Formatting Schemes, Tables

The catalytic alcohol racemization with diruthenium catalyst 1 is based on the reversible transfer hydrogenation mechanism. Meanwhile, the problem of ketone formation in the DKR of secondary alcohols with 1 was identified due to the liberation of molecular hydrogen. Then, we envisioned a novel asymmetric reductive acetylation of ketones to circumvent the problem of ketone formation (Scheme 6). A key factor of this process was the selection of hydrogen donors compatible with the DKR conditions. 2,6-Dimethyl-4-heptanol, which cannot be acylated by lipases, was chosen as a proper hydrogen donor. Asymmetric reductive acetylation of ketones was also possible under 1 atm hydrogen in ethyl acetate, which acted as acyl donor and solvent. Ethanol formation from ethyl acetate did not cause critical problem, and various ketones were successfully transformed into the corresponding chiral acetates (Table 17). However, reaction time (96 h) was unsatisfactory. 

Instructions for formatting figures, tables, and schemes are presented in chapter 16. Consult chapter 16 as you work through this chapter. 

Table 16.3 Some generally accepted guidelines for formatting schemes. (Because formatting conventions vary, consult the appropriate Information for Authors for specific guidelines.)...

Chapter 16 Formatting Figures, Tables, and Schemes Chapter 17 Formatting Citations and References Chapter 18 Finalizing Your Written Work... 

Tn previous work it has been shown that a competition exists during - ozonation of olefins between ozonolysis and epoxide formation (I). As steric hindrance increases around the double bond, the yield of epoxide or subsequent rearrangement products increases. This is illustrated with both old (1) and new examples in Table I for purely aliphatic olefins and in Table II for aryl substituted ethylenes. It was suggested that the initial attack of ozone on an olefinic double bond involves w (pi) complex formation for which there were two fates (a) entrance into 1,3-dipolar cycloaddition (to a 1,2,3-trioxolane adduct), resulting in ozonolysis products (b) conversion to a o- (sigma) complex followed by loss of molecular oxygen and epoxide formation (Scheme 1). As the bulk... 

It has been fonnd that 7,8-digermabicyclooctadiene 26 reacts spontaneonsly with CCLj and benzyl bromide at ambient temperatures. However, these reactions are in fact much slower than the photolysis and do not preclude the observation of CIDNP. Moreover, the presence of these halogenated trapping agents does not hamper the detection of CIDNP effects formed in the photolysis of the initial 26. Thus, the trapping agents do not enter the reaction with the intermediate 1,6-biradical 29 which is responsible for the CIDNP formation (Scheme 14). CIDNP effects detected in these reactions are summarized in Table 13 and the experimental spectra are shown in Figure 19. 

A machine has been under construction at Princeton to investigate the slow plasma formation scheme, MHD instabilities, and plasma transport phenomena. The following considerations were taken into account to determine plasma and machine parameters summarized in Table-2. 

The last two items of Table 9.6 are related. The seventh item shows that the techniques already discussed that employ dicyclohexylcarbodiimide and carbonyl-diimidazole to activate a carboxylic acid for attack by primary and secondary amines in order to forge the bond between the carbon of the carbonyl and the nitrogen of the amine to yield amide (vide supra. Scheme 9.119) can also be employed in ester formation (Scheme 9.122). The particular alcohol chosen, 3-(hydroxymethyl)-3-methyloxetane, although typical in its reactivity for primary alcohols in general and thus capable of serving as a prototype for ester, was also chosen because, as shown in item 8 of Table 9.6, it can subsequently be used to convert the ester to an orthoester of the corresponding carboxylic acid (Scheme 9.123). Such orthoesters are used to protect the carboxylic acid function and preserve it, while manipulations... 

Another scheme for estimating thermocheraical data, introduced by Allen [12], accumulated the deviations from simple bond additivity in the carbon skeleton. To achieve this, he introduced, over and beyond a contribution from a C-C and a C-H bond, a contribution G(CCC) every time a consecutive arrangement of three carbon atoms was met, and a contribution D(CCC) whenever three carbon atoms were bonded to a central carbon atom. Table 7-3 shows the substructures, the symbols, and the contributions to the heats of formation and to the heats of atomization. 

Table 7.3. The Allen scheme substructures, notations, and contributions to heats of formation and heats of atomization (values in kj/mol).

The zeroth-order rates of nitration depend on a process, the heterolysis of nitric acid, which, whatever its details, must generate ions from neutral molecules. Such a process will be accelerated by an increase in the polarity of the medium such as would be produced by an increase in the concentration of nitric acid. In the case of nitration in carbon tetrachloride, where the concentration of nitric acid used was very much smaller than in the other solvents (table 3.1), the zeroth-order rate of nitration depended on the concentrationof nitric acid approximately to the fifth power. It is argued therefore that five molecules of nitric acid are associated with a pre-equilibrium step or are present in the transition state. Since nitric acid is evidently not much associated in carbon tetrachloride a scheme for nitronium ion formation might be as follows ... 

There is clearly a conceptual relationship between the properties called nucleophilicity and basicity. Both describe a process involving formation of a new bond to an electrophile by donation of an electron pair. The pA values in Table 5.7 refer to basicity toward a proton. There are many reactions in which a given chemical species might act either as a nucleophile or as a base. It is therefore of great interest to be able to predict viiether a chemical species Y P will act as a nucleophile or as a base under a given set of circumstances. Scheme 5.4 lists some examples. 

The fourth factor becomes an issue when anti betaine formation is reversible or partially reversible. This can occur with more hindered or more stable ylides. In these cases the enantiodifferentiating step becomes either the bond rotation or the ring-closure step (Scheme 1.12), and as a result the observed enantioselectivities are generally lower (Entry 5, Table 1.5 the electron-deficient aromatic ylide gives lower enantioselectivity). However the use of protic solvents (Entry 6, Table 1.5) or lithium salts has been shown to reduce reversibility in betaine formation and can result in increased enantioselectivities in these cases [13]. Although protic solvents give low yields and so are not practically useful, lithium salts do not suffer this drawback. [18]... 

The synthesis of block copolymers by macromonotner RAFT polymeriza tion has been discussed in Section 9.5.2 and examples are provide in Table 9.9. RAFT polymerization with thioearbonylthio compounds has been used to make a wide variety of block copolymers and examples arc provided below in Tabic 9.28. The process of block formation is shown in Scheme 9.59. Of considerable interest is the ability to make hydrophilic-hydrophobic block copolymers directly with monomers such as AA, DMA, NIPAM and DMAEMA. Doubly hydrophilic blocks have also been prepared.476 638 The big advantage of RAFT polymerization is its tolerance of unprotected functionality. 

The rapid formation of the (Z)-diazoate is followed by the slower (Z/J )-isomeri-zation of the diazoate (see Scheme 5-14, reaction 5). Some representative examples are given in Table 5-2. Both reactions are first-order with regard to the diazonium ion, and the first reaction is also first-order in [OH-], i.e., second-order overall. So as to make the rate constants k and k5 directly comparable, we calculated half-lives for reactions with [ArNj ]0 = 0.01 m carried out at pH = 9.00 and 25 °C. The isomerization rate of the unsubstituted benzenediazonium ion cannot be measured at room temperature due to the predominance of decomposition (homolytic dediazoniations) even at low temperature. Nevertheless, it can be concluded that the half-lives for (Z/ )-isomerizations are at least five powers of ten greater than those for the formation of the (Z)-diazohydroxide (reaction 1) for unsubstituted and most substituted benzenediazonium ions (see bottom row of Table 5-2). Only for diazonium ions with strong -M type substituents (e.g., N02, CN) in the 2- or 4-position is the ratio r1/2 (5)/t1/2 (1) in the range 6 x 104 to 250 x 104 (Table 5-2). 

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