2 CH3>CH.CH2.CH2I + Na2 = 2NaI CH3 CH3 CH3>CH.CH2.CH2.CH2.CH2.CH CH3 It is a colourless oil of faint ethereal odour and burning taste; has sp. gr. 77 and boils at 158°. A hydrocarbon of the same composition results by heating oil of turpentine with much concentrated hydriodic acid to 275° : C10H16 + 6HI= C10H22 + 312. It distils over between 155° and 162°. 158. A number of higher members of the series have been isolated from American petroleum and coal tar by fractional distillation ; their constitution is, however, still unknown. A synthetically prepared dodecane is obtained by the electrolysis of potassic œnanthate, (CH13.CO.OK), as an oil boiling at 202°; the normal hexdecane, C16H34 or CH3(CH2)14-CH3, is obtained as a bye product in the preparation of normal octane from normal octylic iodide; it boils at 278°. 159. Paraffins containing more than 16 carbon atoms are contained in those oils, &c., boiling above 300° contained in petroleum, and obtained in the dry distillation of peat, lignite, &c., but have not yet been isolated. The substance commercially termed paraffin consists essentially of them; this mixture, which probably also contains hydrocarbons of the formula CnH2n, forms a colourless translucent mass, which, according to its source and method of purification, melts between 40° and 80°. It is insoluble in water, little soluble in cold alcohol, more readily in hot alcohol, ether, and liquid hydrocarbons; it is one of the materials used for the manufacture of candles. To prepare it the high-boiling portions of peat or lignite tar, partly solidified by cooling, are heated with concentrated sulphuric acid; this destroys one series of impurities and changes others into sulphur containing acids (sulphonic acids) soluble in water, whilst the fused paraffin is not itself attacked, and collects on the surface as an oily layer. This is separated from the acid aqueous solution, and submitted to distillation after addition of some caustic alkali to neutralise any adhering acid. The distillate is then mixed with not too large a quantity of colourless light tar-oil, brought to crystallisation by cooling, and the oil (which dissolves out colouring matters and oily impurities) expressed by aid of hydraulic presses. The residue is paraffin. On account of its difficult alterability by most of those reagents which act powerfully on organic bodies, it obtained its name of paraffin (from parum affinis), which later was adopted as the general name for the whole series. MONOSUBSTITUTION PRODUCTS OF THE PARAFFINS. General. 160. The monovalent alcohols, CnH2n+1.OH, may be arranged in three classes according to the position of the carbon atom united to hydroxyl in the nucleus, to which methyl alcohol or carbinol, H H OH the first member of the series, may be added as a fourth variety. 1. The primary alcohols contain the hydroxyl group attached to a terminal primarily united carbon atom, which, therefore, is also united to two hydrogen atoms; the group is characteristic of them. From methyl alcohol they are derived by replacement of one methyl hydrogen atom by an alcohol radical: By action of oxidising agents upon them there results, according to the extent of oxidation, two products-namely, by action of one atom of oxygen with elimination of two hydrogen atoms, aldehydes: which are converted by a second atom of oxygen into monobasic The oxidation of the primary alcohols to acids of equal carbon contents can also be effected by action of alkalies at high temperatures: CmH2m+1 CmH2m+1 The primary alcohols can be regenerated from the aldehydes by action of nascent hydrogen: CmH2m+1 CmH2m+1 H -H он 2. Secondary alcohols are those in which hydroxyl is united to a secondarily combined carbon atom (that is, one which is united to two other carbon atoms); they are therefore characterised by the group H From carbinol they are derived by replacement of two hydrogen atoms by alcohol radicals: CH3-CH(OH)-CH, dimethyl carbinol. = Oxidising agents, as long as the carbon chain is not destroyed, act with only one oxygen atom upon the molecule of a secondary alcohol; there results thereby, with removal of two hydrogen atoms (as in the formation of aldehydes), ketones: from which the secondary alcohol can be regenerated by nascent hydrogen: 3. Tertiary alcohols contain their hydroxyl united to a carbon atom, which is united to three other carbon atoms. Therefore they appear as carbinol in which all the non-hydroxylic hydrogen atoms are replaced by alcohol radicals: The lowest tertiary alcohol, therefore, contains four carbon atoms: The tertiary alcohols are not capable of an oxidation similar to that in aldehyde or ketone formation; by action of powerful oxidising agents the nucleus is broken up into several smaller ones. 161. It is evident that the structure of the nucleus must have considerable influence on the nature of the alcohol; there are to be distinguished: 1. Normal alcohols, whose nuclei can contain only primarily and secondarily combined carbon atoms, and therefore a single chain with only two terminal carbon atoms. Normal alcohols may be primary or secondary, but not tertiary: 2. Isoalcohols, which are derived from nuclei containing side chains, and therefore tertiarily or quarternarily united, contain more than two terminal carbon atoms. There are primary, tertiary, and also secondary isoalcohols when with more than five atoms of carbon : 162. Although the alcohols have no action on vegetable colours, still they have the properties of weak basic hydrates, appearing therefore as the hydroxyl compounds of electro-chemically positive radicals. They also react in many ways like the hydrates of the monovalent alkali metals, though with much less energy; they unite pretty readily with acids to saline compounds in which the alcohol radical replaces the acid hydrogen. By action of haloid acids upon them the chlorides of the alcohol radicals result: like CnH2n+1.OH + HCl = CnH2n+1C1 + OH2, KOH + HCl = KCl + OH2; and they yield with the oxyacids (in complete analogy to the oxysalts of alkali metals) the ethereal salts: like like like CnH2n+1.OH + HO.NO2 = C2H2n+1.0.NO2 + H2O; KOH + HO.NO, K.O.NO, + H2O, = CnH2n+1.OH + H2SO1 = CnH2n+ 1.HSO, + H2O; 4 KOH + H2SO1 = K.HSO, + H2O, 4 Formation of Alcohols. 163. Many alcohols of the series CnH2n+1.OH occur in nature as the salts of organic acids, and indeed ready formed in plants and animals; many of them result from the fermentation of saccharine bodies by an organised ferment-yeast-and then accompany ethyl alcohol. In their synthetical preparation from the paraffins the use of the monochlor substitution products of these latter is indispensable, the conversion of the chloride into the alcohol being usually effected in this manner: the chloride is first converted into the acetate by heating with argentic or potassic acetates: CnH2n+1.Cl + KO.C2H2O=CnH2n+1.O.C2H3O+ KCl, and this, on heating with potassic hydrate solution, yields the alcohol and potassic acetate: CnH2n+1.O.C2H30 + KHO = KO.C2H3O+ CnH2n+1.OH. When the paraffin contains more than two carbon atoms, the first action of chlorine produces isomeric chlorides, from the mixture of which, when heated in the above way, secondary, &c., alcohols are obtained as well as primary. For instance, propane, by treatment with chlorine, yields simultaneously primary and secondary propylic chlorides: and there are finally obtained both primary and secondary propylic alcohols. Many primary alcohols have only been obtained by the action of nascent hydrogen upon those aldehydes which they themselves would yield on oxidation. |