____ Experiments _________ 0 MICROSCALE 1. Synthesis of Luminol First heat a tube containing 3 mL of water on the steam bath. Then he at a mixtu acid and 0.4 L of an 8% aque r of 200 mg of 3-nitrophthalic � ous solution hydrazine2 (Caution!) in a 10 x 100 mm reacuon tube over a hot sand 0� bath untiJ Hydra:.ine is a carcinogen. the solid is dissolved. Add 0.6 mL of triethylene glycol, and clam p the tube . Handle with care. Wear gloves a vertical position above the hot sand bath. Insert a boiling chip an d a th �r y vigorously to distill the ln � and carr out this experiment in mometer, and boil the solution excess water. te ­ the hood. tently remove the thermometer, and replace it with an aspirator tub e to facilita: this. There will be a period during which the solution will boil at 11 °c an� ° 0 , then over a 3- or 4-min period it will rise to 215 C. Lift the tube from the hot sand, and by intermittent gentle heating maintain a temperature of 215 ° to 22ooc Remove the tube, cool to about 100 C ( crystals of the Triethylene glycol for 2 min. product often ° bp 290 C appear), add the 3 mL of hot water, cool the tube in cold water, and collect the (8) light-yellow granular nitro compound by vacuum filtration on the Hirsch funnel.3 The dry weight should be about 140 mg. be The two-step synthesis of a The nitro compound need not be dried and can transferred at once, for chemiluminescent substance can reduction, to the uncleaned tube in which it was prepared. Add 1.0 mL of 3 M be completed in 25 min. sodium hydroxide solution, stir with a rod, and to the resulting deep brown-red solution add 0.6 g of fresh sodium hydrosulfite dihydrate (not sodiwn hydrogen NazS204 · 2 H20 sulfite or sodium bisulfite). Wash the solid down the walls with a little water. Sodium hydrosulfite dihydrate Heat to the boiling point, stir, and keep the mixture hot for 5 min, during which {Sodium dithionite) MW 210.15 time some of the reduction product may separate. Then add 0.4 mL of acetic acid, cool the tube in a beaker of cold water, and stir; collect the resulting CAUTION: Contact of solid precipitate of light-yellow luminol (1) by vacuum filtration on the Hirsch funnel. sodium hydrosulfite with moist The filtrate on standing overnight usually deposits a further crop of luminol combustible material may cause (20-40 mg). fire. Cleaning Up Combine the filtrate from the first and second reactions, dilute with a few milliliters of water, neutralize with sodium carbonate, add 3 mL of household bleach (5.25% sodium hypochlorite solution), and heat the mixture to 50°C for I h. This will oxidize any unreacted hydrazine and hydrosulfite. Dilute the mixture, and flush it down the drain. 2. Dilute 3. J 2 g of the commercial 64% hydrazine solution to a volume of 25 mL. e solid is 3. The reason for adding hot water and then cooling rather than adding cold water 1s. tha t th then obtained in more easily filterable form. Chapter 62 Chem 1·1 umm • escence: Syntheses of Cyalume and Luminol 663 cal s po ition in a hot s . an d bath. Insert a thermome e sp1- ra t or tub e c e t r, a boiling chip, and an a onn cted tO an · · e aspirator,· and boil the s to d1st1l I th e xcess water ° solution vigorou ly . (I I0-130 C). e ches ° Let the temp rature rise rapidly until (3-4 min) lt re� 21 S e C. R move the he heating burner, note t time and by intermittent gentle m amta· · m a te ° ° mperature of 21 S-220 C for 2 min. Re e tube, cool to about l00 move th C (crystals of the e e product often app ar), add the IS mL of hot wat r, cool unde e r th tap, and collect e e hesis of a th light-y llow granular nitro compound 7ht rwo-step synt (13). Dry weight 0.7 g.s inescent substance The nitro chem i/um . compound need not be dried and e s e e 25 mm. e can b tran ferr d at onc for be completed in r d�ction, to the unc e es ((J/l lean d t t tube in which it was prepared. Add S mL of •3 sodi�m hyd M roxide solution, stir with a rod, e s e s and to th re ulting d ep brown-red olution add 3 e h g of fr s sodium hydrosulfite dihydrate. Wash the solid down the walls with a little water. Heat to the boiling point, stir, and keep the mixture hot for S min, during which time some of the reduction product may separate. Then add 2 mL of acetic acid, cool under the tap, and stir; collect the resulting precipitate e of light-y llow luminol (6). The filtrate on standing overnight usu­ ally h deposits a furt er crop of luminol (0.1-0.2 g). Cleaning Up Combine the filtrate from the first and second reactions, dilute with a few milliliters of water, neutralize with sodium carbonate, add 40 mL of household bleach (5.25% sodium hypochlorite s olution), ° and heat the mixture to 50 C for I h. This will oxidize any unreacted hydrazine and hydrosulfite. Dilute the mixture, and flush it down the drain. 1 J1_ MICROSCALE J W AND MACROSCALE 4. The Light-Producing Reaction This reaction can be run on a scale five times larger. Dissolve the first crop of moist luminol (dry weight about 40-60 mg) in 2 rnLof 3 M sodium hydroxide solution and 18 mL of water; this is stock solution A. Prepare a second stock solution, B, by mixing 4 mL of 3% aqueous potassium ferricyanide, 4 mL of 3% hydrogen peroxide, and 32 mL of water. N_owdil�te 5 mL of s�lution ':- with 35 mL of water, and in a dark place, pour this solution and solution B simultane­ ously into an Erlenmeyer flask. Swirl the flask and, to increase the brilliance, further small quantities of alkali and ferricyanide crystals. gradually add . Ultrasonic sound also can be used to promote th,s reaction. Prepare stock . B again but omit the hydrogen peroxide. Place the combined soI ut 10n s A and • . s ultrasonic cleaning bath, or immerse an ultrasoruc probe mto the so l u t10n in an · · · h e l reaction mixture. Spots of light are seen where t u trasomc v1b rations pro duce icals. hydroxyl rad . d thes angui nary-minded can mix solutions A and B, onuttmg the fem- Light can be generated by adding blood dropwise to cyanide� from solution B. the reaction mixture. Cleaning Up Add 2 mL of 3 M hydr�chloric acid, dilute the solution with mixture down the dram. water, an d flus h the - ----�. rather than adding cold - ng ho t water and then cooling water is that the solid is 5 . The reason for addi easily filterable fo nn. then ob tame. d ·1n more .