The characteristic flavour and odour of wines and spirits is dependent on the proportion of higher alcohols, aldehydes and esters which may be produced.
Hantzsch (Ber., 1901, 34, p. 3337) has shown that in the action of alcohols on diazonium salts an increase in the molecular weight of the alcohol and an accumulation of negative groups in the aromatic nucleus lead to a diminution in the yield of the ether produced and to the production of a secondary reaction, resulting in the formation of a certain amount of an aromatic hydrocarbon.
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.
The secondary and tertiary alcohols; and with inestimable perspicacity he proved intimate relations between compounds previously held to be quite distinct.
OH, >CH OH, and ?C OH; these compounds are known as alcohols (q.v.), and are termed primary, secondary, and tertiary respectively.
Polymethylenes can give only secondary and tertiary alcohols, benzene only tertiary; these latter compounds are known as phenols.
Thus the thio-alcohols or mercaptans (q.v.) contain the group - CH2 SH; and the elimination of the elements of sulphuretted hydrogen between two molecules of a thio-alcohol results in the formation of a thio-ether or sulphide, R 2 S.
Of these, undoubtedly the simplest are the ethers (q.v.), formed by the elimination of the elements of water between two molecules of the same alcohol, " simple ethers," or of different alcohols, " mixed ethers."
These compounds may be regarded as oxides in just the same way as the alcohols are regarded as hydroxides.
Organic acids also condense with alcohols to form similar compounds: the fats, waxes, and essential oils are naturally occurring substances of this class.
An important class of compounds, termed amines (q.v.), results from the condensation of alcohols with ammonia, water being eliminated between the alcoholic hydroxyl group and a hydrogen atom of the ammonia.
This group may be considered as resulting from the fusion of a carbonyl (:CO) and a hydroxyl (HO-) group; and we may expect to meet with compounds bearing structural resemblances to the derivatives of alcohols and aldehydes (or ketones).
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 phenols more closely resemble the tertiary alcohols, since the hydroxyl group is linked to.
By actual observations it has been shown that ether, alcohol, many esters of the normal alcohols and fatty acids, benzene, and its halogen substitution products, have critical constants agreeing with this originally empirical law, due to Sydney Young and Thomas; acetic acid behaves abnormally, pointing to associated molecules at the critical point.
Thus in the normal fatty alcohols, acids, esters, nitriles and ketones, the increment per CH 2 is 19°-21°; in the aldehydes it is 26°-27°.
Fora similar reason secondary alcohols boil at a lower temperature than the corresponding primary, the difference being about 19°.
This is true of the fatty acid series, and the corresponding ketones and alcohols, and also of the succinic acid series.
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.
The average value for primary alcohols is 44.67 cal., but many large differences from this value obtain in certain cases.
The thermal effects increase as one passes from primary to tertiary alcohols, the values deduced from propyl and isopropyl alcohols and trimethyl carbinol being: - primary =45 08, secondary = 50.39, tertiary = 60.98.
C 4 BUTYL ALCOHOLS H 9 OH.
The acid finds considerable use in organic chemistry, being employed to discriminate between the different types of alcohols and of amines, and also in the production of diazo, azo and diazo-amino compounds.
The aldehydes may be prepared by the careful oxidation of primary alcohols with a mixture of potassium dichromate and sulphuric acid,-3Rï¿½CH OH+K Cr 07+4H SO = K2S04+ Cr (SO) +7H O+3Rï¿½CHO; by distilling the calcium salts of the fatty acids with calcium formate; and by hydrolysis of the acetals.
Nascent hydrogen reduces them to primary alcohols, and phosphorus pentachloride replaces the carbonyl oxygen by chlorine.
Grignard (Comptes Rendus, 1900 et seq.) showed that aldehydes combine with magnesium alkyl iodides (in absolute ether solution) to form addition products, which are decomposed by water with the formation of secondary alcohols, thus from acetaldehyde and magnesium methyl iodide, isopropyl alcohol is obtained.
Unsaturated aldehydes are also known, corresponding to the olefine alcohols; they show the characteristic properties of the saturated aldehydes and can form additive compounds in virtue of their unsaturated nature.
The reactions of the nitroparaffins with nitrous acid are very characteristic and have been used as a method for discriminating between the primary, secondary and tertiary alcohols (V.
The normal esters may be prepared by the action of silver carbonate on the alkyl iodides, or by the action of alcohols on the chlorcarbonic esters.
Our knowledge of the chemical structure of the monosaccharoses may be regarded as dating from 1880, when Zincke suspected some to be ketone alcohols, for it was known that glucose and fructose, for example, yielded penta-acetates, and on reduction gave hexahydric alcohols, which, when reduced by hydriodic acid, gave normal and secondary hexyliodide.
The ketone is also obtained when Bertrand's sorbose bacterium acts on glycerol; this medium also acts on other alcohols to yield ketoses; for example: erythrite gives erythrulose, arabite arabinulose, mannitol fructose, &c.
The plane projection of molecular structures which differ stereochemically is discussed under Stereoisomerism; in this place it suffices to say that, since the terminal groups of the hexaldose molecule are different and four asymmetric carbon atoms are present, sixteen hexaldoses are possible; and for the hexahydric alcohols which they yield on reduction, and the tetrahydric dicarboxylic acids which they give on oxidation, only ten forms are possible.
With nitrous acid, the primary amines yield alcohols, the secondary amines yield nitrosamines and the tertiary amines do not react: Rï¿½NH 2 +0NOH= Rï¿½OH+N2+H20; R2NH+ [[Onoh= R 2 Nï¿½No H]] 2 0.
The mixed secondary amines are prepared by the action of alkyl iodides on the primary amines, or by heating salts of the primary amine with alcohols under pressure.
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.
Ketones, secondary alcohols and tertiary alcohols yield a mixture of acids on oxidation.
Soc., 1905, 27, p. 1019) the iodide differs from the other haloid salts in separating from solution in alcohols with "alcohol of crystallization."
The olefines may be synthetically prepared by eliminating water from the alcohols of the general formula CnH2n+1 OH, using sulphuric acid or zinc chloride generally as the dehydrating agent, although phosphorus pentoxide, syrupy phosphoric acid and anhydrous oxalic acid may frequently be substituted.
In this method of preparation it is found that the secondary alcohols decompose more readily that the primary alcohols of the series, and when sulphuric acid is used, two phases are present in the reaction, the first being the building up of an intermediate sulphuric acid ester, which then decomposes into sulphuric acid and hydrocarbon: C2H 5 OH->C 2 H 5 HSO 4 ->C 2 H 4 +-H 2 SO 4.
Krafft, Ber., 1883, 16, p. 3018): C16H33 CH2 CH2.0H->C161-133CH2 CH2.0 CO R-> C16H33CH: CH 2 -j-R COOH; from tertiary alcohols by the action of acetic anhydride in the presence of a small quantity of sulphuric acid (L.
Many plants, and as the esters of n-hexyl and n-octyl alcohols in the seeds of Heracleum giganteum, and in the fruit of Heracleum sphondylium, but is generally obtained, on the large scale, from the oxidation of spoiled wines, or from the destructive distillation of wood.
They behave in most respects as unsaturated compounds; they combine with hydrogen to form amines; with water to form acidamides; with sulphuretted hydrogen to form thio-amides; with alcohols, in the presence of acids, to form imido-ethers R C(:NH) OR'; with ammonia and primary amines to form amidines R C(:NH) NH 2 i and with hydroxylamine to form amidoximes, R C(:NOH) NH 2.
For the formation of primary and secondary alcohols see Aldehydes and Ketones.
They may be prepared by the oxidation of secondary alcohols; by the addition of the elements of water to hydrocarbons of the acetylene type RC CH; by oxidation of primary alcohols of the type RR' CH CH 2 OH:RR' CH CH 2 OH --> R CO R'+H20+H2C02; by distillation of the calcium salts of the fatty acids, C.H2.02; by heating the sodium salts of these acids CnH2n02 with the corresponding acid anhydride to 190 C. (W.
Sodium amalgam reduces them to secondary alcohols; phosphorus pentachloride replaces the carbonyl oxygen by chlorine, forming the ketone chlorides.
On treatment with the Grignard reagent, in absolute ether solution, they yield addition products which are decomposed by water with production of tertiary alcohols (V.
Jochem (Ber., 1901, 34, p. 3337), who arrived at the conclusion that the normal decomposition of diazonium salts by alcohols results in the formation of phenolic ethers, but that an increase in the molecular weight of the alcohol, or the accumulation of negative groups in the aromatic nucleus, diminishes the yield of the ether and increases the amount of the hydrocarbon formed.
That of the alcohols, which only differ from the hydrocarbons by having a group OH, called hydroxyl, instead of H, hydrogen; these compounds, when derived from the above methane series of hydrocarbons, are expressed by the general formula C7,H27,+10H.
In this case it is readily seen that isomerism introduces itself in the three carbon atom derivative: the propyl alcohols, expressed by the formulae CH 3 CH2 CH 2 0HandCH 3 CHOH CH3, are known as propyl and isopropyl alcohol respectively.
Now in oxidizing, or introducing more oxygen, for instance, by means of a mixture of sulphuric acid and potassium bichromate, and admitting that oxygen acts on both compounds in analogous ways, the two alcohols may give (as they lose two atoms of hydrogen) CH 3 CH 2 COH and CH 3 C0 CH 3.
And so, as a rule, from isomeric alcohols, those containing a group - CH 2.0H, yield by oxidation aldehydes and are distinguished by the name primary; whereas those containing CH OH, called secondary, produce ketones.
These compounds generally behave as ketones; but at the same time they may act as alcohols, i.e.
ESTERS, in organic chemistry, compounds formed by the condensation of an alcohol and an acid, with elimination of water; they may also be considered as derivatives of alcohols, in which the hydroxylic hydrogen has been replaced by an acid radical, or as acids in which the hydrogen of the carboxyl group has been replaced by an alkyl or aryl group. In the case of the polybasic acids, all the hydrogen atoms can be replaced in this way, and the compounds formed are known as "neutral esters."