Reagents carbonates, mixed

Prepare 30-fold and 50-fold dilutions of the test solution. Add 1.25 ml of a mixture prepared the same day by combining 2.0 ml of a 20 g/1 solution of copper sulphate R in water R, 2.0 ml of a 40g/l solution of sodium tartrate R in water R and 96.0 ml of a 40 g/1 solution of sodium carbonate R in 0.2M sodium hydroxide to test tubes containing 1.5ml of water R (blank), 1.5ml of the different dilutions of the test solution or 1.5 ml of the reference solutions. Mix after each addition. After approximately 10 min, add to each test-tube 0.25 ml of a mixture of equal volumes of water R and phosphomolybdotungstic reagent R. Mix each addition. After approximately 30 min, measure the absorbance (2.2.25) of each solution at 750 nm using blank as the compensation liquid. Draw a calibration curve (from the absorbances of the eight reference solutions the corresponding protein contents and read from the curve the content of protein in the test solution. 

Dibromosiloxene is the first product which can be isolated. It is formed in the reaction between a carbon disulphide solution of bromine (about 10%) and a carbon disulphide suspension of siloxene the reagents are mixed while cooling with ice, as in a titration. When the bromine color remains, a dibromosilo-... 

Importantly, a Friedel-Crafts formylation has not yet been successful. Formyl chloride and formic anhydride are not stable reagents. The mixed anhydride H—C(=0)—O—C(=0)CH3 acts as a formylating reagent in reactions with many nucleophiles (cf. Section 6.3.3). However, in reactions with aromatic compounds under Friedel-Crafts conditions, it acts as an acetylating agent rather than as a formylating agent. Last but not least, formic acid and mineral acids proceed to react via the acylium ion H—C=0 to form carbon monoxide and water in an OC-elimination. We ll solve this problem later. 

Addition reactions. Organolithium reagents add to a,(3-unsaturated amides. If the reagents are mixed with t-BuOK the regiochemical sense is reversed (to the a-carbon). 

An even simpler system composed of dibutyltin diacetate and dibutyltin dichloride was examined by both 13C NMR and low-temperature XH NMR because of the report that dibutylchlorotin acetate formed immediately when the reagents were mixed in carbon tetrachloride (16). The 13C spectra of the pure diacetate and the mixed system were obtained using conditions suitable for quantitative analysis. In deuterochloroform, at 30 °C, over a wide range of concentrations, no evidence could be found for the presence of the excess component or the exclusive formation of dibutylchlorotin acetate. The 1H NMR spectra gave similar results and the spectra were unchanged between 50° and — 50° C. 

Allyl carbonates. Mixed carbew rrepared from this reagent in the pre rrcferentially. 

Figure 1.1 Section plots of NMR spectra (100 MHz, CD3OD) showing signals from carbon atoms of the coordinated double bond, (a) Solution obtained by the addition of two equations of MAC to a deuteriomethanol solution of 7 at 25°C. Spectrum measured at 25°C. (b) The same reagents were mixed at -100°C and the...

Reagent 1 ml of a 0.1 iV sodium carbonate mixed with 2 ml 0.6 % alcoholic phenolphthalein solution and 10 ml water... 

A 100 mg amount of sample and 2 ml of reagent are mixed in a 20 ml round-bottomed flask and the mixture refluxed on an oil-bath at 120 C for 2 hours. The contents of the flask are cooled to room temperature and then neutralised with 50% aqueous sodium carbonate solution, followed by extraction with about 20 ml of diethyl eflier. The ether layer is washed with de-ionised water and concentrated to a small volume on a steam bath the concentrate is then injected into the gas chromatograph. The FFAP column is operated isothermally at the appropriate temperature for the purpose of both identifying the base compounds and determining their oxyethylene groups contents. For the analysis of the polyether based on 1,2-diaminoethane or 2,2 -diaminodiethylamine the SE-30 column is used. 

It is usually preferable to oxidise the compound directly as follows. Intimately mix 0 02-0 05 g. of the eompound with 3 g. of sodium peroxide and 2 g. of anhydrous sodium carbonate in a niekel erucible. Heat the crueible and its eontents with a small flame, gently at first, afterwards more strongly until the eontents are fused, and eontinue heating for a further 10 minutes. Allow to stand, extract the contents of the crucible with water, and filter. Add exeess of eoneentrated nitrie acid to the filtrate and test with ammonium molybdate reagent as above. A yellow preeipitate indicates the presenee of phosphorus. It must be borne in mind that the above treatment 1 eonvert any arsenie present into arsenate. 

Dipping solution Mix 2 ml antimony(V) chloride with 8 ml carbon tetrachloride. Storage The reagent solution should always be freshly prepared. 

The aldehyde or ketone, when treated with aluminum triisopropoxide in isopropanol as solvent, reacts via a six-membered cyclic transition state 4. The aluminum center of the Lewis-acidic reagent coordinates to the carbonyl oxygen, enhancing the polar character of the carbonyl group, and thus facilitating the hydride transfer from the isopropyl group to the carbonyl carbon center. The intermediate mixed aluminum alkoxide 5 presumably reacts with the solvent isopropanol to yield the product alcohol 3 and regenerated aluminum triisopropoxide 2 the latter thus acts as a catalyst in the overall process ... 

A second example exploits the fact that the mixed hydride reagent is capable of hydrogenolysis of certain carbon-oxygen bonds. Thus, treatment of cyclohexanone ketal (Chapter 7, Section IX) with lithium aluminum hydride-aluminum chloride results in the rupture of a C-O bond to give the oxyethanol derivative. 

The C2-symmetric epoxide 23 (Scheme 7) reacts smoothly with carbon nucleophiles. For example, treatment of 23 with lithium dimethylcuprate proceeds with inversion of configuration, resulting in the formation of alcohol 28. An important consequence of the C2 symmetry of 23 is that the attack of the organometallic reagent upon either one of the two epoxide carbons produces the same product. After simultaneous hydrogenolysis of the two benzyl ethers in 28, protection of the 1,2-diol as an acetonide ring can be easily achieved by the use of 2,2-dimethoxypropane and camphor-sulfonic acid (CSA). It is necessary to briefly expose the crude product from the latter reaction to methanol and CSA so that the mixed acyclic ketal can be cleaved (see 29—>30). Oxidation of alcohol 30 with pyridinium chlorochromate (PCC) provides alde-... 

It will be recalled that lactone-derived enol triflate 102 was expected to serve as a substrate for a Murai coupling37 with the mixed cuprate reagent derived from iodo ortho ester 103 (see Scheme 17c). If successful, this C-C bond forming process would accomplish the introduction of the remaining carbon atoms needed for the annulation of the seven-membered D-ring lactone. 

Substances which are insoluble or only partially soluble in acids are brought into solution by fusion with the appropriate reagent. The most commonly used fusion reagents, or fluxes as they are called, are anhydrous sodium carbonate, either alone or, less frequently, mixed with potassium nitrate or sodium peroxide potassium pyrosulphate, or sodium pyrosulphate sodium peroxide sodium hydroxide or potassium hydroxide. Anhydrous lithium metaborate has found favour as a flux, especially for materials containing silica 12 when the resulting fused mass is dissolved in dilute acids, no separation of silica takes place as it does when a sodium carbonate melt is similarly treated. Other advantages claimed for lithium metaborate are the following. 

This reagent is prepared from 3.0 mL of diethylamine in chloroform and 1 mL of carbon disulphide in 9 mL of chloroform. Mix carefully and store in a dark bottle in a refrigerator. 

Molybdate-strychnine reagent This reagent is prepared in two parts these are mixed just before use, since the addition of the acid molybdate solution to the strychnine sulphate solution produces a precipitate after 24 hours. Solution A (acid molybdate solution) place 30 g molybdenum trioxide in a 500 mL conical flask, add 10 g sodium carbonate and 200 mL water. Boil the mixture until a clear solution is obtained. Filter the hot solution, if necessary. Add 200 mL 5M sulphuric acid, allow to cool, and dilute to 500 mL. 

Another series of pyrroles, structurally related to amino acids, was obtained in a microwave-assisted solvent-free condensation of a-amino acid methyl esters with chloroenones, which provided the four-carbon unit of the pyrrole. The reaction was carried out by mixing the reagents on silica gel and irradiating for 2-6 min inside a multimode microwave cavity (Scheme 7). The authors reported higher yields and cleaner products when microwaves were used instead of conventional heating [34],... 

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