Hydrocarbon substituents

Mercaptoselenazoies with Q to C,o cyclic hydrocarbon substituents in the 4-position have been mentioned as giving negative images from photosolubie emulsions (38. 39). Equally cited are other heterocycles such as thiazole. oxazole, or imidazole. 

Chloroformates are reactive intermediates that combine acid chloride and ester functions. They undergo many reactions similar to those of acid chlorides however, the rates are usually slower (4—8). Those containing smaller organic (hydrocarbon) substituents react faster than those containing large organic (hydrocarbon) substituents (3). Reactions of chloroformates and other acid chlorides proceed faster with better yields when alkaU hydroxides or tertiary amines are present to react with the HCl as it forms. These bases act as stoichiometric acid acceptors rather than as tme catalysts. 

Low sulfate selectivity of the ion-selective electrodes (ISE) based on lipophilic quaternary ammonium salts (QAS) is usually explained by unfavorable ratio of sulfate hydration and solvation energies. We have been shown that another reason does exist as well namely, low efficiency of sulfate-QAS cation interaction caused by steric hindrance for simultaneous approach of two QAS cations, containing four long-chain hydrocarbon substituents, to sulfate ion. 

It has been found that the influence of the membrane composition on the ISE selectivity is mainly governed by substitution degree of the nitrogen atom, but virtually does not depend upon the length of hydrocarbon substituents. The key factor in the selectivity of DBP-plasticized membranes with both kinds of ion-exchangers and of the o-NPOE-TNOBS-membrane is the ionic... 

SI (Systeme International) The International System of units a collection of definitions of units and symbols and their deployment. It is an extension and rational ization of the metric system. See also Appendix IB. side chain A hydrocarbon substituent on a hydrocarbon chain. 

Like peroxyl radicals (see Section 2.4.4.) alkoxyl radicals with a long hydrocarbon substituent can isomerize to the alkyl radical... 

Attempts to optimize the stability and SOD activity of C-substi-tuted (R = methyl and fused cycloalkyl) [Mn(II)[15]aneN5)Cl2] complexes 95 have shown that increasing the number of hydrocarbon substituents greatly increases the kinetic stability of the complex toward dissociation via protonation (Fig. 19). (443). There is also some enhancement of thermodynamic stability. The trans-fused endohexano Mn(II) complex 96 has a faster dismutation rate constant (9.09 X 107M-1 s1, pH 7.4) and a 10 times higher thermodynamic stability than the unsubstituted complex. 

As demonstrated in most of the other chapters of this book, there is a countless - and growing - number of applications of allenes in preparative organic chemistry. A need for an extra section on the use of allenic hydrocarbons in synthesis may therefore not be apparent. However, since this chapter concentrates on the construction and then preparation of novel jr-systems - neglecting all non-hydrocarbon substituents - some general remarks on the preparative usefulness of the parent systems seem to be in order. 

There is a variation in the differences between the enthalpies of formation of RMgBr(soln) and RLi, depending on the class of hydrocarbon substituent. For the sole example, or the average of multiple examples, the enthalpy of formation differences between the organohthium and the corresponding solution-phase Grignard are methyl (259), primary (268), secondary/tertiary (280) and aryl (256)kJmoP. Generally, the... 

In fact, all derivatives 9-13 show doubling of the peroxidic signals except for 11(11). The authors pointed out that these data serve as a clear indication that hydrocarbon substituents, as well as substituents bearing electron-withdrawing heteroatoms, are sufficient to cause a chemical shift nonequivalence of the two peroxidic oxygens at O NMR. Although the unknown stereochemistry of derivatives 10-13 does not allow us to discuss properly the origin of this nonequivalence, some reasonable hypotheses can be put forth. 

O-propargyl-2-iodophenol in the presence of a palladium catalyst and phenylzinc chloride (3.30.) led to the formation of the 3-alkylidenedihydrobenzofurane in good yield (c.f 3.26.),37 The use of norbomene as capture reagent under similar conditions led to the formation of benzofurane bearing a tetracyclic hydrocarbon substituent.38... 

Table 2. Linear interdependences between lipophilic and steric substituent constants (17 hydrocarbon substituents)... 

Let us start out by a few comments about the terms used to describe carbon skeletons encountered in organic molecules. When considering a hydrocarbon (i.e., a compound consisting of only C and H) or a hydrocarbon group (i.e., a hydrocarbon substituent) in a molecule, the only possible functionalities are carbon-carbon double and triple bonds. A carbon skeleton is said to be saturated if it has no double or triple bond, and unsaturated if there is at least one such bond present. Hence, in a hydrocarbon, the term saturated indicates that the carbon skeleton contains the maximum number of hydrogen atoms compatible with the requirement that carbon always forms four bonds and hydrogen one. A saturated carbon atom is one that is singly bound to four other separate atoms. 

The hydrocarbon substituents derived from alkynes are called alkynyl groups ... 

A variety of substituted benzenes are known that have one or more of the hydrogen atoms of the ring replaced with other atoms or groups. In almost all of these compounds the special properties associated with the benzene nucleus are retained. A few examples of benzenoid hydrocarbons follow, and it will be noticed that the hydrocarbon substituents include alkyl, alkenyl, and alkynyl groups. Many have trivial names indicated in parentheses ... 

TABLE 6A.4. Epoxides from (3/0-Suhsti tuted Allylic Alcohols (Hydrocarbon Substituents)... 

Saturated hydrocarbon substituents in the molecule have little effect on the bond energies with the catalyst. On the contrary, the appearance of stabilization energy, for example, of the carboxyl groups, has a profound influence on QAK ... 

As shown in Figure 17.9, esters of sulfuric acid exist in which either one or both of the ionizable H atoms are replaced by hydrocarbon substituents, such as the methyl group. Replacement of one H yields an acid ester, and replacement of both yields an ester. Metabolically, acid ester sulfates are synthesized in phase II reactions to produce water-soluble products of xenobiotic compounds (such as phenol) that are readily eliminated from the body (see Section 7.4). 

According to Bernardi et al.,109 for (E)-enoates with two y-hydrocarbon substituents, the dominant interaction is with the nucleophile. Therefore, the smallest substituent S should be put in the outside position. For (Z)-enoates, S should be put in the inside position.110 For y-alkoxy-(E)-enoates, a Felkin transition state may rationalize organolithium111 and alkoxyde112 additions, but does not explain the results for... 

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