Double functionalization

Many aromatic aldehydes (having the -CHO group joined directly to the benzene ring) undergo polymerisation when heated with a solution of potassium cyanide in aqueous ethanol. Thus benzaldehyde gives benzoin, a compound of double function, since it contains both a secondary alcoholic and a ketonic... 

Exchanger Performs a double function (1) heats a cold fluid by (2) using a hot fluid which it cools. None of the transferred heat is lost. 

The absorber tower usually performs a double function. It not only recovers the desirable eonstituents from the gas, but also rejeets undesirable lighter... 

If the nucleophilicity of the anion is decreased, then an increase of its stability proceeds the excessive olefine can compete with the anion as a donor for the carbenium ion, and therefore the formation of chain molecules can be induced. The increase of stability named above is made possible by specific interactions with the solvent as well as complex formations with a suitable acceptor 112). Especially suitable acceptors are Lewis acids. These acids have a double function during cationic polymerizations in an environment which is not entirely water-free. They react with the remaining water to build a complex acid, which due to its increased acidity can form the important first monomer cation by protonation of the monomer. The Lewis acids stabilize the strong nucleophilic anion OH by forming the complex anion (MtXn(OH))- so that the chain propagation dominates rather than the chain termination. 

In ATES (Aquifer Thermal Energy Storage) systems groundwater is used to carry the thermal energy into and out of an aquifer. For the connection to the aquifer water wells are used. However, these wells are normally designed with double functions, both as production and infiltration wells, see Figure 29. 

The slightly exothermic hydrolysis reaction is kinetically hindered, but proceeds rapidly on many single and mixed metal oxides [19,22-25], This means that in practice HNCO is usually hydrolyzed on the SCR catalyst itself, which has to be big enough in order to fulfill the double function [19]. 

In a self-reproducing, catalytic hypercycle (second order, because of its double function of protein and RNA synthesis) the polynucleotides Ni contained not only the information necessary for their own autocatalytic self-replication but also that required for the synthesis of the proteins Ei. The hypercycle is closed only when the last enzyme in the cycle catalyses the formation of the first polynucleotide. Hypercycles can be described mathematically by a system of non-linear differential equations. In spite of all its scientific elegance and general acceptance (with certain limitations), the hypercycle does not seem to be relevant for the question of the origin of life, since there is no answer to the question how did the first hypercycle emerge in the first place (Lahav, 1999). 

Similarly, a double functionalization can be reached when an activating group is present in close vicinity to the triple bond. Tsuji et al. have discovered that with a diphosphine palladium(O) complex, a carbonate function in the a-position of the alkyne provides by decarboxylation a palladium methoxy species on which the alkyne moiety can be isomerized into an al-lenyl a -bonded group. CO insertion in the Pd - C bond, reductive elimination with the methoxy group and further cyclization with incorporation of a second CO molecule give rise to the corresponding cyclopentenone as shown in Scheme 21 [127]. 

One characteristic feature of surfactants is their amphiphilic nature. These molecules present two moieties the hydrophobic moiety (usually a hydrocarbon chain) interacts with the nanotube sidewalls, while the hydrophilic part, called polar head group, is generally charged or has zwitterionic character. It has the double function of helping solubility in aqueous solvents and of providing additional stabilization towards tubes aggregation by coulombic charge repulsion. 

Principally the same, but chemically simpler, sequence was used to prepare arylnitro anion-radicals from arylamines, in high yields. For instance, aqueous sodium nitrite solution was added to a mixture of ascorbic acid and sodium 3,5-dibromo-4-aminobenzenesulfonate in water. After addition of aqueous sodium hydroxide solution, the cation-radical of sodium 3,5-dibromo-4-nitro-benzenesulfonate was formed in the solution. The latter was completely characterized by its ESR spectrum. Double functions of the nitrite and ascorbic acid in the reaction should be underlined. Nitrite takes part in diazotization of the starting amine and trapping of the phenyl a-radical formed after one-electron reduction of the intermediary diazo compound. Ascorbic acid produces acidity to the reaction solution (needed for diazotization) and plays the role of a reductant when the medium becomes alkaline. The method described was proposed for ESR analytical determination of nitrite ions in water solutions (Lagercrantz 1998). 

With cyclic enones, Professor Yamamoto has developed (J. Am. Chem. Soc. 2004,126,5962) an enantioselective double functionalization. The organocatalyst 8 mediates conjugate addition of N and a -oxygenation, to give 9. 

When the cluster [Pd4(C0)4(02CMe)4]-2MeC02H was dissolved in styrene and treated with methanol under an atmosphere of carbon monoxide, methyl cinnamate was formed.516 This reaction was also believed to occur by an alkoxycarbonyl route. The reaction became catalytic when [Pd(OAc)2] (106) was used in presence of NaOAc and a stoichiometric amount of copper(II) as reoxidant for the palladium(O) formed. Stille and co-workers have investigated this reaction, sometimes called carboalkoxylation, in detail. A basic difference between this reaction and the hydroesterification described above is that the oxidative nature of carboalkoxylation permits double functionalization of a double bond. Thus (E)- and (Z)-2-butene react readily with CO and methanol in the presence of a catalytic amount of PdCl2 and a stoichiometric amount of CuCl2 to give methyl 3-methoxy-2-methylbutanoate (equation 124).517,518... 

Double functionalization appears to be quite general, since a variety of 5-substituted cycloheptadiene-iron complexes are readily converted to 6-substituted cycloheptadienyliron systems, which in turn undergo regio- and stereo-controlled nucleophile addition.23... 

It is, however, possible to utilise the double function of the azo monofners so that emulsion polymerization can be carried out without any additional initiatior at... 

An interesting variation on the use of azo groups-containing polymers is the use of polyacrylamide prepolymers as both initiator and emulsifying agent for the emulsion polymerization of vinyl acetate. The observed reaction kinetics were typical (see Fig. 4.7) for an emulsion polymerization and, in particular, the slope (a = 1) of the plot of lg Rp vs lg CPrep confirms the double function of these prepolymers very clearly. 

The one-step double functionalization of aromatics—that is, alkylation and acylation—can be accomplished with alkanes or cycloalkanes (in large excess) using the aprotic organic superacids RCO+Al2X7 (R = alkyl, aryl, X = Cl, Br)391 [Eq. (5.152)]. However, the method can be used only for benzene and bromobenzene. 

The "Double Functional Group Transformation" Terminally Unsaturated Nitriles from 1-Nitrocydoalkenes... 

There is much current interest in the design and development of the "double functional group transformation" concept, an excellent illustration of which is the now well known and widely exploited Eschenmoser fragmentation reaction. A recent example of the "double functional group transformation" is the one-flask conversion of 1-nitrocycloalkenes into terminally unsaturated nitriles by treatment first with trimethylsilylmethylmagnesium chloride (1.8 eq.) in THF at -20°C and then, in situ, with PCI3 (2.5 eq.) at 67°C. 2-Nitrobicyclo[2.2.1]hept-2-ene, for example, gave cis-1 -cyano-3-vinylcyclopentane in 33% yield, and similar yields of ene-nitriles were obtained from a variety of monocyclic and bicyclic 1-nitrocycloalkenes. 

Suggest a mechanism for this "double functional group transformation". 

Piperidine that is typically used for this purpose has a double function. As a nucleophile, it releases the damaged base (denoted as HNR2) and assists in the acidification of the H2 by forming a positively charged Schiff base [reaction (8)]. 

Many indicators or substitute measures are in use in public health. Some are exposure indicators. Examples are COhb as an indicator for CO poisoning, nicotine as indicator for tobacco smoke, C02 as ventilation indicator, PM10 as a measure of particulate matter, and Olf/Decipol as an indicator for air pollution with bio-effluents from occupants. Some are health indicators, such as changed lung function for health effects caused by indoor air environment, and some may have a double function as both exposure and effect indicator (such as SBS). 

Aoki, S., Kawatani, H., Goto, T., Kimura, E., Shiro, M. A double-functionalized cyclen with carbamoyl and dansyl groups (cyclen = 1,4,7,10-tetraazacyclododecane) A selective fluorescent probe for Y3+ and... 

Aryl cation chemistry allows a double functionalization of vinyl ethers in a three-component reaction, as depicted in Scheme 3.30. In this case, a 3-arylacetal (e.g., 47) was synthesized after the initial addition of the 4-hydroxyphenyl cation onto ethyl vinyl ether, followed by trapping with the nucleophilic solvent MeOH [77]. For related arylation reactions, see Chapter 10. 

Remote chlorination (6, 298-300). Breslow has extended his remote functionalization of steroids to a double functionalization at C, and Cn of cholestanol. Thus the ester (2) of cholestanol, prepared from a p-iodophenylnicotinic acid, when treated with 1 (1.2 equiv.) is chlorinated selectively at C9 chlorination of the same ester with 3 equiv. of C6H5IC12 results in chlorination at C9 and at C17 in quantitative yield. The para-iodo group of the ester plays an important role in this remote chlorination. 

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