GLYCOLS, in organic chemistry, the generic name given to the aliphatic dihydric alcohols.
They are compounds which greatly resemble the mixed ethers of the aliphatic series.
We now proceed to discuss the types of aliphatic compounds; then, the characteristic groupings having been established, an epitome of their derivatives will be given.
It has already been stated that benzene derivatives may be regarded as formed by the replacement of hydrogen atoms by other elements or radicals in exactly the same manner as in the aliphatic series.
For example: nitric acid and sulphuric acid readily react with benzene and its homologues with the production of nitro derivatives and sulphonic acids, while in the aliphatic series these acids exert no substituting action (in the case of the olefines, the latter acid forms an addition product); another distinction is that the benzene complex is more stable towards oxidizing agents.
Compounds derived by substituting aliphatic radicals in the benzene nucleus; such a compound is methylbenzene or toluene, C 6 H 5 CH 3.
In general, the aliphatic residues in such mixed compounds retain the characters of their class, while the aromatic residues retain the properties of benzene.
The introduction of hydroxyl groups into the benzene nucleus gives rise to compounds generically named phenols, which, although resembling the aliphatic alcohols in their origin, differ from these substances in their increased chemical activity and acid nature.
The amines also exhibit striking differences: in the aliphatic series these compounds may be directly formed from the alkyl haloids and ammonia, but in the benzene series this reaction is quite impossible unless the haloid atom be weakened by the presence of other substituents, e.g.
These observations may be summarized by saying that the benzene nucleus is more negative in character than the aliphatic residues.
X u x?X x x HZ which exist between aliphatic and benzenoid compounds make the transformations of one class into the other especially interesting.
In the first place we may notice a tendency of several aliphatic compounds, e.g.
Decompositions of this nature were first discovered in the naphthalene series, where it was found that derivatives of indene (and of hydrindene and indone) and also of benzene resulted; Zincke then extended his methods to the disintegration of the oxybenzenes and obtained analogous results, R-pentene and aliphatic derivatives being formed (Rsymbolizing a ringed nucleus).
Hantzsch (Ber., 1889, 22, p. 1238) succeeded in ob R taining derivatives of o-diketo-R-hexene, which yield R-pentene and aliphatic compounds on decomposition.
This is obviously unsymmetrical, consisting of an aliphatic and an aromatic nucleus; Claus explained the formation of the same phthalic acid from the oxidation of either nucleus by supposing that if the aromatic group be oxidized, the aliphatic residue assumes the character of a benzene nucleus.
If s-naphthylamine and 0-naphthol be reduced, tetrahydro products are obtained in which the aminoor oxy-bearing half of the molecule becomes aliphatic in character.
During recent years an immense number of ringed or cyclic compounds have been discovered, which exhibit individual characters more closely resembling benzene, naphthalene, &c. than purely aliphatic substances, inasmuch as in general they contain double linkages, yet withstand oxidation, and behave as nuclei, forming derivatives in much the same way as benzene.
As a useful preliminary it is convenient to divide heterocyclic ring systems into two leading groups: (I) systems resulting from simple internal dehydration (or similar condensations) of saturated aliphatic compounds - such compounds are: the internal anhydrides or cyclic ethers of the glycols and thioglycols (ethylene oxide, &c.); the cyclic alkyleneimides resulting from the splitting off of ammonia between the amino groups of diaminoparaffins (pyrrolidine, piperazine, &c.); the cyclic esters of oxycarboxylic acids (lactones, lactides); the internal anhydrides of aminocarboxylic acids (lactams, betaines); cyclic derivatives of dicarboxylic acids (anhydrides, imides, alkylen-esters, alkylenamides, &c.).
These compounds retain their aliphatic nature, and are best classified with open-chain compounds, into which, in general, they are readily converted.
Thelfirst four substances are readily formed from, and converted into, the corresponding dihydroxy open-chain compound; these substances are truly aliphatic in character.
The fifth compound, on the other hand, does not behave as an unsaturated aliphatic compound, but its deportment is that of a nucleus, many substitution derivatives being capable of synthesis.
Reduction, however, converts it into an aliphatic compound.
This is comparable with the reduction of the benzene nucleus into hexamethylene, a substance of an aliphatic character.
As before, only true ring nuclei, and not internal anhydrides of aliphatic compounds, will be mentioned.
The oxidation with nitric acid in sealed tubes at a temperature of 150° to 200° for aliphatic compounds, and 250° to 260° for aromatic compounds, is in common use, for both the sulphur and phosphorus can be estimated, the former being oxidized to sulphuric acid and the latter to phosphoric acid.
Recent researches have shown that the law originally proposed by Kopp - " That the specific volume of a liquid compound (molecular volume) at its boiling-point is equal to the sum of the specific volumes of its constituents (atomic volumes), and that every element has a definite atomic value in its compounds " - is by no means exact, for isomers have different specific volumes, and the volume for an increment of CH 2 in different homologous series is by no means constant; for example, the difference among the esters of the fatty acids is about 57, whereas for the aliphatic aldehydes it is 49.
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.
These formulae, however, only apply to aliphatic amines; the results obtained in the aromatic series are in accordance with the usual formulae.
The azo-group is particularly active, both the aliphatic and aromatic compounds being coloured.
The simplest aliphatic compounds, such as diazo-methane, diazoethane, and azo-formic acid, are yellow; the diamide of the latter acid is orange-red.
Meyer, which are formed when nitrous acid acts on primary aliphatic nitro compounds.
We may notice that ethyl oxalosuccinonitrile is the first case of a fluorescent aliphatic compound.
ACETOPHENONE, or PHENYL-METHYL KETONE, C8H8O or C6H5CO.CH3, in chemistry, the simplest representative of the class of mixed aliphatic-aromatic ketones.
The aromatic aldehydes resemble the aliphatic aldehydes in most respects, but in certain reactions they exhibit an entirely different behaviour.
Nitrosohydrocarbons have been prepared in the aliphatic series by the oxidation of the corresponding hydroxylamino compounds.
The constitution of the benzene ring, the isomerism of its derivatives, and their syntheses from aliphatic or openchain compounds, are treated in the article Chemistry.
Aromatic Amines.-The aromatic amines in some respects resemble the aliphatic amines, since they form salts with acids, and double salts with platinum chloride, and they also distil without decomposition.
On the other hand, they are much weaker bases than the aliphatic amines, their salts undergoing hydrolytic dissociation in aqueous solution.
The aromatic amine resembling the aliphatic amines is benzylamine, C 6 H 5 ï¿½CH 2 ï¿½NH 2, which may be prepared by reducing benzonitrile in alcoholic solution by means of zinc and acetic acid (0.
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.
Aliphatic monobasic acids are further divided according to the nature of the parent hydrocarbon.
Thus primary alcohols and aldehydes, both of the aliphatic and aromatic series, readily yield on oxidation acids containing the same number of carbon atoms. These reactions may be shown thus: - ï¿½ Rï¿½CH 2 OH -> R.
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.
When reduced by sodium in boiling amyl alcohol solution it forms alicyclic tetrahydro-0naphthylamine, which has most of the properties of the aliphatic amines; it is strongly alkaline in reaction, has an ammoniacal odour and cannot be diazotized.
METHYL ALCOHOL (CH 2 OH), the simplest aliphatic alcohol; an impure form is known in commerce as wood-spirit, being produced in the destructive distillation of wood.
Other constituents are cholesterol (0.461.32%), traces of calcium, magnesium, sodium, chlorine and bromine, and various aliphatic amines which are really secondary products, being formed by the decomposition of the cellular tissue.
COOH, the first member of the series of aliphatic monobasic acids of the general formula C.H 2, ,O 2.
The mixed azo compounds are those in which the azo group N: N is united with an aromatic radical on the one hand, and with a radical of the aliphatic series on the other.
On the other hand, it differs from the aliphatic aldehydes in many respects; it does not form an addition product with ammonia but condenses to hydrobenzamide (C 6 H 5 CH) 3 N 2; on shaking with alcoholic potash it undergoes simultaneous oxidation and reduction, giving benzoic acid and benzyl alcohol (S.
The esters of the aliphatic amino acids may be diazotized in a manner similar to the primary aromatic amines, a fact discovered by T.
The first aliphatic diazo compound to be isolated was diazoacetic ester, CH N2 CO 2 C 2 H 5 i which is prepared by the action of potassium nitrite on the ethyl ester of glycocoll hydrochloride,HCl NH2 CH2 C02C2H 5 -1-KNO 2 =CHN 2 CO 2 C 2 H 5+ KCI+2H 2 O.
The esters of the aliphatic and aromatic acids are colourless neutral liquids, which are generally insoluble in water, but readily dissolve in alcohol and ether.
To celebrate his seventieth birthday his scientific papers were collected and published in two volumes (Gesammelte Werke, Brunswick, 1905), and the names of the headings under which they are grouped give some idea of the range and extent of his chemical work: (1) organic arsenic compounds, (2) uric acid group, (3) indigo, (4) papers arising from indigo researches, (5) pyrrol and pyridine bases, (6) experiments on the elimination of water and on condensation, (7) the phthaleins, (8) the hydro-aromatic compounds, (9) the terpenes, (io) nitroso compounds, (11) furfurol, (12) acetylene compounds and "strain" (Spannungs) theory, (13) peroxides, (14) basic properties of oxygen, (15) dibenzalacetone and triphenylamine, (16) various researches on the aromatic and (17) the aliphatic series.
ACETONE, or DIMETHYL KETONE', CH3.CO.CH3, in chemistry, the simplest representative of the aliphatic ketones.
It melts at 64° C. and boils at 250-252° C. The aminopyridines are readily soluble in water, and resemble the aliphatic amines in their general chemical properties.
Mixed aromatic-aliphatic amines, both secondary and tertiary, are also more strongly basic than the pure aromatic amines, and less basic than the true aliphatic compounds; e.g.