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POLYMETHYLENES

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Originally appearing in Volume V22, Page 30 of the 1911 Encyclopedia Britannica.
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POLYMETHYLENES , in See also:

chemistry, cyclic compounds, the simplest members of which are saturated See also:hydrocarbons of See also:general See also:formula C„H2,,, where n may be 1 to 9, and known as tri-, tetra-, penta-, hexa-, and hepta-methylene, &c., or cyclopropane, -butane, -pentane, -hexane, -heptane, &c.: See also:CH2(CIHI, CH2C.H2 CH2\CIH2•CH2, CH2\CH2•CH2TCH2,&c. Cyclo-propane, -butane, -pentane, -hexane. The unsaturated members of the See also:series are named on theCH2.CH/ NCH2—•—C (6) I (5) (6) II. (5) As to the stability of these compounds, most trimethylene derivatives are comparatively unstable, the See also:ring being broken fairly readily; the tetramethylene derivatives are rather more See also:stable and the penta- and hexa-methylene compounds are very stable, showing little tendency to See also:form open See also:chain compounds under See also:ordinary conditions (see CHEMISTRY: Organic). See also:Isomerism.—No isomerism can occur in the monosubstitution derivatives but ordinary position isomerism exists in the di-and poly-substitution compounds. Stereo-isomerism may occur: the simplest examples are the dibasic acids, where a cis-(maleinoid) form and a trans- (fumaroid) form have been observed. These isomers may frequently be distinguished by the facts that the cis-acids yield anhydrides more readily than the trans-acids, and are generally converted into the trans-acids on See also:heating with hydrochloric See also:acid. 0. Aschan (Ber., 1902, 35, p. 3389) depicts these cases by representing the See also:plane of the See also:carbon atoms of the ring as a straight See also:line and denoting the substituted See also:hydrogen atoms by the letters X, Y, Z. Thus for dicarboxylic acids (See also:CO2H=X) the possibilities are represented by X X (cis), X x (trans), x X (I). The trans See also:compound is perfectly See also:asymmetric and so its See also:mirror See also:image (I) should exist, and, as all the trans compounds synthetically prepared are optically inactive, they are presumably racemic compounds (see O.

Aschan, Chemie der alicyklischen Verbindungen, p. 346 seq.). General Methods of Formation. Hydrocarbons See also:

nay be obtained from the dihalogen paraffins by the See also:action of See also:sodium or See also:zinc dust, provided that the halogen atoms are not attached to the same or to adjacent carbon atoms (A. See also:Freund, Monats., 1882, 3, p. 625; W. H. See also:Perkin, jun., Journ. Chem. See also:Soc., 1888, 53, p. 213): CH2•CH2 Br+zNa=zNaBr+ CH2•CH2; by the action of hydriodic acid and See also:phosphorus or of phosphonium iodide on See also:benzene hydrocarbons (F. Wreden, See also:Ann., 1877, 187, p.

153; A. v. See also:

Baeyer, ibid., 1870, 1S5, p. 266), benzene giving methylpentamethylene; by passing the vapour of benzene hydrocarbons over finely divided See also:nickel at 18o-25o° C. (P. See also:Sabatier and J. B. Senderens, Comptes rendus, 1901, 132, p. 210 seq.); and from hydrazines of the type C„H2„_1•NH•See also:NH2 by oxidation with alkaline See also:potassium ferricyanide (N. Kijner, Journ. prak. Chem., 1901, 64, p. 113). Unsaturated hydro-carbons of the series may be prepared from the corresponding See also:alcohols by the elimination of a See also:molecule of See also:water, using either the xanthogenic ester method of L.

Tschugaeff (Ber. 1899, 32, p• 3332): C„H2,,_,ONa-)G,H2„_10-CS•SNa(R) -G,H2,,_2+See also:

COS+R•SH; or simply by dehydrating with anhydrous oxalic acid (N. Zelinsky, Ber., 1901, 34, p• 3249); and by eliminating the halogen acid from mono- or di-halogen polymethylene compounds by heating them with See also:quinoline. Alcohols are obtained from the corresponding halogen compounds by the action of moist See also:silver See also:oxide, or by warming them with silver acetate and acetic acid; by the reduction of See also:ketones with metallic sodium; by passing the vapours of monohydric phenols and hydrogen over finely divided nickel (P. Sabatier and J. B. Senderens, loc. cit.); by the reduction of cyclic See also:esters with See also:Geneva See also:system in which the termination -ane is replaced by-ene, -diene, -triene, according to the number of See also:double linkages in the compound, the position of such double linkages being shown by a See also:numeral immediately following the suffix -ene; for example I. is methyl-cyclo-hexadiene—r. 3. An alternative method employs A. v. Baeyer's See also:symbol 0.. Thus 0 2.4 indicates the presence of two double bonds in the molecule situated immediately after the carbon atoms 2 and 4; for example II. is A 2.4 dihydrophthalic acid. (2) (3) (2) (3) (I)See also:CH3.C~ CH•CH \ CH(4)(t)H02C•CH/C(COzH):CH\CH(4) sodium and See also:alcohol (L.

Bouveault and G. See also:

Blanc, See also:Corn pies rendus, 1903, 136, p. 1676; 137, p. 6o); and by the addition of the elements of water to the unsaturated cyclic hydrocarbons on boiling with dilute acids. See also:Aldehydes and Ketones.—The aldehydes are prepared in the usual manner from See also:primary alcohols and acids. The ketones are obtained by the dry See also:distillation of the See also:calcium salts of di-basic saturated aliphatic acids (J. See also:Wislicenus, Ann., 1893, 275, p. 309): [CH2•CH2•See also:CO2]2Ca--4CH2•CH2]2CO; by the action of sodium on the esters of acids of the adipic and pimelic acid series (W. Dieckmann, Ber., 1894, 27, pp. 103, 2475) CH2•CH2•CH2•CO2R CH2.CH2•CH . CH2•CH,•CO2R ~CH2•CH2C•02 by the action of sodium ethylate on 3-ketonic acids (D. Vor- See also:lander, See also:Bet., 1895, z8, p.

2348) CCH2•CH2\CO2H-> CH CH2•CH2 CH,( \CO; \CO•CH3 CO•CH2 from sodio-malonic ester and ai3-unsaturated ketones or ketonic esters: (See also:

R02C)2CH2+Ph•CH:CH•CO•CH3->PhCH<CH, CO~CH2; CH(CO2R)•CO from aceto-acetic ester and esters of a/3-unsaturated acids, followed by elimination of the carboxyl See also:group: CH,•CR'2 CH3•CO•CH2•CO2R+R'2C:CH•CO2R->CO/ CHCO2R; \CH2•CO by the condensation of two molecules of aceto-acetic ester with aldehydes followed by saponification (E. Knoevenagel, Ann., 1894, 28,, p. 25; 1896, 288, p. 321; Ber., 1904, 37, p. 4461): 2CH3•CO•CH2•CO2R+OHC.R'-->CH3•C/CH2•CHR'\CH2; "CH.—CO from I.5-See also:diketones which contain a methyl group next the keto-group (W. Kerp, Ann., 1896, 290, p.

End of Article: POLYMETHYLENES

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