In considering the chemistry of the official organic substances, it is found convenient first to discuss the hydrocarbons themselves, and then the vast mass of derivatives, and in this work the order of the consideration of the latter will be based on a convenient standard of the number of carbon atoms they contain. In special books on organic chemistry it is usual to consider the derivatives of the hydrocarbons in groups, based on their structural characteristics; thus, all the fatty alcohols are considered together, likewise the fatty aldehydes and acids, but, from the pharmacist's point of view, it is better to discuss them in a different arrangement; namely, to study all the derivatives of ethane together, and then proceed to propane.

A convenient grouping of the derivatives is as follows:

The Halogen Derivatives.-In this case the hydrogen atoms are replaced by the halogen elements, chlorine, bromine, iodine. Thus, from CH, we can get CH,Cl, CH,C,, CHCI,, and CC,.

The first three of these can be expressed by the formulas:

RIX, R"X2, and RX.

R standing for the radicle, X for the appropriate halogen element, the Roman numerals above R expressing the number of free bonds the same possesses.

Methane treated with bromine yields respectively

CH,Bг, CH2Bг2, CHBг ̧, CBг1,

and such is the case with iodine. Likewise, with ethane, one or even all the halogens can be replaced with chlorine, bromine, or iodine.

Of these halogen derivatives chloroform, bromoform, and iodoform are of pharmaceutic interest.

The Alcohols.-The formulas of these can be expressed by:

R1OH, R""(OH),, R(OH)。, etc.

Alcohols are substitution products of the hydrocarbons, in which one or more of the hydrogens are replaced by hydroxyl groups (OH). Official examples of this class are:

Ethyl alcohol.

Glycerin..
Mannitol.

C2H2OH.

.C,H,(OH),.

CH(OH).

These alcohols are divided into primary, secondary, and tertiary alcohols, being classified according to their action under the influence of oxidation.

A primary alcohol oxidizes to an aldehyde and then to an acid; thus, ethyl alcohol, CH,CH,OH, on being treated with an oxidizing agent, yields first an aldehyde, CH,CHO, and finally the acid, CH,COOH.

A general formula of a primary alcohol shows as distinguishing characteristic the group RCH2OH, that is, the carbon atom to which the hydroxyl is attached has also attached one radicle and two hydrogen atoms.

A secondary alcohol, on oxidation, does not yield an aldehyde and an acid, but yields a substance called a ketone.

Thus, secondary propyl alcohol, CH,CHOHCH,, yields on oxidation the ketone, acetone, CH,COCH,.

The rational formula of a secondary alcohol shows the characteristic grouping

In other words, connected with the carbon atom to which the hydroxyl is attached are found two radicles and only one hydrogen atom.

A tertiary alcohol is one which, on oxidation, yields neither an aldehyde nor a ketone, but breaks up under such treatment. The rational formula of tertiary alcohol can best be expressed as

R,COH;

in other words, to the carbon atom to which the hydroxyl is attached there are fastened three radicles and no hydrogen atoms at all.

Perhaps the differentiation in the three classes of alcohols can better be understood by a comparison of three such alcohols from the same hydrocarbon and the oxidation derivatives of each.

Thus, primary butyl alcohol, CH,CH,CH,CH2OH, yields on oxidation butyric aldehyde and butyric acid.

Secondary butyl alcohol, CH,CH>CHOH, under same treatment, yields

CH,

methylethylketone, while tertiary butyl alcohol, CH, COH, breaks up into CH simpler compounds.

Another classification of alcohols is to call them monatomic, diatomic, and triatomic, etc., the Greek prefixes signifying the number of hydroxyls the alcohol possesses; thus glycerin, C,H,(OH),, is a triatomic alcohol.

It will be seen that the characteristic radicle of alcohols is hydroxyl (OH). To express the same thing differently, alcohols are hydroxides of the organic radicles, just as the bases (p. 372) are inorganic hydroxides.

Thus, NaOH, sodium hydroxide, has an organic analogue in C,H,OH, ethyl hydroxide. Similar to Ca(OH)2, calcium hydroxide, is CH(OH)2, glycol, and as mate to Fe(OH),, ferric hydroxide, we have the organic hydroxide, C,H,(OH)3, glycerin.

All three organic hydroxides cited above are classed among the alcohols. Those alcohols formed by adding hydroxyl to the benzene group of radicles (C.H, CH, etc.) are called phenols, of which the type is ordinary phenol, carbolic acid, CH2Oн.

As alcohols represent organic hydroxides, so the class of ethers represent organic oxides. In a preceding chapter (p. 372) it was noted that sodium hydroxide, NaOH, was evolved from sodium oxide, Na,O, by adding water thereto. Likewise, by taking water away from sodium hydroxide, sodium oxide is produced. In a somewhat analogous way, by removing water from ethyl hydroxide (alcohol), ethyl oxide (ether) is formed.

The general formula of ethers can, therefore, be expressed as RIOR'.

Esters may be defined as salts of the alcohols.

We have seen the analogy between hydroxides and alcohols; between oxides and ethers; let us now show similarity between salts and esters. Suppose we take sodium hydroxide and add nitrous acid, we get water and sodium nitrite:

An ester is the combination of a positive organic radicle with an acid radicle, just as a salt is a combination of a positive element with an acid radicle. The acid of the ester, just like the acid of the salt, can be either inorganic or organic, as is shown by the formulas of the official esters:

Emphasis should be laid on the fact that esters are not in every respect similar to inorganic salts, a most striking difference being that while inorganic salts in solution dissociate into ions (p. 118), esters do not undergo ionic dissociation. Another point of difference is that, while the reaction occurring in the manufacture of salts usually runs in one direction, viz.,

The latter reaction, whereby esters are dissociated, is called the process of saponification.

Aldehydes. This class of organic compounds has no analogues among the inorganic compounds, it being the product of the oxidation of a primary alcohol. An explanation of the same has just been given under the classification of the alcohols, and specific details will be left until we consider the official aldehydes; so here suffice it to say that the general formula of aldehyde is RCHO. An example of the official aldehyde is benzaldehyde, the chief constituent of oil of bitter almond.

Ketones. As mentioned above, ketones are oxidation products. from secondary alcohols, and their general formula is R,CO. Thus, the secondary propyl alcohol, CH,CHOHCH,, under influence of

oxidizing agents, loses the two hydrogen atoms, becoming CH,COCH ̧, the official acetone.

Acids. The true organic acids are the oxidation products of primary alcohol or aldehydes, and their general formula is RCOOH, the group COOH being called carboxyl, as mentioned on p. 630.

As alcohols are monatomic, diatomic, and triatomic, according to the number of hydroxyls, so organic acids are monobasic, dibasic, and tribasic, according to the number of carboxyls they contain. Thus, acetic acid is an official example of the monobasic organic acid, while succinic acid, C2H,(COOH)2, is an illustration of a dibasic acid. Acids with alcohol radicles, that is, containing carboxyl and hydroxyl, are called oxyacids, and an official illustration is furnished in tartaric acid, which is a dibasic, diatomic oxyacid, as shown by the graphic formula. (See p. 685.)

In true acids only those hydrogen atoms in carboxyl groups are replaceable by a metal. This is why carbolic acid (C,H,OH) is not a true acid, but a phenol (p. 758).

Amines can be expressed by the general formulas

RNH2, R2NH, or R,N.

They can also be considered as ammonia in which one, two, or three hydrogens have been replaced by radicles. Thus we can obtain methylamine, CH,NH2, dimethylamine, (CH,),NH, and trimethylamine, (CH3),N.

The manufacture of these products is so simple and clear that it serves admirably for explaining their exact composition. Thus ammonia treated with methyl iodide gives the hydriodic acid salt of methylamine, and when the acid is removed by treating with potassa, methylamine remains.

Methylamine, being treated with methyl iodide, will yield the hydriodic acid salt of dimethylamine, and this by treatment with potassa yields the free dimethylamine.

(b) NH(CH,),HI + KOH

NH(CH,),HI.

NH(CH,), + KI + H,O. Dimethylamine, being treated with methyl iodide, yields the hydriodic acid salt of trimethylamine, and the free base is obtained by treatment with potassa as above. Lastly, if trimethylamine is treated with methyl iodide, we get a very interesting body called tetramethylammonium iodide.

In the latter case the nitrogen shows the valence v, exactly as it does in the ammonium compounds. The similarity of these four bodies, the amines and the ammonium compounds respectively, is best shown by comparison of the four graphic formulas:

It might be added that for methyl can be substituted ethyl, propyl, or any other monovalent radicle. All the amines are quite similar to ammonia; the mono-amines have ammoniacal odor and all are decidedly basic.

The amines of the fatty series are of but little importance, but several of the aromatic series are of the utmost value; for example, aniline (p. 767).

CHAPTER XXXVI

HYDROCARBONS AND METHANE DERIVATIVES

THE FATTY SERIES OF HYDROCARBONS

THIS series of hydrocarbons, having the general formula CnH2n+ 2, are sometimes called the aliphatic series. As mentioned in the preceding chapter, representatives of these series are the homologues, methane, ethane, butane, pentane, hexane, etc., all similar and manufactured one from the other. Substances possessing the same general formula, but differing in relative number of atoms, are called homologues.

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Manufacture. That the members of this class can be made one from the other has already been mentioned; thus, methane, CH,, can be converted into methyl iodide, (CH,I), and methyl iodide, on treatment with metallic sodium, yields ethane by the following reac

tion:

2CH,I + Na2

=

2NaI + CH,-CH, or C2H..

This is the usual way of making such hydrocarbons, although several other methods have been devised.

Chemical Behavior.-These hydrocarbons are saturated bodies; that is, they will absorb no more hydrogen nor will they combine with halogens except through the loss of hydrogen atoms. The halogen derivatives are formed as follows:

Physical Properties.-The first of these series of hydrocarbons are gases. Hydrocarbons from CH1, are liquids, the first being quite volatile, the higher ones, that is, from C,H30, thick and stable liquids, while the higher hydrocarbons of the series, say from C2H12, are solid.

Considering the hydrocarbons as individuals, the first of the series, methane, CH, is commonly called marsh-gas, because formed by decaying vegetable matter, and thus it can be easily collected from the surfaces of some marshes. It is the chief constituent of natural gas. Methane is usually made by heating in a retort sodium acetate with sodium hydroxide, as shown in the following equation:

CH,COONa + NaOH = CH、 + Na,CO,