272

ON THE HYDROCARBON RADICLES OF THE ALCOHOLS.

The hydrocarbons of this group have not hitherto been made to combine directly with chlorine, bromine, or iodine, so as to reproduce the corresponding hydrochloric, hydrobromic, or hydriodic ether; no action occurs between these bodies and chlorine, or the other halogens, so long as light is excluded, but if light be admitted various substitution compounds are produced. Some chemists, including Hofmann and Gerhardt, when Frankland first announced the isolation of these bodies, considered the nonoccurrence of direct combination with chlorine as a strong argument against the admission of the view that they were truly alcohol radicles, and they proposed to regard them as homologues of marsh gas but the subsequent isolation of the true homologues of marsh gas which constitute the hydrides of the alcohol radicles (1207) has neutralized this objection. The bodies which have been termed alcohol radicles, may very consistently be regarded as analogues of hydrogen gas, which, when in its free state, seems not to be a simple body, but a compound of hydrogen H with itself,-in short, a hydride of hydrogen and the so-called H

radicle of alcohol may in like manner be considered as ethylide of ethyl, a view, the correctness of which the discovery of the double radicles of Wurtz (to which we shall presently refer) may be said to have proved. The alcohol radicles are not absorbed by sulphuric anhydride or by oil of vitriol, but are completely soluble in alcohol.

These hydrocarbons appear to belong to the hydrogen or H metallic type €1H2n+1) and are represented by the formula

HJ

28 2n+1

a molecule of the compound (CH2n+1)2 yielding 2 volumes of vapour. They would therefore stand to the third series of hydrocarbons (EH2n+2), which are to be described shortly (1206), in a relation similar to that of ether to alcohol, e.g. :—

Wurtz (Ann. de Chimie, III. xliv. 275), following up the ideas of Williamson and of Brodie upon the double ethers, has succeeded in obtaining compounds in which the second semi-molecule of the hydrocarbon is displaced by the semi-molecule of the hydrocarbon of a different alcohol, thus forming a series of double radicles corresponding with Williamson's double ethers.

DOUBLE HYDROCARBON RADICLES OF THE ALCOHOLS.

273

If a mixture of the hydriodic ethers of the two alcohols in equivalent proportions be decomposed by means of sodium, the two radicles combine at the moment of their liberation, and form a new double radicle. For example, in the preparation of ethyl

amyl, the following reaction occurs :—

Wurtz's double radicles are therefore merely compounds in which the place of the semi-molecule of hydrogen, or of the ethyl, is supplied by a different hydrocarbon :—

It is interesting to remark, that the boiling point of these double radicles rises gradually as the number of atoms of carbon and hydrogen increases in the molecule, and that this regular progression is observed in the simple alcohol radicles when compared with them, as in the following table; the boiling point and vapour density of the simple alcohol radicles being such as would theoretically be assigned to them upon the view above given; showing that both the simple and the double radicles are formed upon a similar molecular plan :

It may further be remarked, in illustration of the persistence of the original molecular arrangement of the component groups of these compound bodies, that Wurtz finds that amyl preserves its rotatory action on a ray of polarized light when it passes into these compounds, ethyl-amyl displaying the power of rotating a polarized ray to the right; whilst amylene, valeric acid, and other derivatives of amylic alcohol, in which there is reason to suppose that the molecule of amyl is destroyed, exert no rotatory

power.

274

METHYL, ETHYL, AND TRITYL.

(1204) 1. Methyl [(CH3)2. Sp. gr. 10365; Rel. wt. 15] is a gaseous body which burns with a bluish feebly luminous flame : it is not liquefied by a cold of o° F. Methyl is obtained by acting upon methyl iodide with zinc, exactly in the manner directed for the preparation of ethyl. When mixed with twice its bulk of chlorine in the dark, and afterwards brought into diffused daylight, no change of volume takes place, but a mixture of 2 volumes of hydrochloric acid, and I volume of a chlorinated compound, ЄH,Cl, is formed.*

2. Ethyl (H.). Sp. gr. of gas 2'046; Rel. wt. 29.-When a mixture of granulated zinc and ethyl iodide is scaled up in a strong glass tube from which air has been exhausted, and exposed for two hours in an oil bath to a temperature of 302° (150° C.), the ethyl iodide is gradually decomposed; the sides of the tube become coated with a white crystalline substance, and a colourless mobile liquid, equal in bulk to about half that of the ethyl iodide employed, is formed. This liquid is a mixture of ethyl, with other hydrocarbons (olefiant gas, and ethyl-hydride, the product of a secondary decomposition), the hydrocarbons having been liquefied by the pressure of their own vapour, whilst the crystals consist of a compound of zinc-ethyl with zincic iodide. On breaking off the capillary extremity of the tube under water, the whole of the liquid portion disappears rapidly and escapes in the gaseous form. By collecting the portions which pass off last, the ethyl, which off last, the ethyl, which is the least volatile of these gases, is obtained nearly in a state of purity (Frankland, Q. J. Chem. Soc. ii. 281). Ethyl may also be obtained, mixed with ethylene and ethyl hydride, when ethyl iodide is exposed over mercury to the sun's rays, mercuric iodide being produced.

2

Ethyl is a colourless gas with a slight ethereal smell; it burns with a highly luminous flame. At a temperature of o° it remains gaseous under the ordinary atmospheric pressure, but it becomes liquefied at 38° (3°3 C.) under a pressure of 2 atmospheres. Frankland estimates its boiling point at about -9°4 (-23° C.), when the barometer stands at 30 inches (760 millim.). Ethyl is insoluble in water, but freely soluble in alcohol, which dissolves about 18 times its bulk of the gas, and gives it off when diluted with water. Chlorine has no action upon ethyl in the dark, but in diffused daylight it immediately combines with it and forms a colourless liquid.

3. Trityl (EH).-The properties of this compound have

*Schorlemmer, however, considers methyl to be really ethyl hydride, and not merely isomeric with it; and he has extended this view to others of so-called alcohol radicles. (Liebig's Annal. cxxxvi. 257.)

DOUBLE OR MIXED HYDROCARBON RADICLES.

275

not been minutely examined; but it formed one of the hydrocarbons separated by Williams from the lighter portion of the distillate from Boghead cannel at low temperatures.

4. Tetryl, Butyl, or Valyl (EH)2. Sp. gr. of liquid 0.7057 at 32°; of vapour 4070; Rel. wt. 57; Boiling pt. 2220-8 (106° C.).— This compound is one of the products of the distillation of coal at low temperatures, and it may likewise be obtained during the electrolysis of potassic valerate (289). It may also be prepared by the action of sodium upon tetryl iodide, in a flask connected with a vertical condenser, so arranged that the volatilized products shall return constantly into the flask as fast as they are volatilized and condensed. When the reaction has terminated, the tetryl may be distilled off by a temperature not exceeding 302° (150° C.).

5. Amyl (E.H11)2. Sp. gr. at 32°, 0·7413; of vapour 4'899 ; Rel. wt. 71; Boiling pt. 311° (155° C.).—Frankland obtained this hydrocarbon by heating amyl iodide with an amalgam of zinc in sealed tubes for some hours to a temperature of from 320° to 360°. It is one of the products of the distillation of coal, and may also be procured by the electrolysis of potassic caproate, or still more easily as devised by Wurtz, by the action of sodium on amyl iodide. It is a colourless liquid, with a somewhat aromatic odour. It exerts a right-handed rotatory action on a ray of polarized light, the degree of which appears to vary in different specimens, being connected with the power exerted by that of the fousel oil from which the radicle was prepared, some samples of fousel oil having a greater rotatory power than others.

6. Hexyl, or Caproyl (H1), was obtained by the voltaic decomposition of potassic œnanthylate. It is a liquid of an agreeable aromatic odour: its boiling point is about 395° (202° C.).

2

(1205) DOUBLE or MIXED HYDROCARBON RADICLES.—Ethyltetryl (ЄH ̧‚¤H). Sp. gr. of liquid at 32°, 07011; of vapour 3053; Rel. wt. 43.-This compound was obtained by decomposing a mixture of 40 parts of tetryl iodide, and 34 of ethyl iodide, with 11 of sodium, in the manner already described for procuring tetryl: by distillation of the product, collecting the portion which passes over between 140° and 155°, and again rectifying it, a mobile liquid is obtained, the boiling point of which when pure is stationary at 143°6. By a similar method, employing mixtures of the corresponding hydriodic ethers, Wurtz succeeded in obtaining other analogous compounds, which are enumerated in the table, page 273.

(b) Hydrocarbons homologous with Marsh Gas (ЄnH2n+2)°.

(1206) 1. When the hydriodic ethers are submitted to the action of zinc at a high temperature, other hydrocarbons are formed in addition to the radicles already described; the alcohol radicle itself undergoing a secondary decomposition into two hydrocarbons, which are complementary to each other. Ethyl, for example, breaks up into ethylene (olefiant gas) and ethyl hydride; and amyl, in like manner, yields amyl hydride, and a corresponding hydrocarbon :

€2H,2H becoming €,H,,H+¤‚H ̧; and

2. These hydrocarbons may also be formed by the regulated action of water upon the metallic compounds of zinc with the alcohol radicles. For example :—

(¤ ̧H1),Zn+2 H2 = 2 (Є,H,,,H) + ZnO,H2O.

3. Berthelot procures the homologues of marsh gas by decomposing the bromide of the corresponding hydrocarbon in the ethylene series, by heating it in a sealed tube to 482° (250° C.) with water and potassic iodide. Tritylene bromide (E,H.Br.) thus yields trityl hydride.

4. In addition to marsh gas, many of these hydrocarbons are found as natural products, and according to the researches of Pelouze and Cahours, the American petroleum consists of a mixture of the homologues of marsh gas; these chemists consider that they have isolated thirteen consecutive terms of the series from trityl hydride to palmityl hydride inclusive, and they believe other higher terms also exist in the heavier portions of the oil.

The following table embodies the chief numerical results of their experiments (Ann. de Chimie, IV. i. 5) :—