Benzene experimental procedure

Tetrakis(di-[Pg.40]

Nevertheless the Elbs reaction is a valuable method for the preparation of dihydroxy benzenes. The experimental procedure is simple, and the reaction conditions are mild a variety of functional groups is tolerated. 

Oxabicyclo[4.1.0]hept-3-enes with a bromo substituent in position 2 can be converted to oxepins 11 by reaction with an appropriate base such as potassium ter+butoxide or triethylamine (see the experimental procedures for the preparation of the parent system in Houben-Weyl, Vol. 6/ld, pi78 and Vol. 6/4, p462).12,156,157 Usually the reaction products are mixtures of oxepin 11 and benzene oxide 12. In the case of ZerZ-butyl 7-oxabicyclo[4,1.0]hept-3-ene-2-carboxylate, the equilibrium lies completely on the benzene oxide side 12a.158... 

The experimental procedure is outlined schematically in Fig. 13 a detailed description was given by Hartog et al. 37). Benzene vapor and deuterium gas, in the molar ratio of 1 18, were passed through a catalyst bed and then through a cold trap immersed in liquid nitrogen in which the hydrocarbons were frozen out. The temperature of the catalyst bed was... 

Fig. 13. Schema for the experimental procedure of the reaction of benzene with deuterium.

The next step involved cooling the reaction mixture to -196°C, removing the H2 at low pressure, and sealing the tube. This sealed tube was then used in the equilibrium measurements. When it warmed up, a fraction of the hydride complex reacted with benzene, yielding H2 and the phenyl complex, according to equilibrium 14.12. Therefore, the total amount of substance of H2 in equation 14.18 is given by the sum of the initial amount of substance of H2 (no) and the amount of substance of Sc(Cp )2Ph in equilibrium. The latter is easily calculated from the relative concentrations of Sc(Cp )2Ph and Sc(Cp )2H determined by H NMR, and the known initial concentration of Sc(Cp )2H (5.4 x 10-5x 1000/0.5 = 0.108 mol dm-3). To evaluate the initial amount of substance of H2, consider the experimental procedure before and after reaction 14.19 takes place. When this reaction occurs (at 25 °C) a certain amount of H2 remains in solution, and it can be calculated by an equation similar to 14.17. This amount will be equal to no, by assuming that (1) there is no further H2 solubilization when the tube is rapidly cooled to — 196 °C, and (2) only the H2 dissolved in the frozen reaction mixture is not removed by the evacuation procedure. 

The experimental procedures were essentially the same as reported (Figure 1, (16, 17)). Reagents other than those described in (16. 17) were as follows. Acrylic acid(Wako Pure Chemicals) was distilled once under reduced pressure under a nitrogen stream. Solvents(acetonitrile, n-hexane, and benzene) were purified by accepted procedures. 

The experimental proeedures in this text are intended for use only by persons skilled in organie synthesis, and are condueted at ones own risk. WILEY-VCH and the author diselaim any liability for any injuries or damages claimed to have resulted from the experimental procedures described herein. In many of the reactions presented benzene is used as solvent. The replacement of benzene by a less toxic solvent, such as, e.g., toluene, might in many instances lead to comparable results, and is strongly recommended. 

The [YCo] systems catalyze this reaction only above 130°C, and hence, the reaction must be carried out in dilute benzene or toluene solutions to keep the TON values below —500. Only very active catalysts can be used for the reaction of Eq.(13) when carried out in pure acrylonitrile. Every cobalt catalyst sufficiently active below 125°C was tested in a batch reactor. A solution of the catalyst in pure acrylonitrile was saturated with acetylene at —2.0 MPa and then heated to 130°C (for experimental procedures, see 84MI5). The TON values after 2 hrs are summarized in Table II. The best results were obtained with the i7 -phenylborininato complex (9), which produced 2.78 kg VP/g Co. 

To better compare modern protocols for the Reformatsky reactions, hereinafter discussed in this section, it is interesting to read, as an example, the experimental procedure reported by R. B. Woodward and coworkers in 1956 for the synthesis of the Lysergic acid precursor 3 (equation 2)14. The procedure adopted was a Barbier-like protocol, involving the addition of Zn and of methyl bromoacetate (la) in three portions to a solution of 2 in hot benzene. 

In a convenient experimental procedure, nitrogen heterocycles 3 are alkylated by a mixture of a carboxylic acid 4 and [bis(trifluoroacetoxy)iodo]benzene in boiling benzene or under irradiation in dichloromethane at room temperature (Scheme 2) [11, 12]. A similar procedure has been used for the stereoselective synthesis of C-nucleosides and their analogs via photolysis of the gulonic acid derivatives, (diacetoxy)iodobenzene, and the appropriate heteroaromatic bases [13]. 

Acetaldehyde decomposition, reaction pathway control, 14-15 Acetylene, continuous catalytic conversion over metal-modified shape-selective zeolite catalyst, 355-370 Acid-catalyzed shape selectivity in zeolites primary shape selectivity, 209-211 secondary shape selectivity, 211-213 Acid molecular sieves, reactions of m-diisopropylbenzene, 222-230 Activation of C-H, C-C, and C-0 bonds of oxygenates on Rh(l 11) bond-activation sequences, 350-353 divergence of alcohol and aldehyde decarbonylation pathways, 347-351 experimental procedure, 347 Additives, selectivity, 7,8r Adsorption of benzene on NaX and NaY zeolites, homogeneous, See Homogeneous adsorption of benzene on NaX and NaY zeolites... 

Bromination of 14 is achieved by reaction with three equiv of W-bromo-succinimide in boiling benzene under light irradiation. This reaction gives a mixture of the desired tribromide derivative 15a and also the dibromide and tetrabromide derivatives, 15b and 15c respectively (Scheme 9.12). The separation of these compounds is very difficult, and so the mixture is best used without purification for the next step. The experimental procedure is given in Protocol 10. 

We performed extensive studies to determine the Cl-atom rate constant of benzene. n-Butane and ethane were among first molecules that were used as references to measure the relative rate constant of Cl-atom reaction of benzene. By the end of these experiments, the concentration of reference molecules reduced close to the detection limits whereas no decay of benzene outside the uncertainty limits was observed. Although the relative rate technique is particularly powerful in the measurement of reactions with comparable rate constants, for reactions with very different rate constants, this method is less accurate. Since it has become clear that the Cl-atom rate constant of benzene is slow, chloromethane, dichloromethane, and trichloromethane (chloroform) were used as references. These sets of experiments consisted of 20 individual experiments in which the concentration of hydrocarbons ranged from 10 to 15 mTorr and the concentration of CI2 varied from 10 to 100 mTorr. The relative rate constants for chloromethane and dichloromethane have been previously measured by Niki et al. [65]. Specifically, they were combined as a check on the experimental procedures. No difference in the values of the rate... 

Surprisingly, little new research on the prototypal tung-sten-arene complex see Arene Complexes), r] -Ceih)f, has appeared, possibly because of the low-yielding and elaborate experimental procedures required for its synthesis. Photolysis of W(CO)6 in the presence of ethyne leads to the formation of benzene and rf-CdRf) W(CO)3 (101), and the solid-state molecular structure of this complex was... 

Schiff base condensation reactions have also been widely used in the preparation of new imine-functionalized tertiary phosphines (64) (68).122-129 The most frequently used experimental procedure involves the condensation of a carbonyl compound (often 2-Ph2PCeH4CHO)176 and the appropriate amine in ethanol, benzene, or THF under refluxing conditions. To ensure complete reaction, a Dean-Stark trap or the addition of molecular sieves is often necessary, to remove water formed during the reaction. Evaporation of the solvent and recrystallization yield the desired ligand in good to excellent yields. This approach can be used to prepare bis-phosphines, e.g., (66)-(68).127- 29 The iminophosphine (69) was prepared by a series of coupling reactions at a palladium template, and was liberated from the metal by treatment with aqueous cyanide.130... 

The reactor system and general experimental procedures were similar to those described by Zmcevic et al. [11] and are discussed in detail in our former paper [12]. Deactivation measurements were carried out in an isothermal fixed-bed reactor with a hydrogen partial pressure of 99.82 kPa, benzene partial pressure of 7.55 kPa, thiophene partial pressure of 0.032 kPa and reaction temperatures fi om 403 to 473 K. The size of commercial cylindrical catalyst pellets suppli by BASF was 5x5 mm (21% Ni on alumina). The catalyst was activated by reduction with hydrogen at 743 K for 10 h. 

Thermal decomposition of 2-diazohexafluoropropane, or 2-diazo-3,3,3-trifluoro-propanenitrile in excess benzene (150-200 "C, autoclave) resulted in efficient cyclopropanation of an aromatic C-C double bond. In solution, the 7-trifluoromethylnorcaradiene 9 (-bicyclo[4.1.0]hepta-2,4-diene) so formed is in rapid valence equilibrium with the corresponding cycloheptatriene 10 however, this equilibrium is shifted predominantly or completely to the cycloheptatriene side. As a byproduct in the synthesis, the product of carbene insertion into an aromatic C-H bond is obtained. An experimental procedure for the synthesis of 10b can be found in Houben-Weyl, Vol. 19 b, p 1031. 

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