To this attitude he offered uncompromising opposition, and by the synthetical production of numerous hydrocarbons, natural fats, sugars and other bodies he proved that organic compounds can be formed by ordinary methods of chemical manipulation and obey the same laws as inorganic substances, thus exhibiting the "creative character in virtue of which chemistry actually realizes the abstract conceptions of its theories and classifications - a prerogative so far possessed neither by the natural nor by the historical sciences."
It readily condenses with aromatic hydrocarbons in the presence of sulphuric acid.
The solution is diluted with water, and the hydrocarbons are thereby precipitated and separated.
This heat of formation, like that of most hydrocarbons, is comparatively small: the heat of formation of saturated hydrocarbons is always positive, but the heat of formation of unsaturated hydrocarbons is frequently negative.
The calorific power of Baku oil appears to be highest, while this oil is poorest in solid hydrocarbons, of which the American petroleums contain moderate quantities, and the Upper Burma oils the largest amount.
The principal elements are found in various combinations, the hydrocarbons of the Pennsylvania oils being mainly paraffins (q.v.), while those of Caucasian petroleum belong for the most part to the naphthenes, isomeric with the olefines (q.v.).
The " cracking " process, whereby a considerable quantity of the oil which is intermediate between kerosene and lubricating oil is converted into hydrocarbons of lower specific gravity and boiling-point suitable for illuminating purposes, is one of great scientific and technical interest.
It is generally understood that the products of fractional distillation, even in the laboratory, are not identical with the hydrocarbons present in the crude oil, but are in part produced by the action of heat upon them.
They found that the paraffin was thus converted, with the evolution of but little gas, into hydrocarbons which were liquid at ordinary temperatures.
In an experiment on 3500 grams of paraffin produced from shale (melting point 44'5° C.) they obtained nearly 4 litres of liquid hydrocarbons, which they subjected to fractional distillation, and on examining the fraction distilling below loo° C., they found it to consist mainly of olefines.
The result of this treatment is that the comparatively heavy oils undergo dissociation, as shown by the experiments of Thorpe and Young, into specifically lighter hydrocarbons of lower boiling points, and the yield of kerosene from ordinary crude petroleum may thus be greatly increased.
Under such conditions, distillation takes place at higher temperatures than the normal boiling-points of the constituent hydrocarbons of the oil, and a partial cracking results.
In the American petroleum refineries it is found that sufficient cracking can be produced by slow distillation in stills of which the upper part is sufficiently cool to allow of the condensation of the vapours of the less volatile hydrocarbons, the condensed liquid thus falling back into the heated body of oil.
The rationale of this treatment is not fully understood, but the action appears to consist in the separation or decomposition of the aromatic hydrocarbons, fatty and other acids, phenols, tarry bodies, &c., which lower the quality of the oil, the sulphuric acid removing some, while the caustic soda takes out the remainder, and neutralizes the acid which has been left in the oil.
In France, the standard is 35° C. (Granier tester, equivalent to 98° F.), and according to their flashpoint, liquid hydrocarbons are divided into two classes (below and above 35° C.), considered differently in regard to quantities storable and other regulations.
A consequence of this empirical division was that marsh gas, ethylene and cyanogen were regarded as inorganic, and at a later date many other hydrocarbons of undoubtedly organic nature had to be included in the same division.
Taking as types hydrogen, hydrochloric acid, water and ammonia, he postulated that all organic compounds were referable to these four forms: the hydrogen type included hydrocarbons, aldehydes and ketones; the hydrochloric acid type, the chlorides, bromides and iodides; the water type, the alcohols, ethers, monobasic acids, acid anhydrides, and the analogous sulphur compounds; and the ammonia type, the amines, acid-amides, and the analogous phosphorus and arsenic compounds.
An apt definition of organic chemistry is that it is "the study of the hydrocarbons and their derivatives."
This description, although not absolutely comprehensive, serves as a convenient starting-point for a preliminary classification, since a great number of substances, including the most important, are directly referable to hydrocarbons, being formed by replacing one or more hydrogen atoms by other atoms or groups.
Two distinct types of hydrocarbons exist: (1) those consisting of an open chain of carbon atoms - named the " aliphatic series " (i.XEicAap, oil or fat), and (2) those consisting of a closed chain - the " carbocyclic series."
Let us now consider hydrocarbons containing 2 atoms of carbon.
Hydrocarbons containing any number of double or triple linkages, as well as both double and triple linkages, are possible, and a considerable number of such compounds have been prepared.
From n-butane we may derive, by a similar substitution of methyl groups, the two hydrocarbons: (I) CH 3 CH 2 CH 2 CH 2 CH 3, and (2) CH 3.
These three hydrocarbons are isomeric, i.e.
(methylene) groups and the molecule consists of a single chain; such hydrocarbons are referred to as being normal; (2) has a branch and contains the group; CH (methine) in which the free valencies are attached to carbon atoms; such hydrocarbons are termed secondary or iso-; (3) is characterized by a carbon atom linked directly to four other carbon atoms; such hydrocarbons are known as tertiary.
Deferring the detailed discussion of cyclic or ringed hydrocarbons, a correlation of the various types or classes of compounds which may be derived from hydrocarbon nuclei will now be given.
We proceed to consider various simple derivatives of the alcohols, which we may here regard as hydroxy hydrocarbons, R OH, where R is an alkyl radical, either aliphatic or cyclic in nature.
Cyclic Hydrocarbons and Nuclei.
Having passed in rapid review the various types of compounds derived by substituting for hydrogen various atoms or groups of atoms in hydrocarbons (the separate articles on specific compounds should be consulted for more detailed accounts), we now proceed to consider the closed chain compounds.
By fusing two nuclei we obtain the formula of naphthalene, C 1 oH 8; by fusing three, the hydrocarbons anthracene and phenanthrene, C14H10; by fusing four, chrysene, C18H12, and possibly pyrene, C16H1n; by fusing five, picene, C22 H 14.
This and other facts connected with the stability of benzenoid compounds are clearly shown when we consider mixed aliphatic-aromatic hydrocarbons, i.e.
Thomsen then investigated heats of combustion of various benzenoid hydrocarbons - benzene, naphthalene, anthracene, phenanthrene, &c. - in the crystallized state.
But, at the same time, the constants in the above relation are not identical with those in the corresponding relation empirically deduced from observations on fatty hydrocarbons; and we are therefore led to conclude that a benzene union is considerably more stable than an ethylene union.
These isomeric hydrocarbons, of the formula C14H10, are to be regarded as formed by the fusion of three.
An ethylenic or double carbon union in the aliphatic hydrocarbons has, apparently, the same effect on the boiling-point as two hydrogen atoms, since the compounds C 0 H 2 „ +2 and CoH2n boil at about the same temperature.
The same difference attends the introduction of the methyl group into many classes of compounds, for example, the paraffins, olefines, acetylenes, aromatic hydrocarbons, alcohols, aldehydes, ketones and esters, while a slightly lower value (157.1) is found in the case of the halogen compounds, nitriles, amines, acids, ethers, sulphides and nitro compounds.
It contains four independent constants; two of these may be calculated from the heats of combustion of saturated hydrocarbons, and the other two from the combustion of hydrocarbons containing double and triple linkages.
As a general rule, hydrocarbons are colourless; the exceptions include the golden yellow acenaphthylene, the red bidiphenylene-ethylene, and the derivatives of fulvene CH: CH >CH 2, which have been discussed by CH: CH J.
Hydrocarbons of similar structure have been prepared by Thiele, for example, the orange-yellow tetraphenyl-para-xylylene, which is obtained by boiling the bromide C6H4[CBr(C6H5)2]2 with benzene and molecular silver.
When solid caoutchouc is strongly heated it breaks down, without change in its ultimate composition, into a number of simpler liquid hydrocarbons of the terpene class (dipentene, di-isoprene, isoprene, &c.), of which one, isoprene (C5H8), is of simpler structure than oil of turpentine (C 10 H 16), from which it can also be obtained by the action of an intense heat.
At higher temperatures the viscous liquid suffers decomposition with the formation of various liquid hydrocarbons, principally members of the terpene series.
Schultz, Ann., 1879, 196, p. 35); or the two hydrocarbons may be separated by carbon bisulphide, in which anthracene is insoluble.
Secondary reactions take place at the same time, yielding more particularly hydrocarbons of the paraffin series.
Tertiary nitro compounds may also be obtained by the oxidation of the corresponding amino-, hydroxyl amino-, and nitroso-hydrocarbons with monopersulphuric acid (E.
The nitro compounds of the lower members of the paraffin series cannot be prepared by the direct action of nitric acid on the hydrocarbons themselves, but, in the case of some of the higher members of the series direct nitration is possible (M.
The primary aromatic amines may be prepared by the reduction of the nitro-hydrocarbons, the reducing agents used being either alcoholic-ammonium sulphide (N.
It is convenient to distinguish between aliphatic and aromatic acids; the first named being derived from open-chain hydrocarbons, the second from ringed hydrocarbon nuclei.
Dibasic acids of the paraffin series of hydrocarbons have the general formula C n H 2 (000H) 2 "; malonic and succinic acids are important members.
Other reactions which introduce carboxyl groups into aromatic groups are: the action of carbonyl chloride on aromatic hydrocarbons in the presence of aluminium chloride, acid-chlorides being formed which are readily decomposed by water to give the acid; the action of urea chloride Clï¿½COï¿½NH 2, cyanuric acid (CONH) 3, nascent cyanic acid, or carbanile on hydrocarbons in the presence of aluminium chloride, acid-amides being obtained which are readily decomposed to give the acid.
An important oxidation synthesis of aromatic acids is from hydrocarbons with aliphatic side chains; thus toluene, or methylbenzene, yields benzoic acid, the xylenes, or dimethyl-benzene, yield methyl-benzoic acids and phthalic acids.