The characteristic flavour and odour of wines and spirits is dependent on the proportion of higher alcohols, aldehydes and esters which may be produced.
By the action of dehydrating agents they are converted into aldehydes or ketones.
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.
Compounds containing the group - CH: O are known as aldehydes (q.v.), while the group >C: O (sometimes termed the carbonyl or keto group) characterizes the ketones (q.v.).
Thio-aldehydes, thio-ketones and thio-acids also exist.
By the action of hydroxylamine or phenylhydrazine on aldehydes or ketones, condensation occurs between the carbonyl oxygen of the aldehyde or ketone and the amino group of the hydroxylamine or hydrazine.
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).
Experience has shown that such mono-derivatives as nitro compounds, sulphonic acids, carboxylic acids, aldehydes, and ketones yield as a general rule chiefly the meta-compounds, and this is independent of the nature of the second group introduced; on the other hand, benzene haloids, amino-, homologous-, and hydroxy-benzenes yield principally a mixture of the orthoand para-compounds.
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.
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°.
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.
OXIMES, in organic chemistry, compounds containing the grouping > C: N OH, derived from aldehydes and ketones by condensing them with hydroxylamine.
Those derived from aldehydes are known as aldoximes, those from ketones as ketoximes.
Beckmann, Ber., 1886, 1 9, p. 9 8 9; 188 7, 20, p. 2580), yielding as final products an acid-amide or anilide, thus: RC(:N OH)R'-RC(OH) :NR' ---> As regards the constitution of the oximes, two possibilities exist, namely >C: NOH, or > C' ?, and the first of these is presumably correct, since on alkylation and subsequent hydrolysis an alkyl hydroxylamine of the type NH 2 OR is obtained, and consequently it is to be presumed that in the alkylated oxime, the alkyl group is attached to oxygen, and the oxime itself therefore contains the hydroxyl group. It is to be noted that the oximes of aromatic aldehydes and of unsymmetrical aromatic ketones frequently exist in isomeric forms. This isomerism is explained by the HantzschWerner hypothesis (Ber., 1890, 23, p. II) in which the assumption is made that the three valencies of the nitrogen atom do not lie in the same plane.
They are prepared by condensing thio-amides with a-haloid ketones or aldehydes, the thio-amide reacting as the tautomeric thio-imino acid.
ALDEHYDES, a class of chemical compounds of the general formula Rï¿½CHO (R=an alkyl or an aryl group).
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.
Soc. chim., 1904 [31, 31, p.1306) prepares aldehydes by the gradual addition of disubstituted formamides (dissolved in anhydrous ether) to magnesium alkyl haloids, the best yields being obtained by the use of diethyl formamide.
The aldehydes are characterized by their great chemical reactivity.
With hydrocyanic acid aldehydes form the cyanhydrins Rï¿½CH(OH)ï¿½CN.
Semioxamazid, NH ï¿½COï¿½COï¿½NHï¿½NH, has also been employed for the identification of aldehydes (W.
Aldehydes are converted into resins by the action of caustic alkalies.
The reaction is a general one for all aldehydes with zinc methyl and zinc ethyl, but not with the higher zinc alkyls.
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.
17) has shown that aldehydes in the presence of nitrohydroxylaminic acid form hydroxamic acid.
The chief aldehydes are shown in the following table: - For formaldehyde see Formalin.
The higher aldehydes of the series resemble acetaldehyde in their general behaviour.
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 aromatic aldehydes resemble the aliphatic aldehydes in most respects, but in certain reactions they exhibit an entirely different behaviour.
It combines with aromatic aldehydes in the presence of alcoholic potash to form addition products which are converted by acids into styrol derivatives (J.
These compounds may be considered as 5-triazolones, a series of isomeric 3-triazolones resulting from the condensation of phenylsemicarbazide with aromatic aldehydes in the presence of an oxidant.
In organic chemistry, his study of the ketones and aldehydes, begun in 1857, provided him with the subject of his other doctoral thesis.
It is found also that some monosaccharoses behave as aldehydes whilst others contain a keto group; those having the first character are called aldoses, and the others ketoses.
Wallach, Ber., 1881, 14, P. 421); by the action of reducing agents on nitroparaffins; by the action of zinc and hydrochloric acid on aldehyde ammonias (German Patent 73,812); by the reduction of the phenylhydrazones and oximes of aldehydes and ketones with sodium amalgam in the presence of alcohol and sodium acetate (J.
They form condensation products with aldehydes, benzaldehyde and aniline forming benzylidene aniline, C 6 H 5 N: CHC 6 H 5, and when heated with acids they form anilides.
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.
The calcium salts distilled with calcium formate yield aldehydes r distilled with soda-lime, ketones result.
It condenses with aldehydes and ketones to produce semioxamazones.
Aldehydes also combine directly with ammonia.
It combines with aldehydes and ketones to form the nitriles of oxy-acids, for example, CH 3 CHO+HCN=CH 3 CH(OH)(CN).
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.
Hantzsch has shown that aldehydes condense with aceto-acetic ester and ammonia to produce the homologues of pyridine, thus: R R [[Rooc Ch 2 Cho Ch 2 Coor Rooc C - Ch - C Coor]] + + 1 = Ii II +3H20.
For the formation of primary and secondary alcohols see Aldehydes and Ketones.
This solution is frequently used as a test reagent for the detection of aldehydes, giving, in most cases, a red coloration on the addition of a small quantity of the aldehyde.
They also condense with aldehydes, under the influence of alkalis or sodium ethylate (L.
Hinsberg, Ann., 1887,237, p. 327), and with ammonia and aldehydes to form imidazoles.
It unites with aldehydes to form esters of ketonic acids, and with aniline yields anilido-acetic acid.
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.
Villiger (Be y ., 1901, 34, pp. 2679, 3612) showed that many organic compounds (ethers, alcohols, aldehydes, ketones, &c.) behave towards acids, particularly the more complex acids, very much like bases and yield crystallized salts in which quadrivalent oxygen must be assumed as the basic element.
Y-Oxyacids are formed when aldehydes are heated with sodium succinate and sodium acetate.
Tetrahydro-oxazoles or oxazolidines result from the action of aldehydes on amino-alcohols (L.