO",... 

The diamids correspond to the diamins (see p. 333), from which they differ in that the substituted groups are oxidized in place of hydrocarbon. The imids differ from the secondary monamids (see p. 278) in that the group TfH is attached to a bivalent group in place of to two univalent groups. The -amic acids are dibasic acids of the series mentioned above in which an OH is replaced by NH,. 

The nomenclature adopted by lUPAC rests upon selection of preferred constitutional repeating units from which the polymer is a multiple. The unit is named wherever possible according to the definitive rules for nomenclature of organic chemistry. For single stranded polymers this unit is a bivalent group. An example is a polymer with oxy(l-fluoroethylene) constitutional repeat unit ... 

Sulfate sol- fat [F, fr. L sulfur] (1790) n. SO4. (1) A salt or ester of sulfuric acid. (2) A bivalent group or anion characteristic of sulfuric acid and the sulfates. 

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