Degassed acetonitrile

Figure 14 Separation of 1,2/1,4 ketal with and without protection from oxidative degradation. Chromatographic conditions were column 25 cm x 4.6 mm Zorbax C8 (5-pm) column mobile phase 100 mM KH2P04 (pH 6.5) acetonitrile (50 50) flow rate 1.0 ml/min column temperature 35°C detector wavelength 220 nm. (A) Acetonitrile degassed. (B) Acetonitrile not degassed.

Photolysis of several 2-azidophenazines has been shown to afford quinoxahnes. Thus irradiation of 2-azidophenazine (576, R = H) in cyclohexane or acetonitrile gave, among other products, 3-(2-cyanovinyl)-2-quinoxalmecarbaldehyde (577) in <17% yield and irradiation of 2-azido-l-methoxyphenazine in degassed benzene or acetonitrile gave, among other products, a separable mixture of cis- and frawi-isomers of methyl 3-(2-cyanovinyl)-2-quinoxalinecarboxylate (578), each in low yield. 3 ... 

Figure 5.11 Emission and excitation spectra of [Au3(p-dpmp)2] (SCN)3 in degassed acetonitrile at room temperature. Reproduced with permission from [38]. Copyright (1993) Royal Society of Chemistry.

Figure 5.14 UV/Vis spectral changes of [Au2(dcpm)2](Cl04)2 in degassed acetonitrile at room temperature as a function of [NBu4]I concentration. Reproduced with permission from [6b]. Copyright (2001) Wiley-VCH.

Figure 5.16 Excitation (left, emission monitored at 500 nm) and emission (right) spectra of [Au2(dcpm)2]X2 (X = CF3S03 and T), with kex at 280 nm, in degassed acetonitrile at room temperature, and emission spectrum of [Au2(dcpm)2](SCN)2, with at 280nm, in EtOH/MeOH (1 4 v/v) at 77 K. Reproduced with permission from [6b]. Copyright (2001) Wiley-VCH.

Figure 5.19 Room temperature emission spectra ofiAuiP P)] (CIO4) in the presence of PPh3 in degassed acetonitrile solution. Molar ratio of PPh3 [Au(P P)] =X 1. Inset a plot ofthe emission intensityofiAuiP P)(PPh3)] vs.X l (concentrationofiAuiP P)] (CIO4) = 10 mol dm ). Reproduced with permission from [12b]. Copyright (1998) Royal Society of Chemistry.

Solvent A water containing 0.1% (v/v) formic acid Solvent B acetonitrile containing 0.1% (v/v) formic acid A gradient is run from 90% A to 10% A over 12 min. The solvent composition is taken back to 90% A at 12.5 min and equilibrated until 17.5 min (solvents degassed)... 

Although the method is simple and straightforward, there are a few important points to consider. First, since 200 pL are being injected on to a 2-mm diameter HPLC column, compatible solvents must be injected on to the column and the amount of acetonitrile used in the prepared samples should be exactly as directed. Second, the temperature of the column and the use of a degassing system for the mobile phase are critical components required to guarantee reproducible chromatography. In addition, the standards should be stored in a refrigerator when not in use. 

During the LANA process, we observed the decomposition of 1,2/1,4 ketal (compound 2) in 2 hours in HPLC grade acetonitrile. A noticeable color change was observed. Since previous experience with sample decomposition led us to suspect that oxygen played a role in the decomposition reaction, a sample was prepared in acetonitrile with or without degassing. After 1 hour,... 

Method 3 was modified to an internal standard method into Method 5 by changing the bonded phase and the mobile phase composition. Biphenyl was used as an internal standard added into the reaction. Aliquots were withdrawn, diluted with degassed acetonitrile, and analyzed according to Method 5. This internal standard method, Method 5, was helpful in the optimization of the desired ris-1,2/1,4 product of the key step of the LANA reaction (scheme 5). 

Degassed acetonitrile solutions of 4 show little or no decomposition upon prolonged heating at 80°C, but photolysis (A, > 300 nm) of thoroughly degassed CH CN solutions of [P H -... 

The photolysis of 4-nitroanisole in degassed acetonitrile or benzene yields 4-nitro-soanisole and 2-nitro-4-methoxyphenol is). Triphenylene (Et = 67 kcal mole i 4-nitroanisole t=59.5 kcal mole i has been used to sensitize the reaction, which is suppressed completely by nitric oxide. A rationale for the formation of the products observed is given below. 

Irradiation of a thiete 1,1-dioxide in degassed solutions of acetonitrile or dichloromethane at 253 nm leads to the formation of vinyl ketones (241) via... 

A mixture of 0.27 mtnol of tricyclo[3.3.1.1 3,7]decane (adamantane), 0.054 mmol of (Bu4N)4Wl()032, and 3 mg of platinum in 10 mL of acetonitrile under argon in a Pyrex Schlenk flask is irradiated with a 550 W mercury arc lamp. The reaction turns deep blue on photolysis. Every 16 h, photolysis is Stopped, the catalyst is reoxidized under air, the sample is degassed and again placed under an argon atmosphere, and irradiation is resumed. After a total of 64 h there is 58% conversion of adamantane and a 40% yield of the methyl ketone (by VPC). 

Curve (a) displays the voltammogram of a red solution of 7 in degassed acetonitrile. A reversible redox wave at 0.68 V (versus SCE) attests to the tetrahedral... 

Reagents. Organic solvents for HPLC separations—methylene chloride, methanol, isopropyl alcohol, hexane, and acetonitrile—were obtained as HPLC grade from Fisher Scientific. Type I water for HPLC and for the preparation of other aqueous solutions was purified as described previously (7). All HPLC solvents were filtered through a 0.45-/zm Millipore membrane filter (Millipore Corporation) and degassed... 

An investigation of the surface acidity of the Al-modified PCH was carried out by acetonitrile-d3 CD3CN adsorption. A pellet of the Al-PCH mixed in KBr was pressed at 2 ton and degassed at 450°C for 6 hours (heating rate l°C/min) prior to the reaction. CD3CN was adsorbed at room temperature for 10 minutes after which the IR-spectrum has been recorded. Subsequently, different IR-spectra were taken after evacuation of the sample at 25°C, 60°C, 120°C and 150°C. 

Using a graduated cylinder, measure 300 ml deionized water into a vacuum flask. Add 700 ml HPLC-grade acetonitrile to the flask. Mix solution with stir bar and magnetic stir plate. Degas the mobile phase daily in an ultrasonic bath under vacuum or using an in-line degasser. Prepare fresh for each analytical run. 

Figure A. Hydroxylation of benzene in acetonitrile under degassing (0) and under oxygen (Q) ...

Farid et al. reported the formation of two types of (4 + 2) photocycloadduct of 9,10-dicyanoanthracene (DCA) with 3-carbomethoxy-l,2-diphenylpropene [192,193], The product ratio depends on the solvent polarity. In benzene, exo-125 is selectively obtained via exciplex (Scheme 38). In acetonitrile, endo-125 is obtained as a sole product via the radical ion pair. Photochemical reactions of DCA with 1,2-diarylcyclopropanes gave (4 + 3) cycloadducts [194,195], In degassed acetonitrile solution, (4 + 3) photocycloaddition occurred to give cis and trans cycloadducts in a 3 1 ratio in good chemical yields, although the quantum yields... 

Even the best solvents need to be filtered. I have received HPLC-grade acetonitrile, from what I considered to be the best manufacturer of that time, that left black residue on a 0.54-/im filter. There is a second reason to filter solvents. Vacuum filtration through a 0.54-/im filter on a sintered glass support is an excellent way to do a rough degassing of your solvents. Because of filter... 

Mobile phase Prepare a filtered and degassed mixture of Phosphate buffer and acetonitrile (3 1). Make adjustment if necessary (see system suitability under Chromatography, in the general procedure (621)). 

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