Gas bubblers

Place 3 3oz packets of Mildewcide into a 1L flask with an electric heating mantle and cork in the neck connected to a gas bubbler immersed in at least 550mL of distilled water. Heat the paraformaldehyde (what is in the Mildewcide) to between 180-200C (a temp, regulator is absolutely necessary for this step or use a silicone oil bath). The paraformaldehyde will depolymerize making formaldehyde gas in about 91% yield. Alternatively, the gas can be bubbled through the Ammonia solution directly (only for the brave ). If the Formaldehyde solution will not be used immedi-... 

The cinnamate ester prepared as above (23.2 g. 79 mmol) was added as a solid slowly to refluxing xylene (500 ml) over a period of 3 h at a rate that prevented accumulation of unreacted azidocinnamate in the solution (monitored by gas evolution through a gas bubbler). The solution was refluxed for an additional 2 h after gas evolution ceased. The reaction mixture was cooled and the solvent removed in vacuo. The residue was recrystallized from methanol to give pure product (20.7 g, 99% yield). 

D. 3,3-Diahlarothietane 1,1-dioxide. Thietane 1,1-dioxide (5.0 g, 0.047 mol) Is placed In a 500-mL, three-necked, round-bottomed flask equipped with a reflux condenser, magnetic stirrer, and chlorine gas bubbler. Carbon tetrachloride (350 mL) Is added and the solution Is irradiated with a 250-watt sunlamp (Note 5) while chlorine Is bubbled through the stirred mixture for 1 hr (Note 9). Irradiation and chlorine addition are stopped and the reaction mixture is allowed to cool to room temperature. The product Is collected by filtration as a white solid (4.0-4.4 g, 49-53%), mp 156-158°C (Note 10). The product can be used without further purification or It can be recrystallized from chloroform. 

A 500-ml, three-necked, round-bottomed flask fitted with a sealed mechanical stirrer and an outlet leading to a gas bubbler, is charged with a solution containing 4.0 g (0.0208 mole) of cyclobutadieneiron tricarbonyl2 [tricarbonyl( 4-l,3-eyclobutadiene)iron] and 2.0 g. (0.0185 mole) of freshly sublimed p-benzoquinone (2,4-cyclohexadiene-l,4-dione) (Note 1) in 72 ml. of acetone and 8 ml. of water. To the vigorously stirred, ice-cold solution, approximately 40-42 g of ceric ammonium nitrate [ammonium hexanitrocerate(IV)] (Note 2) is added portion-wise over a period of 10-12 minutes (Note 3), until the carbon monoxide evolution has ceased. The reaction mixture is then poured into 600 ml. 

PET waste was glycolyzed at different weight ratios of PET to propylene glycol in die presence of 0.5% (w/w) zinc acetate, based on the weight of PET, as the catalyst. The reaction was carried out at about 200°C under redux in a nitrogen atmosphere for 4 h in a four-necked round-bottom dask fitted widi a redux condenser, gas bubbler, thermometer, and stirrer. 

Unsaturated polyesters were obtained by reacting the glycolyzed product widi maleic anhydride at a hydroxy-to-carboxyl ratio of 1 1. The hydroxyl number was determined without separation of die free glycol. The polyesterification reaction was conducted in a 2-L round-bottom dask equipped with a condenser, a gas bubbler, a thermowell, and a stirrer. The reaction mixture was heated from room temperature to 180°C in about 1-1.5 h. The temperature was maintained at 180°C for about 3 h, dien raised to 200°C and maintained until die acid value reached 32 mg KOH/g. 

Glycerol was inadvertently used as the fluid in a gas bubbler on a nitric acid plant. It nitrated and detonated two days later. 

C. Methyl 3,3-dimethyl-4-oxobutanoate (3). A 50-mL flask, connected to a gas bubbler and equipped with a magnetic stirring bar, is charged with 20 mL of dichloromethane (or tetrahydrofuran), 2.16 g (10.0 mmol) of siloxycyclopropane 2 and 3.64 g (30.0 mmol) of triethylamine hydrofluoride (NEt3-HF) prepared in situ (Note 15). This mixture is stirred for 1 hr at room temperature (Note 16) and diluted with 20 mL of water. The aqueous phase is extracted with three 20-mL portions of dichloromethane. The combined organic phases are dried with magnesium sulfate, filtered, and concentrated on a rotary evaporator (bath temperature below 40°C). Crude product 3 is distilled with a Kugelrohr oven (oven temperature 105°C, 10 mm) to provide 1.26 g (87%) of pure 3 as a colorless liquid (Note 17). 

Figure 2. Schematic of the apparatus. Key 1, He cylinder 2, O cylinder 3, CO cylinder 4, molecular sieve dryer 5, rotameter 6, fine-control needle valve 7, solenoid valve 8, pressure gauge 9, sand bath 10, preheater 11, reactor 12, IR spectrometer 13, gas bubbler and 14, automatic timer. 

N-(10-Undecenoyloxy)pyridine-2-thione (3). To an oven-dried, one-necked, 250-mL, round-bottomed flask equipped with a nitrogen inlet with gas bubbler, a magnetic stirrer, and a dropping funnel are added 3.61 g (28.4 mmol) of N-hydroxythiopyridone (2) (Note 1), 6.20 g (30.0 mmol) of dicyclohexylcarbodiimide... 

General procedure To a flame-dried, three-necked, 250 mL, round-bottomed flask equipped with argon inlet, addition funnel and gas bubbler was added 100 mL of dry 1,2-dimethoxyethane (DME) with 0.20 g (0.98 mmol) of triflate [R, R =Me] and 0.50 g (1.2 mmol) of diphenyl diteUuride. The reaction mixture was cooled to 50°C and a solution of potassium f-butoxide (0.15 g, 1.3 mmol) in 50 mL of dry DME was added dropwise. After the addition, stirring was continued for 15 min at -50°C, then the reaction was aUowed to warm to room temperature. DME was then removed on a rotary evaporator and the residue taken up in hexane and filtered. The resulting coloured solution was chromatographed on activated silica (hexane as eluent). Isolated yield was 0.12 g (26%), as an orange oil. 

The TGA apparatus becomes very hot and caution should be exercised while using it. In order to safely handle volatile materials or polymer decomposition products which may be irritating and harmful, it is suggested that a gas bubbler be constructed to scrub the gaseous effluent from the instrument (Fig. 15.5). Care must be taken to prevent excessive gas pressure from building up if the system is being operated under vacuum or with gases, both inert and flammable. Consult the instrument operations manual for any special safety instructions. 

Fig- 15.5 A type of gas bubbler to absorb gases from the TGA experiment. 

For the gas-measuring device, the submitters used an inverted, calibrated 10-1. bottle, filled with saturated sodium chloride solution, resting in an enamel bucket big enough to hold the volume to be displaced. The checkers used a gas meter. However, the rate of gas evolution can be estimated by using a simple gas bubbler. 

A. 2-Cyanoethylthiouronium hydrochloride (3). To a 5-L, flanged-top, spherical Morton flask equipped with a supporting clamp (Note 1) are added water (380 mL), thiourea (575 g, 7.53 mol), and 3-chloropropionitrile (500 g, 5.58 mol) (Note 2). The flask is equipped with a three-necked (with thermometer inlet) flanged-top, mechanical stirring rod (600 mm) with Teflon paddle (110 mm), temperature probe, reflux condenser, gas bubbler, and 5-L heating mantle. The reaction mixture is slowly... 

The solid (12.8 g) is placed in a 250-mL, two-necked, round-bottomed flask containing a Teflon-coated magnetic stirring bar. One neck is capped with a rubber septum and the other is equipped with a reflux condenser with a gas inlet adapter connected to an argon flow line and an exit-gas bubbler. 

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