00:00:00 Part 5 of the Techniques in Organic Chemistry films covers synthesizing the dye Martius yellow using sulfonation and nitration reactions.

00:00:30 This synthetic sequence involves preparation from five grams of alpha-naphthol of the seven compounds shown in the chart.

00:00:45 The first is Martius yellow, number one. The sample is crystallized and saved. The rest is reduced to the air-sensitive diamine.

00:00:57 This is dissolved in dilute hydrochloric acid, and the clarified solution is divided in two parts.

00:01:04 One part is oxidized, and in a successful experiment, the compound two separates as beautiful, fiery red needles.

00:01:14 The part is crystallized and saved. The part is converted to the yellow diacetate, and a part is hydrolyzed to the orange amino-naphthaquinone.

00:01:26 The second half of the solution is treated with acetic anhydride and sodium acetate to produce the diacetate.

00:01:35 And if everything goes right, this separates as pure white solid.

00:01:40 The part is crystallized, sometimes with a little difficulty, and a part is oxidized to the yellow acetylamino compound.

00:01:49 This is then hydrolyzed to the last compound of the series.

00:01:54 In my class, this series of experiments is the basis for an annual Martius yellow prize competition.

00:02:03 Among those who succeed in securing satisfactory samples of all seven compounds,

00:02:10 the decision of the judges is based largely on the amount of time spent.

00:02:16 Consequently, the competitor is well advised to plan his work so that the experiments are dovetailed,

00:02:23 so that needs are anticipated, and so there's no idle time.

00:02:29 The initial step of sulfonation requires strong heating on the steam bath.

00:02:34 The flask is placed in a slanting position so that it is bathed in steam and rotated for mixing.

00:02:42 While the reaction is proceeding, there is time for measuring water to dissolve the product,

00:02:48 for putting water on to heat,

00:02:57 and for measuring nitric acid for nitration.

00:03:08 In a few minutes, crystals appear.

00:03:14 On further heating, the mixture goes solid.

00:03:21 A solution of the product in water is cooled, and nitric acid is added in portions,

00:03:27 keeping the temperature at 15 to 20 degrees.

00:03:36 When the addition is complete, the mixture is warmed gently and finally heated strongly.

00:03:45 Meanwhile, preparations are made for filtration and for conversion to the ammonium salt.

00:04:14 When the reaction is complete, water is added.

00:04:26 The mixture is stirred.

00:04:33 The thermometer is rinsed and removed,

00:04:38 and precipitated martyrish yellow is collected on a suction filter.

00:04:58 The cake is washed with water,

00:05:19 and then blown out into a beaker.

00:05:26 The funnel is rinsed with water from a wash bottle,

00:05:29 and care is taken to avoid getting the dye on the hands.

00:05:34 Ammonia is added to form the ammonium salt,

00:05:42 and hot water is added to dissolve it.

00:05:50 The mixture is heated and stirred.

00:05:57 Meanwhile, preparation is made for suction filtration of the hot solution,

00:06:13 and for ice cooling of the filtrate.

00:06:19 When the ammonium salt is dissolved,

00:06:26 the solution is filtered.

00:06:32 During the process, foaming over of the filtrate is prevented

00:06:36 by frequent operation of the pressure release device of the filter trap.

00:07:05 Ammonia is added to the mixture.

00:07:34 The hot filtrate is transferred to an Erlenmeyer flask,

00:07:44 which is better suited for cooling than the thick-walled filter flask.

00:08:00 Ammonium chloride is added to decrease the solubility of the ammonium salt,

00:08:07 and the flask is cooled in an ice bath.

00:08:13 The orange ammonium salt is collected.

00:08:44 It is washed, not with water, which would dissolve the product,

00:08:48 but with ammonium chloride solution.

00:09:18 A sample is transferred to a flask for solution in water

00:09:36 and conversion into free Martius yellow, which will be crystallized and saved.

00:09:54 The remainder is washed into a beaker.

00:09:57 The filter paper will be removed in a subsequent filtration.

00:10:21 Hydrosulfide is added to affect reduction,

00:10:24 and the mixture is stirred frequently until the orange salt has given place

00:10:28 to a tan precipitate of the diaminonaphthol.

00:10:32 Water and hydrochloric acid are measured into a beaker

00:10:38 for dissolving the air-sensitive tan precipitate.

00:10:43 A suction flask with funnel is made ready for collecting the precipitate.

00:10:51 Another funnel is made ready for filtering the hydrochloric acid solution.

00:11:18 This funnel is provided with a pad of norite

00:11:36 and set aside.

00:11:51 Before collection of the precipitate,

00:11:54 the ammonium salt is acidified for liberation of Martius yellow.

00:12:14 The tan precipitate is then collected.

00:12:32 It is rinsed in with water

00:12:44 and washed with hydrosulfide solution.

00:13:05 It is then quickly transferred, paper and all, to the beaker of hydrochloric acid.

00:13:35 The dirty solution is clarified by filtration through the norite pad.

00:13:54 Diminished air pressure helps avoid air oxidation.

00:14:24 The filtrate is divided into two equal parts,

00:14:53 divided into two equal portions.

00:15:10 One is oxidized with ferric chloride.

00:15:16 Hydrochloric acid is added,

00:15:24 and the red solution cooled.

00:15:29 The second half is acetylated by addition of acetic anhydride with shaking,

00:15:36 followed by slow addition of sodium acetate solution containing a little hydrosulfide.

00:15:59 The red hydrochloride supersaturates badly,

00:16:02 but crystallization can often be induced by prolonged scratching.

00:16:14 One portion of the red hydrochloride is recrystallized.

00:16:19 Another is heated with sodium acetate and acetic anhydride to form the yellow diacetate.

00:16:27 The other is treated with hot water and ammonia for hydrolysis to the orange quinone seven.

00:16:37 One-third of the white diacetate is set aside to crystallize,

00:16:43 and a solution of the rest in acetic acid is diluted with hot water

00:16:53 and oxidized with ferric chloride.

00:16:59 Half of the product is crystallized,

00:17:03 and the rest is hydrolyzed with sulfuric acid to the quinone six, which separates on dilution.

00:17:12 Eventually, the last of the seven compounds is set aside for crystallization.

00:17:22 The next day, all the samples have crystallized satisfactorily.

00:17:37 And so, when the last sample has been bottled,

00:17:46 the experiment is at an end.

00:17:52 Some students have made satisfactory samples of all seven compounds in four hours or less.

00:18:00 A few have been under three hours, and a very few have been closer to two than to three hours.

00:18:07 Perhaps you would like to try your hand.

00:18:10 Good luck.