Experimental procedure derivatives

More specific values of the fracture toughness are obtained by the application of the experimental procedures derived from the fracture mechanics theories. In the case of no plastic deformation in front of the crack tip, the LEFM is employed, obtaining the values of the stress critical intensity factor (fQ) or critical stress energy release rate (G,.). On the other hand, when there is plasticity in front of the crack tip, we must use the principles of the elastoplastic fracture mechanics in this sense, two experimental procedures are widely employed the J-integral analysis and the EWF. 

The experimental procedure to be followed depends upon the products of hydrolysis. If the alcohol and aldehyde are both soluble in water, the reaction product is divided into two parts. One portion is used for the characterisation of the aldehyde by the preparation of a suitable derivative e.g., the 2 4-dinitrophenylhydrazone, semicarbazone or di-medone compound—see Sections 111,70 and 111,74). The other portion is employed for the preparation of a 3 5-dinitrobenzoate, etc. (see Section 111,27) it is advisable first to concentrate the alcohol by dis tillation or to attempt to salt out the alcohol by the addition of solid potassium carbonate. If one of the hydrolysis products is insoluble in the reaction mixture, it is separated and characterised. If both the aldehyde and the alcohol are insoluble, they are removed from the aqueous layer separation is generally most simply effected with sodium bisulphite solution (compare Section Ill,74),but fractional distillation may sometimes be employed. 

Many reagents are able to chlorinate aromatic pyrazole derivatives chlorine-water, chlorine in carbon tetrachloride, hypochlorous acid, chlorine in acetic acid (one of the best experimental procedures), hydrochloric acid and hydrogen peroxide in acetic acid, sulfuryl chloride (another useful procedure), etc. iV-Unsubstituted pyrazoles are often used as silver salts. When methyl groups are present they are sometimes chlorinated yielding CCI3 groups. Formation of dimers and trimers (308 R = C1) has also been observed. 

The synthetic procedure described is based on that reported earlier for the synthesis on a smaller scale of anthracene, benz[a]anthracene, chrysene, dibenz[a,c]anthracene, and phenanthrene in excellent yields from the corresponding quinones. Although reduction of quinones with HI and phosphorus was described in the older literature, relatively drastic conditions were employed and mixtures of polyhydrogenated derivatives were the principal products. The relatively milder experimental procedure employed herein appears generally applicable to the reduction of both ortho- and para-quinones directly to the fully aromatic polycyclic arenes. The method is apparently inapplicable to quinones having an olefinic bond, such as o-naphthoquinone, since an analogous reaction of the latter provides a product of undetermined structure (unpublished result). As shown previously, phenols and hydro-quinones, implicated as intermediates in the reduction of quinones by HI, can also be smoothly deoxygenated to fully aromatic polycyclic arenes under conditions similar to those described herein. 

The only heterocyclic seven-membered ring system with maximum unsaturation containing six heteroatoms is 1,3A4,5,2,4,6-trithiatriazepine (1). The methoxycarbonyl derivative 2 is a minor product (14%) of the complex reaction of tetrasulfur tetranitride with dimethyl acetylenedicarboxylatc in refluxing toluene, which gives mainly dimethyl l,2,5-thiadiazole-3,4-dicarboxylate (3, 67%) (see Houben-Wcyl, Vol. E8d, pl54ff which includes an experimental procedure). Two other products are the trithiadiazepine 4 (5%, see Section 4.4.1.1.1.) and the 1,2,4-thiadiazole derivative 5 (3%).385... 

Much of our present day knowledge of sweetness intensity, both at the threshold level, where taste begins, and above the threshold level, derives from the application of psychophysical techniques. It is now evident that the psychophysical procedure used measure separate aspects of sweetness perception. Hedonic responses cannot be predicted from intensity of discrimination data, and vice versa. The taste-panel evaluation of sweetness is of fundamental importance in the development of worthwhile structure-taste relationships. Therefore, it is vital that the appropriate psychophysical method and experimental procedure be adopted for a particular objective of investigation. Otherwise, false conclusions, or improper inferences, or both, result. This situation results from the failure to recognize that individual tests measure separate parameters of sensory behavior. It is not uncommon that the advocates of a specific method or procedure seldom... 

In order to confirm that the absorption bands appeared at 3668, 2936 and 2870 cm are derived from the reaction of CH4 with the adsorbed peroxide, CD, was used instead of CH,. The IR spectra recorded in the regions of 4000-2000 cm and of 1500-700 cm are show n in Fig. 7. The experimental procedures for the results of Fig. 7 were the same as those for Fig. 6. When the temperature w as increased to 473 K in the presence of CD4, the bands at 895 cm, ascribed to the adsorbed peroxide, decreased remarkably. The new bands at 2692, 2208 and 2124 cm w ere observed simultaneously. Obviously, these are the isotopic bands of those... 

Annual Volume 71 contains 30 checked and edited experimental procedures that illustrate important new synthetic methods or describe the preparation of particularly useful chemicals. This compilation begins with procedures exemplifying three important methods for preparing enantiomerically pure substances by asymmetric catalysis. The preparation of (R)-(-)-METHYL 3-HYDROXYBUTANOATE details the convenient preparation of a BINAP-ruthenium catalyst that is broadly useful for the asymmetric reduction of p-ketoesters. Catalysis of the carbonyl ene reaction by a chiral Lewis acid, in this case a binapthol-derived titanium catalyst, is illustrated in the preparation of METHYL (2R)-2-HYDROXY-4-PHENYL-4-PENTENOATE. The enantiomerically pure diamines, (1 R,2R)-(+)- AND (1S,2S)-(-)-1,2-DIPHENYL-1,2-ETHYLENEDIAMINE, are useful for a variety of asymmetric transformations hydrogenations, Michael additions, osmylations, epoxidations, allylations, aldol condensations and Diels-Alder reactions. Promotion of the Diels-Alder reaction with a diaminoalane derived from the (S,S)-diamine is demonstrated in the synthesis of (1S,endo)-3-(BICYCLO[2.2.1]HEPT-5-EN-2-YLCARBONYL)-2-OXAZOLIDINONE. 

The number of surface groups (Z), branch cells (BC) and molecular weights for a dendrimer series can be calculated with the math expressions shown below. These parameters, as well as hydrodynamic dimensions for the series [EDA](G 0-10)de dn-PAMAM-(NH2)n are presented in Figure 25.1. The experimental procedures are general for a wide range of alkylenediamine initiator cores (e.g., NH2-(CH2)-nNH2). Characterization data for dendri-PAMAMs derived from these cores are included, where n = 2, 3,4, 5, 6. 

There are several serious problems that we are likely to encounter when using the potentiometric approach to electroanalysis. The most serious of these derive from the mathematical components found within the Nemst equation, since an exponential function will magnify all errors. Worse, though, is the way that such magnification increases exponentially as the difference between Eq.r and fo.R increases thus magnification of errors is particularly problematic when low concentrations are to be investigated or when a combination of poor experimental procedures pertain. 

On the other hand, the method of Mukaiyama can be succesfully applied to silyl enol ethers of acetic and propionic acid derivatives. For example, perfect stereochemical control is attained in the reaction of silyl enol ether of 5-ethyl propanethioate with several aldehydes including aromatic, aliphatic and a,j5-unsaturated aldehydes, with syir.anti ratios of 100 0 and an ee >98%, provided that a polar solvent, such as propionitrile, and the "slow addition procedure " are used. Thus, a typical experimental procedure is as follows [32e] to a solution of tin(II) triflate (0.08 mmol, 20 mol%) in propionitrile (1 ml) was added (5)-l-methyl-2-[(iV-l-naphthylamino)methyl]pyrrolidine (97b. 0.088 mmol) in propionitrile (1 ml). The mixture was cooled at -78 °C, then a mixture of silyl enol ether of 5-ethyl propanethioate (99, 0.44 mmol) and an aldehyde (0.4 mmol) was slowly added to this solution over a period of 3 h, and the mixture stirred for a further 2 h. After work-up the aldol adduct was isolated as the corresponding trimethylsilyl ether. Most probably the catalytic cycle is that shown in Scheme 9.30. 

A case study of the identification of a counterfeit drug molecule is discussed in Section IX. C. This is a step-by-step discussion of the experimental procedure using FTMS to address this important issue. After the exact mass of the unknown componnd has been determined, the next step is to derive its elemental composition. The minimnm and maximum number of expected atoms present in the componnd mnst be specified in the search criteria to allow the compnter program to calculate possible elemental compositions. A nniqne fit of only one elemental composition is rarely obtained. The nnmber of possible compositions increases with the increasing nnmber of elements present and with increasing mass. However, other information, snch as the number of double bond eqnivalency and the isotopic distribution of the parent ion mass spectrnm, can be used to reduce the possible elemental compositions to a reasonable nnmber. Fnrther discussion can be fonnd in Section IX. C. 

The reaction of acceptor-substituted carbene complexes with alcohols to yield ethers is a valuable alternative to other etherification reactions [1152,1209-1211], This reaction generally proceeds faster than cyclopropanation [1176], As in other transformations with electrophilic carbene complexes, the reaction conditions are mild and well-suited to base- or acid-sensitive substrates [1212], As an illustrative example, Experimental Procedure 4.2.4 describes the carbene-mediated etherification of a serine derivative. This type of substrate is very difficult to etherify under basic conditions (e.g. NaH, alkyl halide [1213]), because of an intramolecular hydrogen-bond between the nitrogen-bound hydrogen and the hydroxy group. Further, upon treatment with bases serine ethers readily eliminate alkoxide to give acrylates. With the aid of electrophilic carbene complexes, however, acceptable yields of 0-alkylated serine derivatives can be obtained. 

Experimental Procedure 4.2.4. Etherification of a Serine Derivative by Intermo-lecular O-H Insertion Methyl (25)-3-[(Ethoxycarbonyl)methoxy]-2-(benzyloxy-carbonylamino)propanoate... 

To avoid the formation of dimers, high-dilution conditions have been used for the synthesis of intrachain trisulfides derivatives of vasopressin1 11 and a peptide related to the C-terminal region of human growth hormone.1131 Typically, a 0.07 mM solution of a peptide containing two thiol groups is reacted with one equivalent of A(A -thiobisphthalimide under the conditions described in the experimental procedure of Section 6.2.1.2.1.1 workup, purification procedures, and yield are identical. 

A greatly improved experimental procedure for the synthesis of thieno[2,3-d]-1,2,3-thiadiazole caiboxylates 68 was reported by Stanetty et al. and involved diazotisation of aminothiophene derivatives 67 <99JHC761>. In these systems, substituents could be introduced into the 5-position by nucleophilic displacement of a chlorine atom or by metallation of the unsubstituted compound (68 R = H) and subsequent electrophilic quenching <99JPR391>. 

Small amounts of ethylene glycol have been reported as products after ruthenium-catalyzed reactions in NMP and toluene solvents at 2000 atm (39). However, observations of minor amounts of this product must be viewed with caution unless great care is taken in the experimental procedure. For example, it was earlier reported that a catalyst derived from Ru,(CO)l2... 

This experimental procedure in section 6.5.7 can be used to epoxidize certain cyclic as well as acychc cw-olefins with good enantioselectivity and no cis/trans-isomerization (Table 6.7). Promising results have also been observed for some terminal olefins with this new glucose-derived catalyst, which complements our previously reported trans- and trisubstituted olefin catalyst 1. 

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