From rubber septa

McDonough, L. M., Brown, D. F., and Aller, W. C. (1989). Insect sex pheromones. Effect of temperature on evaporation rates of acetates from rubber septa.. Journal of Chemical... 

To determine the versatility of the apparatus for measuring release rates in general, the release of (acetyl-l-1 C)-gossy-plure was measured from rubber septa, a pheromone release device frequently used in field experiments. After 21 days of measurements, the septa were extracted and any residual activity in the apparatus was measured. The average recovery, detailed in Table II, was 97% indicating that the usefulness of the mini-airflow device was not limited to hollow fibers alone. 

Table II. Half-lives and heat of evaporation of aldehydes from rubber septa...

The effect of temperature on t was striking. When the temperature changed from 30 to 20 C, t values changed from 1.96 to 4.91 days (a factor of 2.5) for 10 Ac and from 553 to 2,070 days (a factor of 3.7) for 16 Ac. These results show that male moths responding to their synthetic sex pheromone evaporating from rubber septa will experience substantial variation in evaporation rates. 

There are only a few reports in the literature on the effect of air speed on evaporation rates of pheromone components from rubber septa. Teal et al. reported a linear change of evaporation rate of the sex pheromone of Heliothis virescens with air speed over an air speed change of 4-fold (23). Also, in a study of behavioral response of moth species to their sex pheromones, Landolt and Heath (24) reported that the evaporation rates of Z7-12 Ac at two... 

Dimethylamine was obtained in a cyclinder from the Linde Division, Union Carbide Chemical Corporation, and condensed in a dry, two-necked flask fitted with a rubber septum and cooled to -78° under nitrogen. 

The submitters recommend that the solvent be distilled under nitrogen into a two-necked receiving flask fitted with a three-way stopcock. The receiving flask is separated from the distillation apparatus under a rapid nitrogen flow and fitted quickly with a rubber septum. The solvent is then transferred to the reaction vessel by needlestock techniques. 

B. Cyclohexanol from cyclohexyl methyl ether. In a 25-mL, oven-dried, round-bottomed flask is placed 1.722 g. (0.0151 mole) of cyclohexyl methyl ether (Note 7). The flask is purged with nitrogen and sealed with a rubber septum. By means of oven-dried syringes, 4 ml, of chloroform (Note 8), 0.5 g. (0.5 ml., 0.006 mole) of pyridine (Notes 8 and 9), and 4.8 g. (3.5 ml., 0.024 mole) of... 

The earliest injection method in hplc used a technique borrowed from gc in which a microlitre syringe was employed to inject the sample through a self-sealing rubber septum held in an injection unit at the top of the column. In another method, (stopped flow), the flow of mobile phase through the column was halted and when... 

FIGURE 4. Electrochemical reactor composed of a 2 cm3 capacity filter funnel and (A) stainless steel wire, (B, G) stainless steel needles for N2 entry and exit ports, (C) rubber septum, (D) lead foil cathode, (F) fine porosity glass filter, (H) plug of silicone glue and (I) silver wire anode. (Taken from Reference 176.)... 

All extraneous water present in the surrounding air and in the solvents used must be eliminated. Moisture from the air is prevented from entering the system by sealing off the cell from laboratory air. This is accomplished by the use of a rubber septum for sample injection and by the use of water-absorbing material in the other openings to the system. 

B. 3-Cyclopentene-1 -carboxylic acid. A 250-mL, one-necked, round-bottomed flask is charged with 35.8 g of 3-cyclopentene-1,1-dicarboxylic acid and then fitted with a reflux condenser capped with a rubber septum and connected to a Nujol-filled bubbler by means of a syringe needle. The contents of the flask are heated in an oil bath at 170-175°C until carbon dioxide evolution is complete (ca. 2 hr) and then allowed to cool to room temperature. The resulting oil is transferred to a 50-mL flask and vacuum distilled without fractionation to provide 23.0 g (89% or 82% overall from dimethyl malonate) of 3-cyclopentene-1-carboxylic acid as a clear, colorless oil, bp 88°C (2 mm) (Note 7). 

A 1.5 M solution of butyllithium in hexane was purchased from Aldrich Chemical Company, Inc. Aliquots were transferred to a 100-mL graduated cylinder, stoppered with a rubber septum using a 15-gauge cannula and argon. 

Di-tert-butyl-4H-tellurin A solution of 1.60 g (5.0 mmol) of 2,6-di-ferf-butyl-4-oxo /7-tellurin in 15 mL dry tetrahydrofuran is placed into a flame-dried, 50 mL, two-necked flask equipped with a rubber septum cap and a dry-argon inlet. The flask is cooled to 0°C 7.5 mL of a 1.5 M solution (10.5 mmol) of diisobutyl aluminium hydride in toluene are dropped to the cold solution with the help of a syringe. The reaction is quenched by addition of 10 mL of moist diethyl ether. The resulting solution is poured into 100 mL diethyl ether. The organic phase is washed with three 25 mL portions of 5% hydrochloric acid and then with two 50 mL portions of brine, dried with anhydrous sodium sulphate, filtered and the filtrate concentrated. Cold pentane (5 mL) is added to the residual oil and the mixture is cooled to -20°C. The pentane is decanted from the yellow aystals. The decantate is chromatographed on sihca gel with dichloromethane as the mobile phase to give a yellow oil. Yield 62%. 

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