Trimethylamine buffers

Fig. 34. Wave of pyridoxal and pyridoxal-5-phosphate in acid media and trimethylamine buffers.

The Values of Observed Absorbance (Ao, ) at 300 nm as a Function of Reaction Time (t) of a Reaction Mixture Containing Phthalimide (PTH) and 0.50-M Trimethylamine Buffer of pH 10.95... 

A few common volative buffer mixtures, along with their respective pH range are pyridine-formic acid (2.3-3.5) trimethylamine-formic acid (or acetic acid) (3.0-6.0) triethanolamine-HCl (6.8-8.8) ammonia-formic acid (or acetic acid) (7.0-10.0). See Buffers... 

Final adjustment with HC1 may be needed if the pH is more than one unit away from a pfCa value. When two buffering materials are present, the composition should be calculated independently for each. The measurement of pH should always be done with great care because it is easy to make errors. Everything depends upon the reliability of the standard buffers used to calibrate the pH meter.7 Often, especially during isolation of small compounds, it is desirable to work in the neutral pH region with volatile buffers, e.g., trimethylamine and C02 or ammonium bicarbonate,... 

The main contaminants in an ionic liquid will be introduced from the synthesis, absorbed from the atmosphere or produced as breakdown products through electrolysis (see above). The main contaminants for eutectic-based ionic liquids will be from the components. These will be simple amines (often trimethylamine is present which gives the liquid a fishy smell) or alkyl halides. These do not interfere significantly with the electrochemical response of the liquids due to the buffer behavior of the liquids. The contaminants can be effectively removed by recrystallization of the components used to make the ionic liquids. For ionic liquids with discrete anions the major contaminants tend to be simple anions, such as Li+, K+ and Cl-, present from the metathesis technique used. These can give significant difficulties for the deposition of reactive metals such as Al, W and Ti as is demonstrated below with the in situ scanning tunnelling microscope. 

Alkylborinic esters, obtained from alkylboronic esters and an organometallic reagent, are converted into the corresponding ketones by the reaction with dichloromethyl methyl ether in the presence of a hindered base, followed by oxidation with hydrogen peroxide in pH 8 buffer or with anhydrous trimethylamine Ar-oxide18. 

Figure 7.12. We make a peptide iadder You need a 100-)il glass tube, a heating block, two vacuum pumps, and two solvent traps one for trimethylamine/trifluoroethanol (coupling buffer) and TFEITC and one for heptafluorobutyric acid (cleaving reagent). Aerial oxygen does not interfere, and nitrogen gassing is unnecessary.

Trimethylamine has been used as a basic catalyst for the derivatization of phenols. The phenols (up to 1 mg) in benzene (500 /il) were mixed with 0.1 M trimethylamine in benzene (100 /il) and acylated with HFBA (10 /il) at room temperature for 10 minutes. Excess reagents were removed by a 30 second wash with pH 6 phosphate buffer, the phases were separated by centrifugation, and the benzene solution was taken for gas chromatography. As with other O-perfluoroacyl derivatives, these compounds could be analysed with excellent sensitivity using the ECD [92]. 

Anhydrous trimethylamine oxide added with stirring in three portions to a soln. of diisopropyl (4R)-/ri7 5-2-[(Z)-but-2-en-2-yl]-l, 3,2-dioxaborolane-4,5-dicarboxylate in dry dichloromethane at 10, after 1 h at room temp, the mixture cooled to 0°, volatiles removed under reduced pressure, the residue re-dissolved in dichloromethane, cooled to —78°, treated with benzaldehyde, stirred for 10-14 h while the temp, was raised to - 50°, and quenched with phosphate buffer (pH 7) - (3S,4S)-(-)-j 7w-4-hydroxy-3-methyl-4-phenylbutan-2-one. Y 75% (e.e. 65%). Both (E)- and (Z)-dioxaborolanes gave the 5 y/2-ketol. F.e.s. T. Basile et al., J. Chem. Soc. Perkin Trans. 1 1989, 1025-9. 

Carbonyl compounds are an important class among organic molecules. Literature records several methods for their synthesis. However, there are very few methods to convert carbon-carbon unsaturation to carbonyl compounds. Hydroboration of acetylenes, followed by oxidation provides a novel method for carbonyl synthesis. It has been noted that regioselectivities achieved in the monohydroboration of internal acetylenes with thexylborane [1], disiamylbo-rane [1], dicyclohexylborane [1], and catecholborane [2] are similar to, but less pronounced than, that realized by 9-BBN [3]. The B-alkenyl-9-BBN derivatives undergo oxidation to the corresponding ketones or aldehydes under aprotic conditions with trimethylamine N-oxide [4, 5] or under protic conditions by inverse addition to buffered hydrogen peroxide [3]. The inverse addition, i.e., the slow addition of the B-alkenyl-9-BBN in THF to the buffered H O, suppresses the otherwise undesirable protonolysis reaction and favors the oxidation pathway to the desired aldehyde or ketone. 

Figure 12 (A) Chromatogram of a reference mixture of NADH and NADPH. (B) Chromatogram of an extract of rat hver. Conditions column, (xBondpak Cij (150 X 4.6 mm) mobile phase, 0.2 M ammonium phosphate buffer (pH 6.0)-methanol-trimethylamine (82 17.87 0.13) flow rate, 1.1 mL/ min detection wavelength, 340 nm column temperature, ambient. (From Ref. 37.)...

The absence of catalytic cleavage of nonionized phthalimide in the presence of carbonate buffer solution cannot be attributed to the steric requirement of carbonate dianion, because trimethylamine and DABCO may be considered to have the same or even more steric requirements than carbonate dianion. The most... 

An example of catalysis almost ceasing owing to steric hindrance destabilization of TS is the tertiary-amine-buffer-catalyzed hydrolysis of maleimide. The brief reaction scheme for the aqueous cleavage of maleimide (Ml) in the buffer solutions of DABCO, trimethylamine, and triethylamine is expressed by Equation 2.14... 

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