Crystal Violet, from condensation

Crotonic acid, esterification with sec-butyl alcohol, 41, 60 Crystal Violet, from condensation of oxalyl chloride with dimethyl-aniline, 41, 2-4... 

Similar to the history of many other elements, iodine s discovery was serendipitous in the sense that no one was looking for it specifically. In 1811 Bernard Courtois (1777—1838), a French chemist, attempted to remove sodium and potassium compounds from the ash of burned seaweed in order to make gunpowder. After removing these chemicals from the ash, he added sulfuric acid (H SO j) to the remaining ash. However, he mistakenly added too much acid, which produced a violet-colored vapor cloud that erupted from the mixture. This violet vapor condensed on all the metallic objects in the room, leaving a layer of sohd black iodine crystals. Sir Humphry Davy (1778—1829) confirmed this discovery of a new element and named it iodine after the Greek word iodes, which means violet, but it was Courtois who was given credit for the discovery of iodine. 

H. Klinger made the di-iodate by mixing 20 grms. of potassium chlorate, 21 grms. of iodine, and 100 c.c. of water in a half-litre tubulated retort with a thermometer fitted in the tubulure, and the neck directed upwards. The mixture is heated by a small flame. The liquid becomes yellow, and violet vapours condense in the neck of the retort. The materials begin to react at about 85°, and the reaction is complete at about 95°. Only a little chlorine is evolved when the liquid is heated up to its b.p. When the colourless liquid is cooled, crystals of the di-iodate separate, and these can be purified by recrystallization from hot water. The yield is over 70 per cent. Some barium di-iodate can be recovered by adding barium chloride to the mother-liquid. 

The dark violet color appearing on addition of the alkali is probably due to the presence of acenaphthenone. Crystalline acenaphthenol begins to separate almost immediately after the alkali has been added. Care must be taken in heating to refluxing because when heated too rapidly the acenaphthenol crystallizes suddenly from solution and the heat evolved may blow part of it out through the condenser. 

Crystal violet (20) can be produced directly from formaldehyde and dimethyl-aniline. The methane base (18), WAfW,W-tetramethyl-4,4 -mcthylcncdianilinc, is formed initially. This is then oxidized to Michler s hydrol (12), which condenses with another molecule of dimethylaniline to give leuco crystal violet (19). The latter is converted to the dye in a second oxidation step. Pararosaniline, methyl violet, and Victoria blue can also be obtained by this reaction sequence. 

The alkylation process enters into dye manufacture in two ways, because dyes may be formed from alkylated intermediates, or in a lesser numt>er of instances, an intermediate may be subjected to alkylation as a final step. For instance, dimethylaniline is condensed with phosgene to give tetra-methyldiaminobenzophenone (Michler s ketone). From this ketone are formed many dyes, such as crystal violet and Victoria blue. On the other hand, the alkylation process may be almost the last step in the manufacture of a dye, for example, when the disazostilbene dye, paper yellow 3G, is ethylated to give crysophenine G. 

Bernard Courtois (1777-1838). When sulfuric add was added to the ashes obtained from seaweed, a violet gas was given off that condensed as dark crystals with a metallic luster. 

A solution of 10.5 g. (0.046 mol) of freshly distilled bis(tri-fluoromethyl)-l,2-dithiete (Note 2) in 200 ml. of n-pentane is cooled to —10° in a 1-1. round-bottomed flask equipped with an efficient reflux condenser and protected from moist air by a dry nitrogen blanket. A solution of 3.0 ml. (0.023 mol) of nickel carbonyl dissolved in 100 ml. of w-pentane is added down the condenser in one portion to this solution. The mixture is swirled to mix. An intense blue-violet color develops in about 15 to 20 seconds and after 1 to 2 minutes, vigorous evolution of carbon monoxide occurs. This evolution subsides in 10 minutes and the deep violet solution is allowed to warm to 0° during 2 hours to ensure complete reaction. Most of the pentane is removed by distillation at atmospheric pressure, the remaining 50 to 60 ml. is removed in vacuo (0.1 mm.), and the resultant crystalline mass is evacuated (0.1 mm.) at 50° for 4 hours. The crude product consists of shiny black-purple needles and weighs 11.8 g. (98%). Recrystallization from dry benzene (Note 3) gives shiny black crystals, m.p. 134 to 135° (sealed tube). The complex is air-stable but should be kept out of contact with moist air. 

The mother-liquors of the lye obtained from varec contain a tolerably large quantity of a singular and curious substance. It can easily be obtained. For this purpose it is sufficient to pour sulphuric acid upon the mother-liquid and to heat the whole in a retort connected with a receiver. The new substance which, on the addition of the sulphuric acid, is at once thrown down as a black powder is converted on heating into a vapour of a superb violet colour this vapour condenses in the tube of the retort and in the receiver in the form of brilliant crystalline plates, having a lustre equal to that of crystallized lead sulphide. On washing these plates with a little distilled water the substance is obtained in a state of purity. The wonderful colour of its vapour suffices to distinguish it from all other substances known up to the present time, and it has further remarkable properties which render its discovery of the greatest interest. 

Law of Successive Reactions.— When sulphur vapour is cooled at the ordinary temperature, it first of all condenses to drops of liquid, which solidify in an amorphous form, and only after some time undergo crystallisation or when phosphorus vapour is condensed, white phosphorus is first formed, and not the more stable form, violet phosphorus. It has also been observed that even at the ordinary temperature (therefore much below the transition point) sulphur may crystallise out from solution in benzene, alcohol, carbon disulphide, and other solvents, in the monoclinic form, the less stable crystals then undergoing transformation into the rhombic form a similar behaviour... 

After the fumes had condensed on the cold surface of the tank, Courtois noticed a residue of dark purple, metallic-looking crystals. A sample of this made its way into the hands of French chemist Joseph Gay-Lussac. He d heard that Sir Humphrey Davy also had a sample, and he didn t want an Englishman to make a big discovery based on a Frenchman s shrewd observation, so he got to work. Gay-Lussac experimented feverishly and discovered that the purple material was a new element. He named it iode, from the Greek for violet. Davy suggested iodine, echoing chlorine, an element that iodine resembles. 

Working in his father s business, which produced niter (saltpeter, potassium nitrate) from seaweed by treating it with strong acids, Courtois noticed that when he added excess sulfuric acid, clouds of violet vapor rose over the solution, then condensed into dark, shiny crystals. Courtois investigated the chemical properties of the new material during the next few months and prepared some of its compounds. However Courtois was busy with the war effort (niter is a component of gunpowder), and he may have been feeling the financial strain of his research, so he told two other chemists about his crystals and asked them to continue the work. 

At the end of 1811 he noticed that the mother-liquor of varec gave with concentrated sulphuric acid a violet vapour from which he condensed a small quantity of what was known as the substance X in black crystals. He gave a specimen to Clement. On 29 November 1813 Desormes and Clement read a short memoir to the Institut, describing the substance, its compounds with phosphorus, alkalis and metals, a detonating substance formed by the action of ammonia, and an acid (then thought to be muriatic acid). A notice says Desormer (sic) and Clement showed the Institut ... 

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