Substitution moiety

The Cl—ArCO+ peak is larger than the Cl—Ar+ peak, and the ArCO+ peak is larger than the Ar+ peak (ft cleavage favored). If the fragment + 2 peaks for the Cl-substituted moieties are taken into account, there is little difference in abundance between Cl—ArCO+ and ArCO+, or between ClAr+ and Ar+ the inductive and resonance affects of the para-substituted Cl are roughly balanced out. 

In principle, the synthesis of unsymmetrically substituted moieties of borazine may be achieved by the same reactions which are suitable for preparing the symmetrical compounds. 

The enantioselective synthesis (51) of the side chain 30 of taxol had been achieved by way of stereospecific Sharpless epoxidation of cij-cinnamyl alcohol (29a), giving 29b (see Scheme 6). Following oxidation of the alcohol group, protection of the resulting carboxylic acid, regioselective opening of the epoxide with azide, benzoylation, and reduction, a suitably substituted moiety (28) was available which, after protection and deprotection of the acid function to form 30, was coupled to baccatin III. 

Alternatively compound 54 reacted with mono-6-O-tosyl-p-CD to give mainly the cyclic diesters involving 0-6 at the A,C related units furthest from the tosyl-substituted moiety. When these trisulfonates were treated with thiophenol the 6, 6S 6 trithio product was obtained. Similarly, 54 formed the 6 6 cyclic diester with a-CD. By use of heptakis 2,6-di-Tbdms-P-CD the heptakis 3-0-methyl-2,6-disulfate was made as a possible chiral resolving agent for capillary electrophoresis. ... 

Tables 1, 2, and 3 show the properties of many compositions which have characteristics that we associate with nematic, liquid crystalline melts. Several of the compositions were obtained by modification of the copolyester of I and II by replacement of a fraction of I or II by other planar, para-substituted moieties expected to yield liquid crystalline polymers. Although the examples represent only a small fraction of the many compositions prepared, they clearly illustrate the generality of the phenomenon under study. As the number of dicarboxylate and diol moieties increases, the number of distinct repeat units, i.e., pairs connected in the sense of urits II, III, or IV, grows as m n, where m is the number of dicarboxylates and n is the number of diols. Therefore, several of the copolymers have five distinct repeat units potentially present. We have synthesized liquid crystalline polymers having as many as eight different repeat units, so complexity of composition does not appear to severely limit the pol3nners which can exhibit the behavior.

The proton chemical shifts of the protons directly attached to the basic three carbon skeleton are found between 5.0 and 6.8 ppm. The J(H,H) between these protons is about -5 Hz. The shift region is similar to the region for similarly substituted alkenes, although the spread in shifts is smaller and the allene proton resonances are slightly upfield from the alkene resonances. We could not establish a reliable additivity rule for the allene proton shifts as we could for the shifts (vide infra) and therefore we found the proton shifts much less valuable for the structural analysis of the allene moiety than the NMR data on the basic three-carbon system. 

Another synthesis of a bridged hydrocarbon takes advantage of high elearon release from the /wra-position of phenolate anions, which may be used to transform the phenol moiety into a substituted cross-conjugated cyciohexadienone system (S. Masamune, 1961, 1964). 

As discussed earlier in Section lOC.l, ultraviolet, visible and infrared absorption bands result from the absorption of electromagnetic radiation by specific valence electrons or bonds. The energy at which the absorption occurs, as well as the intensity of the absorption, is determined by the chemical environment of the absorbing moiety. Eor example, benzene has several ultraviolet absorption bands due to 7t —> 71 transitions. The position and intensity of two of these bands, 203.5 nm (8 = 7400) and 254 nm (8 = 204), are very sensitive to substitution. Eor benzoic acid, in which a carboxylic acid group replaces one of the aromatic hydrogens, the... 

Pyrethroids from Chiysanthemic Acid. The unsaturated side chains of the aHethrolone alcohol moieties of the natural pyrethrins are readily epoxidized by microsomal oxidases and converted to diols, thus detoxifying the insecticides. Esterification of chrysanthemic acid (9), R = CH3, with substituted ben2yl alcohols produces usehil insecticides barthrin [70-43-9J, 2-chloro-3,4-methylenedioxyben2yl (+)-i7j ,/n7 j -chrysanthemate, and dimethrin [70-38-2] 2,4-dimethylben2yl (+)-i7j ,/n7 j -chrysanthemate. These have alimited spectmm of insecticidal activity but are of very low mammalian toxicity, ie, rat oralLD s >20,000 mg/kg. 

Conjugate addition to a P-halogen substituted methaciylate results in an addition—elimination reaction which regenerates the tZ,/ -unsaturated moiety (19-21). 

The term naphthenic acid, as commonly used in the petroleum industry, refers collectively to all of the carboxyUc acids present in cmde oil. Naphthenic acids [1338-24-5] are classified as monobasic carboxyUc acids of the general formula RCOOH, where R represents the naphthene moiety consisting of cyclopentane and cyclohexane derivatives. Naphthenic acids are composed predorninandy of aLkyl-substituted cycloaUphatic carboxyUc acids, with smaller amounts of acycHc aUphatic (paraffinic or fatty) acids. Aromatic, olefinic, hydroxy, and dibasic acids are considered to be minor components. Commercial naphthenic acids also contain varying amounts of unsaponifiable hydrocarbons, phenoHc compounds, sulfur compounds, and water. The complex mixture of acids is derived from straight-mn distillates of petroleum, mosdy from kerosene and diesel fractions (see Petroleum). 

Primary nitroparaffins react with two moles of formaldehyde and two moles of amines to yield 2-nitro-l,3-propanediamines. With excess formaldehyde, Mannich bases from primary nitroparaffins and primary amines can react further to give nitro-substituted cycHc derivatives, such as tetrahydro-l,3-oxa2iaes or hexahydropyrimidines (38,39). Pyrolysis of salts of Mannich bases, particularly of the boron trifluoride complex (40), yields nitro olefins by loss of the amine moiety. Closely related to the Mannich reaction is the formation of sodium 2-nitrobutane-1-sulfonate [76794-27-9] by warming 1-nitropropane with formaldehyde and sodium sulfite (41). 

Properties have been determined for a series of block copolymers based on poly[3,3-bis(ethoxymethyl)oxetane] and poly [3,3-bis(methoxymethyl)oxetane]- (9-tetrahydrofuran. The block copolymers had properties suggestive of a thermoplastic elastomer (308). POX was a good main chain for a weU-developed smectic Hquid crystalline state when cyano- or fluorine-substituted biphenyls were used as mesogenic groups attached through a four-methylene spacer (309,310). Other side-chain Hquid crystalline polyoxetanes were observed with a spacer-separated azo moiety (311) and with laterally attached mesogenic groups (312). 

The aminophenols are chemically reactive, undergoing reactions involving both the aromatic amino group and the phenoHc hydroxyl moiety, as weU as substitution on the benzene ring. Oxidation leads to the formation of highly colored polymeric quinoid stmctures. 2-Aminophenol undergoes a variety of cyclization reactions. 

The hydroxyben2oic acids have both hydroxyl and the carboxyl groups and, therefore, participate in chemical reactions characteristic of each of these moieties. In addition, these acids can undergo electrophilic ring substitution. The following reactions are discussed in terms of saUcyhc acid, but are characteristic of all the hydroxyben2oic acids. 

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