This heat of formation, like that of most hydrocarbons, is comparatively small: the heat of formation of saturated hydrocarbons is always positive, but the heat of formation of unsaturated hydrocarbons is frequently negative.
PROPIOLIC ACID, CH:C CO 2 H, acetylene mono-carboxylic acid, an unsaturated organic acid prepared by boiling acetylene dicarboxylic acid (obtained by the action of alcoholic potash on dibromsuccinic acid) or its acid potassium salt with water (E.
According to this view, it is necessary to assume that, in all unsaturated compounds, two, or some even number of affinities are disengaged; and also that all elements which combine with an even number of monad atoms cannot combine with an odd number, and vice versa, - in other words, that the number of units of affinity active in the case of any given element must be always either an even or an odd number, and that it cannot be at one time an even and at another an odd number.
These last two compounds are termed unsaturated, whereas ethane is saturated.
A similar behaviour has since been noticed in other trimethylene derivatives, but the fact that bromine, which usually acts so much more readily than hydrobromic acid on unsaturated compounds,, should be so inert when hydrobromic acid acts readily is one still.
From the fact that reduction products containing either one or two double linkages behave exactly as unsaturated aliphatic compounds, being readily reduced or oxidized, and combining with the halogen elements and haloid acids, it seems probable that in benzenoid compounds the fourth valencies are symmetrically distributed in such a manner as to induce a peculiar stability in the molecule.
Systems which are generally unsaturated compounds, often of considerable stability, and behave as nuclei; these compounds constitute a well-individualized class exhibiting closer affinities to benzenoid substances than to the open-chain series.
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.
They may also be prepared by the reduction of primary nitro compounds with stannous chloride and concentrated hydrochloric acid; by the reduction of unsaturated nitro compounds with minium amalgam or zinc dust in the presence of dilute acetic acid' Bouveault, Comptes rendus, 1902, 134, p. 1145):R2C:[[Chno 2 -R 2 C: Ch Nhoh - R 2 Ch Ch: Noh]], and by the action of alkyl iodides on the sodium salt of nitro-hydroxylamine (A.
Caoutchouc, like other "unsaturated" molecules, forms compounds with chlorine, bromine, iodine and sulphur.
As this complete desilverization is only possible by the use of an excess of zinc, the unsaturated zinc-silver-lead alloy is put aside to form part of the second zincking of the next following charge.
These aldols generally lose the elements of water readily and pass into unsaturated compounds; aldol itself on distillation at ordinary atmospheric pressure gives crotonaldehyde, CH 3 ï¿½ CH: CH.
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.
Citronellal, rhodinal and geranial are also unsaturated aldehydes (see Terpenes).
Cinnamic aldehyde ((3-phenyl acrolein), C6H5ï¿½CH: CHï¿½CHO, an unsaturated aromatic aldehyde, is the chief constituent of cinnamon oil.
We may also notice the disruption of unsaturated acids at the double linkage into a mixture of two acids, when fused with potash.
The isothermals are approximately equilateral hyperbolas (pv= constant), with the axes of p and v for asymptotes, for a gas or unsaturated vapour, but coincide with the isopiestics for a saturated vapour in presence of its liquid.
Henry, Comptes rendus, 1907, 1 44, P. 552) (CH 3) 2 C(OH) CH(CH3)2--> (CH3)2C :C(CH 3) 2 +CH 2 :C(CH 3) CH (CH3)2; from unsaturated alcohols by the action of metal-ammonium compounds (E.
As unsaturated compounds they can combine with two monovalent atoms. Hydrogen is absorbed readily at ordinary temperature in the presence of platinum black, and paraffins are formed; the halogens (chlorine and bromine) combine directly with them, giving dihalogen substituted compounds; the halogen halides to form monohalogen derivatives (hydriodic acid reacts most readily, hydrochloric acid, least); and it is to be noted that the haloid acids attach themselves in such a manner that the halogen atom unites itself to the carbon atom which is in combination with the fewest hydrogen atoms (W.
Being an unsaturated acid it combines directly with hydrochloric acid, hydrobromic acid, bromine, &c. On nitration it gives a mixture of ortho and para nitrocinnamic acids, the former of which is of historical importance, as by converting it into orthonitrophenyl propiolic acid A.
Iodine finds application in organic chemistry, forming addition products with unsaturated compounds, the combination, however, being more slow than in the case of chlorine or bromine.
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.
Wade (loc. cit.) explains the formation of nitriles from potassium cyanide, and of isonitriles from silver cyanide by the assumption that unstable addition products are formed, the nature of which depends on the relative state of unsaturation of the carbon and nitrogen atoms under the varying conditions: KNC--KN :C(:C 2 H 5 I) --SKI +C2H5CN, AgNC->AgN(:C2H51)C---AgI-f-C2H5NC; that is, when the metal is highly electro-positive the carbon atom is the more unsaturated, the addition takes place on the carbon atom, and nitriles are produced.
On the other hand, when there is but little electro-chemical difference between the radical of the cyanide and that of the reacting compound then the nitrogen atom is the more unsaturated element and.
It is an unsaturated compound, and on oxidation with potassium permanganate gives succinic acid.
With unsaturated alkyl halides the products are only slightly soluble in ether, and two molecules of the alkyl compound are brought into the reaction.
Acid esters yield carbinols, many of which are unstable and readily pass over into unsaturated compounds, especially when warmed with acetic anhydride: R.
This material must be picked out, as such underburnt stuff contains free lime or unsaturated lime compounds.
His most important contribution to organic chemistry was a series of researches, begun in 1835, on the haloid and other derivatives of unsaturated hydrocarbons.
They behave as unsaturated compounds, combining with oxygen to form peroxides and with the halogens to form triarylmethane halides.
Hofmann (Ber., 1881, 14, p. 660), by a process of exhaustive methylation and distillation, obtained the unsaturated hydrocarbon piperylene, CH 2 :CH CH 2 CH: CH2, from piperidine (see also A.
Unsaturated hydrocarbons of the series may be prepared from the corresponding alcohols by the elimination of a molecule of water, using either the xanthogenic ester method of L.
Blanc, Comptes rendus, 1903, 136, p. 1676; 137, p. 60); and by the addition of the elements of water to the unsaturated cyclic hydrocarbons on boiling with dilute acids.
CH2 CHz?CU; CO CH 3 CO CH2 from sodio-malonic ester and 0-unsaturated ketones or ketonic esters: /CH, CO (R02C)2CH2+ Ph CH :CH /CH:>; CH(C02R) C07 from aceto-acetic ester and esters of a$-unsaturated acids, followed by elimination of the carboxyl group: CH2 CR', CH 3 CO CH 2.
The esters of the acids may also be obtained by condensing sodio-malonic ester with a-halogen derivatives of unsaturated acids: CH H?
C02R CH 3 CH: CBr CO 2 R+NaCH (CO 2 R) 2 --->CH 3 C. I C(C02R)2 by the action of diazomethane or diazoacetic ester on the esters of unsaturated acids, the pyrazoline carboxylic esters so formed losing nitrogen when heated and yielding acids of the cyclo- propane series (E.
Attempts to eliminate water from this acid and so produce an unsaturated acid were unsuccessful; on warming with sulphuric acid, carbon monoxide is eliminated and cyclo-butanone (keto-tetramethylene) is probably formed.
Cyclo-octane, C 8 H, 6 is obtained by the reduction of the above unsaturated hydrocarbon by the Sabatier and Senderens's method.
The hydrocarbons, upon which the luminosity of the flame entirely depends, are divided in the analysis into two groups, saturated and unsaturated, according to their behaviour with a solution of bromine in potassium bromide, which has the power of absorbing those termed "unsaturated," but does not affect in diffused daylight the gaseous members of the "saturated" series of hydrocarbons.
The chief unsaturated hydrocarbons present in coal gas are: ethylene, C2H4, butylene, C 4 H 8, acetylene, C 2 H 2, benzene, C 6 H 61 and naphthalene,C 10 H 8, and the saturated hydrocarbons consist chieflyof methane, CH 4, and ethane, C2H6.