In CH4, by substituting 3 Cl for 3 H,—
H Cl
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H-C-H becomes H-C-CI, or CHCl3,the symbol for chloroform.
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H Cl
Replace successively one, two, and four atoms with Cl, and write the common symbols. Make the same changes with Br. For each atom of H in CH4 substitute the radical CH3, giving the graphic and common formulae. Also substitute C2H5. Are these radicals positive or negative? From the above series of formulae, of which CH4 is the basis, are derived, in addition to the alcohols and ethers, the natural oils, fatty acids, etc.
302. Olefines.—A second series of hydro-carbons is represented by the general formula CnH2n. The first member of this series is C2H4 or, graphically,—
H H | | C = C. | | H H
Compare it with that for C2H6, in the first series, noting the apparent molecular structure of each.
H H | | C = C - C - H, or C3H6 is the second member. | | | H H H
Write formulae for the third and fourth members.
Write the common formulae for the first ten of this series. This is the olefiant-gas series, and to it belong oxalic and tartaric acids, glycerin, and a vast number of other compounds, many of which are derived by replacements.
303. Other Series.—In addition to the two series of hydro- carbons above given, CnH2n+2 and CnH2n, other series are known with the general formulm CnH2n-2, CnH2n-4, CnH2n-6, CnH2n-8, etc., as far as CnH2n-32, or C26H2O. Each of these has a large number of representatives, as was found in the marsh-gas series. Not far from two hundred direct compounds of C and H are known, not to mention substitutions. The formula CnH2n-6 represents a large and interesting group of compounds, called the benzine series. This is the basis of the aniline dyes, and of many perfumes and flavors.