Benzene, as solvent

Quantum yield data for several processes that occur on photolysis of 5-4-methyl-1-phenyl-l-hexanone have been determined. The results are tabulated below for benzene as solvent. 

At the same time, Dale and Kristiansen reported a successful synthesis of 18-crown-6 from the diol and ditosylate just as shown in Eq. (3.2), but using benzene as solvent. They obtained the product as its potassium tosylate complex (mp 164°) in 33% yield. The free macrocycle was liberated by chromatography over a column of alumina, eluting with a benzene-cliloroform mixture. Dale and Kristiansen note that the cyclic ether cannot be liberated from its complex by simple heating . ... 

The electron transfer step is typically fast and efficient. Griller et a/.292 measured absolute rate constants for decay of benzophenone triplet in the presence of aliphatic tertiary amines in benzene as solvent. Values lie in die range 3-4x109 M 1 s 1 and quantum yields are close to unity. 

The rates of reaction for a wide range of alkyl halides with benzene (as solvent)... 

Interaction of the pentafluoride and methoxide proceeded smoothly in trichlorotrifluoroethane at 30-40°C, whereas in benzene as solvent repeated explosions occurred. 

Our first experiments were performed with benzene as solvent, which generally provides very good yields.3 Use of the less hazardous solvent ethyl acetate gives inferior yields if the silyl enol ether contains triethyiamine. Ethyl acetate was distilled from potassium carbonate. 

Samec and Backvall found that the dinuclear Shvo complex catalyzes the transfer hydrogenation of imines using benzene as solvent and isopropanol as the hydrogen source (Eq. (45)) [76]. These catalytic hydrogenations were typically carried out at 70 °C, and gave >90% yields of the amine in 4 h or less. 

Owing to the very low degree of polymerisation of the polymers obtained, molecular weights (Mn) were determined with a MECROLAB Vapour Pressure Osmometer, model 301 A with benzene as solvent. For values of Mn ranging between 400 and 2000 the reproducibility was 30 units. 

The kinetics of the reaction of p-nitrobenzenesulfenyl chloride with aromatic amines in benzene as solvent follow the form (175) (Ciuffarin and Griselli, 1970 Ciuffarin and Senatore, 1970). This is indicative of a mechanism of the... 

A kinetic smdy has been reported of substituent effects on the reactions of 2-phenoxy- and 2-(4-nitrophenoxy)-3-nitro-5-X-thiophenes with benzylamine and with A-methylbenzylamine in benzene as solvent. The intramolecularly hydrogen-bonded intermediate (14) is postulated. Reactions of the 5-unsubstimted thiophenes (X = H) are not base-catalysed, indicating that nucleophilic attack is rate limiting, and the more basic secondary amine shows higher reactivity than the primary... 

Anhydrous NIPAAM Homopolymers and NIPAAM-NASI Copolymers using Benzene as solvent. The procedure was the same as described for... 

A subsequent elimination of hydrogen halide prompted by the lability of halogen on the carbon attached to nitrogen, a second halogen addition, and a repetition of the cycle must account for the reported formation of 9-pentachloro- and 9-pentabromoethylcarbazoles on reaction with excess halogen in methanol and acetic acid, respectively. Addition of bromine to IV-vinylcarbazole in benzene as solvent was accompanied by 3,6-dibromi-nation in ethanol, 3,6-dibromo-9-(2-bromo-l-ethoxyethyl)carbazole was reportedly formed (cf. ref. 230). 

The measurements have indicated a linear relation between P (or dP) and pK. The following components were used C H COOH, CH JCOOH, OH,C1COOH, CHCljCOOH, CClgCOOH, N-methylpyperidine, diethylamine, ethylamine. The majority of systems contained benzene as solvent and in two cases dioxan solution was used in order to test the stability of complexes with hydrogen bond, and to confirm the absence of their additional association. The attention was paid to the role of the so-called polar hydrogen bond in acid-base interactions. 

Selective oxidation of alcohols. Primary alcohols are oxidized by this RuCL complex about 50 times as rapidly as secondary alcohols. Use of benzene as solvent is critical lor this high selectivity. Little or no reaction occurs in CH3CN, THF, or DMF. Most oxidants, if they show any selectivity, oxidize secondary alcohols more rapidly than primary ones. However, ruthenium-catalyzed oxidations with N-mcthylmorpholine N-nxide and oxidations with PCC4 proceed about three times as rapidly with primary alcohols as with secondary ones. 

Carbonylchlorocopper(I) (A) is a valuable precursor for the synthesis of organometallic and coordination compounds of copper(I). Previous methods11 utilizing water, tetrahydrofuran, methanol, or benzene as solvent may yield lower-purity products because copper(I) chloride is not soluble in these solvents without excess halide ligand. The synthetic method described here also provides a convenient way of growing large crystals of X-ray quality of carbonylchlorocopper(I). 

Cryoscopic determinations of the molecular weight, using benzene as solvent, give results agreeing with the formula NaS5. 

In early studies of these reactions, the turnover efficiency was not always high, and stoichiometric amounts of the promoters were often necessary to obtain reasonable chemical yields (Scheme 105) (256). This problem was first solved by using chiral alkoxy Ti(IV) complexes and molecular sieves 4A for reaction between the structurally elaborated a,/3-unsaturated acid derivatives and 1,3-dienes (257). Use of alkylated benzenes as solvents might be helpiul. The A1 complex formed from tri-methylaluminum and a C2 chiral 1,2-bis-sulfonamide has proven to be an extremely efficient catalyst for this type of reaction (258). This cycloaddition is useful for preparing optically active prostaglandin intermediates. Cationic bis(oxazoline)-Fe(III) catalysts that form octahedral chelate complexes with dienophiles promote enantioselective reaction with cyclopentadiene (259). The Mg complexes are equally effective. 

The reaction of ethyl acetoacetate with malonyl dichlorides has been used to synthesize a range of substituted 4-hydroxypyran-2-ones (58CB2849). Yields and purity of the products were best using benzene as solvent either without a catalyst or using magnesium acetate in this role. Hydrolysis of the C-5 ester function and subsequent decarboxylation are both feasible. 

Addition of DMAD to l-methyl-2-pyrrolidine dimethylacetal (69) in dioxane108 gave no 70, but the indoline 75, the isomeric pyrrolidones 71 and 72, and the pyrroline 76 were obtained using benzene as solvent the 1 1 adduct (73) was the major product. With DMAD, compound 73 gave 75, presumably via 74. 

Moffatt et al. found that the optimized reaction conditions developed for the oxidation of testosterone (14), worked ideally in the oxidation of other alcohols. Later, researchers tended to apply, on reactions run at room temperature on very diverse alcohols, these optimized conditions involving 3 equivalents of DCC or other carbodiimide, 0.5 equivalents of pyridinium trifluoroacetate with some extra pyridine added, and neat DMSO or a mixture of DMSO and benzene as solvent. The only substantial changes to this standard protocol involve the growing use of the water-soluble carbodiimide EDC,17 instead of DCC, in order to facilitate the work-ups, and the occasional employment of dichloroacetic acid,18 which proved very effective in the oxidation of some complex polar alcohols, instead of pyridinium trifluoroacetate. 

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